Although the only FDA-approved regimen for the treatment of patients with pleural malignant mesothelioma is the chemotherapy combination of pemetrexed and cisplatin, clinical trials of combination immunotherapy are showing impressive overall survival (OS) data.
MAPS2, an academic Intergroupe Francophone de Cancérologie Thoracique-sponsored, non-comparative randomized phase II trial, evaluated the PD-1 inhibitor nivolumab (Opdivo) alone and in combination with the CTLA-4 inhibitor ipilimumab (Yervoy) in patients with mesothelioma who relapsed on prior treatment with pemetrexed and platinum chemotherapy.
Lead MAPS2 study author Gerard Zalcman, MD, presented the OS results during the 2017 ESMO Congress. These results showed that the 1-year OS rate was 51% with nivolumab (Opdivo) and 58% with the combination of nivolumab and ipilimumab.
In an interview with OncLive
, Zalcman, head of Thoracic Oncology Department, Hôpital Bichat-Claude Bernard, Université Paris-Diderot, reviewed the MAPS2 trial and discussed the promise of immunotherapy in patients with mesothelioma.
OncLive: Can you comment on the MAPS2 results?
: We presented the updated results of the randomized phase II trial MAPS2, or IFCT-1501, on behalf of the French Intergroup. This was a trial assessing nivolumab, or nivolumab plus ipilimumab, in patients with mesothelioma in the second- or third-line setting. It was a noncomparative randomized trial, so we are not allowed to compare the 2 arms directly. The median follow-up was 15 months.
The most remarkable data of this presentation are the OS data. This showed that, with nivolumab, the median OS is 13.6 months, which is amazing in this setting and these patients. The median OS of the nivolumab plus ipilimumab arm has not yet been reached after 15 months of follow-up, suggesting that it could be over 15 months.
This trial ran very fast because we accrued 125 patients within 5 months, and the last patient was accrued in September 2016. There were no specific signals to worry about in this toxicity profile. There were slightly more immunological side effects in the combination arm, but nothing that was statistically significant. There were 3 toxic deaths in the combination arm, which occurred very early in the study course, and with no more grade 5 events after. This suggests that the investigators have learned how to manage such immunologic toxicities.
We also presented data about PD-L1 immunohistochemistry (IHC) expression, showing that PD-L1 expression as defined by more than 1% of tumors cell stain with the anti–PD-L1 antibody was associated with overall response. When we selected the stronger expressers—meaning more than 25% of tumor cells—this was associated with overall response and disease control rates.
For OS, it is more complex. In the nivolumab arm, PD-L1–positive patients did better than the PD-L1–negative group. However, in the combination arm, the PD-L1 IHC had no influence on OS. Therefore, PD-L1 as a biomarker could be a good marker for nivolumab, but is not a good biomarker for the combination.
What is the first-line standard of care for patients with mesothelioma?
Currently, first-line mesothelioma treatment is based on the backbone of pemetrexed/cisplatin chemotherapy plus or minus bevacizumab (Avastin). The median OS ranges from 15 to 19 months and there is currently no recognized second-line treatment for this disease. Therefore, the positivity of this MAPS2 trial support the use of immunotherapy as second- and third-line therapy. This has actually been written as an option by the NCCN panel. The company developing these drugs is going to seek a breakthrough application with the FDA.
There is a large phase III trial running in the first-line setting comparing the combination of immunotherapy with standard chemotherapy. In the near future, we will use chemotherapy in the second- and third-line settings. Moreover, if the phase III trial is positive, it could go to the first-line setting with double immunotherapy of nivolumab plus ipilimumab.
In terms of PD-L1 testing, how many patients tested positive? What about other potential biomarkers?
Roughly 50% of patients are expressing at least 1% of PD-L1, there are few patients expressing over 25%. Globally, although mesothelioma is an inflammatory tumor, the tumor's PD-L1 expression is not so high—at least not in the clone that we use, the 28-8 antibody.
Currently we don't know what could be a good biomarker for mesothelioma. One reason is that this is a tumor where the mutational tumor burden is very low. In the famous schematic representation that has been published in Nature
, mesothelioma stands at the left of the scheme, meaning that there are few mutations. Therefore, something like mutational burden will not be a good biomarker. We will try to test, but I don't think we are expecting it to be a good biomarker.