Disparities in Biomarker Testing Impact Nonsquamous NSCLC Outcomes: Surbhi Singhal, MD

Biomarker testing is a crucial step for those diagnosed with stage IV nonsquamous non–small cell lung cancer (NSCLC), but nearly one-third of eligible patients did not receive guideline-recommended testing, and there were clear disparities in biomarker testing in a study being presented at the 2025 World Conference on Lung Cancer.

Study author Surbhi Singhal, MD, assistant professor in the division of oncology at the University of California Davis and thoracic medical oncologist at the UC Davis Comprehensive Cancer Center, discussed the findings and how they can inform tailored interventions to improve biomarker testing uptake.

This transcript was lightly edited; captions are auto-generated.

Transcript

What patterns in testing disparities did the study find, and how can these patterns inform tailored interventions to increase uptake in underserved populations?

That's a great question. In our study, nearly one-third of patients did not have biomarker testing, and that's a big deal because this was a highly preselected patient population. We looked at only patients newly diagnosed with stage IV disease, nonsquamous disease, and we required them to receive first-line therapy, so they were well enough to receive that treatment—really a population we would be getting biomarker testing for.

There were several subgroups that emerged as having lower rates of biomarker testing. The big ones were older adults, male sex, and patients from lower socioeconomic status neighborhoods. And then on the converse, the flip side of that, there were the patients who were more likely to get tested: female, younger, and those who identified as Asian. And that's not particularly surprising, because that is the enriched population for these driver mutations.

The results suggest that oncologist perception or pretest probability is likely driving these decisions for the biomarker testing. I think the provider education of not just using pretest probability but also testing all patients with stage IV non-squamous disease who should be getting tested, is 1 huge area that we can tackle as a community, and as an academic community, as well. The other issue that often comes up in the literature that oncologists will provide is they're worried about payer coverage for the testing. In our study, we did not see any differences between public or private insurance and the rates of biomarker testing. But I think as a larger issue when we think about for biomarker testing, really all oncologic treatments, is really transparency in pricing and coverage from payers.

What factors other than biomarker testing status could have affected outcomes in the study population, and how were these addressed in the analysis?

This is a big limitation of the study. This is a population-based cohort study. It's definitely subject to confounding; we found a difference in the overall survival for patients who did or did not have biomarker testing. We ran a multivariable Cox proportional hazards regression. We did multiple adjustments for age, sex, race and ethnicity, socioeconomic status, comorbid conditions, insurance, treatment at an NCI Cancer Center or not at an NCI Cancer Center, and then a number of metastatic disease sites to examine that association with overall survival, and the lack of biomarker testing was associated with a 74% increased hazard of death. And the only other stronger association we identified in that multivariable Cox hazard was older age, and so I think absolutely—this is a population-based study, it's subject to confounding, but given the magnitude that we've seen with the multiple adjustments, not getting biomarker testing is at least somewhat driving that worse overall survival.

Given the survival benefit seen with biomarker testing, what practical steps can oncology practices take to ensure that testing happens early and consistently for all eligible patients?

This is a great question, and I would love to see a big answer for this in our state of California, where we did the study, but also internationally. It's something that we're working on as an institution. One way is routine testing. You could think of reflexive testing for all new tissue diagnoses of non–small cell lung cancer at the point of the pathologist, not necessarily at the point of the medical oncologist. That's one avenue we could be looking at. Another one is routine liquid biopsy testing, or blood testing. In our oncology practice where I work, we're fortunate to be in an academic site where our nurses are very familiar with and working with the thoracic oncologists. Even if a thoracic oncologist, for whatever reason, may have forgotten or didn't notice that the biomarker testing wasn't sent, the nurses are also catching it. Having multiple layers of quick checks and really increasing that awareness of routine testing for everyone with a new stage IV, nonsquamous diagnosis.

Reference

Singhal S, Keegan T, Riess J, Parikh-Patel A, Hofer B, Maguire FB. Stage IV nonsquamous non-small cell lung cancer (NSCLC) biomarker testing disparities and outcomes: a population-based study. Presented at: 2025 World Conference on Lung Cancer; September 6-9, 2025; Barcelona, Spain. Abstract P1.17.03.