Since 1993, more than 7,200 treatments for various diseases have been performed at our hospital with Radiosurgery using Gamma Knife.
This technology is applied at some of the world's most prestigious centres (Karolinska Hospital in Stockholm, Mayo Clinic in Minnesota, University of Pittsburgh, Munich, etc.), with whom we share both equipment and procedure.
There are currently around 350 Gamma Knife treatment units in the world, with more than one million procedures carried out since 1986.
Our results are similar to and have been verified against those from series produced at these centres through the close contact between the various Gamma Knife Units, through personal visits and at the annual and biannual meetings held in this regard where new advances are shared and the methodologies of each work group are compared.
The first treatments were carried out in 1993 at the Ruber Internacional Hospital with second generation equipment (Gamma Knife B model), which at that time was No. 43 in the world. In the year 2000, the change to model C was made (our equipment was No. 11 in the world with these characteristics), improved with automatic positioning system from April 2001. In 2007, in line with the constant technological improvement at our centre, the following model was introduced, Perfexion (with its updated version in 2011), which represented a real improvement both for medical practice (planning, conforming and minimizing peripheral doses) and for practical aspects for the patient (speed and comfort). The latest model, in operation at our unit since August 2017, is the Gamma Knife ICON. It is one of 62 units in use in the world today, according to the Elekta records of 2018. It incorporates a Cone-Beam CT system that optimizes treatment quality control and allows treatments to be carried out using a thermoplastic mask instead of using the stereotactic frame, when it is necessary to apply the treatment over several days (fractionated radiosurgery). This system combines the advantages of precision, accuracy and low peripheral radiation offered by Gamma Knife with the advantages of fractionation, when the clinical case requires it.
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RADIOSURGERY WITH GAMMA KNIFE: INTRODUCTION
Radiosurgery is an advanced irradiation technique that combines the concepts of high dose and optimally precise application. This aims to achieve the optimal result between tumour control and minimized side effects by reducing the dose applied to healthy tissues near the lesion.
Life expectancy has been prolonged in recent decades, including that of neuro-oncological patients, so the concept of "quality of life" is now as or more important than that of "quantity of life". While treating brain and spinal tumours, it is especially important to control potential adverse reactions, especially those that are chronic in nature, that is, those that will remain in time, some indefinitely. For this reason, and depending on the nature of the lesions, Radiosurgery plays an essential role since it is the technique that achieves the greatest precision and accuracy, as well as a high gradient of the dose in the periphery of the irradiated area.
Precision and accuracy involve having a correct spatial location of the target (malignant or benign tumour, vascular malformation or anatomically normal tissues, but with abnormal functioning such as in neuralgias, epilepsies, tremor or obsessive-compulsive disorders) and ensuring that the target to be treated is attained. All this is partly achieved thanks to a thorough control of the imaging methods used and their corresponding distortion and a sophisticated planning system, and partly thanks to different immobilization mechanisms such as the placement of a stereotactic frame in the case of Gamma Knife Radiosurgery or some treatments with LINAC or thermoplastic masks, used for years for linear accelerator (LINAC) or CyberKnife and recently adapted for certain treatments in which it is not possible to use the stereotactic frame in the Gamma Knife Icon system. These systems are used both to treat and obtain the images used to plan the treatment (magnetic resonance imaging, computerized axial tomography, molecular imaging tests, and arteriography).
The rapid drop in dose (high dose gradient) allows us to apply a very high dose to the target, thus enabling the dose to drop rapidly around the target. This means that the dose received by healthy peripheral tissues is very low, which is an important factor in the case of the nervous system.
Currently, Gamma Knife Radiosurgery is the technique that best combines optimal mechanical precision with the highest possible dose gradient in practical terms.
Another secondary but not negligible advantage is the simplicity of this technique. In the case of Gamma Knife Radiosurgery, the procedure is performed on a single day. In the case of using CyberKnife or Linear Accelerators, the imaging tests are carried out on one day and, several days later, the treatment is applied on a number of days varying between one and five. These are outpatient treatments that, generally, do not require extraordinary measures in terms of additional medication or special care. The patient can return to their normal lifestyle almost immediately.
