Immunotherapy experience in malignant pleural mesothelioma in a single tertiary center.

e20565 Background: Malignant pleural mesothelioma (MPM) is a rare and aggressive cancer. Prognosis is generally poor, with a median overall survival (mOS) of approximately 12 months. MPM appears to be directly linked to immunosuppressive mechanisms, leading to use of checkpoint inhibitors for patients with this disease. Methods: We performed a retrospective chart review of patients with MPM at our institution between January 2015 to December 2020. All patients were over 18 years at the time of diagnosis of mesothelioma, a total of 8 patients were retrieved from the pathology database of The American British Cowdray Medical Center. The clinical-pathologic features collected were sex, age, performance status, risk factors, pTNM stage (AJCC 8th edition), histology type, sintomatology of onset, metastases sites and treatment. Clinical response rate and other outcomes were assessed. Descriptive statistics were used to describe a patient's demographic and disease characteristics. Results: 8 patients, aged 49 to 71 years (median of 65) at diagnosis of MPM were treated in our center. Both sex presented 4 patients in total. An identifiable risk factor was recorded in 4 patients (2 with asbesto exposure and 2 with heavy smoking). 7 patients (87.5%) had PS 0 or 1, the remaining has PS 2. The clinical stage at diagnosis was unresectable in 7 patients. 3 patients were assessed with PD-L1 expression (SP263 or 22C3), only one with expression of 20%. All patients received at least one scheme of chemotherapy prior to receiving immunotherapy, 25% received bevacizumab/platinum/anti-folate agents. Checkpoint inhibitors were introduced as a second line in 20% and in 80% has a third or more lines. Pembrolizumab was used in 20% and Nivolumab in 80%. The tumor responses with immunotherapy were as follows: partial response 12.5%, stable disease 75% and progressive disease 12.5%. Median progression-free survival of the first line treatment was 18.9 months (4.6-33.6 months), and for the line with checkpoint inhibitors was 11.2 weeks (7-21.2). In the full cohort, mOS was 37.0 months (95% CI:14.5-39.6). According to histology, the mOS for epithelioid-type was 36.6 months and for biphasic-type was 14.6 months (p = 0.42). mOS was 37.0 months for the group with immunotherapy and 15.0 months for those with standard chemotherapy (p = 0.14). The most frequently reported immune mediated adverse events were hypothyroidism and colitis (each one with one patient). Conclusions: In this real-world analysis, mOS was superior to those obtained in the MAPS2 trial (mOS 11.9 months), despite the fact that 80% of the population that received immunotherapy was in third or more lines. Limitations include limited numbers of patients, retrospective review, single institution, and inclusión of many heavily pretreated patients. Also molecular and immunohistochemical results such as PD-L1 status were only available on a limited number of patients.