An individual patient data meta-analysis of patients undergoing stereotactic ablative body radiotherapy for primary renal cell carcinoma gives support for SABR as a treatment option for patients unwilling or unfit to undergo surgery, shows a study published in The Lancet Oncology.
The analysis, led by Shankar Siva, PhD, of the Peter MacCallum Cancer Centre, Melbourne, also showed that single-fraction SABR might yield less local failure than multifraction SABR.
The incidence of renal cell carcinoma is rising especially in patients older than 70 years, particularly among those with a greater burden of medical comorbidities who face additional risks from anesthesia and major surgery. As alternatives to radical or partial nephrectomy, guidelines recommend nephron-sparing approaches such as thermal ablation and SABR, a noninvasive procedure that avoids anesthesia. While a 2019 meta-analysis revealed promising safety and efficacy for SABR in patients with comorbidities, tumors of stage T1b or higher (that is, ≥ 4 cm) and in solitary kidneys, follow-up was only 28 months and long term outcome data have been awaited.
The current study assessed 5-year outcomes after SABR in primary renal cell carcinoma from the International Radiosurgery Consortium of the Kidney database plus patient data from 12 new contributing institutions in Australia, Canada, Germany, Japan and the United States. The primary endpoint was investigator-assessed local failure. Among 190 patients (median age, 73.6 years), 81 patients (43%) received single-fraction SABR and 109 (57%) received multifraction SABR, with all fractions greater than 5 Gy. Median tumor diameter was 4.0 cm (interquartile range, 2.8-4.9). Among patients with operability details available, referring urologists deemed 75% inoperable; 29% had a solitary kidney.
The cumulative incidence of local failure at 5 years was 5.5% (95% confidence interval, 2.8%–9.5%) overall. Patients receiving single-fraction SABR were observed to have improved local failure and progression-free survival, but not cancer-specific survival, compared with those receiving multifraction SABR.
“We found that multifraction SABR was associated with a 6-times higher risk of local failure after adjustment for baseline characteristics. This data is provocative and needs to be tested in a randomized trial,” Dr. Siva said in a Lancet Oncology podcast interview. There were no grade 3 toxic effects or treatment-related deaths. One patient developed an acute grade 4 duodenal ulcer and late grade 4 gastritis.
Reductions in estimated glomerular filtration rate (eGFR), from a median of 60.0 mL/min per 1.73 m2 at baseline were 10.0 mL/min per 1.73 m2 at 3 years and by 14.2 mL/min per 1.73 m2 at 5 years post SABR. “Most of these patients had severe chronic kidney disease, the median eGFR being only 33 mL/min,” Dr. Siva stated. “So overall the kidney function declines were quite acceptable.”
The results show, Dr. Siva and colleagues stated, thatIn the audio interview, Dr. Siva said, “I would suggest that we consider SABR for those patients who have larger, inoperable kidney cancers. SABR, in this context, is particularly attractive because these patients don’t have any alternative cure or treatment options. In my opinion, this group should be given compassionate access to SABR. It would be a great place to start.”
The authors acknowledged that because toxicity data were collected retrospectively, low rates of treatment-related toxic effects might be caused by underreporting.
Dr. Siva and colleagues reported no outside funding. Dr. Siva was supported by the Cancer Council Victoria Colebatch Fellowship.