In the case of tumours, Radiosurgery may be used on high-grade malignant tumours as a complementary treatment or in the event of recurrences and as a single treatment for low-grade malignant tumours. Currently, Gamma Knife Radiosurgery is the technique of choice, provided that the appropriate conditions are met, for benign tumours, functional treatments and a large percentage of brain metastases, since the best results are obtained using a single dose of radiation in these processes.
Sometimes it is not possible to apply the single dose to properly protect the healthy brain. This can occur in cases where previous radiation has already been applied or where the lesion is large in volume. Since 2017, we have the Gamma Knife Icon system, which adds the technical advantages of the previous system (high precision and accuracy, together with very low irradiation of healthy tissues) to the possibility of providing treatments in three or five sessions. It also offers the possibility, as mentioned above, of using the thermoplastic mask if the stereotactic frame is not possible or convenient, even though this is the preferred option.
The Gamma Knife Icon system also allows us to carry out a final verification with the patient in a treatment position, checking and confirming the precision of all imaging and immobilization systems before beginning the procedure.
Technical advances have expanded the range of patients who can be candidates for radiosurgical treatment. These include complex cases in which both the diagnostic and therapeutic approach should be carried out within the context of a multidisciplinary team. At our centre, a Committee composed of all the specialists involved in neuro-oncological processes meets regularly to assess, discuss and programme the best alternative for each patient.
Benign tumours usually grow slowly, but can end up causing serious symptoms, so once diagnosed, they should be treated as soon as possible.
Meningiomas grow in the meninges that surround the entire central nervous system, so they can appear in almost any location. The symptoms caused by these lesions vary greatly depending on the area where they grow. The classic treatment of choice is surgery. But in some areas, such as at the base of the skull, complications associated to surgery can be numerous and serious and the lesion is not usually completely removed. Radiosurgery offers similar or greater control than surgery with far fewer side effects, although its indication will depend on the type and degree of meningioma.
More than 1400 cases of single meningiomas have been treated at our Unit. For meningiomas at the base of the skull and, mainly, those implanted into the cavernous sinus, GK radiosurgery has been the main treatment of choice. Overall, 50% of cases had been operated on previously. No tumour progression has been observed in 98% of cases, with a significant reduction in volume in 55% of patients. In 4% of cases, we observed an increase in some already present neurological deficits and cerebral oedema (local inflammation around the treated area) controlled with temporary corticosteroid treatment.
There are patients with multiple meningiomas: "meningiomatosis". In these patients, different treatments (surgery or radiosurgery) must be provided throughout the progression of their disease. Since more lesions usually appear over the years in these cases, it is particularly important to not irradiate or injure healthy brain tissue, so GK radiosurgery is the best therapeutic option in many cases. We have applied more than 250 treatments to patients with multiple meningiomas. Most of these cases had been operated on previously. Results are similar to irradiation of single meningiomas.
1.2. SCHWANNOMAS (sometimes called "neurinomas")
Schwannomas are benign tumours that grow within the sheath that covers nerves.
1.2.1. VESTIBULAR SCHWANNOMA
These lesions are tumours in the vestibular nerve (the 8th cranial pair or vestibulocochlear nerve). When they grow, they prevent the nerve from functioning properly, causing hearing loss, the feeling of an annoying noise (tinnitus) or vertigo. But in this area, there are other structures that can be damaged by the growth of this tumour and that are critical when surgery is performed: the cerebellar peduncle, brainstem and, above all, the facial nerve.
