Radiothérapie en conditions stéréotaxiques des métastases cérébrales

Organs at risk radiation dose constraints

Dose constraints are essential for performing dosimetry, especially for intensity modulation and for radiotherapy under stereotaxic conditions. We present the update of the recommendations of the French society of oncological radiotherapy for the use of these doses in classical current practice but also for reirradiation.

[Stereotactic radiotherapy for pelvic tumors]

Extracranial stereotactic radiotherapy is booming. The development and spread of dedicated accelerators coupled with efficient methods of repositioning can now allow treatments of mobile lesions with moderate size, with high doses per fraction. Intuitively, except for the prostate, pelvic tumours, often requiring irradiation of regional lymph node drainage, lend little to this type of treatment. However, in some difficult circumstances, such as boost or re-radiation, stereotactic irradiation condition is promising and clinical experiences have already been reported.

[Differential diagnosis of local tumor recurrence or radionecrosis after stereotactic radiosurgery for treatment of brain metastasis]

Magnetic resonance imaging (MRI) is a method of choice for follow-up of irradiated brain metastasis. It is difficult to differentiate local tumour recurrences from radiation induced-changes in case of suspicious contrast enhancement. New advanced MRI techniques (perfusion and spectrometry) and amino acid positron-emission tomography (PET) allow to be more accurate and could avoid a stereotactic biopsy for histological assessment, the only reliable but invasive method. We report the case of a patient who underwent surgery for a single, left frontal brain metastasis of a breast carcinoma, followed by adjuvant stereotactic radiotherapy in the operative bed. Seven months after, she presented a local change in the irradiated area on the perfusion-weighted MRI, for which the differentiation between a local tumour recurrence and radionecrosis was not possible. PET with 2-deoxy-((18)F)-fluoro-D-glucose (FDG) revealed a hypermetabolic lesion. After surgical resection, the histological assessment has mainly recovered radionecrosis with few carcinoma cells. The multimodal MRI has greatly contributed to refine the differential diagnosis between tumour recurrence and radionecrosis, which remains difficult. The FDG PET is helpful, in favour of the diagnosis of local tumour recurrence when a hypermetabolic lesion is found. Others tracers (such as carbon 11 or a fluoride isotope) deserve interest but are not available in all centres. Stereotactic biopsy should be discussed if any doubt remains.

Stereotactic radiotherapy for large solitary brain metastases

PURPOSE

To assess effectiveness and toxicity levels of stereotactic radiation therapy without whole brain radiation therapy in patients with solitary brain metastases larger than 3cm.

PATIENTS AND METHODS

Between June 2007 and March 2009, 12 patients received fractionated stereotactic radiation therapy and 24 patients underwent stereotactic radiosurgery. For the fractionated stereotactic radiation therapy group, 3×7.7Gy were delivered to the planning target volume (PTV); median volume and diameter were 29.4 cm(3) and 4.4cm, respectively. For the stereotactic radiosurgery group, 14Gy were delivered to the PTV; median volume and diameter were 15.6 cm(3) and 3.7cm, respectively.

RESULTS

Median follow-up was 218 days. For the fractionated stereotactic radiation therapy group, local control rates were 100% at 360 days and 64% at 720 days; for the stereotactic radiosurgery group, rates were 58% at 360 days and 48% at 720 days (P=0.06). Median survival time was 504 days for the fractionated stereotactic radiation therapy group and 164 days for the stereotactic radiosurgery group (P=0.049). Two cases of grade 2 toxicity were observed in the fractionated stereotactic radiation therapy group, and 6 cases of grade 1-2 toxicity, in the stereotactic radiosurgery group.

CONCLUSIONS

This study provides data to support that fractionated stereotactic radiation therapy without whole brain radiation therapy with a margin dose of 3 fractions of 7.7Gy for treatment of solitary large brain metastases is efficient and well-tolerated. Because of the significant improvement in overall survival, this schedule should be assessed in a randomized trial.

[Clinical aspects of brain metastases from nasopharyngeal carcinoma]

Metastasis to the central nervous system, either through a hematogenous route or through the cerebrospinal fluid, is extremely rare in nasopharynx cancer. We aim to expose clinical aspects, therapeutic features and prognosis of nasopharyngeal carcinoma with brain metastases. We retrospectively reviewed the medical history of about 420 patients with nasopharyngeal carcinoma treated during 17 years at the university hospital of Sfax (Tunisia). Among them, three patients had brain metastasis. We excluded patients with direct extension to the brain. Tumours of the nasopharynx were locally advanced. The first patient had brain metastases at the initial diagnosis. The two other patients had brain metastases at 10 and 16 months during the follow-up. Ocular signs were the symptoms. Lesions were unique in two patients. Synchronous bone metastases were recorded in the three cases. All patients had whole brain radiation therapy and palliative chemotherapy. All patients had a progression of the disease and died. Brain metastases in nasopharynx cancer represent a rare event. Prognosis is poor, depending on age, surgical excision and synchronous metastases. Survival does not exceed 6 months.

