Carbon ion radiation therapy for primary renal cell carcinoma: initial clinical experience

Abstract

Purpose: Renal cell carcinoma (RCC) is known as a radioresistant tumor, and there are few reports on radiotherapy for primary RCC. We evaluated the efficacy of carbon ion radiotherapy (CIRT) for patients with RCC.

Methods and materials: Data for patients with RCC who received CIRT were analyzed. A median total dose of 72 GyE (gray equivalents) in 16 fractions was administered without any additional treatment. Clinical stage was determined based on TNM classification by the International Union Against Cancer (UICC). Local recurrence was defined as definite tumor regrowth after treatment.

Results: Data for 10 patients were included in the analyses, including 7 patients with Stage I and 3 patients with Stage IV (T4NxM0 or TxN2M0) disease. The median maximum diameter of the tumor was 43 mm (24-120 mm). The median follow-up for surviving patients was 57.5 months (9-111 months). The 5-year local control rate, progression-free survival rate, cause-specific survival rate, and overall survival rates were 100%, 100%, 100%, and 74%, respectively. Interestingly, treated tumors showed very slow shrinkage, and the tumor in 1 case has been shrinking for 9 years. One patient with muscular invasion (T4 tumor) developed Grade 4 skin toxicity, but no other toxicity greater than Grade 2 was observed.

Conclusions: This is one of the few reports on curative radiotherapy for primary RCC. The response of the tumor to treatment was uncommon. However despite inclusion of T4 and massive tumors, favorable local controllability has been shown. The results indicate the possibility of radical CIRT, as well as surgery, for RCC.