From the Journals

SABR response rate falls short in early NSCLC



For patients with resectable stage I non–small cell lung cancer (NSCLC), stereotactic ablative radiotherapy (SABR) may lack the efficacy needed to replace surgical intervention, according to a recent phase II trial.

SABR provided a pathologic complete response rate (pCR) of 60%, which was “lower than hypothesized,” reported lead author David A. Palma, MD, PhD, of London (Ont.) Health Sciences Centre, and his colleagues.

“In patients with cancer who are fit for resection ... the role of SABR is controversial,” the investigators wrote in JAMA Oncology. “Although some recent studies suggest that SABR may achieve outcomes similar to surgery, others do not, and randomized clinical trials are currently under way to compare these 2 modalities.”

The present trial involved 40 adult patients with stage I NSCLC, good pulmonary function, and good performance status. Of these, 35 were evaluable for the primary endpoint, which was tumor pCR rate after SABR. Secondary endpoints were toxic effects, quality of life, distant control, regional control, and local control. Patients with tumors no larger than 3 cm in diameter were given 54 Gy in 3 fractions, while bigger tumors received 55 Gy in 5 fractions. Patients with tumors 2 cm or closer to the brachial plexus or mediastinum were given 60 Gy in 8 fractions. Ten weeks after SABR, sublobar resection or lobectomy was performed, via an open approach or with video-assisted thoracoscopic surgery (VATS).

Analysis revealed a pCR rate of 60%, which was lower than anticipated. One-month and 3-month survival rates were both 100%. After a median follow-up of 19 months, local control rate was 100%, but only three out of four patients (76%) had distant control, and half (53%) had regional control. After 2 years, three out of four patients were still alive (77%). Eighteen percent of patients experienced grade 3 or higher toxic effects.

“[T]he pCR rate of 60% at 10 weeks suggests that practitioners should be cautious in the use of SABR in patients with cancers who are fit for resection,” the investigators concluded.

The Ontario Institute for Cancer Research funded the study. Dr. Palma and Dr. Ward are patent holders for a computed tomography technology that assesses responses after radiotherapy. Dr. Louie reported honoraria from AstraZeneca and Varian Medical Systems Inc.

SOURCE: Palma et al. 2019 Feb 21. doi: 10.1001/jamaoncol.2018.6993.

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