New clinical and experimental approaches for studying tumor dormancy: does tumor dormancy offer a therapeutic target?

Tumor dormancy is a significant clinical problem. Primary treatment of a cancer may be apparently successful, and yet the tumor may recur either locally or as distant metastases years or even decades later. The ability to predict which patients are likely to develop recurrences is imprecise, relying on probabilities of recurrence based on features of the primary cancer. This uncertainty presents clinical challenges regarding who to treat and how, in order to prevent recurrence after periods of dormancy. Recent clinical trials in breast cancer support the idea that some patients may harbor tumor cells that are capable of forming late-developing metastases years after removal of the primary tumor, and that these dormant cancer cells may in some cases be effectively treated with long-term therapy. Advances in experimental studies of tumor dormancy are shedding light on the nature of dormancy, and are providing both new technologies and conceptual approaches for studying tumor dormancy. A better understanding of mechanisms responsible for tumor dormancy and recurrence will be important for improving care of patients at risk for late-developing metastases.