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MA20 - Thymic Tumors: From Molecular to Clinical Results and New Challenges in Other Rare Thoracic Tumors (ID 149)
- Event: WCLC 2019
- Type: Mini Oral Session
- Track: Thymoma/Other Thoracic Malignancies
- Presentations: 1
- Now Available
- Moderators:Kazuya Kondo, Edith Michelle Marom
- Coordinates: 9/10/2019, 11:30 - 13:00, San Francisco (2009)
MA20.05 - Follow-Up Update of 2 Phase II Studies of Pembrolizumab in Thymic Carcinoma (Now Available) (ID 1120)
11:30 - 13:00 | Author(s): Jinhyun Cho
Two phase II studies of pembrolizumab 200 mg every 3 weeks in advanced thymic carcinoma have recently been published (Giaccone et al. Lancet Oncol. 2018, study #1; Cho et al. JCO 2018, study #2). Both studies reported a response rate in about 20% of patients and a rate of autoimmune disorders that is higher than in other tumor types.Method
This report provides a follow-up update of these 2 studies, with particular emphasis on duration of response, and occurrence of autoimmune disorders. Both studies included patients with thymic carcinoma who had progressed after at least one line of chemotherapy.Result
In study #1 a total of 40 patients with advanced thymic carcinoma were treated, with a median follow up of 40.6 months. The response rate did not change (22.5%) compared to the original publication, however one patient who had developed myositis, myocarditis and myasthenia gravis (MG), continues to be in nearly complete response after only two cycles of pembrolizumab, 36 months from initiation of treatment. One patient who had developed myositis and hepatitis with unclear signs of MG developed overt MG symptoms several months after the interruption of therapy. No other new autoimmune disorders were observed (6/40 = 15%). Five patients completed 2 years of treatment according to protocol and 4 of them elected to continue treatment. Three patients who had been off therapy were rechallenged with pembrolizumab upon progression (one responded). Median duration of response was 38 months (from 22.4 in initial report), median PFS was 4.2 months (identical) and median survival was 25.8 months (24.9 in the initial report).
At completion of this study, an amendment was introduced to add epacadostat 10 mg BID to pembrolizumab in the same patient population. Four patients were treated before the study was closed after the results of a randomized trial of the combination in melanoma failed to meet its primary endpoint. No patient responded (2 stable and 2 progressions). One patient developed grade 2 myocarditis.
In study #2 a total of 26 patients with advanced thymic carcinoma were included, with a median follow up of 33.4 months. The response rate (19.2%) did not change, and no other autoimmune disorder appeared since the initial publication (5/26 = 19%). Median duration of response (9.7 months), median PFS (6.1 months) and median survival (14.5 months) did not change compared to the initial publication. No additional autoimmune disorders were documented compared to the original publication. A total of 5 patients received 2 years of pembrolizumab according to protocol; no patient continued beyond 2 years or was retreated upon progression with pembrolizumab.Conclusion
These two studies confirm definite activity of pembrolizumab in advanced thymic carcinoma. Recently pembrolizumab was included in the NCCN guidelines for thymic carcinoma. No additional autoimmune disorders were noted after discontinuation of pembrolizumab. There are significant differences in duration of response and overall survival in the 2 studies and potential factors are being investigated. In study #1 pembrolizumab was continued beyond 2 years in several patients and rechallenge was an available option.
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