Main Session
Sep
29
PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement
3395 - Stereotactic Body Proton Therapy for Primary Kidney Tumors: Early Outcomes from a Community Cancer Center
Presenter(s)
Chiachien Wang, MD, PhD - Willis-Knighton Cancer Center, Shreveport, LA
C. J. Wang1, H. T. Wu1, O. G. Moncrief1,2, and Y. A. Walter1,3; 1Willis Knighton Cancer Center, Shreveport, LA, 2Louisiana State University Health Shreveport, Shreveport, LA, 3University of Jamestown, Fargo, ND
Purpose/Objective(s):
Stereotactic ablative radiotherapy is an effective, non-invasive treatment option for renal cell carcinoma (RCC). For primary tumors, proton beam therapy may carry additional dosimetric benefits compared to photons. The purpose of this study is to characterize the early efficacy and toxicity profile of stereotactic body proton therapy (SBPT) for primary RCC.Materials/Methods:
Data were collected for patients treated with SBPT on an IBA ProteusONE between 2020 and 2025. Plans used two to three coplanar beams to deliver the prescribed dose of 50.0 Gy (RBE 1.1) in 5 fractions or 42.0 Gy (RBE) in 3 fractions. Follow-up imaging was acquired every 6 months following therapy until 2 years posttreatment, and annually thereafter. Local control (freedom from local progression) was evaluated on CT imaging using RECIST 1.1 criteria and changes to metabolic uptake if PET was available at follow-up. Overall survival (OS), progression-free survival (PFS), incidence of adverse events (AE, CTCAE version 4.0) and changes in the estimated glomerular filtration rate (eGFR) were recorded.Results:
25 patients with primary renal cell carcinoma (median age 71 years) were included. Pretreatment internal clinical target volumes (iCTV) ranged from 8.3 mL to 211.3 mL (median 69.0 mL). Tumor histologies were clear cell RCC (n=6), papillary RCC (n=5), clear cell papillary RCC (n=1), and RCC, not otherwise specified (n=2). Histological confirmation was not available for 11 tumors (44.0%), 10 of which progressed on pre-treatment imaging. 24 patients were treated to 50.0 Gy (RBE) in five fractions. One patient received 42.0 Gy (RBE) in 3 fractions. The median follow-up interval was 11.0 months (IQR 7.4-14.2 months). A 100.0% local control rate was observed. There were no instances of disease progression. Three deaths occurred over the study period. The one-year OS and PFS were 90.8% (95% CI: 68.1 to 97.6%). The baseline eGFR was 60.5 ± 25.5 mL/min. 14 patients (56.0%) had stage 1-2 chronic kidney disease (CKD) at baseline. 9 patients had stage 3-4 CKD, and two patients had stage 5 CKD at baseline. The eGFR at follow-up was not available for three patients. For the remaining 22 patients, eGFR decreased within 1 year of treatment (mean 14.3 ± 16.4% drop). Following SBPT, two patients had grade 5 CKD, 16 patients had grade 3-4 CKD, and 4 patients had grade 1-2 CKD. There were four instances of grade 1 AE (pain, n=2; dyspnea on exertion, n=2). No grade =2 AE were reported. One patient remained on dialysis pre- and post-therapy.Conclusion:
SBPT is safe and effective for treatment of primary RCC. To our knowledge, this study is among the first to report clinical results in SBPT for primary RCC. Despite treating large tumor volumes, adequate nephron sparing was achieved while avoiding significant GI toxicity, highlighting potential benefits of a proton-based approach. Future trials comparing proton- and photon-based SBRT are merited.