Epidemiologic perspectives on immunosuppressed populations and the immunosurveillance and immunocontainment of cancer.

The advent in the last several years of effective immunotherapy for cancer has renewed interest in the role of the immune system in controlling cancer. The idea that the immune system can help control cancer has a long history. Solid organ transplant recipients (SOTRs) as well as human immunodeficiency virus (HIV)-infected people are affected by cell-mediated immune dysfunction. Epidemiologic studies of these populations reveal a pattern characterized by a strongly increased incidence of virus-related cancers (eg, Kaposi sarcoma, non-Hodgkin lymphoma, and anogenital cancers). In addition, recent epidemiologic studies have evaluated cancer-specific mortality among SOTRs and HIV-infected people following a cancer diagnosis. For a wider range of cancers-not limited to those caused by viruses, and including melanoma and cancers of the colorectum, lung, and breast- these immunosuppressed cancer patients have higher cancer-specific mortality than other cancer patients. This latter group of cancers somewhat mirrors those for which immunotherapy with checkpoint inhibitors is approved. These epidemiologic observations suggest that there are 2 distinct immune selection processes in humans: immunosurveillance directed against premalignant cells before cancer diagnosis (most relevant for preventing virus-related cancers), and "immunocontainment" directed against established cancers. These processes thus appear relevant for different groups of malignancies and may have different mechanisms.