Pathologic complete response in renal cell carcinoma brain metastases treated with stereotactic radiosurgery

Renal cell carcinoma (RCC) is often regarded as a radiation-resistant tumor. However, radiation therapy (RT) in the form of stereotactic radiosurgery (SRS) or whole-brain irradiation has been used to treat brain metastases from RCC. To date, there have been no clinical pathologic correlative findings before and after RT. Herein, we present a case of a patient with brain metastases from RCC treated with SRS. The diagnosis of clear-cell RCC was made in 2001 after right radical nephrectomy. He was also found to have lung metastases at diagnosis. He presented with neurologic symptoms in 2004, and magnetic resonance imaging showed 3 brain lesions with a significant amount of edema consistent with brain metastases. The largest lesion caused a midline shift and was surgically resected. Pathology revealed metastatic RCC. The other 2 smaller brain lesions were treated at 20 Gy respectively with shaped-beam SRS using the BrainLab Novalis system. No whole-brain irradiation was delivered. However, the patient had difficulty weaning off his steroids, and a magnetic resonance imaging performed 6 months after SRS was read as "progression of the lesions." He then underwent resection of both the irradiated brain lesions. Pathologic examination revealed necrotic tissues without any viable tumor identified. The patient has since been doing very well, now 18 months after SRS and 5 years from the initial diagnosis. This is the first reported case that demonstrates that precise high-dose radiation in the form of SRS can cause significant tumor cell death (pathologic complete response) in radiation-resistant brain metastases from RCC. This finding also provides a rationale to deliver stereotactic body RT for primary and metastatic RCC extracranially. A prospective clinical trial using stereotactic body RT for primary and metastatic RCC is under way.