Income inequality and access to advanced immunotherapy for lung cancer: the case of Durvalumab in the Netherlands

Abstract

With the introduction of immunotherapy with non-small lung cancer, prognosis of these patients has improved. However, socio-economic differences in access to various immunotherapy treatments have been reported. In the Netherlands, such differences are not expected due to universal insurance coverage. We investigated the existence of differential susceptibility by socioeconomic status (SES) of the effect of distance to treatment hospital on access to Durvalumab in patients with stage III non-small lung cancer who received chemoradiation, and the influence of differential mortality. We used data from the Netherlands Cancer Registry (n = 3774) from the period 2017-2021. First, we fitted Bayesian discrete failure time models and compared SES-by-distance-to-hospital interaction to a baseline model including age, distance, SES and performance score. We then fitted a time to mortality model and used both models in a g-formula to simulate a scenario where mortality levels were equalized. Our results showed that the high SES group received Durvalumab more often than the low SES group (HR = 1.23, CI95% = [1.07, 1.53]), and showed a strong negative effect of distance (OR = 0.63, CI95% = [0.54, 0.72]). Bayes factor < 3 indicated inconclusive evidence for a SES by distance interaction effect, while g-formula results showed virtually no influence from differential mortality on SES differences. Secondary analyses showed strong evidence that SES differences in using Durvalumab were constant over the years (Bayes factor > 17). Overall, these results are significant for understanding how socio-economic inequality affects proper care and can be vital for public policy.