Relative survival in patients with cancer and kidney failure.

Background: The population with kidney failure is at increased risk of cancer and associated mortality. Relative survival can provide insight into the excess mortality, directly or indirectly, attributed to cancer in the population with kidney failure.

Methods: We estimated relative survival for people all ages receiving dialysis (n = 4089) and kidney transplant recipients (n = 3253) with de novo cancer, and for the general population with cancer in Australia and New Zealand (n = 3 043 166) over the years 1980-2019. The entire general population was the reference group for background mortality, adjusted for sex, age, calendar year and country. We used Poisson regression to quantify excess mortality ratios.

Results: Five-year relative survival for all-site cancer was markedly lower than that for the general population for people receiving dialysis [0.25, 95% confidence interval (CI) 0.23-0.26] and kidney transplant recipients (0.55, 95% CI 0.53-0.57). In dialysis, excess mortality was more than double (2.16, 95% CI 2.08-2.25) that of the general population with cancer and for kidney transplant recipients 1.34 times higher (95% CI 1.27-2.41). There was no difference in excess mortality from lung cancer between people with kidney failure and the general population with cancer. Comparatively, there was a significant survival deficit for people with kidney failure, compared with the general population with cancer, for melanoma, breast cancer and prostate cancers.

Conclusion: Decreased cancer survival in kidney failure may reflect differences in multi-morbidity burden, reduced access to treatment, or greater harm from or reduced efficacy of treatments. Our findings support research aimed at investigating these hypotheses.