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OA08 - Mesothelioma: Immunotherapy and microRNA for Diagnosis and Treatment (ID 907)
- Event: WCLC 2018
- Type: Oral Abstract Session
- Track: Mesothelioma
- Presentations: 1
- Coordinates: 9/24/2018, 15:15 - 16:45, Room 201 BD
OA08.03 - Phase II Trial of Pembrolizumab (NCT02399371) In Previously-Treated Malignant Mesothelioma (MM): Final Analysis (ID 12045)
15:35 - 15:45 | Author(s): Christopher Straus
We conducted a phase II trial to assess the activity of pembrolizumab in a non-selected population of mesothelioma patients and determine a PD-L1 expression threshold.a9ded1e5ce5d75814730bb4caaf49419 Method
Eligible patients had histologically-confirmed pleural or peritoneal MM, PS 0-1, prior pemetrexed/platin, disease progression on ≤2 prior regimens. Pembrolizumab 200 mg was administered Q21 days; CT scans were obtained Q9 weeks. The primary endpoints determined: 1) the objective response rate (ORR) in an unselected and a PD-L1 positive population; 2) the optimal threshold for PD-L1 expression using the 22C3 IHC tumor cell/tumor proportion score (TPS) assay. Proceeding to a second stage required ≥3 responses in 35 PD-L1 unselected patients in Part A. Part B would PD-L1 preselect only if a threshold was determined in Part A. At WCLC 2016, we reported 7 responses in Part A, and no PD-L1 threshold was identified (ROC 0.62). Thus, Part B enrolled 30 additional patients without biomarker enrichment.
65 patients enrolled 5/15-2/18; 1 withdrew. PS 0: 53%; male: 77%; median age: 68 (range 26-85); 1 prior chemotherapy 61%; pleural 87.5%; epithelioid 76.6%, biphasic 15.6%, sarcomatoid 7.8%. Mean cycles: 9 (range 1-34). Partial response: 19%, stable disease: 47%, disease control rate: 66%. ORR by histology: epithelioid 16%, biphasic 10%, sarcomatoid 40%. ORR by disease site: pleural 20%, peritoneal 12.5%. Median progression-free survival: 4.5 months (95% CI: 2.3, 6.2). Median overall survival: 11.5 months (95% CI: 7.6, 14). Grade ¾ toxicity: adrenal insufficiency 3%, pneumonitis 3%, rash 3%, colitis 1.6%, confusion 1.6%, hepatitis 1.6%, hyperglycemia 1.6%. Grade 5: hepatitis 1.6%, unknown 1.6%. PD-L1 expression by TPS (N = 62): none (< 1%) 45%; low (1-49%) 32%; high (≥50%) 23%. ORR by TPS: none 7%, low 26%, high 31%. PD-L1 did not correlate with RR as a continuous metric (ROC area 0.65; 95% CI: 0.48, 0.82), though there was a trend towards a higher ORR in PD-L1 ≥1% (28%) compared with PD-L1 <1% (7%). Median PFS by TPS: none 3.1 months, low 6.2 months, high 6.1 months; 1-year PFS by TPS: none 7%; low 7%; high 31%.8eea62084ca7e541d918e823422bd82e Conclusion
Single-agent pembrolizumab has robust activity in PD-L1 unselected, previously-treated mesothelioma. There were no unexpected toxicities. Responses were more frequent in pleural and sarcomatoid MM. Although an optimal PD-L1 threshold could not be identified, a trend towards a higher response rate and more durable PFS with increasing PD-L1 expression was observed. Funded in part by a Mesothelioma Foundation grant.6f8b794f3246b0c1e1780bb4d4d5dc53
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