On review of our experience with treatment for brain metastases since 2009, we have treated over 100 patients with 6 or more metastases in a single radiosurgery session. In the past year and a half (2015-16) there have been approximately 50 patients treated with six or more metastases, indicating that there has been a shift in management of intracranial metastatic disease with increasing preference for radiosurgery despite the presences of greater metastatic burden. The phase I component will accrue 7-15 patients at each dose cohort until the MTD is determined. Once the MTD is reached, the phase II component will commence with a total of 50 patients total enrolled at the MTD, with a study time of 3 years. The primary endpoint of the phase I component is toxicity. The primary endpoint of the phase II component is the change in neurocognitive function, defined by a decline in the Hopkins Verbal Learning Test- Revised delayed recall. Data from the WBRT-alone arm of the PCI-P-120-9801 phase III trial evaluating WBRT plus motexafin gadolinium demonstrated a 30% mean relative decline in the HVLT-R delayed recall score from baseline to 4 months, with a standard deviation of 41% 9,10. More recently, in patients treated with SRS alone for 1-3 metastases versus SRS plus whole brain radiotherapy, the 4-month rates of HVLT-R delayed recall deterioration were 6% and 22% for the SRS alone arm and SRS + whole brain radiotherapy arm, respectively. Given the greater intracranial burden of disease, we estimate the mean relative decline in HVLT-R delayed recall to be intermediate between SRS alone for 1-3 metastases and whole brain radiotherapy. We predict that after SRS for multiple metastases the mean relative decline in delayed recall as 15%, an improvement over the historical control of whole brain radiotherapy alone which had a mean relative decline in HVLT-R delayed recall of 30%.
The phase I component of the study is to identify maximal tolerated dose (MTD). The phase II is to evaluate neurocognitive decline.