Stereotactic radio-surgery in the treatment of brain metastases from radio-resistant tumors

Abstract

1552 Background: Melanoma and renal cell carcinoma are generally considered resistant to conventional fractionated radiation. However, there is some evidence that suggests that they may respond better to higher dose per fraction. We retrospectively studied the clinical outcome of melanoma and renal cell carcinoma (RCC) patients who were treated with single fraction stereotactic radiosurgery (SRS) for metastatic lesions in the brain. Methods: Forty-nine melanoma patients with 92 lesions and 20 RCC patients with 27 lesions received SRS as the primary method of treatment for their brain metastases. Treatment spanned from January of 2001 through December of 2003, with a minimum follow up of 1 year. SRS was delivered using a 6MV linear accelerator using mini-micro multileaf collimation. The median dose prescribed was 2100cGy (range 1400–2400 cGy) based on tumor size. Patients were monitored with serial MRI’s that were done every three months to measure local control, development of new metastases and radiation necrosis. Results: The local control of the treated lesions was worse in melanoma when compared to RCC (6 months 72% Vs 83%, 1-year 50% vs. 71%; p=0.02). Development of new brain metastases was the dominant method of intracranial failure in both groups (Median time 3.9 vs. 4.0 months; p=NS). Survival was dismal in both the groups when measured from the date of SRS (Median 6.0 Vs 6.9 months p=NS). Radiation dose was the only factor that correlated with improved local control (p>0.002) for both sites. Karnofsky status of > 90 and Age < 70 turned out to be better prognostic indicators for increased survival at the time of SRS. Addition of whole brain radiation therapy had no impact on either local control or survival in either tumor. The incidence of radiation necrosis was higher in melanoma when compared to RCC (9.8% Vs 2.4%). Conclusions: Response to single fraction SRS is different between RCC and melanoma. The improved local control with SRS did not translate into improved survival in RCC due to failure at other sites in the brain as well as progression of systemic disease. Failure in the brain as well as radiation necrosis still remains a concern with melanoma. No significant financial relationships to disclose.