Most schwannomas treated at our centre correspond to this type. To date, more than 1200 patients with these lesions have been treated. Volumes are very varied, including very small intracanalicular schwannomas (which account for 2% of treated patients). We have managed to control, stabilize or reduce growth in 96% of patients. Subsequent surgery was necessary in 0.02% of irradiated cases: in most cases, not because of an increase in size, but to place a ventricular bypass. In 18% of patients with preserved hearing, we have observed a decrease of up to 30% in the threshold of hearing frequency perception after 18 to 24 months of treatment. They do not usually experience any further decrease. Compromise of the facial nerve is less than 0.5% and the appearance of temporary vertigo or face sensitivity disorders is around 3%, depending on tumour volume and boundaries.
1.2.2. OTHER SCHWANNOMAS
There are schwannomas located in other cranial pairs whose frequency is lower but whose treatment and lesion control expectations are similar to those of the acoustic nerve. In all of these cases, treatment aims to slow the disturbance of the compromised nerve and prevent the appearance of new symptoms due to the compromise of the rest of the CNS. In our case, out of the more than 110 schwannomas treated, the majority were schwannomas of the trigeminal nerve (5th cranial nerve), followed by schwannomas of the lower cranial pairs, the facial nerve and others.
This is a disease with a genetic component in which multiple tumours grow. In the case of type II Neurofibromatosis, these tumours are mostly schwannomas, especially unilateral or bilateral vestibular tumours, and meningiomas. After assessing each patient individually, and if required, treatment can be applied using Radiosurgery, with the aim of slowing lesion growth and delaying the progression of the disease. The results of meningioma treatment are similar to meningiomas in the general population, although the possibility of the appearance of new lesions is not prevented. In the case of schwannomas, since their nature is different to that of regular schwannomas, local control is somewhat less. Out of nearly 100 treatments to date at our Unit, with several patients treated more than once for different tumours, we have observed the overall control of lesions in 72% of cases.
1.3. PITUITARY ADENOMAS
Adenoma is a type of benign tumour. When it grows in the pituitary gland, it can cause damage to nearby areas, especially the visual pathway, and cause gland function disorders in the secretion of certain hormones, either causing hormone deficiency or resulting in a hypersecretion of one of the hormones. Pituitary adenoma treatment has two purposes: to hinder adenoma growth to prevent damage to peripheral structures and, in the cases of adenomas that secrete excess hormones, to decrease or stop this secretion and control the clinical problems derived from it (Cushing's syndrome due to ACTH hypersecretion, acromegaly due to excess GH or growth hormone, hyperprolactinaemia, etc.).
Radiosurgery must be planned and executed with particular care in these cases given the proximity of the visual pathways. High resolution images are used to assess these healthy structures that must be avoided and functional studies are used to precisely locate the producing areas in the case of adenomas with excessive hormone secretion (safety and precision).
After treating 425 patients (approximately 50% of them with non-secretory adenomas), we have not observed damage to visual pathways after radiosurgery in any patients. The progression of tumour volume is controlled in 95% of cases, and in 70% of cases the tumour volume has been reduced and even prior oculomotor symptoms have improved. In the case of hormone secretory adenomas, growth control has been achieved (similar to in non-secretory adenomas) in addition to the significant reduction of hormonal figures in 50% of cases. This percentage of improvement in hormone overproduction is higher in the cases of ACTH secretion (Cushing's syndrome), where improvement ranges between 80-60% of cases.l adenoma es un tipo de tumor benigno. Cuando crece en la glándula hipófisis, puede dar lugar a daño en las zonas cercanas, sobre todo la vía óptica, y producir alteraciones en la función de la glándula que es la secreción de determinadas hormonas, bien provocando un déficit de las mimas o bien dando lugar a una hipersecreción de alguna de las hormonas. El tratamiento de los adenomas de hipófisis persigue dos finalidades: impedir su crecimiento para evitar ese daño a estructuras periféricas y, en los casos de adenomas que segregan hormonas en exceso, para disminuir o frenar esta secreción y controlar los problemas clínicos derivados de ella (síndrome de Cushing por hipersecreción de ACTH, acromegalia por exceso de GH u hormona del crecimiento, hiperprolactinemia,…).
