The emerging world of breast cancer immunotherapy

Over the last few years, the developments around cancer immunotherapy (CIT) have led to a paradigm shift in the treatment of many different cancers, in particular melanoma, renal, bladder and lung cancers with a remarkable impact on response rate and, most importantly, overall survival. Breast cancer is most commonly considered to be a 'non-inflamed' cancer and so this shift has been less marked within its treatment. However, some subsets of breast cancer, most notably triple negative breast cancer, are deemed to be more 'inflamed' and therefore may prove to be an appropriate cohort for CIT. This review looks back at the theory of the cancer immunity cycle and mechanism of action behind immune checkpoint inhibitors and goes on to explore their role within the various subtypes of breast cancer. It looks at the first trials performed using CIT monotherapy which demonstrated that breast cancer could respond to CIT with a small population reaping considerable benefit. It then examines the continuing body of work being undertaken to explore CIT in combination with chemotherapy to try to increase the proportion of patients who might reap the considerable rewards on offer.