A Phase I/II Study of Fractionated Stereotactic Radiosurgery to Treat Large Brain Metastases

Brain metastases are the most common intracranial tumors and occur in approximately 25% of patients with cancer. In the US, approximately 170,000 cancer patients a year are diagnosed with brain metastases.

The prognosis of patients with brain metastases is variable and depends on several factors, including performance status, age, control of the primary tumor, and extent of extracranial disease. Historically, patients with brain metastases who receive supportive care only have median survival of 1 to 2 months. However, a subgroup of patients with favorable prognosis who undergo treatment can enjoy an extended life expectancy with median survival of 10 to 16 months. Treatment options for brain metastases include medical management, surgery, and radiation therapy (radiotherapy). Both surgery and radiotherapy have an important role in management of brain metastases, and an optimized treatment plan may include both. It is well-established that surgery followed by conventional whole brain radiation (WBRT) decreases local recurrence and improves median survival compared to WBRT alone. Conventional WBRT is administered as radiotherapy to the whole cranium delivered in 10 to 20 daily treatments.

For this study, radiotherapy will be delivered using stereotactic radiosurgery (SRS) to treat individual metastases. SRS has the advantage of sparing normal brain tissue. In SRS, high energy radiation is precisely directed at the target lesion. Due to the steep fall-off of the radiation dose away from the target, the advantage of relative sparing of the normal brain may be realized. The present study is based on a rationale of treating brain metastases with surgical resection followed by adjuvant SRS to the resection cavity, while deferring conventional WBRT for salvage therapy.

WBRT is associated with a short-term decline in quality of life and long-term deficits in neurocognitive function ("late effects"). Late toxicity of WBRT, such as memory impairment and dementia, is usually irreversible and is likely due to demyelination, vascular damage, and necrosis. Following WBRT, the actuarial rate of neurocognitive toxicity at 2 years can be up to 49%. Recipients of WBRT may demonstrate a > 2 standard deviation decline in their performance at 6 months. Compared to SRS alone, WBRT was reported to be associated with a marked decline in learning and memory function at 4 months (49% vs 23%, in favor of SRS).

To minimize the potential late effects of WBRT, investigators have explored the use of SRS alone, deferring the use of WBRT for salvage treatment if needed. Both retrospective analyses and a prospective randomized trial reported no apparent survival benefit to combining WBRT with SRS compared to SRS alone