Low immune index correlates with favorable prognosis but with reduced benefit from chemotherapy in gallbladder cancer

Use of immune index is a new potential approach for cancer classification and prediction. To investigate the status and clinical effect of immune index in gallbladder cancer (GBC), 238 GBC patients from Zhongshan Hospital affiliated to Fudan University were involved in the present study, including 113 patients in a training set and 125 patients in a validation set. Five immune cells (macrophages, neutrophils, regulatory T cells, cytotoxic T cells and mast cells) were selected based on a literature review and the immune index for each patient was calculated using the LASSO regression. A low immune index (<1) was defined as immunotype A and a high immune index (≥1) was defined as immunotype B. The 5‐year overall survival rate for immunotype A was higher than that for immunotype B in the training set and the validation set (70.0% vs 37.0%, P  < 0.001; 68.9% vs 47.5%, P  = 0.002; respectively). Moreover, the immune index showed higher prediction efficiency compared with all the single immune cells which we selected. When combined with the immune index, the areas under the curve (AUC) of the TNM staging system in both sets were elevated from 0.677 to 0.787 and from 0.631 to 0.694, respectively. Interestingly, gemcitabine‐based chemotherapy only benefits stage II patients of immunotype B and stage III patients of both immunotype A and immunotype B ( P  = 0.015, P  = 0.030, P  = 0.011, respectively) but does not work in stage II patients of immunotype A ( P  = .307). Taken together, the immune index could effectively predict prognosis and the benefits of gemcitabine‐based chemotherapy and might improve on the TNM staging system.