Peripheral blood eosinophil count is associated with response to chemoimmunotherapy in metastatic triple-negative breast cancer

There is evidence for an association between peripheral blood eosinophil count (PBEC) and response to cancer immunotherapy; however, such data is limited in metastatic triple-negative breast cancer (mTNBC). This report presents patients (n = 14) who received a combination of durvalumab and paclitaxel for mTNBC (NCT02628132). There was a statistically significant correlation (p = 0.028) between an increase in PBEC (>300/mm ) during treatment and response to the combination therapy. Survival analysis showed a statistically significant association between progression-free survival and increased PBEC, after therapy (p = 0.005). A similar trend existed for overall survival, although it did not reach statistical significance (p = 0.167). : This is the first study to report on eosinophilia in mTNBC treated with chemoimmunotherapy and supports a role for eosinophils in immunotherapy for mTNBC. Previous reports have shown that an increase in peripheral blood eosinophil count is associated with a good response to cancer immunotherapy; however, data on this association is limited in a subtype of breast cancer called metastatic triple-negative breast cancer (mTNBC). The eosinophil count in patients who received the combination of an immunotherapeutic agent, durvalumab and a chemotherapeutic agent, paclitaxel, in mTNBC was assessed. There was a statistically significant association between an increase in eosinophils during treatment and the response to therapy. The progression of the disease was slower or less likely to occur in patients with increased eosinophils. This study supports the role of eosinophils in immunotherapy for mTNBC.