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

With the introduction of immunotherapy with nonsmall cell lung cancer, prognosis of these patients has improved. However, socioeconomic 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 nonsmall cell 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 (hazard ratio = 1.26; 95% credible interval = [1.06, 1.53]), and even 4 km distance increase leads to less Durvalumab (hazard ratio = 0.93; 95% credible interval = [0.86, 0.99]). Bayes factor < 3 indicated inconclusive evidence for a SES by distance interaction effect, while g-formula results showed that differential mortality does not affect 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 socioeconomic inequality affects proper care and can be vital for public policy.