A commentary notes that this is a thought-provoking and hypothesis-generating piece of work, and advises caution before jumping directly to radical conclusions and before changing the current standard of care among approved indications for immune checkpoint inhibitors. It stresses that female patients who are otherwise indicated for treatment with any immune checkpoint inhibitor should not be denied treatment solely on the basis of these findings. It calls for further prospective studies that are disease-specific and that account thoroughly for potential confounders before a final judgment can be made about the effect of the patient's gender on the efficacy of these agents. It adds that the results of ongoing studies of immune checkpoint inhibitors in cancers that mainly or solely affect women might provide an additional insight into the mechanism of action of these drugs in women, as well as further establishing whether the apparently decreased efficacy activity of these drugs in women is a reflection of differences in patients' sex, or a reflection of differences in tumour biology.