Comorbidity burden in cancer patients with rheumatologic diseases: A retrospective cohort analysis.

531 Background: Patients with rheumatologic diseases who develop malignancy may carry a distinct comorbidity burden that affects clinical outcomes. Understanding these patterns is critical for risk stratification and optimizing multidisciplinary care. The purpose of this study is to evaluate the prevalence and risk of common comorbidities in cancer patients with underlying rheumatologic diseases compared to those without rheumatologic disease. Methods: We conducted a retrospective cohort study using the I2B2 database to evaluate the association between rheumatologic disease and comorbidity burden in adult cancer patients. Patients with both cancer and a rheumatologic disease were identified and compared to a control group of cancer patients without rheumatologic disease using ICD-9 and ICD-10 codes. The prevalence of six major comorbidities including hypertension (HTN), heart failure (HF), ischemic heart disease (IHD), chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), and diabetes mellitus (DM) was assessed in each group. The control group population was determined by excluding each comorbidity in patients who had cancer. Statistical analysis was performed using relative risks (RRs), odds ratios (ORs), and 95% confidence intervals (CI) to quantify the strength of associations. Results: A total of 8,724 cancer patients with rheumatologic disease and 347,489 cancer patients without rheumatologic disease were included in the analysis. The presence of rheumatologic disease was associated with a significantly increased burden of all six evaluated comorbidities. Specifically, interstitial lung disease showed the strongest association with cancer patients having rheumatologic disease being approximately five times more likely to have ILD compared to those without rheumatologic disease (RR: 5.01; 95% CI: 4.77–5.26). Similarly, chronic obstructive pulmonary disease risk was nearly fivefold higher (RR: 4.81; 95% CI: 4.61–5.01). Cardiovascular comorbidities, including hypertension (RR: 3.86; 95% CI: 3.76–3.97), heart failure (RR: 3.94; 95% CI: 3.80–4.10), and ischemic heart disease (RR: 3.50; 95% CI: 3.41–3.61), were also significantly more prevalent in the rheumatologic group. Diabetes mellitus was similarly elevated (RR: 3.15; 95% CI: 3.06–3.25). The odds ratios mirrored these findings, reinforcing the strong association between rheumatologic disease and comorbidity burden in cancer patients. Conclusions: Cancer patients with underlying rheumatologic diseases may have a higher burden of cardiopulmonary and metabolic comorbidities, highlighting the need for integrated care and early risk mitigation. Regular monitoring is essential. Further research should explore factors like age and race to better understand and guide clinical decision-making.