Dr Tang on Metastasis-Directed Radiotherapy Without Systemic Therapy in Oligometastatic ccRCC

"What we found was that the systemic therapy–free survival was 34 months, with a lower bound [of the 95% CI] exceeding the 24 months that we [had] prespecified. Patients could be off systemic therapy for [approximately] 3 years."

Chad Tang, MD, an associate professor in the Department of Radiation Oncology of the Division of Radiation Oncology; in the Department of Translational Molecular Pathology; and in the Department of Investigational Cancer Therapeutics at The University of Texas MD Anderson Cancer Center, discussed findings from a phase 2 trial (NCT03575611) evaluating metastasis-directed radiotherapy without systemic therapy in oligometastatic clear cell renal cell carcinoma (ccRCC).

Previously, a phase 2 trial—findings from which were published in 2016 by Brian Rini, MD, of the Vanderbilt-Ingram Cancer Center, and coauthors—showed that patients with metastatic RCC who underwent surveillance alone achieved a median time off systemic therapy of 14.9 months (95% CI, 10.6-25.0). Since the upper bound of the 95% confidence interval (CI) in that study was 25.0 months, Tang and colleagues designed the present phase 2 trial to evaluate whether patients with oligometastatic ccRCC who received stereotactic radiation with or without surgical local therapy could achieve a median systemic therapy–free survival of at least 24 months.

In this phase 2 trial, the median systemic therapy–free survival was 34 months (n = 121; 95% CI, 28-54). Notably, the lower bound of the 95% CI for that outcome exceeded the trial's prespecified median duration of at least 24 months, Tang emphasized. The median progression-free survival was also encouraging, at 18 months (95% CI, 15-22), he stated. Furthermore, the use of radiation with or without surgery in this patient population did not compromise overall survival (OS), Tang noted. The median OS was not reached, and the 3-year OS rate was 87%.

The investigators also showed that this local therapy approach was associated with a lower rate of grade 3 or higher toxicities compared with the expected rate of these toxicities associated with systemic therapy, Tang said. The rate of grade 3 or higher toxicities was 6.5%.