Long-Term Stereotactic Ablative Body Radiotherapy Demonstrates Lasting Efficacy/Safety in Kidney Cancer Subtype

Findings from a meta-analysis indicated that patients with primary renal cell carcinoma who were treated with stereotactic ablative body radiotherapy (SABR) experienced durable safe and efficacy, potentially supporting the use of renal SABR as an option for those who are unwilling or unsuitable for surgery.

Investigators reported that 4% (n = 7/190) of patients required dialysis after receiving SABR. The cumulative incidence of local failure at 3 years, 5 years, and 7 years among the overall population was 5.5% (95% CI, 2.8%-9.5%), 5.5% (95% CI, 2.8%-9.5%), and 8.4% (95% CI, 4.2%-14.3%), respectively. Investigators observed no failure in 86% (n = 164/190) of patients.

Single-fraction SABR yielded fewer incidence of local failure compared with muli-fraction SABR (Gray’s P = .02). However, the study authors indicated that these data should not be interpreted as definitive, citing a need for further research via a dedicated randomized clinical trial.

The authors of the study conducted a meta-analysis of patient data involving those who underwent SABR for primary renal cell carcinoma in 12 institutions across Australia, Canada, Germany, Japan, and the United States between 2007 and 2018.

The primary end point was investigator-assessed local failure per RECIST v1.1 criteria. Secondary end points of the study included evaluating treatment-related adverse effects (AEs), patterns of failure, survival, and renal function outcomes.

Patients 18 years and older who had a minimum potential follow-up of 2 years, any performance status, no previous local therapy, and non-metastatic renal cell carcinoma were included in the analysis.

With a median follow-up of 5 years, a total of 190 patients included in the analysis received SABR between 2007 and 2018. Single-fraction and multi-fraction SABR was delivered to 43% (n = 81/190) and 57% (n = 109/190) of patients, respectively.

The median patient age at the time of SABR was 73.6 years (interquartile range [IQR], 66.2-82.0), and the median tumor diameter was 4.0 cm (IQR, 2.8-4.9). Most patients (75%) with available operability information were determined to be medically inoperable by the referring urologist. Moreover, 29% of patients had a solitary kidney and baseline tumor complexity was moderate.

The median baseline estimated glomerular filtration rate (eGFR) was 60.0 ml per minute per 1.73 m² (IQR, 42.0-76.0). From baseline, eGFR decreased by a median of 5.5 ml per min per 1.73 m² (IQR, 0.0-14.2) after 1 year, 10.3 ml per minute per 1.73 m² (IQR, 3.2-18.8) after 3 years, and 14.2 ml per minute per 1.73 m² (IQR, 5.4-22.5) after 5 years of SABR (P <.0001).

In the exploratory analysis, patients who received single-fraction SABR for tumors smaller than 4 cm had the best progression-free survival (PFS; P = .028) and cancer-specific survival (P = .25) behind patients receiving single-fraction SABR for tumors 4 cm or larger (Gray’s P = .064).

Grade 1 to 2 AEs were observed in 37% of patients, and there were no deaths related to treatment. One patient who received multi-fraction SABR had treatment-related acute grade 4 duodenal ulcer and late grade 4 gastritis 1.4 months and 15.8 months after beginning treatment, respectively.

In terms of other AEs observed in the overall population, single-fraction subgroup, and multi-fraction subgroup, respectively, grade 1/2 fatigue was seen in 27%, 21%, and 31% of patients. Additionally, grade 1/2 nausea was observed in 13%, 20%, and 8%; chest wall pain was observed in 6%, 6%, and 6%; and skin-related AEs were seen in 2%, 2%, and 1% of patients in each respective group.

Reference

Siva S, Ali M, Correa R, et al. 5-year outcomes after stereotactic ablative body radiotherapy for primary renal cell carcinoma: an individual patient data meta-analysis from IROCK (the International Radiosurgery Consortium of the Kidney). Lancet Oncol. 2022;23(12):1508-1516. doi:10.1016/S1470-2045(22)00656-8