medwireNews: Definitive radiotherapy without systemic therapy may be a feasible strategy for the treatment of oligometastatic renal cell carcinoma (RCC), phase 2 study findings indicate.
Chad Tang (The University of Texas MD Anderson Cancer Center, Houston, USA) and colleagues say that a sequential radiotherapy-based approach “could be used for treatment de-escalation to delay, avoid, or hold systemic therapy in patients with oligometastatic renal cell carcinoma.”
Their trial included 30 patients (median age 65 years, 20% women) with clear cell RCC and up to five metastatic lesions who had all undergone nephrectomy and received no more than one previous systemic therapy that must have been stopped at least 1 month before enrollment.
Participants were treated with up to five fractions of stereotactic body radiotherapy (≥7 Gy/fraction) to all lesions without systemic therapy. In cases where lesion location meant that stereotactic body radiotherapy was unsafe, hypofractionated intensity-modulated radiotherapy (60–70 Gy in 10 fractions or 52.5–67.5 Gy in 15 fractions) was given instead.
As reported in The Lancet Oncology, all patients completed at least one round of radiotherapy with fewer than 7 days of unplanned breaks, and therefore met the criteria for the coprimary endpoint of feasibility.
The longest unplanned delay during the first round of radiotherapy was 3 days and no patients required dose reduction or discontinuation due to adverse events.
Thirteen (43%) participants received further local radiotherapy for subsequent sites of progression, and again they all completed the treatment course with fewer than 7 days of unplanned treatment delays.
Disease progression occurred in 43% of patients during a median 17.5 months of follow-up. Median progression-free survival, the second coprimary endpoint, was 22.7 months, with 64% of participants alive and progression-free at 12 months.
Overall survival was 100% at 12 months, and all patients were still alive at data cutoff, note Tang and co-investigators.
During follow-up, 23% of patients initiated systemic therapy. Median systemic therapy-free survival was not reached, but the 1-year systemic therapy-free survival rate was 82%.
In terms of safety, there were three serious adverse events which all occurred within 3 months of radiotherapy completion. These included one case each of grade 3 back pain, grade 3 muscle weakness, and grade 4 hyperglycemia.
Tang et al conclude that although the study included a highly selected population, their findings indicate that “sequential radiotherapy to defer systemic therapy is a feasible strategy with encouraging progression-free survival and overall survival in patients with low-volume metachronous oligometastatic renal cell carcinoma who have undergone previous nephrectomy.”
They add: “Future larger randomised trials investigating the risks and benefits of the stereotactic body radiotherapy monotherapy approach are warranted, and if the current results are confirmed, they would validate this treatment approach for select patients with metastatic renal cell carcinoma.”
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