La planificación y ejecución de la radiocirugía en estos casos conlleva un especial cuidado dada la proximidad de las vías ópticas. Se utilizan imágenes de gran resolución para valorar estas estructuras sanas que hay que evitar y estudios funcionales para localizar con precisión las zonas productoras en el caso de los adenomas con secreción hormonal excesiva (seguridad y precisión).
Después de tratar 425 pacientes (aproximadamente el 50% de ellos son adenomas no secretores), no hemos observado daño a las vías ópticas tras la radiocirugía en ningún paciente. El control de la progresión con respecto al volumen tumoral es de un 95% de los casos, con un 70 % de casos en los que se ha reducido el volumen del tumor e incluso mejoría de la clínica oculomotora previa. En el caso de los adenomas secretores de hormonas) se ha conseguido además del control de crecimiento (similar al de los adenomas no secretores) la reducción significativa de las cifras hormonales en el 50% de los casos, siendo este porcentaje de mejora en la sobreproducción hormonal mayor en los casos de secreción de ACTH (síndrome de Cushing), donde oscila la mejoría entre el 80–60 % de casos.
1.4. GLOMUS JUGULARE TUMOURS (PARAGANGLIOMAS)
Glomus are tumours that originate in the middle ear (glomus tympanicum) or on the jugular vein (glomus jugulare). Surgery of the glomus tympanicum is relatively easy. In the case of glomus jugulare, as it affects the base of the skull, including nerves such as the facial nerve, auditory nerve, lower pairs (which regulate the movement of the tongue, pharynx, vocal cords, etc.), surgery can be complicated, leading to serious complications and can be incomplete in many cases.
So far, our Unit has treated more than 90 cases, all of which have controlled the volume of the lesion, with a volume reduction of between 10-60% in 66% of cases. Only two cases have resulted in clinical deterioration, consisting of greater hearing loss than the patient had at the time of treatment. The rest of the patients remain stable and 30% of them have improved their previous clinical conditions. Ours is one of the longest published series of paragangliomas.
These are histologically benign, but locally aggressive tumours. Due to their location and relationships, especially with visual pathways, their manipulation is complicated and Radiosurgery acquires a dominant role in their treatment because of the protection it offers to risk organs thanks to its high precision and accuracy. They frequently present an associated cystic component that causes part of the patient's symptomatology. The cyst can be drained before Radiosurgery, even on the same day, and this reduces the volume that needs to be treated.
To date, we have treated more than 90 craniopharyngiomas at our Unit, the majority of which had been previously operated on. In two cases, due to the size of the cyst, it was drained using stereotaxy and then the solid part was irradiated. This is a fast and comfortable procedure and both treatments, drainage and irradiation, can be carried out on the same day or on consecutive days. Growth is controlled in 90% of cases. In some cases, the cyst has required subsequent drainage due to its increase in size at some point during the follow-up. In 54% of cases, there has been a significant reduction (between 10-80%) in the size of the lesion. In addition, an improvement of the visual symptoms has been obtained in half of the patients with visual alterations prior to treatment and there have been no side effects associated to Radiosurgery..
1.6. OTHER BENIGN TUMOURS
Around one hundred cases of other benign tumours have been treated, such as plexus papilloma, neurotomas, ganglioneuromas, angiofibromas, haemangiomas, etc. Their control ranges from 80-90% depending on size, location and prior history of relapses from other treatments. Side effects range from 0-5%.
1.1. ARTERIOVENOUS MALFORMATIONS (AVM) and DURAL ARTERIOVENOUS FISTULAE
These are abnormal vessel formations that can lead not only to bleeding, but also to other symptoms due to lack of vascularization in other brain areas or seizures due to irritation of the peripheral parenchyma. The risk of bleeding from AVMs increases every year of the patient's life. Each case must be assessed to decide the most appropriate treatment: embolization (closure of abnormal vessels using a material inserted into them), different surgeries and radiosurgery. For this last procedure, results take some time to emerge, since closure occurs in the following years (from one to four years), but this is the treatment that has registered the least side effects.
