Serial radiation therapy safe, effective for oligometastatic kidney cancer
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Sequential radiotherapy to defer systemic therapy appeared to be a feasible strategy with encouraging PFS and OS among select patients with oligometastatic renal cell carcinoma, according to a study published in The Lancet Oncology.
Results of the single-arm, single-institution phase 2 trial also showed minimal toxicity with the sequential radiotherapy-based, monotherapy among patients with low-volume metachronous oligometastatic renal cell carcinoma who have undergone previous nephrectomy.
“Renal cell carcinoma is a very heterogeneous clinical phenotype. It may just be a series of local diseases in which you have one spot and another spot, and if you control local diseases, you may not have to subject the person to what is now mostly doublet systemic therapy combinations,” Chad Tang, MD, assistant professor in the department of radiation oncology at The University of Texas MD Anderson Cancer Center, told Healio. “Patients loved it because they were not having to come in for weekly infusions of their [anti-PD-1 therapy]. It’s a lot cheaper for them and for the insurance companies. And they had a lot fewer side effects. They weren't being admitted to the ICU and nearly dying due to the drugs.”
Tang described the MD Anderson study as the first to investigate and report the use of stereotactic body radiation therapy as an alternative to standard-of-care systemic therapy for renal cell carcinoma, and he said it challenged the dogma in radiation oncology that renal cell carcinoma is biologically radioresistant.
The analysis included 30 patients with oligometastatic renal cell carcinoma (median age, 65 years; range 59-72; 80% men; 67% white) who had received at least one round of definitive radiotherapy (with fewer than 7 days of unplanned breaks). Eligible patients had to have five or fewer metastatic lesions, an ECOG performance status of 0 to 2, and no more than one previous systemic therapy (if the therapy was stopped at least 1 month before enrollment).
Tang and colleagues treated all lesions with SBRT and did not administer systemic therapy. Other patients received hypofractionated intensity-modulated radiotherapy regimens of 60Gy to 70 Gy in 10 fractions or 52.5Gy to 67.5 Gy in 15 fractions. Investigators administered additional rounds of radiotherapy to treat subsequent sites of progression.
PFS and feasibility, defined as all planned radiotherapy completed with fewer than 7 days of unplanned breaks, served as the co-primary endpoints.
Median follow-up was 17.5 months (interquartile range, 13.2-24.6).
Results showed serial SBRT as monotherapy demonstrated antitumor activity and resulted in median PFS of 22.7 months (95% CI, 4 to not reached), with a 1-year PFS rate of 64% (95% CI, 48-85). Adverse events occurred among three patients (10%) — including two cases of grade 3 back pain and muscle weakness and one case of grade 4 hyperglycemia. No treatment-related deaths occurred.
“What surprised me was the pace of disease was quite indolent, even if we saw a 3 mm nodule that we could not see before. So that speaks to the heterogeneous biology,” Tang said. “But on the flip side, we have had patients where we treat and then the next scan we see five new spots, so we’re thinking we need to get this working — we need to switch. We're trying to figure out who those patients are. But I was surprised by how for some patients, even if there was untreated gross disease, it was OK and they did fine.”
Tang and colleagues wrote that larger, randomized trials are warranted to investigate the risks and benefits of SBRT monotherapy and that if results are confirmed, the treatment would be validated and could be practice changing.
“I tell my patients, we're going to try this and hopefully you’ll get a couple years out of it. We're going to take the drugs that you were going to receive and put them in our back pocket, but they’re still going to be there,” Tang said. “It's really appealing to patients.
“In some patients, where the clinical template allows for it, it could really buy some time of good quality of life and it may, over the course of longer follow up, keep buying time up front and you may even end up with longer OS,” Tang added.
For more information:
Chad Tang, MD, can be reached at Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030; email: ctang1@mdanderson.org.
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