Stereotactic radiotherapy emerges as ‘new standard’ for inoperable kidney cancer
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Key takeaways:
- Stereotactic ablative body radiotherapy provided 100% disease control for 3 years.
- Only one patient required dialysis after stereotactic ablative body radiotherapy.
Stereotactic ablative body radiotherapy conferred 100% disease control and cancer-specific survival over a 3-year follow-up period among older adults with inoperable kidney cancer, results from a phase 2 study showed.
The approach led to few reported treatment-related adverse events and mild renal dysfunction despite being evaluated in an older treatment population with baseline renal impairment and other comorbidities.
Findings from the FASTRACK II trial — presented during American Society for Radiation Oncology Annual Meeting — suggest the noninvasive method could emerge as a new standard of care for individuals who are not suitable for nephrectomy, investigators noted.
“These results were exceptional and quite unexpected given our expectations going into the trial and the size of the tumors that were being treated in many of these patients,” Shankar Siva, PhD, MBBS, radiation oncologist and head of the stereotactic ablative body radiotherapy service at Peter MacCallum Cancer Centre, told Healio.
Background
The incidence of kidney cancer has grown over the past 3 decades, with the most rapid increase seen among those aged 70 years or older, according to Siva.
“The standard of care for these patients is typically surgery, but there are some limitations for patients that have other medical issues that may preclude them from surgery or lead them to the risk of dialysis after surgery,” he said. “These patients have very limited treatment options available for a cure.”
Stereotactic ablative body radiotherapy may be “an ideal treatment for kidney cancer,” Siva added. “It has some specific advantages.... It’s a totally noninvsive treatment, it avoids the need for an anesthetic, it has the capacity to treat tumors that are close or central to the middle of the kidney — which are difficult to treat with other approaches — and has the ability to treat larger tumors.”
Methodology
FASTRACK II is an international multicenter study conducted at seven centers in Australia and one in the Netherlands via the TransTasman Radiation Oncology Group and the Australian and New Zealand Urogenital and Prostate Cancer Trials Group. The phase 2 trial aimed to evaluate the safety and efficacy of stereotactic ablative body radiotherapy for adults with primary renal cell carcinoma who are ineligible for surgery, with high-risk tumors or who declined surgery.
The analysis included 70 adults (median age, 77 years; 70% men) enrolled between July 2016 and Feb. 2020 with primary renal cell carcinoma with a single lesion in a kidney.
Researchers reported a median BMI of 32, median Charlson comorbidity score of 7 and median RENAL complexity score of 8 (interquartile range, 7-10) for the entire study group.
Investigators gave patients with tumors 4 cm or smaller a single fraction of 26 Gy, whereas those with tumors larger than 4 cm received 42 Gy in three fractions.
Local tumor control based on RECIST criteria served as the study’s primary outcome measurement. Investigators established a 1-year benchmark of 90% local control rate for the study group, with a null hypothesis of 80% to determine whether a subsequent randomized controlled trial evaluating stereotactic ablative body radiotherapy should be pursued.
Key findings
Over a median follow-up of 43 months, researchers reported 100% local tumor control rate (P < .001) and 100% cancer-specific survival rate, both of which lasted the duration of the trial period.
Further analysis showed an overall survival rate of 99% (95% CI, 90-100) at 1 year and 82% (95% CI, 70-89) at 3 years.
Most patients had mild baseline kidney dysfunction, according to Siva. Post-treatment results showed “mild loss of kidney function,” he said, with a mean eGFR reduction of 10.8 mL/min (95% CI, 13 to 8.6) at 1 year and a further 14.6 mL/min (95% CI, 17 to 12.2) reduction at 2 years, followed by a plateauing thereafter.
Only one patient required dialysis after stereotactic ablative body radiotherapy, Siva added.
Clinical implications
The results could be practice changing and showed an effective way to treat “quite large tumors” using a noninvasive method, Siva told Healio.
“Stereotactic ablative body radiotherapy is a new standard of care for primary kidney cancer among those whose disease is not suited for surgery, and I believe the outcomes of our study support a future randomized trial comparing it with surgery for primary renal cell carcinoma,” he said.
Perspective
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Mark A. Hallman, MD, PhD
Cryoablation has been the preferred option for patients who are not candidates for partial nephrectomy due to comorbidities; however, there are technical limitations of cryoablation that prevent effective treatment of tumors larger than 3 cm or those located near the hilum. The FASTRACK II trial has demonstrated excellent efficacy of stereotactic ablative body radiotherapy, with results showing no local progression among 70 patients combined with favorable sparing of renal function that is comparable to partial nephrectomy. Importantly, many patients included in this trial presented with tumors not amenable to cryoablation. This is compelling evidence that supports stereotactic ablative body radiotherapy as the favored treatment for patients with inoperable primary renal cell carcinoma.
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Siva S, et al. Abstract 5. Presented at: American Society for Radiation Oncology Annual Meeting; Oct. 1-4, 2023; San Diego.
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