For patients with localized renal cell carcinoma (RCC), stereotactic ablative body radiotherapy (SABR) may be an effective alternative to surgery, according to findings from a retrospective study.
Patients with smaller tumors and nonmetastatic disease achieved the best outcomes with SABR, reported lead author Rodney E. Wegner, MD, of Allegheny Health Network Cancer Institute, Pittsburgh, and colleagues.
“Radiation therapy is often overlooked in [RCC] as historic preclinical data reported RCC as being relatively radioresistant to external beam radiation at conventional doses,” the investigators wrote in Advances in Radiation Oncology. However, SABR may be able to overcome this resistance by delivering “highly conformal dose escalated radiation,” the investigators noted, citing two recent reports from the International Radiosurgery Oncology Consortium for Kidney (IROCK) that showed promising results (J Urol. 2019 Jun;201[6]:1097-104 and Cancer. 2018 Mar 1;124[5]:934-42).
The present study included 347 patients with RCC from the National Cancer Database who were treated with SABR and not surgery. Most patients (94%) did not have systemic therapy. Similar proportions lacked lymph node involvement (97%) or distant metastasis (93%). About three-quarters of patients (76%) had T1 disease. The median SABR dose was 45 Gy, ranging from 35 to 54 Gy, most frequently given in three fractions.
After a median follow-up of 36 months, ranging from 1 to 156 months, median overall survival across all patients was 58 months. SABR was most effective for patients with nonmetastatic disease who had smaller tumors.
An inverse correlation between tumor size and overall survival was apparent given that patients with tumors 2.5 cm or smaller had the longest median overall survival, at 92 months, with decrements in survival as tumors got larger. Survival dropped to 88 months for tumors 2.6-3.5 cm, 44 months for tumors 3.5-5.0 cm, and finally to 26 months for tumors larger than 5.0 cm. In addition to tumor size and metastatic disease, age was a risk factor for shorter survival.
“The results presented demonstrate excellent post-SABR outcomes, with median overall survival in the range of 7-8 years for smaller lesions,” the investigators wrote. “This is particularly impressive considering that many of these patients were likely medically inoperable.”
The researchers noted that most of kidney SABR is done at academic centers, which highlights the importance of appropriate technology and training for delivering this treatment.
“Further prospective research is needed to verify its safety and efficacy,” the investigators concluded.
No external funding was provided for the project and the investigators reported no conflicts of interest.
SOURCE: Wegner RE et al. Adv Rad Onc. 2019 Aug 8. doi: 10.1016/j.adro.2019.07.018.