Ongoing challenges of using immunotherapy in special populations: Poor performance status patients, elderly patients,...

Immunotherapy with immune checkpoint inhibitors (ICIs) represents a breakthrough in lung cancer treatment. The efficacy of monoclonal antibodies targeting the programmed cell death protein 1 (PD-1), its ligand L1 (PD-L1), and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) pathways has been demonstrated in several randomized trials, resulting in significantly improved survival rates in lung cancer patients, especially those with non-small-cell lung cancer (NSCLC), compared to standard chemotherapy. Hence, new therapeutic options have been opened up for advanced-stage lung cancer patients. However, most clinical trials on ICIs conducted so far have either excluded patients with poor performance status (PS) or chronic infections like human immunodeficiency virus (HIV), or accrued only a minor proportion of elderly patients despite the lack of an upper age limit. Our review paper provides a brief summary on the ICI data obtained so far in these special populations. Further dedicated studies are urgently needed to enable us to draw definitive conclusions on the usefulness of ICI in these special patient populations. The combination of ICI and chemotherapy must also be further assessed. It would, additionally, be useful to determine reliable biomarkers that should help us identify those patients who are more likely to benefit from ICI therapy.