[Brain metastases from breast cancer]

Breast cancer is the second leading cause of brain metastases and account for 15 % of metastatic breast cancer patients. Several patient- and tumor-related characteristics have been identified as risk factors for developing brain metastases. Treatment is based on local and/or systemic therapies, tailored to breast cancer brain metastases-specific prognostic factors. This article is an update on the current knowledge of the incidence, prognosis and prognostic factors, treatment and perspectives in brain metastases from breast cancer.

[Cognitive evaluation during brain radiotherapy in adults: a simple assessment is possible]

Brain irradiation can be used for the treatment of cancers in different protocols: focal radiotherapy, whole brain radiotherapy, with or without additive dose on the tumour. Different modalities (conformational, stereotactic radiosurgery) can be used for curative or prophylactic treatment. Brain radiotherapy leads to cognitive deterioration with subcortical profile. This cognitive deterioration can be associated to radiation-induced leukoencephalopathy on brain MRI. Taking into account radiation induced cognitive troubles is becoming more important with the prolonged survival allowed by treatment improvement. Concerning low-grade gliomas, radiation-induced cognitive troubles appear about 6 years after treatment and occur earlier when the fraction dose is important. Primitive cerebral lymphoma treatment can induce cognitive troubles in 25 to 30% surviving patients. These deficits are more frequent in elderly patients, leading to radiotherapy delay in those patients. Patients treated for brain metastasis often have cognitive impairment before radiotherapy (until 66%), this pretreatment impairment is related to global survival. The use of conformational radiation therapy, particularly with hippocampal sparing is conceptually interesting but has not proved its efficiency for cognitive preservation in clinical trials yet. Stereotactic radiation therapy could be an interesting compromise between metastatic tumoral volume reduction and cognitive preservation. Taking care of radiotherapy induced cognitive troubles is a challenge. Before considering its treatment and prevention, we need to elaborate a way of detecting them using a reliable and easy way. CSCT, a computerized test whose execution needs 90 seconds, could be used before treatment and during the clinical follow-up by the patient's oncologist or radiotherapist. If the patient's performance reduces, he can be oriented to a neurologist in order to perform fuller evaluation of its cognitive capacities and be treated if necessary.

[Radiotherapy of brain metastases according to the GPA score (Graded Prognostic Assessment)]

The management of patients with brain metastases remains a difficult and controversial subject. For years, the standard treatment has been whole-brain radiation therapy alone, but its validity is now under question because of improvements in surgery and the development of radiosurgery or novel targeted therapies and also because whole-brain radiation therapy is responsible for long term neurocognitive toxicity. Therefore it is important to assess diagnosis-specific prognostic factors and indexes when scheduling treatments. The GPA score (Graded Prognostic Assessment), established for various histologic tumor types, includes five prognostic factors: age, Karnofsky Performance Status, presence of extracranial metastases, number of brain metastases and also genetic subtype for breast cancer. We propose an adaptation of the management of brain metastases according to the GPA score.

[Brain metastasis of carcinoma of the cervix]

Les métastases cérébrales des cancers du col de l′utérus sont extrêmement rares. Elles sont généralement supra-tentorielles, survenant à un stade avancé de la maladie et dans un cadre de néoplasie polymétastatique. La tumeur primitive est le plus souvent un carcinome épidermoïde peu différencié. Leur pronostic reste sombre malgré toutes les options thérapeutiques. Vu la rareté de cet événement et le peu de cas publiés dans la littérature, nous rapportons l'observation clinique d'une jeune patiente de 44 ans, opérée pour un carcinome du col utérin et qui présente 14 mois plus tard des métastases cérébrales sus et sous tentorielles associées à des métastases ganglionnaires lombo-aortique, médiastinale et sus-claviculaire. Elle a bénéficié d'un traitement palliatif associant une chimiothérapie et une radiothérapie pan encéphalique. Devant l'altération rapide de l'état général, la patiente a été mise sous un traitement symptomatique et des soins de support.

[Stereotactic radiotherapy of intracranial benign tumors]

Stereotactic radiotherapy can be delivered in one fraction or in multiple fractions schedule. It is used in benign tumours such as meningiomas, mainly localized in the base of the skull, for acoustic schwannoma and pituitary tumours. Whatever the tumour, results with the Gamma Knife(®) are the most numerous, but those obtained by linear accelerators, adapted or dedicated, are comparable. The peripheral dose is preferred to the dose delivered to the isocentre. One fraction stereotactic irradiation should be proposed in small lesions and fractionated treatment for tumours larger. Whatever the tumour, the results are satisfactory with a control rate of 90%. However, this value reflects a disparity assessment, radiological stability for meningiomas, radiological stability and preservation of useful hearing in schwannoma and radiological stability and a decrease in hormonal secretions for pituitary adenomas. Overall complication rates are low. In total, the treatment of benign lesions with stereotactic irradiation gives satisfactory results with few complications.