3342 - Stereotactic Body Radiotherapy in Medically Inoperable Urinary Tract Urothelial Carcinoma: A Retrospective Experience
Presenter(s)
H. Onishi1, T. Komiyama1, C. Zhe2, M. Matsuda1, K. Marino1, T. Akita1, H. Nonaka3, H. Nemoto1, K. Ueda4, R. Tozuka5, T. Van Ton2, N. Sano6, T. Suzuki7, Z. Mochizuki8, and M. Saito1; 1Department of Therapeutic Radiology, University of Yamanashi, Chuo, Japan, 2University of Yamanashi, Yamanashi, Japan, 3Fuji City General Hospital, Fuji, Japan, 4University of Yamanashi, Chuo, Japan, 5Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan, 6Kasugai CyberKnife Rahabilitation Hospital, Yamanashi, Japan, 7CyberKnife Center, Kasugai General Rehabilitation Hospital, 436 Kou, Kasugai-cho, Fuefuki-city, Yamanashi, 406-0014, Japan, 8CyberKnife Center, Kasugai General Rehabilitation Hospital, 436 Kou, Kasugai, Fuefuki-city, Yamanashi, Japan
Purpose/Objective(s): Radical surgery is the standard treatment for localized urinary tract urothelial carcinoma (UTUC); however, a subset of patients are medically inoperable or unsuitable for prolonged conventional radiotherapy. Stereotactic body radiotherapy (SBRT) offers a short-course treatment alternative for such cases but its evidence supporting in this setting remains limited. We evaluated the safety and clinical outcomes of SBRT in medically inoperable UTUC.
Materials/Methods: This retrospective study included patients with UTUC treated with SBRT. Medical records were reviewed to assess local control, symptom improvement, toxicity, and survival outcomes. Tumor response on follow-up CT or MRI was evaluated according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1.
Results: Between 2015 and 2025, 14 patients with UTUC (7 ureteral, 4 renal pelvic, and 3 bladder tumors) were treated with SBRT. The mean maximum tumor diameter was 41 mm (range, 16–115 mm). One patient had a prior history of surgically treated bladder cancer. The median age at treatment was 83 years (range, 66–94). All patients were considered unsuitable for undergoing surgery or prolonged conventional radiotherapy due to advanced age or frail condition and chose to receive SBRT after multidisciplinary consultation. Treatment intent was curative in 11 patients and palliative in 3.
The prescribed dose was calculated at D95-PTV. The dose-fractionation schedules for SBRT were as follows: 7 patients received 50-60 Gy in 10 fractions, and the other 7 patients 30-37.5 Gy in 5 fractions. All patients successfully completed SBRT as planned. Among 13 symptomatic patients, 12 (92%) experienced clinical improvement following treatment. Tumor response included complete response in 6 patients (46%), partial response in 4 (31%), stable disease in 2 (15%), and progressive disease in 1(7%), yielding a total response rate of 92%. One patient did not have follow-up imaging and was excluded from the analysis of tumor response and recurrence. With a median follow-up of 22 months (range, 2–54), local recurrence occurred in 2 patients, new urothelial tumor within the urinary tract in 2, and distant or lymph node metastases in 4. The 2-year overall and cause-specific survival rates were 53.6% and 74.0%, respectively. Even after a relatively low-dose SBRT regimen of 30 Gy in 5 fractions, one patient of the bladder cancer remained disease-free at 48 months. Renal function remained stable in all patients. No grade 3 or higher treatment-related toxicities or gastrointestinal adverse events were observed. Two patients with ureteral tumors developed hydronephrosis due to post-irradiation ureteral wall thickening despite tumor regression.Conclusion: In medically inoperable patients due to high age or frail condition with UTUC, SBRT was feasible and well tolerated, with encouraging local tumor control. These findings suggest that SBRT may be a reasonable treatment option in such selected patients and warrant further investigation.