Raising the bar for enthusiasm when looking at results of randomized phase II trials—the case of sunitinib in small-cell lung cancer

With the advent of targeted agents, randomized phase II trials designed with explicit comparative intent, to allow a better interpretation of the results obtained with experimental treatment, have become a common approach for anti-cancer drug development. In the Cancer and Leukemia Group B (CALGB) 30504 randomized phase II trial, patients with extensive-stage small-cell lung cancer (SCLC), without progression after four to six cycles of standard chemotherapy with cisplatin or carboplatin plus etoposide, were randomized to sunitinib or placebo, until disease progression. Primary endpoint of the study was progression-free survival (PFS), and the results were formally positive [hazard ratio (HR) 0.62; one-sided P=0.02]. However, the prognosis of patients with extensive-stage SCLC is particularly bad, and even a relevant relative benefit (i.e., an encouraging HR) will likely correspond to a debatable absolute benefit: the difference in median PFS between patients treated with sunitinib and patients assigned to control arm was slightly higher than 1.5 months. Is this difference in median PFS big enough to predict a clinically relevant benefit in overall survival? Unfortunately, we do not know. From a “clinical” point of view, is this small absolute improvement in PFS relevant enough to further invest in the strategy? Probably not, also considering the absence of known predictive factors. If the results of the phase II trial had been really promising, the subsequent phase III study should have been promptly conducted, but this was not the case. It seems that, this time, the bar for enthusiasm was already raised in the phase II setting.