Background: Cancer cachexia is defined by weight loss that nutritional support cannot fully reverse, leading to worse pt outcomes. Cachexia prevalence across cancer types relies on outdated studies. This study assesses the frequency of cachexia diagnosis using ICD9/10 codes or observed weight loss consistent with real-world cachexia diagnosis and its impact on survival. Methods: Retrospective, observational, real-world analysis using deidentified adult pt data from Clinformatics Data Mart database (Aug 1, 2016-Jul 31, 2021). Pts with at least 1 of 23 cancer types were identified using diagnostic and procedure codes and classified in 1 of 3 cachexia categories: (1) diagnosed (diagnostic code identified); (2) observed (BMI decrease: >10% within 12 mo, >5% within 6 mo, or >2% with a BMI <20 kg/m²), (3) none (with no cachexia diagnostic code/observed). For observed, pts required ≥10 BMI records. Summary statistics presented as mean, median, or n (%). Survival rates compared using Cox proportional hazards model. Results: 672,665 pts were identified; 278,923 met inclusion criteria. Diagnosed + observed (subgroup) cachexia rates are shown for the 5 most prevalent cancer types (Table). Over 5 y, diagnosed cachexia rates ranged from 0.9-6.3%; observed from 60-83% (in subgroup with ≥10 BMI records). After cancer diagnosis, observed cachexia was identified on average 0-11 mo, while formal diagnosis occurred on average 11-24 mo. At least 16% of diagnosed and 31% observed pts received diagnosis or met observed criteria at or before cancer diagnosis. Average percent BMI decrease over 5 y was 22.0% ± 12.1, 17.8% ± 9.5, and 6.8% ± 5.5 for diagnosed, observed, and none, respectively. Compared with no cachexia, diagnosed and observed showed worse survival (HR 10.72 [95% CI 10.56-10.88]; HR 2.35 [95% CI 2.32-2.38]), respectively. Conclusions: Across all cancer subtypes, prevalence of observed cachexia cases documented by weight loss far exceeded cachexia prevalence based on diagnostic coding. After cancer diagnosis, pts met diagnostic criteria of cachexia within 1 y, but formal diagnosis took up to 2 y. The presence of cancer cachexia (diagnosed or observed), with or without metastatic disease, was associated with lower survival.

*Pts with ≥10 BMI records.