3147 - Clinical Efficacy and Adverse Effects of Adjuvant Radiotherapy Following Surgery in High-Risk Renal Cell Carcinoma(RCC) Patients - A Single Center Experience

J. Y. Chen, X. S. Gao, M. Ma, H. Li, S. Qin, X. Li, X. Ren, and Y. Bai; Department of Radiation Oncology, Peking University First Hospital, Beijing, China

Purpose/Objective(s): The role of adjuvant radiotherapy (RT) following surgery for renal cell carcinoma (RCC) remains controversial. The patients with high-risk factors were reported a locoregional recurrence rate exceeding 30%. Despite some research indicated that adjuvant RT can reduce local recurrence, previous clinical trials showed conflicting results. These historical trials included low-risk patients. The significant toxicities due to outdated technology may offset the benefits of RT. The present study aims to analyze clinical data on adjuvant RT after renal cancer surgery, exploring its role among RCC patients with high-risk of local recurrences, in the era of precision radiotherapy. Materials/

Methods: We retrospectively analyzed the patients who received adjuvant RT after radical nephrectomy for RCC. All eligible patients exhibited at least one of the following high-risk factors: 1) T3/T4, 2) N1, 3) special pathological features such as higher than G3, sarcomatoid change, or molecularly defined RCC, e.g.TFE3. The patients who experienced isolated regional recurrence were also included. The patients with distant metastases and loss to follow-up were excluded. All patients received radiation targeting the renal fossa and para-aortic region. The median adjuvant dose was 50 Gy (45-50 Gy). Synchronous dose escalation was performed for visible recurrent lesions or metastatic lymph nodes, with a median dose of 65 Gy (60-70 Gy). All patients underwent intensity-modulated RT and daily image-guided RT.
Results: From 2018 to 2023, a total of 31 patients were analyzed. The median age was 50 years (17-65 years). 90.3% (28/31) of the patients were in stage III-IV. 77.4% (24/31) had special pathological features. 48.4% (15/31) had recurrent tumors or regional lymph nodes at the time of RT. The median follow-up time was 19.4 months (5.1-53.0 months). The 1-year, 2-year, and 3-year of locoregional control (LC) rates were 100%, 93.3%, and 93.3%, respectively. The 1-year, 2-year, and 3-year of PFS rates were 71.4%, 44.9%, and 41.6%, respectively. Only one patient experienced local recurrence after RT. The process of recurrence was halted by RT in 4 patients with second regional lesions. No acute grade 3 or higher gastrointestinal (GI) toxicity was observed. The rates of grade 2 gastrointestinal (GI) toxicity were 41.9%. No late grade 2 or higher GI toxicity was observed. 41.9% (13/31) of patients received concurrent systemic therapy, including targeted therapy or immunotherapy. There was no significant difference in the incidence of toxicities or progression between the patients with and without systemic therapy.
Conclusion: Adjuvant radiotherapy (RT) shows a promising role of locoregional control in high-risk patients after surgery. Patients with repeated isolated regional recurrences are particularly likely to benefit from RT. Notably, the toxicities of adjuvant RT are considerably lower than historical data. The combination of adjuvant RT and systemic therapies appears to be well-tolerated.