Stereotactic ablative radiation therapy for metastatic RCC achieves excellent local control

By Liz Meszaros, MDLinx
Published May 7, 2017

Key Takeaways

Treatment with stereotactic ablative radiation therapy (SAbR) may achieve over 90% control of metastases in patients with metastatic renal cell carcinoma, and carries a favorable safety profile when adequate doses and coverage are achieved, according to results from a study published in the May 2017 issue of the International Journal of Radiation Oncology, Biology, and Physics.  

“This study shows that stereotactic radiation provides a good noninvasive alternative to conventional treatment, and that it effectively controls the disease,” said Raquibul Hannan, MD, PhD, assistant professor, radiation oncology, UT Southwestern Medical Center’s Kidney Cancer Program of the Harold C. Simmons Comprehensive Cancer Center, Dallas, TX, co-leader of the Kidney Cancer Program, and senior author of the study. “It may also offer an alternative to patients who are not candidates for surgery due to the number and location of the metastases.”

In this study, Dr. Hannan and his fellow researchers sought to assess both the safety and efficacy of SAbR for extracranial renal cell carcinoma metastases. They reviewed 175 metastatic lesions from 84 patients treated with SAbR between 2005 and 2015. Using the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 and Common Terminology Criteria for Adverse Events (CTCAE) version 40, they assessed both local control (LC) and toxicity after SAbR. Then, they analyzed predictors of local failure with X2, Kaplan-Meier, and log-rank tests.

Most patients (74%) received SAbR in total doses of 40 to 60 Gy in 5 fractions, 30 to 54 Gy in 3 fractions, and 20 to 40 Gy in one fraction. Researchers found that the median biologically effective dose (BED) using the universal survival model was 134.5 Gy.

After SAbR, the 1-year LC rate was 91.2% (95% CI: 84.9%-95.0%; median follow-up: 16.7 months).

Prior radiation therapy was associated with local failures (HR: 10.49; P < 0.0001), as were palliative-intent radiation therapy (HR: 4.63; P=0.0189), spinal location (HR: 5.36; P=0.0041), previous systemic therapy (0-1 vs > 1; HR: 3.52; P=0.0217), and BED < 115 Gy (HR: 3.45; P=0.0254).

The strongest dosimetric predictor for LC was the dose received by 99% of the target volume, and after multivariate analysis, dose received by 99% of the target volume greater than BED of 98.7 Gy and systemic therapy status remained significant (HR: 0.12 and 3.64; P=0.0014 and P=0.0472, respectively).

Researchers also found that in those patients who have received previous systemic therapies, a higher radiation dose may be necessary.

Three patients (1.7%) demonstrated acute toxicities attributed to SAbR, and five (2.9%) had late grade 3 toxicities.

SAbR may soon become an alternative treatment for patients with metastatic kidney cancer.

“This study, which represents possibly the largest experience reported in the medical literature, may also help medical oncologists, since stereotactic radiation could be used for patients who have limited sites of progression while receiving systemic therapy,” said James Brugarolas, MD, PhD, associate professor of internal medicine, UT Southwestern, and leader of the Kidney Cancer Program.

The research was conducted in the Kidney Cancer Program, one of two programs in the country to be recognized with an $11 million SPORE (Specialized Program of Research Excellence) from the National Cancer Institute. As part of the SPORE, researchers are improving the ways in which radiation is given by evaluating combinations with drugs and identifying those tumors that are most likely to respond. In particular, investigators are evaluating combinations with immunotherapy, iSABR – immunotherapy and Stereotatic Ablative Radiation Therapy.

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