ABSTRACT: Improving the timeliness and quality of care for lung cancer (LC) and head and neck cancer (HNC) patients is of utmost importance because delays in treatment initiation are associated with cancer recurrence, lower survival, and poor patient outcomes (e.g., distress). Rural LC and HNC patients experience significant treatment delays. Compared to urban patients, patients in rural areas face added challenges such as needing to travel long distances to access care, having lower socio-economic status, and having less availability of cancer treatment. The objective of this study is to improve the timeliness and quality of care for LC and HNC patients who are underserved (e.g., low-income, underinsured) and from rural and frontier counties in the Rocky Mountain States, treated by the University of Colorado Health System that serves patients from Colorado and Wyoming and the Sisters of Charity of Leavenworth Health System that serves rural patients from Colorado, Utah, and Montana. We will apply the CARES (Cancer Advocacy, Resources Education, and Support) intervention to target factors specific to rural LC and HNC patients who are underserved and factors that due to their statistical and clinical significance are associated with suboptimal initiation of treatment and poor quality of care for these patients. The hallmark of the CARES intervention is implementing it at key points during LC and HNC treatment, likely augmenting its effects on the outcomes more effectively and more efficiently than current usual care practices. Using a randomized controlled clinical trial (RCT) design, we will compare the CARES intervention effects to the effects of usual care practice on the: (a) time to treatment initiation and (b) time to treatment completion. The CARES intervention also targets (c) quality of care outcomes (e.g., patient communication, coordination of care, providing information to patients) and (d) patient-reported outcomes (e.g., coping, distress, quality of life). Approximately 440 LC and HNC patients will be recruited and randomly assigned to either the intervention (n=220) or to the usual care condition (n=220). We will employ intent-to-treat analyses with linear mixed models (LMMs) to analyze the primary outcome of time to treatment initiation and the secondary outcomes. We predict that those who receive the CARES intervention will improve in all study outcomes to a greater degree than those who received usual care. Our ultimate goal is the dissemination and implementation of the CARES intervention into rural clinical practice to improve the timeliness and quality of care for rural and underserved patients and reduce disparities in LC and HNC morbidity and mortality. Thus, we will assess the pragmatic implementation and scalability of the CARES intervention by evaluating the overall effectiveness of the intervention's strategies, as well as "how and why" they work in real-world practice.