PROJECT ABSTRACT Cancer is a large and growing problem among people living with HIV (PLWH). PLWH are far less likely to receive cancer treatment compared to uninfected counterparts. Even PLWH that receive cancer treatment experience worse cancer survival, suggesting that there are additional drivers of outcomes disparities. The disparity in cancer treatment and survival is especially concerning given the near normal life expectancy of PLWH in the era of antiretroviral therapy and the mortality burden faced by PLWH who develop cancer. Although PLWH experience more clinician-reported cancer treatment toxicity leading to early discontinuation of cancer treatment and hospital admission, little is known about the patient perspective of cancer treatment toxicity. Patient-reported outcomes (PROs) provide unique information on how delivered care affects patient health and well-being, and are predictors of poor cancer outcomes in the general cancer population. In Aim 1, we will assess the type, frequency, and severity of PROs for PLWH compared to cancer patients without HIV using the validated PROMIS to measure physical, mental, and social health for all cancer sites. We hypothesize that PLWH with cancer will experience more frequent and severe symptoms compared to HIV- negative cancer patients. In Aim 2, we will examine the relationship between PROs and cancer outcomes, including treatment completion, treatment delays, inpatient admission, cancer recurrence and survival. We hypothesize that higher patient-reported symptom burden will be associated with adverse treatment outcomes, particularly among PLWH. This retrospective study will identify disparities in cancer treatment toxicity for PLWH and HIV-negative cancer patients utilizing a validated PRO and measure associations between toxicity and real world clinical outcomes. Early identification and management of cancer treatment side effects will improve patient-centered, personalized and equitable cancer care for PLWH, thereby reducing cancer disparities and improving survival for this marginalized population.