The treatment of AVMs and fistulae with Radiosurgery requires not only Magnetic resonance imaging and Magnetic resonance angiography, but also an arteriography, all under stereotactic conditions, in order to correctly assess malformation areas, flow, areas of prior angiogenesis or embolizations and the corresponding brain parenchyma. Currently, out of the more than 1350 cases that we have treated, closure is observed 3-4 years after radiosurgery, in 75% of AVMs, with stabilized or improved symptoms in 89% of patients and deterioration of previous symptoms in less than 4% of cases.
The more than 100 cases of dural arteriovenous fistulae we have treated to date have a closing rate of 90% for those in the cavernous sinus and 50% in other locations.
1.2. CAVERNOUS HAEMANGIOMAS
Cavernous haemangiomas are "mulberry"-shaped formations with some blood vessel cells but without a complete structure. They can also cause symptoms, not only because of their growth, but also because of frequent bleeding. Their progress is very variable. If they are located in accessible locations, surgery can be performed. But those located in critical areas where the risk of surgery is not acceptable pose a particular problem.
In the case of cavernous haemangiomas, with more than 130 cases treated to date, 60% of them decrease in size and the risk of bleeding in the total group decreases to 0.2% three years after treatment. No side effects have been recorded related to radiosurgery.
The use of Radiosurgery treatments for functional disorders is rapidly expanding. The aim is to create change in brain areas that function abnormally and give rise to different pathologies. Different studies are being carried out by several groups of GK users. The following functional treatments are performed at our centre (after thorough assessment of each particular case, sometimes by several specialists):
Neuralgia is pain that affects an area of the body whose sensitivity is collected by a certain nerve.
1.1.1. TRIGEMINAL NEURALGIA
This more or less frequent piercing pain affects half of the face (forehead, cheek and/or jaw), which is the area where the trigeminal nerve perceives sensations.
To date, a total of 534 cases have been treated with this procedure, of which more than 400 are cases corresponding to Typical Trigeminal Neuralgia (a special type of neuralgia with specific characteristics for its diagnosis and which is more suited to irradiation). This type of neuralgia is treated with radiosurgery, radiating this nerve between its insertion into the brainstem and the gasserian ganglion. It is a comfortable and fast treatment with good results. But some time is required to achieve results (between 3-9 months). Nevertheless, 16% of patients show an immediate response, and do not have any pain again from the first day of treatment. In total, pain fully disappears in more than 80% of patients and 40% of them do require medication to remain asymptomatic. Toxicity includes the appearance of some degree of hypoesthesia (a decrease in sensitivity on the side of the face affected) in 30% of patients.
There is a facial pain chart (Atypical Facial Pain) that presents different characteristics to those of typical neuralgia and which are more difficult to control, with a worse response to medical and surgical treatments. We have treated more than 75 cases, which have been carefully selected as not all of these patients are good candidates for this treatment, and their response has been positive, although somewhat less than for typical neuralgia: one third of patients remain pain-free after the procedure. Side effects are similar.
We have also treated a group of patients with neuralgia due to the presence of Multiple Sclerosis, with good results: 43% of cases with pain control and sensitivity disorders similar to other groups.
1.1.2. GLOSSOPHARYNGEAL NEURALGIA
Neuralgia of this nerve causes acute and stabbing pain in the back of the throat, tongue, tonsils and external auditory canal.
To date, we have treated 21 cases at our centre, with a positive response with pain completely disappearing in 85% of cases. Some patients have even been able to stop taking all of their pain medication. No side effects have been reported in any cases.
1.2. HEMIFACIAL SPASM
The hemifacial spasm is a tic, an abnormal movement of the face and eyelid muscles. Several treatments have been performed on patients with hemifacial spasm, and the treatment has been applied to the facial nerve itself. In these cases, clinical condition has improved with the disappearance of spasms and no adverse effects on such an important nerve.
