532P - The changes of the serum SMRP levels is useful to predict the antitumor efficacy of ipilimumab plus nivolumab combination therapy in patients with malignant pleural mesothelioma

Background

Immune checkpoint inhibitors (ICIs) have come to be used for the treatment of the patients with malignant pleural mesothelioma (MPM). Although modified RECIST (mRECIST) criteria is the standard method to evaluate the antitumor efficacy of ICIs, it is sometimes difficult to distinguish progressive disease from pseudoprogression (PsPD). While serum soluble mesothelin related peptide (SMRP) is commonly known as a specific tumor marker of MPM, the significance of SMRP levels in determining the efficacy of ICI treatment has not been established.

Methods

We investigated the relationship between changes of serum SMRP levels and treatment response in MPM patients treated with ipilimumab plus nivolumab combination therapy at our hospital between June 2021 and January 2023.

Results

Twenty-eight patients were included in the study. Median age was 75 years (59-85). The number of histological subtypes of epithelioid, sarcomatoid, biphasic and desmoplastic were 18, 6, 3 and 1, respectively. Treatment response was evaluated by mRECIST. The number of patients who achieved partial response (PR), stable disease (SD) and progressive disease (PD) were 9, 16 and 3, respectively. Among 25 patients with PR and SD, PsPD was observed in 5 patients (PR/SD: 3/2). The median serum SMRP before treatment in all patients was 0.90 nmol/L (0.4 - 16.9)., and the change from baseline at the time of first evaluation was +0.1 nmol/L (-4.5 - +24.5), The median change of serum SMRP level from baseline in patients with PR, SD, PsPD and PD was 0.0 nmol/L (-1.0 - +1.4), +0.1 nmol/L (-4.5 - +4.5), +0.2 nmol/L (-0.9 - +0.9) and +19.5 nmol/L (+0.1 - +24.5), respectively. These results indicated that serum SMRP level in patients with PD already tended to increase at the time of first evaluation.

Conclusions

Our results suggested that changes in serum SMRP levels was useful in determining the efficacy of ICI treatment. We are planning to accumulate more cases in the future for further investigation.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.