We have previously found that use of the H1-antihistamines desloratadine and loratadine is associated with substantially improved survival in both breast cancer [30] and cutaneous malignant melanoma [31], and in this meta-analysis of our data, we investigate whether a similar association can be seen across multiple tumor types, with and without a known response to treatment with immune checkpoint inhibitors, such as anti-CTLA-4 or anti-PD-1, to shed further light on the possible anti-tumor effect of these antihistamines, and whether it may be immunological in nature. The gene discussed is CTLA4; the disease is breast carcinoma.