Stereotactic Ablative Radiation for Systemic Therapy-naïve Oligometastatic Kidney Cancer

Evidence-based guidelines for the management of systemic therapy-naïve oligometastatic renal cell carcinoma (RCC) are lacking.

To evaluate the potential of stereotactic ablative radiotherapy (SAbR) to provide longitudinal disease control while preserving quality of life (QOL) in patients with systemic therapy-naïve oligometastatic RCC.

RCC patients with three or fewer extracranial metastases were eligible. SAbR was administered longitudinally to all upfront and, as applicable, subsequent metastases.

This prospective phase II single-arm trial was powered to achieve a primary objective of freedom from systemic therapy for >1 yr in >60% of patients (using the Clopper and Pearson methodology). Secondary endpoints included progression-free survival (PFS), defined as the time from first SAbR to progression not amenable to SAbR (local failure at SAbR-treated sites, new metastases not amenable to SAbR, more than three new metastases, or brain metastases); patient-reported QOL metrics; local control (LC) rates; toxicity; cancer-specific survival (CSS); and overall survival (OS).

Twenty-three patients received SAbR to 33 initial and 57 total sites. The median follow-up was 21.7 mo (interquartile range 16.3-30.3). Exceeding the prespecified 60% benchmark, freedom from systemic therapy at 1 yr was 91.3% (95% confidence interval [CI]: 69.5, 97.8). One-year PFS was 82.6% (95% CI: 60.1, 93.1). QOL was largely unaffected. LC was 100%. There were no grade 3/4 toxicities, but there was one death due to immune-related colitis 3 mo after SAbR while on subsequent checkpoint inhibitor therapy, where a SAbR contribution could not be excluded. One-year OS was 95.7% (95% CI: 72.9, 99.4); one-year CSS was 100%.

SAbR for oligometastatic RCC was associated with meaningful longitudinal disease control while preserving QOL. These data support further evaluation of SAbR for systemic therapy-naïve oligometastatic RCC.

Sequential stereotactic radiation therapy can safely and effectively control metastatic kidney cancer with limited spread for over a year without compromising patients' quality of life.