This is a disease where the imbalance in neuronal activity in an area of the brain leads to recurring seizures. Epilepsy ends up causing cognitive, neurobiological and psychological problems affecting the patient's social life. In these cases, the Unit works together with the Epilepsy Unit and the Hospital's Neurology Department, which studies and assesses all patients by deciding on the indication together. Monitoring is also performed together.
1.3.1. Epilepsy secondary to temporary mesial sclerosis
In the 36 cases with seizures secondary to temporary mesial sclerosis treated to date, all but one have improved significantly with a reduction in the number and intensity of seizures. The decrease in the number and frequency of seizures is observed in 94% of patients and 60% are seizure-free, with the improvement being noticeable at approximately 6 months. In a couple of cases, significant brain oedema is observed, approximately 9 months after radiosurgery, which has required treatment with corticosteroids and has subsequently been resolved.
1.3.2. Hypothalamic hamartomas
This type of congenital hypothalamic lesion can be asymptomatic or lead to early puberty, epileptic seizures (especially laugh-induced seizures, sometimes also associated to crying-induced seizures). The seriousness of these seizures can result in significant psychomotor retardation with behavioural disorders, especially aggressiveness. These diagnoses are often found in children and the precocity of their treatment greatly improves their results, especially at a cognitive and behavioural level (aggression is reduced by 90% in the cases treated and seizures improve by 80%). To date, after 44 treatments applied at our Unit, no permanent side effects have been registered (including 25% of patients who, although their condition has improved, have required another treatment to increase seizure control).
1.3.3. Heterotopias and dysplasias
In brain development, changes can occur that affect the movement of neurons towards the brain cortex. This is how areas of conglomerated neurons appear in abnormal areas that can cause epilepsy. Once these areas have been located in the MRI and the neurological study confirms that these are the areas that give rise to epilepsy, they can be treated with Gamma Knife Radiosurgery. We have treated six patients to date and there has been an improvement in more than 50% of seizures without side effects from treatment. As with other functional treatments, it takes time for seizures to improve or disappear (from 11 to even 60 months).
Tremor, both in patients with Essential Tremor and in those who present it as part of Parkinson's Disease. Usually, if medication failed or was not tolerated, surgical techniques that were increasingly less invasive were used (such as radiofrequency or deep brain stimulation), acting on a brain nucleus where the lesion caused a decrease or disappearance of pain. Currently, this lesion is also performed with radiosurgery, with excellent results (improvement of approximately 80% of cases) and few side effects. At our centre, 23 cases have been treated with a similar response and without any registered adverse reactions.
1.5. MENTAL DISORDERS
1.5.1. Obsessive-compulsive disorders (OCD)
To ensure that the location is appropriate, a brain tractography has also been performed (a special magnetic resonance imaging test which reveals the pathways through which certain information passes through in the brain). We have already performed 20 treatments, most of which are intended to perform a capsulotomy and in some cases through cingulotomy or the combination of several targets. 80% of patients have improved significantly, and two of them show full healing criteria several years after treatment. No relevant side effects have been reported in any cases.
Depending on very specific characteristics and comprehensive consultations, candidate patients are selected for Radiosurgery treatment. Some treatments of this type include selected cases of: neuropathic pain, anorexia, etc.
A total of ten patients with other disorders have been treated. Anxiety control in these cases has been significant, with an improvement in the perception of pain and behavioural patterns, resulting in an improvement in the quality of life of patients and their gradual reintegration into normal social life. No significant side effects have been registered regarding radiosurgery.
