Lack of everolimus diffusion in pleural fluid during pleural progression of breast cancer: A case report

Background We report here a case where no everolimus pleural diffusion was evidenced at the same time of pleural progression of a metastatic breast cancer treated with everolimus and exemestane. Case description A 69-year-old woman was diagnosed in October 2006 with stage III invasive ductal breast adenocarcinoma. After nine months of everolimus and exemestane treatment, she presented with a pleural progression. Everolimus concentration was measured in blood and in pleural fluid. Residual blood concentration was at 9.1 ng/mL, while no everolimus was observed in the pleural fluid. Management and outcome Due to inefficacy of everolimus in this patient, she was switched to palbociclib and fulvestrant. Conclusion Everolimus seems to have a poor diffusion in the pleural fluid.