Contrary to its role in lung cancer, PD-L1 expression does not predict benefit from immunotherapy in mesothelioma. Data from major trials shows similar outcomes regardless of PD-L1 status, leading clinicians to omit this test entirely and streamline treatment decisions.

Given that PD-L1 scores for gastroesophageal cancers can be exceptionally variable between labs, some clinicians prefer a simple CPS cutoff of 1. This 'some expression versus no expression' approach is considered more reproducible and practical for decision-making than relying on specific higher scores that may not be consistent across different testing sites.

Data from the KEYNOTE-671 trial demonstrates a meaningful survival benefit from perioperative pembrolizumab even in patients with PD-L1 negative (<1%) tumors. This finding supported broad regulatory approval without PD-L1 restrictions, suggesting the biomarker is not an absolute requirement for benefit in this setting.

With the rise of targeted therapies, about 25% of gastric cancers are now considered "triple negative": Claudin-negative, HER2-negative, and PD-L1 negative. This newly defined subgroup represents a significant unmet need and highlights the necessity for novel treatment strategies beyond current biomarkers.

In the increasingly common scenario of gastric cancer with multiple biomarkers (HER2, PD-L1, Claudin), experts recommend a clear hierarchy. Based on data maturity, HER2-targeted therapy is the first choice, followed by PD-L1 immunotherapy, with Claudin-targeted therapy third.

A PD-L1 CPS score of zero should not automatically disqualify patients with metastatic anal cancer from receiving immunotherapy. The clinical distinction between a CPS of zero and one is marginal, and given the therapy's potential for benefit and low toxicity, clinicians should give patients the benefit of the doubt and offer the treatment.

An expert argues forcefully that the PD-L1 biomarker should be "ditched" in bladder cancer. Citing its repeated failure to predict overall survival benefit across multiple major trials, it is deemed an oversimplified and unreliable tool that leads to both over- and under-treatment of patients.

Despite stratifying patients by PD-L1 status, the AGO-OV-229 trial found it was not a predictive marker. Hazard ratios for survival were similar for both PD-L1 positive and negative tumors, challenging its utility for patient selection.

Unlike in lung cancer, PD-L1 expression levels do not guide treatment for nonmelanoma skin cancers. Patients with low or even negative PD-L1 levels still show significant response to anti-PD-1 therapy, making the test an unhelpful discriminator for treatment decisions.