ECOG Performance in Malaysian Oral Cavity Carcinoma: Treatment, Demographics, and Clinical Factors Eastern Cooperative Oncology Group (ECOG) is gaining importance as a valuable outcome measure in the field of oral cavity carcinoma (OCC). This study aimed to assess pre- and post-treatment ECOG changes in Malaysian OCC patients undergoing various treatments. We conducted a 12–36 months longitudinal observational study with 63 squamous cell carcinoma patients, evaluating ECOG perfomance, medical history, symptoms, sociodemographics, clinical details, and treatment modalities (surgery, surgery + radiotherapy, or surgery + chemotherapy and radiotherapy [CCRT]). OCC patients aged 50–70 years are at risk for impaired quality of life (QOL) up to several years after diagnosis.The analysis of the association between baseline ECOG Performance Status (ECOG-PS) scores and demographic data revealed a statistically significant correlation only within the age group, emonstrating a p-value of 0.031. CCRT treatment has a more pronounced effect on patient performance status, with significant results in the 3-year overall survival rate and poor ECOG-PS score in patients post-CCRT, as well as radiotherapy. These results highlight the need to provide OCC patients with specialised interventions and support, especially while they are undergoing CCRT, to lessen the potential negative effects on their general well-being and quality of life.