ESTRO 2024 - Abstract Book

S2451

Clinical - Urology

ESTRO 2024

Miriam Torrisi 1,2 , Chiara Lucrezia Deantoni 1 , Andrei Fodor 1 , Laura Giannini 1,2 , Martina Midulla 1,2 , Roberta Tummineri 1 , Italo Dell'Oca 1 , Sara Broggi 3 , Antonella Del Vecchio 3 , Stefano Arcangeli 4 , Nadia Gisella DiMuzio 1,5 1 IRCCS Ospedale San Raffaele, Radioterapia, Milano, Italy. 2 Università degli studi Milano-Bicocca, Radioterapia, Monza, Italy. 3 IRCCS Ospedale San Raffaele, Fisica Medica, Milano, Italy. 4 IRCCS San Gerardo dei Tintori, Radioterapia, Monza, Italy. 5 Università Vita Salute San Raffaele, Radioterapia, Milano, Italy

Purpose/Objective:

Renal cell carcinoma (RCC) is an aggressive malignancy, and often carries a poor prognosis, especially in metastatic patients. RCC has traditionally been considered radio-resistant with a limited role for conventional fractionation as a local approach. However, since the advent of stereotactic body radiation therapy (SBRT), radiotherapy has been increasingly used in the management of metastatic RCC (mRCC). The aim of our analysis is to evaluate the role of SBRT as Metastasis-Directed Therapy for synchronous and metachronous oligo- metastatic (OMD) RCC pts in terms of local control and delay of prescription of Next-line Systemic Therapy (NEST).

Material/Methods:

A monocentric retrospective data collection was performed. Between 02/2019-07/2023, 97 treatments in 61 pts were delivered with CyberKnife ™ (Accuray, Sunnyvale, CA, USA). All metastatic sites were considered. Tumor response was evaluated using the response evaluation criteria in solid tumors (RECIST). Time to NEST was calculated from the end of SBRT to the start of any new systemic therapy. Progression-free survival (PFS), Local Control (LC) and overall survival (OS) were calculated via the Kaplan-Meier method.

Results:

Median follow-up was 13.9 (0-61.9) months. Median time between primary tumor diagnosis and SBRT for OMD was 62.2 (0-356.7) months. Median prescribed dose was 30 Gy (16-60) in a median of 3 (1-8) fractions, at a median isodose of 80% (63%-85%). For 47 treatments (48.4%) concomitant systemic therapy was prescribed. Median Biological Equivalent Dose (BED), calculated with tumor specific a/b coefficient of 3, was 146.7 (66.7-378) Gy. OS of all pts at 12- and 24-months was 87.1% and 63.6%, respectively. Twelve- and 24-month LRFS was 81.8% and 78.7%, respectively. At the last follow-up NEST was necessary for 11 pts (25 lesions). Median time to NEST was 8 (1.6-30.8) months. NEST-free survival at 12- and 24-months was 70.7% and 63.2%, respectively. Median NEST-free survival for pts with SBRT only was not reached, and was 30.8 months for pts with SBRT and systemic therapy. Six-, 12- and 24 months NEST-free survival was 85.1%, 82%, and 69% for pts with SBRT only vs 76.5%, 56.6% and 56% for pts with SBRT and systemic therapy (p=0.15), probably due to the selection of pts with more advanced disease for systemic therapy.

Conclusion:

SBRT is a feasible and effective treatment in patients with mRCC with good LC. These results of combined local and systemic treatments should be verified in prospective trials.