More negative data for checkpoint inhibition in treatment of mCRPC

Alas … once again we hear that the combination of  androgen receptor blockade (with enzalutamide/Xtandi) + a checkpoint inhibitor (the PD-L1 inhibitor atezolizumab/Tecentriq) has had no clinically meaningful impact on the overall survival (OS) of men with metastatic, castration-resistant prostate cancer (mCRPC) compared to enzalutamide alone.

The results of the randomized, Phase III IMbassador250 trial were presented by Sweeney and colleagues at the recent (virtual) meeting of the American Association for Cancer Research.

There is a nice report on Dr. Sweeney’s presentation here, on the MedPage Today web site. Basically:

  • Men treated with enzalutamide + atezolizumab had a median OS of 15.2 months.
  • Men treated with Aenxalutamide had a median OS of 16.6 months.
  • Radiographic progression-free survival (rPFS) was comparable for men in both arms of the trial.
  • Time to PSA progression also did not differ between the treatment groups.
  • Treatment-related adverse effects were more evident in men on the enzalutamide + atezolizumab regimen.

At this time, it appears that the only patients with advanced prostate cancer who may benefit significantly from treatment with a checkpoint inhibitor is the very small subset of men with certain types of microsatellite instability-high (MSI-H) or mismatch repair deficient tumors.

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