Radiation therapy as monotherapy effective in oligometastatic renal cell carcinoma

Radiation therapy as monotherapy may be a safe and effective treatment for patients with oligometastatic renal cell carcinoma (RCC), according to findings from a phase 2 study published in The Lancet Oncology.^1,2

Use of the modality resulted in median progression-free survival of 22.7 months in patients with RCC, according to a news release about the study.

Chad Tang, MD

“These findings are exciting because we’re challenging the dogma in radiation oncology that RCC is biologically radioresistant. Our strategy to iteratively radiate tumors as they grow and appear has demonstrated promising results. This adds to a growing body of evidence suggesting/indicating radiation therapy could offer an alternative treatment beyond systemic therapy for patients with this disease,” said lead author Chad Tang, MD, assistant professor of radiation oncology at MD Anderson Cancer Center, Houston, Texas.

The study (NCT03575611) evaluated patients aged 18 years or older who had 5 or fewer metastatic lesions, an ECOG status of 0 to 2, and no more than 1 previous systemic therapy without limitations on RCC histology. Patients received stereotactic body radiotherapy consisting of 5 or fewer fractions with at least 7 Gy per fraction directed to all lesions and maintained off systemic therapy.

The co-primary end points were feasibility and profession-free survival. The study also included a second cohort, in whom investigators will evaluate the feasibility of sequential stereotactic body radiotherapy alone in patients with low-volume metastatic disease. That cohort will be reported separately, according to the investigators.

A total of 30 patients were enrolled in the study, all of whom had clear cell histology and had underwent nephrectomy prior to enrollment. The patient population comprised 20 Caucasian (67%), 7 Hispanic (23%), 2 Black (7%), and 1 Native American (3%) participants. Median age was 65 years, and 24 of the patients were men. The entire cohort completed at least 1 round of radiotherapy with less than 7 days of unplanned breaks.

“At a median follow-up of 17.5 months, median progression-free survival was 22.7 months (1-year progression-free survival 64%,” the investigators wrote.

At 3 months after treatment, biopsies confirmed the efficacy of radiation therapy for eliminating viable tumor cells or significantly reducing their proliferation. At first follow-up, investigators conducted CT-guided biopsy on 14 patients, of whom 6 tested negative for viable malignancy. In the remaining patients whom investigators were able to test, a meaningful reduction in tumor cell proliferation (15% before radiation therapy dropping to 6% after treatment) was observed. A total of 23 patients remained off systemic therapy at the end of the study period.

Two patients experienced a grade 3 adverse event (AE, back pain and muscle weakness), and 1 patient experienced a grade 4 AE (hyperglycemia). No treatment-related deaths were reported.

“Given these results, I’m encouraged that serial radiation therapy for oligometastatic RCC has the potential to be practice-changing,” Tang said. “We are giving patients another option for treatment that minimizes the burden of toxicity on the body, while extending survival and maximizing their quality of life. We plan to continue studying this strategy on patients with slightly larger burdens of disease and to analyze biomarkers from these treated patients to improve our ability to select patients who benefit from this treatment.”

References

1. Tang C, Msaouel M, Hara K, et al. Definitive radiotherapy in lieu of systemic therapy for oligometastatic renal cell carcinoma: a single-arm, single-centre, feasibility, phase 2 trial. Lancet Oncol. 2021;S1470-2045(21)00528-3. doi:10.1016/S1470-2045(21)00528-3

2. Serial radiation therapy is safe and effective as alternative treatment to systemic therapy for kidney cancer. News release. MD Anderson Cancer Center. October 27, 2021. Accessed November 2, 2021. https://www.mdanderson.org/newsroom/serial-radiation-therapy-is-safe-and-effective-as-alternative-treatment-to-systemic-therapy-for-kidney-cancer.h00-159464790.html