Any type of cancer may result in the appearance of brain lesions at some point during its progression: metastasis. They can even be the first manifestation of these cancers. Radiosurgery represents essential progress in the treatment of brain metastasis. Until radiosurgery emerged, it could only be operated on by applying Fractioned External Radiation Therapy. The survival and quality of life of these patients has now increased thanks to the possibility of applying higher doses of radiation in a focused manner with Radiosurgery. We have treated more than 850 patients with metastasis with excellent results. Approximately half of them had more than one metastasis, which were treated simultaneously. The number of lesions is not a limiting factor for treatment. Treatment may be applied to a single lesion or several metastases, size and location permitting. 20% of cases have been treated on more than one occasion for different lesions during follow-up. This is one of the great advantages of treatment with Gamma Knife: peripheral radiation is so low that patients can be treated several times over the years if new lesions appear. In 40% of them, holocraneal irradiation had been carried out previously with fractionated radiotherapy. This did not pose a problem for radiosurgery since both treatments can complement each other and, as mentioned beforehand, peripheral radiation is very low when using the Gamma Knife system. We have managed to control (stabilize or reduce) the lesion in 95% of patients, with a decrease in size in 70% of them. The quality of life and symptomatology of patients have been maintained or improved in 90% of cases. The side effect observed was mild brain oedema on the periphery of metastases, that was controlled with temporary corticosteroid treatment.
1.2. LOW-GRADE GLIAL TUMOURS
Although their classification includes them in malignant tumours, their progression is slower than the rest, with years of survival and even cures. In total, we have treated about 150 patients with different types of low-grade glial tumours: pilocytic astrocytomas, grade II astrocytomas, polymorphic xanthoastrocytomas, childhood desmoplastic astrocytoma, grade II oligodendrogliomas, etc.
The lesion is controlled in a variable percentage between 60-90%, and the pilocytic astrocytomas were the most favourable group. The only complications observed were: perilesional oedema in 5% of cases treated, within 6 months of treatment, and cystic degeneration with a temporary increase in volume in 5% of cases.
1.3. HIGH-GRADE GLIAL TUMOURS
High-grade glial tumours, such as anaplastic astrocytoma and glioblastoma multiforme, are a very heterogeneous group of glial tumours with different prognoses depending on their degree and other factors. Radiosurgery treatment is applied after surgery has been ruled out or, in certain cases, after treatment with Fractioned External Radiation Therapy and/or chemotherapy, when a recurrence occurs. MRI scanning is very important, including perfusion studies that allow us to know the specific areas where the tumour spreads and distinguish areas of post-surgical disease in patients with previous operations. We have treated more than 70 cases of this type of tumour. The aim is to prolong survival, reaching an average of 24-35 months in treated cases, except for in the case of glioblastoma multiforme, where the average survival rate after radiosurgery is 17 months. But this aim must come with a low rate of side effects, since prolonged survival must be combined with proper quality of life.
1.4. OTHER MALIGNANT TUMOURS
As in the previous group, Radiosurgery can be used in conjunction with other treatments or in progressions, recurrences or sowing at a distance.
At our unit we have treated around 90 cases of recurrences of nasopharynx cancer, adenoid cystic carcinoma, chondrosarcoma, germinoma, medulloblastoma, pinealoma, plasmacytoma, DNET, sarcoma, malignant or atypical meningiomas, etc.
No side effects have been registered and treatment is comfortable and fast, so although prolonged survival is very variable with these tumours, it is a very positive result. In addition, symptoms are improved or stabilized in more than 50% of cases. In some cases, very carefully selected patients are able to become long-term survivors. Therefore, it is important to use a technique such as Gamma Knife that irradiates very little healthy brain tissue, in order to avoid potential future problems. This is especially important in this group of patients where many are children or young adults, their nervous systems are still developing, and they have probably already received prior conventional radiotherapy.
There is a particular type of malignant tumour, CHORDOMA, which is slow but very aggressive and that appears at the base of the skull, so that treatment with surgery involves a significant number of severe neurological complications and treatment with conventional radiotherapy is also limited due to the proximity of critical structures such as the brainstem. Therefore, radiosurgery is not only a rescue treatment for these tumours, but it is the first choice of treatment in some cases. More than 35 chordomas have been treated at our Unit, with only two cases showing progression. In the rest of the patients, lesions have either stabilized (72%) or decreased (22%). There has been no associated toxicity and patients also show stabilized (86%) or improved (14%) symptoms.
