Response to re-challenge of a MEK inhibitor in a patient with recurrent low-grade serous carcinoma of the peritoneum.

Low-grade serous carcinoma of the ovary/peritoneum is a rare epithelial cancer subtype characterized by younger age at diagnosis, relative chemoresistance, and prolonged overall survival compared with high-grade serous carcinoma. In addition, alterations in the mitogen activated protein kinase pathway are frequent and play a major role in the pathogenesis of this tumor. MEK inhibitors have demonstrated promising activity in the treatment of recurrent low-grade serous carcinoma. Although prevailing wisdom in cancer therapy is that the re-treatment with a drug after emergence of resistance is futile, we report the initial case of a patient with recurrent low-grade serous carcinoma who experienced a partial response when re-challenged with a MEK inhibitor after previously having prolonged stable disease followed by disease progression on a MEK inhibitor.