Chronic kidney disease (CKD), defined as Stages 3-5, including end stage renal disease (ESRD)) at the time of cancer diagnosis is believed to influence cancer outcomes, but the base of evidence for such effects is limited. We seek in this proposal to extend the understanding of CKD as a risk factor for cancer mortality, and to quantify the development of incident CKD in patients treated with specific potentially nephrotoxic cancer regimens. In particular, cisplatin, carboplatin, capecitabine, irinotecan, and etoposide are components of standard cancer treatment protocols, and treated individuals have had an increased CKD risk in some cancers, but the risk following standard lung or colorectal cancer treatment is unknown. Approximately 15% of adults in the United States are estimated to be affected with CKD as of 2020. There is a pressing need to understand the risks of CKD incidence, progression and mortality in the setting of cancer treatment. We will utilize a large, population-based dataset, that of the Surveillance Epidemiology End Results (SEER) program of the National Cancer Institute, linked to Medicare (SEER-Medicare), to address question of import to prognosis in both CKD and cancer. Surprisingly little of the existing literature concerns long-term follow-up. Such evidence could be crucial to reduce nephrotoxicity, acute kidney injury, and ensure that dose-limiting side effects of antineoplastic agents do not prevent effective therapy of the cancer of interest. We will analyze claims data to evaluate whether those with CKD are at greater risk of cancer or CKD-related mortality after cancer treatment, and whether particular therapies might increase the risk of CKD incidence. These analyses should greatly heighten awareness of CKD at diagnosis and that which develops during therapy, leading to additional monitoring, personalized therapy, and potential survival benefits for patients with cancer and CKD alike.