Results of a Phase I Trial of Dose Escalation for Preoperative Stereotactic Radiosurgery for Patients with Large Brain Metastases

PURPOSE/OBJECTIVE(S)

Single session stereotactic radiosurgery (SRS) alone for brain metastases larger than 2 cm in diameter results in unsatisfactory local control. Surgical resection alone also produces unreliable local control and perioperative radiation is required. We conducted a prospective phase I trial (NCT01891318) for brain metastases greater than 2 cm to determine the safety of preoperative SRS at escalating doses followed by surgical resection.

MATERIALS/METHODS

Radiosurgery dose started at RTOG 9005 dose levels for the 3 cohorts based on maximum tumor diameter of the index lesion: 18 Gy for >2-3 cm, 15 Gy for >3-4 cm, and 12 Gy >4-6 cm. Concurrent SRS alone to other smaller lesions was allowed using standard RTOG dose. Dose limiting toxicity (DLT) was defined as grade 3 or greater acute toxicity within 3 to 4 months after SRS. Patients underwent surgical resection within 2 weeks and were followed with imaging and neurological evaluations every 3 months.

RESULTS

A total of 35 patients were enrolled into the trial (see Table 1 below). The median age was 63, and median interval between SRS and surgery was 2 days. The most common histology was non-small cell lung cancer (57.1%), followed by breast cancer (14.3%). For tumor size >2-3 cm, patients were enrolled up to the 2nd dose level (21 Gy); for >3-4 cm and >4-6 cm cohorts the 3rd dose level (21 Gy and 18 Gy, respectively) was reached. There was a total of 3 DLTs: 2 in the >3-4 cm cohort and 1 in the >4-6 cm cohort (Table 1). The maximum tolerable dose (MTD) was 18 Gy (2nd dose level) for >3-4 cm, and 18 Gy (3rd dose level) for >4-6 cm. With a median follow-up of 64 months, the 6- and 12-month local control rates were 88.8% and 79.1%, respectively. The 6- and 12-month distant brain control was 63.1% and 55.3%, respectively. Overall survival at 6 and 12 months was 82.9% and 59.0%. The rate of leptomeningeal disease (LMD) at 2 years was 0%.

CONCLUSION

Preoperative SRS with dose escalation followed by surgical resection for brain metastases greater than 2 cm in size results in local control comparable to postoperative SRS or whole-brain radiation therapy and demonstrates acceptable acute toxicity. The Phase II portion of the trial will be conducted at the maximum tolerated SRS doses.

Evidence-based adjuvant therapy for gliomas: current concepts and newer developments

The incidence of gliomas is increasing worldwide, including India. Of the 18,820 new cases of primary central nervous system (CNS) tumors diagnosed annually in the United States, gliomas account for over 60% with 30-40% of them being glioblastoma multiforme (GBM), 10% being anaplastic astrocytoma (AA), and 10% being low grade gliomas (LGGs). This is in contrast to one study from West Bengal, India, in which only 7.9% of the brain tumors were GBMs, while 46.8% were astrocytomas. Of all adult primary CNS tumors, GBM is the most common and the most malignant with about 7,000 to 8,000 new cases annually in the United States. Given poor outcomes, a number of treatment approaches have been investigated. Common to these approaches is the use of adjuvant radiation therapy, even as surgery alone, with or without chemotherapy, may be the mainstay for some lower grade and low-risk gliomas. Today, treatment typically involves external beam radiation, with concurrent and adjuvant chemotherapy for more aggressive histologies. Although gliomas are relatively uncommon, active research is ongoing. Results of landmark trials along with some of the recently published trials are presented. These trials and management strategies as well as evolving concepts are found by reviewing over 200 articles in the National Library Medical (NLM) database, PubMed, more than 60 of which are refrenced. Specifically, the database is searched using the following keywords, with various combinations: glioma, low-grade, anaplastic, astrocytoma, oligodendroglioma, oligoastrocytoma, glioblastoma multiforme, chemotherapy, radiation, new concepts, phase III, MGMT, CDX-110 (Celldex), temozolomide, 1p/19q deletion, and bevacizumab.