Stereotactic Radiosurgery For Metastatic Tumors Research Articles

Safety and utility of kyphoplasty prior to spine stereotactic radiosurgery for metastatic tumors: a clinical and dosimetric analysis.

OBJECTIVE The aim of this study was to evaluate the safety and efficacy of kyphoplasty treatment prior to spine stereotactic radiosurgery (SRS) in patients with spine metastases. METHODS A retrospective review of charts, radiology reports, and images was performed for all patients who received SRS (single fraction; either standalone or post-kyphoplasty) at a large tertiary cancer center between January 2012 and July 2015. Patient and tumor variables were documented, as well as treatment planning data and dosimetry. To measure the photon scatter due to polymethyl methacrylate, megavolt photon beam attenuation was determined experimentally as it passed through a kyphoplasty cement phantom. Corrected electron density values were recalculated and compared with uncorrected values. RESULTS Of 192 treatment levels in 164 unique patients who underwent single-fraction SRS, 17 (8.8%) were treated with kyphoplasty prior to radiation delivery to the index level. The median time from kyphoplasty to SRS was 22 days. Four of 192 treatments (2%) demonstrated local tumor recurrence or progression at the time of analysis. Of the 4 local failures, 1 patient had kyphoplasty prior to SRS. This recurrence occurred 18 months after SRS in the setting of widespread systemic disease and spinal tumor progression. Dosimetric review demonstrated a lower than average treatment dose for this case compared with the rest of the cohort. There were no significant differences in dosimetry analysis between the group of patients who underwent kyphoplasty prior to SRS and the remaining patients in the cohort. A preliminary analysis of polymethyl methacrylate showed that dosimetric errors due to uncorrected electron density values were insignificant. CONCLUSIONS In cases without epidural spinal cord compression, stabilization with cement augmentation prior to SRS is safe and does not alter the efficacy of the radiation or preclude physicians from adhering to SRS planning and contouring guidelines.

Stereotactic radiosurgery for metastatic tumors in the pituitary gland and the cavernous sinus

Metastases to the pituitary gland and cavernous sinus occasionally occur. Metastases of this nature are problematic because they are adjacent to eloquent structures such as cranial nerves, including the optic pathways and nerves for extraocular movement and facial sensation. Stereotactic radiosurgery has been reported to be safe and effective for metastases in various sites of brain parenchyma, providing the tumors are not large. Radiosurgery can be performed to treat a precisely defined target, and the risk of radiation side effects on the surrounding structures is reduced. The results of Gamma Knife surgery (GKS) for the treatment of metastases in the pituitary gland and the cavernous sinus are evaluated. Among 623 patients with brain metastases treated by GKS, 13 patients (2.1%) had pituitary and/or cavernous metastases. The primary malignancies included lung cancer (five cases), breast cancer (two cases), parotid cancer (two cases), renal cell carcinoma, thyroid cancer, nasal cancer, and gastrointestinal stromal tumor (one case each). The location of the tumors was the pituitary gland (Type 1) in four patients, the cavernous sinus (Type 2) in five patients, and both the cavernous sinus and the sellar region (Type 3) in four patients. The patients' symptoms included dysfunction of the pituitary gland (two patients), visual disturbance (four patients), oculomotor palsy (one patient), abducent palsy (five patients), and trigeminal dysfunction (five patients). A margin dose of 12 to 12.3 Gy was delivered to pituitary metastases. A margin dose of 14.4 to 20 Gy was delivered to cavernous lesions. The dose selection depended on the spatial relationship between tumors and the cranial nerves. Imaging and clinical follow-up data have been obtained in nine of 13 patients for 2 to 12 months (median 4 months) after GKS. Three pituitary and/or cavernous tumors are stable in size, and six tumors have disappeared or decreased in size; full or partial improvement of visual function, extraocular movement, and facial sensation have been achieved in these six patients. These preliminary results seem to indicate that GKS is a safe and effective treatment for pituitary and cavernous metastases, as it is effective for parenchymal metastases and promptly improved some patients' symptoms.