Improved cancer survival with use of common antihistamines. Epidemiological studies on the use of H1-antihistamines and survival in cancer

Abstract: Cancer often results from chronic inflammation, and anti-inflammatory medications are therefore potential candidates for drug repurposing for cancer therapy. H2-antihistamines such as cimetidine have long been studied for their promise as cancer medications, but H1-antihistamines have thus far not been studied widely for this purpose. We have previously shown an association with improved breast cancer survival for use of some H1-antihistamines, and other studies have shown similar results for non-localized cancer, non-small cell lung cancer and ovarian cancer, while evidence is mounting that some H1-antihistamines normally used to alleviate allergic reactions may also have anti-tumor effects. In the four studies that form the basis of this dissertation, we show that some of the most commonly used H1-antihistamines in Sweden – desloratadine and loratadine – are associated with substantially improved survival for patients with melanoma (Study I), breast cancer (Study II) as well as several other immunogenic tumor types (Study III) and quantify the potential effect of a desloratadine intervention, showing that numerous lives may be spared should desloratadine be integrated into cancer therapy (Study IV). We suggest a desloratadine effect as the explanation of our findings, one that is likely immunological in nature, and call for randomized clinical trials of desloratadine as treatment of immunogenic cancers, and if effective, further studies to quantify and elucidate the mechanism.