medwireNews: A post-hoc analysis of the OAK trial suggests that patients with advanced non-small-cell lung cancer (NSCLC) who are performing well clinically at radiographic progression could benefit from continuation of treatment with atezolizumab.
Although the findings are “encouraging,” they require confirmation in a randomized clinical trial, emphasized David Gandara (University of California Davis Comprehensive Cancer Center, Sacramento, USA), who presented the research at the 2017 annual meeting of the American Society of Clinical Oncology in Chicago, Illinois, USA.
He explained that cancer immunotherapy “may alter tumor biology such that survival benefit extends beyond radiographic progression,” prompting the team to evaluate the outcomes of post-progression treatment with atezolizumab using data from the phase III OAK trial. The trial was a head-to-head comparison of the programmed cell death ligand 1 (PD-L1) inhibitor with docetaxel in patients with stage IIIB or IV NSCLC.
Of the 425 patients initially randomly assigned to the atezolizumab arm, 332 experienced disease progression as per the RECIST criteria, and just over half (51%) were allowed to continue treatment with the PD-L1 inhibitor as they were considered to be deriving clinical benefit.
Treatment beyond progression for a median of three cycles led to a subsequent partial response in 7% of these 168 patients and stable disease in 49%.
Post-progression overall survival (OS) was a median of 12.7 months for those who continued atezolizumab, 8.8 months for the 94 patients who received other anticancer therapy after progression, and 2.2 months for the 70 patients who did not.
The presenting author noted that continuation of atezolizumab beyond progression was not associated with “increased safety risk.” Considering just the 168 patients who received post-progression atezolizumab, grade 3 or 4 adverse events were experienced by around 11% prior to progression and by 6% afterwards.
He highlighted the non-randomized nature of the comparison and the inherent bias introduced by the criteria for continuing atezolizumab, but concluded by saying that these data suggest that post-progression atezolizumab “is associated with a positive benefit–risk profile for patients who are performing well at the time of progression.”
Discussant Solange Peters, from Lausanne University Hospital in Switzerland, was more circumspect. She noted that data on the median duration of response were unavailable, but available information on the median number of cycles – that is, three, which equates to 9 weeks – suggests that the response is not long-lasting.
Peters continued: “We know, however, that 4% of patients in this trial continued treatment for more than 12 months, meaning again that benefit is to be observed but in a minority of patients.”
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