A major breakthrough in cancer immunotherapy was the discovery of immune checkpoint proteins, which function to effectively inhibit the immune system through various mechanisms. The first of such molecules shown to inhibit both T-cell proliferation and IL-2 production was cytotoxic T-lymphocyte associated protein 4 (CTLA-4). With this discovery, efforts turned to blocking this inhibitory pathway in an attempt to activate dormant T-cells directed at cancer cells. The first antibody directed against CTLA-4, ipilimumab, was quickly ushered into clinical trials and was approved by the US Food and Drug Administration (FDA) for the treatment of metastatic melanoma in 2011. Following the success of ipilimumab, other immune checkpoints were studied as possible targets for inhibition. One such interaction was that of the programmed cell death-1 (PD-1) T-cell receptor and its ligand found on many cancer cells, programmed death-ligand 1 (PD-L1). Unfortunately, the untoward effects of blocking the immune system's natural inhibitory mechanisms have manifested clinically as diarrhea, rash, and hepatitis. Nevertheless, the exciting field of immune checkpoint inhibitors offers a potential curative option for many cancer patients who previously had a more dismal prognosis. The authors aim to provide a comprehensive review of the literature and update on the use of CTLA-4, PD-1 and PD-L1 targeted therapy in the treatment of cancer and other molecules still in the early development phase.

Background The aim of this study was to prospectively screen patients with a positive family history of carcinoid small intestine neuroendocrine tumors (SI-NETs) to elucidate the benefits of early detection and operative intervention. Methods A single-center, prospective trial was conducted from 2008 to 2014 that evaluated patients with 2 or more blood relatives with carcinoid SI-NETs. All eligible patients were screened with urine/serum biochemistries and various imaging modalities. Operative intervention was elected in patients found to have at least 1 positive diagnostic study. Results Twenty-nine patients from 13 families had occult carcinoid SI-NETs (15 female, 14 male). Twenty-four of the 29 patients (83%) had multifocal disease found in either the distal jejunum or ileum. On average, 75.9 cm (range, 13–195) of bowel was resected in 1 segment. Three patients were found to have stage IV disease at operation. All stage I-IIIB patients who had R0 resections have remained disease-free, with a median follow-up of 35 months. Conclusion Familial carcinoid SI-NETs often are asymptomatic and can be diagnosed with aggressive screening. With early detection, there may be a window of opportunity for operative resection to change the natural history of this disease and even prove to be curative.

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