1854P - Pemetrexed/cisplatin versus gemcitabine/cisplatin as first-line treatment for Egyptian patients with malignant pleural mesothelioma

The combination of cisplatin and pemetrexed is considered the standard of care front line regimen for malignant pleural mesothelioma (MPM). Several phase II trials demonstrated comparable response and survival rates with the use of gemcitabine and cisplatin. Few retrospective studies have compared the two regimens and with conflicting results. However, no prospective clinical trial has compared them directly. Between June 2015 and September 2017, 51 chemotherapy-naïve MPM Pts were randomized 1:1 to receive either pemetrexed (500mg/m2) and cisplatin (75mg/m2) (PC) or gemcitabine 1000mg/m2 on days 1 and 8 combined with cisplatin (75mg/m2) on day 1 (GC). Chemotherapy was repeated every 3 weeks for a maximum of six cycles unless there was earlier evidence of disease progression or unacceptable toxicity. We used modified RECIST criteria for mesothelioma to evaluate treatment response and CTCAE v4.0 to assess toxicity. The mean age was 52.5 years with males representing 51% of Pts. The ECOG PS was 0, I, and II in 3.9, 86.3, and 9.8% of cases, respectively. Epithelial histology was the most common (88.2%) followed by biphasic (9.8%) and sarcomatoid (2%). 6 pts had stage II disease, whereas 45 had stage III or IV. The baseline characteristics of the PC arm (N=26) and GC arm (N=25) were well-balanced in the age, gender, ECOG, pathology, and stage. RR with PC was 53.8% compared with 36% for GC (p value= 0.132). Significant superiorities in PFS and OS were observed with PC therapy. For the PC pts, the median PFS was 10.45 vs. 8.4 months for the GC Pts (log-rank p-Value < 0.001, HR=3.23, CI (95%) = 1.693 − 6.175). The median OS was 16.15 months for the PC arm and 13.1 months for the GC arm (log-rank p-Value = 0.020, HR=1.91, CI (95%) = 1.042 − 3.496). In general, hematological toxicities were more frequent in both arms in comparison to other types of toxicities. Neutropenia tended to be more severe with GC, whereas nausea was more frequent with PC. However, these differences in toxicity were statistically insignificant. First-line treatment of MPM with PC resulted in statistically significant improvement in PFS and OS compared to GC, therefore it should remain the standard of care for this group of pts. Ain Shams Faculty of Medicine IRB. Has not received any funding. All authors have declared no conflicts of interest.