GAMMA RADIOSURGERY: PROCEDURE
The term "Radiosurgery" does not mean that this is a surgical procedure. This is a treatment without incisions that does not require general anaesthesia (except for special cases such as children). No special preparation is required during the previous days, unless the patient wears metal braces, in which case it is advisable to remove them so that the magnetic resonance imaging studies are of appropriate quality. Fixed implants and the fastening bar that is placed behind teeth after wearing braces are not an issue.
Two types of procedure can be performed, always under medical decision and depending on the characteristics of each case:
TREATMENT WITH STEREOTACTIC FRAME ON A SINGLE DAY
On the day of treatment, a stereotactic frame is placed on the patient. This is a system with measurements that provide the data required for the treatment to meet precision and accuracy standards. The frame consists of a hollow square base with four posts that are fixed to the forehead and back of the head. For this purpose, local anaesthesia (similar to that used by dentists) is applied to the area where the posts are attached with a pointed part. The wound left afterwards is millimetric. With the frame in place, the patient can walk, talk... they only feel slight pressure (as if wearing a tight headband) that subsides after a few minutes. The tests necessary for the treatment are performed with this system: Magnetic resonance imaging, CAT scan and/or Arteriography. This allows us to know the exact location of the treatment target. The team of physicists and doctors works with the tests and plans the treatment. Sometimes the patient returns to their room while everything is prepared, and they are given a sedative if they show discomfort. But the planning does not take very long, between thirty minutes and an hour. Then the patient is transferred back to the treatment room where they will be lying on a trolley bed. The patient's head is fitted into the system thanks to the frame, so there is no need to worry about staying still; they can cough, cover or uncover themselves. There are no annoying noises, nor does the radiation produce any noticeable sensation, so most patients usually fall asleep. In addition, some medicine is usually given to help the patient relax. The duration depends on the pathology and other factors, but it can vary from less than one hour to several. At all times, we monitor the patient through cameras and a sound system that allows us to speak and listen to the patient. For this reason, if the patient requests it and it is necessary, the treatment can be paused for them to have a rest or go to the bathroom, for example.
Afterwards, the frame is removed without the need for anaesthesia. There is no need for stitches either. The patient stays in their room for a couple of hours with a bandage around their head to prevent the frame support area from swelling because, since it was tight, it can cause the appearance of bumps. This swelling appears in half of the patients, usually 24-48 hours after the procedure. It is usually painless and does not require treatment, subsiding after a variable amount of time. The small, isolated support wounds heal in a couple of days, with any antiseptic, like any other type of wound. The patient is discharged at midday and can return to their usual routine the following day.
TREATMENT WITH THERMOPLASTIC MASK ON A SINGLE DAY OR ON SEVERAL DAYS
On the day of the consultation, a thermoplastic mask is made for the patient. It is a large sheet of plastic-like material that is heated and placed over the patient's head. When dry, the mask is shaped like the patient's face. It does not burn and has multiple holes, as well as an opening for the nose so that the patient can breathe and speak normally, as well as open and close their eyes. The tests necessary for the treatment are performed on that same day: Magnetic resonance imaging, CAT scan and/or Arteriography. The team of physicists and doctors works with the tests and plans the treatment. When everything is ready, the patient comes to receive the treatment, usually several days after undergoing the tests.
The patient lies on a trolley bed and the mask is placed on their head. They must remain still during the treatment, which can be paused if the patient moves (to return to proper treatment position) or if they request a break to rest or to go to the bathroom, for example.
One, three or five sessions may be required, which are performed during the same week. The patient does not have to fast or come prepared in any way. The procedure is painless. Radiation does not cause any perceptible sensation. The duration of each session is variable, around one hour or less. At the end of each session, the patient can continue with their usual routine on that day.