Most patients with non–small cell lung cancer (NSCLC) who are long-term responders to immunotherapy will continue receiving treatment beyond 2 years. However, the best available evidence to date indicates that receiving immunotherapy after this 2-year mark likely offers no survival benefit.
Is it an overabundance of caution? A desire for more definitive data? Or is it simply a judgment call oncologists make on the basis of the individual patient?
Lova Sun, MD, MSCE, of the University of Pennsylvania in Philadelphia, believes the general inconsistency between the data and clinical practice “likely reflects significant hesitation on the part of clinicians, patients, or both to stop a treatment that is still ‘working.’ ”
H. Jack West, MD, agreed, adding that “in an ambiguous situation, a U.S.-based population is going to err on the side of overtreatment.”
Without “incontrovertible evidence” that immunotherapy should stop at 2 years, “many, many, many patients and clinicians are going to favor continuing ‘doing what you’re doing’ in the absence of either prohibitive toxicity or clinically significant disease progression,” said Dr. West of the City of Hope Comprehensive Cancer Center, Duarte, Calif.
One factor adding to this ambiguity: Most pivotal studies that examine first-line immunotherapy in NSCLC limit therapy duration to 2 years.
Another key factor is the absence of prospective data as to when to stop treatment for these patients, according to Martin Reck, MD, PhD, head of thoracic oncology at the Lung Clinic Grosshansdorf (Germany).
“We have never prospectively investigated the correlation of the duration of a checkpoint blockade and the efficacy of treatment,” Dr. Reck said. “And this is a big problem.” It means “we really do not know how long we should treat the patient.”
To make matters muddier, some data do suggest that more therapy may be better. The recent Checkmate 153 trial, for instance, found that patients who had no signs of disease progression and who received 1-year fixed-duration nivolumab had significantly shorter progression-free and overall survival than those who received treatment indefinitely.
However, randomized trials with longer-term follow-up suggest durable responses can be maintained for years after immunotherapy is stopped.
Data from the KEYNOTE-024 trial, for instance, showed that more than 45% of patients with metastatic NSCLC and high tumor PD-L1 expression who received pembrolizumab for 2 years remained alive at 5 years without further treatment or disease progression. Another trial, KEYNOTE-407, demonstrated similar 5-year survival outcomes among patients with advanced squamous NSCLC, regardless of PD-L1 status, who completed 2 years of chemotherapy plus pembrolizumab followed by maintenance pembrolizumab.
With these studies, however, “we can only speculate about whether the proportion of patients alive without progression would be substantially higher if treatment with immunotherapy continued longer,” Dr. West wrote in a recent editorial .
Perhaps the most telling data so far come from a recent retrospective analysis from Dr. Sun and colleagues. The researchers directly compared survival outcomes among patients who continued receiving immunotherapy indefinitely with outcomes among patients for whom immunotherapy was discontinued at 2 years.
The JAMA Oncology study, which focused on 706 patients with NSCLC who completed 2 years of therapy, found that only 16% stopped receiving immune checkpoint inhibitor therapy at 2 years, whereas the remaining 84% continued receiving treatment indefinitely.
Among patients who continued receiving immunotherapy for 2 additional years, overall survival was not better than among those who stopped receiving immunotherapy at the 2-year mark. Even among the 11 patients whose condition progressed when therapy was discontinued, most still did well after treatment was resumed.
However, the retrospective design of the study limits its impact.
Without more definitive “data about when the treatment can be stopped,” many continue “indefinitely as long as the patient is tolerating treatment and the disease is not progressing,” Conor E. Steuer, MD, and Suresh S. Ramalingam, MD, of Winship Cancer Institute at Emory University, Atlanta, wrote in a recent review.