3327 - Metastasis Directed Radiation Therapy for Oligometastatic and Oligoprogressive Renal Medullary Carcinoma
Presenter(s)
S. Mohanty1, P. Msaouel2, S. S. Krebs3, P. Rao4, J. Karam5, P. T. Tran6, C. J. Hassanzadeh6, N. Tannir2, and C. Tang6; 1McGovern Medical School at UTHealth Houston, Houston, TX, 2Department of Genitourinary Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 3Department of Nuclear Medicine, Division of Diagnostic Imaging, The University of Texas MD Anderson Cancer Center, Houston, TX, 4Department of Anatomical Pathology, Division of Pathology-Lab Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, 5Department of Urology, Division of Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, 6Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX
Purpose/Objective(s):
Renal medullary carcinoma (RMC) is a rare, aggressive renal cell carcinoma (RCC) subtype characterized by SMARCB1 loss and poor survival. RMC exhibits a unique association with race, given its pathogenesis from chronic kidney damage induced by sickle cell trait. This cancer predominantly affects young, Black patients, and treatment often relies on cytotoxic chemotherapy unlike most RCC subtypes. Data on definitive-intent radiation therapy (RT) are limited.Materials/Methods:
We retrospectively reviewed patients with pathologically confirmed metastatic RMC treated with definitive-intent RT (April 2019–January 2026). Oligometastatic disease was defined as =5 total lesions and oligoprogressive disease as =5 progressive lesions in otherwise disseminated disease. RT was delivered using stereotactic body radiation therapy (SBRT) or intensity-modulated radiation therapy (IMRT). Endpoints included local control (LC), progression-free survival (PFS), and overall survival (OS). Tumor response was assessed per RECIST 1.1.Results:
Twenty-three patients were included. Median age was 35 years (range, 15–60), 65% male and 65% Black. The most common metastatic sites were lymph nodes (61%), lung (26%), and bone (17%). Patients had progressed through a median of two systemic therapies (range, 0–4) prior to RT. RT was delivered using SBRT in 57% and IMRT in 43%, with 39% of patients receiving low biologically effective doses (BED10 = 60 Gy). Five (22%) patients had passed away at the median follow-up of 13.6 months. One- and two-year OS proportions were 89% and 64%. One- and two-year PFS proportions were 34% and 14%. First progression was mainly distant and most common in new lymph nodes (65%). LC at 12 and 24 months was 100% and 96%, respectively. No in-field failures were observed. Among 14 patients with RECIST-eligible lesions and appropriate follow-up imaging, all irradiated lesions exhibited an objective response: complete responses in 64% and partial responses in 36%. On univariable analysis, a greater number of metastases at diagnosis was associated with worse OS (HR 1.7, 95% CI 1.1–2.7, p=0.03) and PFS (HR 1.5, 95% CI 1.2–1.9, p=0.002). Higher numbers of lesions treated with RT were associated with worse PFS (HR 1.7, 95% CI 1.1–2.7, p=0.02), but not OS. Oligoprogressive versus oligometastatic disease was not associated with OS or PFS. RT was well tolerated, with only grade 1–2 acute toxicities and no grade =3 events.Conclusion:
Definitive-intent RT for heavily pre-treated oligometastatic and oligoprogressive RMC achieved excellent local control, high complete response rates, and encouraging survival in this rare and lethal disease. Of note is the high complete response rate, often achieved with low RT doses, given the lack of radiographic responses seen with most RCC histologies. These findings suggest RMC exhibits distinct radiosensitivity compared to other RCC subtypes. Furthermore, integration of definitive RT into the treatment for RMC deserves prospective validation.