265 - Long-Term Follow-Up Results after Stereotactic Body Radiotherapy for Primary Renal Cell Carcinoma: A Prospective Multicenter Phase 2 Trial
Presenter(s)
H. Onishi1, T. Yamamoto2, H. Yamashita3, H. Sato4, K. Nakata5, K. Ito6, T. Komiyama1, Z. Chen7, T. Akita1, K. Mrino8, S. Okabayashi1, Y. Maehata9, K. Kuriyama1, and H. Nonaka10; 1University of Yamanashi, Chuo, Japan, 2Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan, 3Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan, 4Department of Radiation Oncology, Yamagata University Faculty of Medicine, Yamagata, Japan, 5Department of Radiation Oncology, Sapporo City General Hospital, Sapporo, Japan, 6Department of Radiation Oncology, Tokyo Metropolitan Cancer and Infectious Diseases Center, Komagome Hospital, Tokyo, Japan, 7Department of Therapeutic Radiology, University of Yamanashi Hospital, Chuo, Japan, 8University of Yamanashi, Yamanashi, Japan, 9Yamanashi Prefectural Central Hospital, Kofu, Japan, 10Fuji City General Hospital, Fuji, Japan
Purpose/Objective(s): Stereotactic body radiotherapy (SBRT) is a less-invasive curative treatment option for primary renal cell carcinoma (RCC), but long-term data remain limited. This study aimed to evaluate the long-term efficacy and safety of SBRT for localized RCC.
Materials/Methods: This multicenter, prospective, phase 2 study was conducted at six centers in Japan. Patients with an Eastern Cooperative Oncology Group (ECOG) performance status of 0–2 and a clinical diagnosis of RCC, regardless of biopsy confirmation, were enrolled if they were medically inoperable, had a high surgical risk, or declined surgery. The prescribed SBRT dose, defined as D95 of the PTV, was selected from 50 Gy, 60 Gy, or 70 Gy, adhering to normal organ dose constraints. SBRT was delivered in 10 fractions. The primary endpoint was local control, defined as the absence of tumor progression within the irradiated area. Secondary endpoints included treatment-related adverse events, progression-free survival (PFS), overall survival (OS), and cause-specific survival (CSS).
Results: Between August 2007 and May 2017, 49 patients (40 males, 9 females) were enrolled and treated. SBRT was performed in 40 cases as the primary treatment for RCC and in 9 cases with a history of total nephrectomy for contralateral renal cancer. The median age was 73 years (range: 57–86), and the median tumor size was 27 mm (range: 9–57). All patients had no lymph node or distant metastases. SBRT doses were 70 Gy in 26 patients, 60 Gy in 15, and 50 Gy in 8. The median follow-up duration was 76 months (range: 16–169). Local recurrence was observed in only one case at 11.4 years post-SBRT, yielding 5- and 10-year local control rates of 100%. Grade 3 and 4 gastrointestinal adverse events were observed in one patient each, both cases involving tumors located near the duodenum or colon. A total of 12 patients (24.5%) experienced an increase in blood creatinine levels of =1.0 mg/dL during the follow-up duration after SBRT, and the decline in renal function was more frequently observed in patients with a single kidney. The 5- and 10-year PFS rates were 84.9% and 70.8%, respectively, while OS rates were 73.2% and 49.8%, respectively. The 5- and 10-year CSS rates were 95.2% and 87.2%, respectively. CSS was significantly higher in patients treated with SBRT as the initial therapy compared to those who had undergone prior nephrectomy for contralateral renal cancer, with a 10-year CSS of 97.3% in the former group.
Conclusion: SBRT demonstrated excellent long-term local control and cause-specific survival with almost acceptable safety for primary RCC. These results support SBRT as a curative treatment option for patients unwilling or unfit for surgery and provide a basis for future randomized trials comparing SBRT with surgery for primary RCC.