Pemetrexed in patients with thymic malignancies previously treated with chemotherapy

Thymic malignancies are rare, with limited published trials of chemotherapy activity. We performed a retrospective analysis of pemetrexed activity in patients with thymic malignancies.

Patients with unresectable histologically confirmed invasive, recurrent, or metastatic thymoma or thymic carcinoma seen at the Stanford Cancer Center between January 2005 and November 2013 were identified, and those who were treated with pemetrexed in the second-line setting and beyond were included in this analysis.

A total of 81 thymic malignancy patients were identified, of whom 16 received pemetrexed alone (N=14) or in combination (N=2). There were 10 patients (62.5%) with thymic carcinoma and 6 patients (37.5%) with thymoma. Among the 6 patients with thymoma, best response was 1 (17%) with a partial response (PR) and 5 (83%) with stable disease (SD). At a median follow-up of 21.2 months, the median PFS in the thymoma patients was 13.8 months (95% CI, 4.9-22.6 months) and the median OS was 20.1 months (95% CI, 16.4-23.9 months). Among the 10 patients with thymic carcinoma, best response to treatment was 1 (10%) PR, 5 (50%) SD, and 4 (40%) progressive disease (PD). At a median follow-up of 13.5 months, the median PFS in patients with thymic carcinoma was 6.5 months (95% CI, 0.2-12.8 months) and the median OS was 12.7 months (95% CI, 2.9-22.5 months).

This small retrospective study demonstrates modest pemetrexed activity and disease stabilization in thymic malignancies with a clinically meaningful duration, and supports previous reports of pemetrexed efficacy in these rare diseases.