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Objective: To determine whether serum squamous cell carcinoma antigen (SCC-Ag) is predictive of treatment response in patients with squamous cell cervical carcinoma (SCC) undergoing chemoradiation therapy, and to establish the mean normal serum SCC-Ag level in age-matched, apparently healthy female controls.Methods: Patients with histologically confirmed cervical SCC scheduled for concurrent chemoradiation were recruited (75 cases, alongside 75 age-matched apparently healthy controls, N = 150). Blood samples were collected before treatment and 6 weeks post-external beam radiotherapy to assess serum SCC-Ag levels, which were correlated with tumor stage and grade. Age-matched apparently healthy controls were also phlebotomized at baseline and 12 weeks later to determine normal SCC-Ag levels. Serum SCC-Ag was analyzed using Alinity i SCC reagent and analyzer (Abbott Laboratories, Chicago, IL, USA). The manufacturer's reference value for SCC-Ag is ≤1.5 ng/ml. Treatment response was assessed via pre- and post-treatment abdominopelvic computed tomography scans and classified as either complete or partial response. Data analysis was performed using SPSS v22.0, and logistic regression was used to evaluate predictors of treatment response. A P value <0.05 was considered statistically significant.Results: The mean age was 55.1 ± 11.6 years for cases and 55.5 ± 11.4 years for controls. Among cervical cancer patients, the median pre-treatment SCC-Ag level was 7.4 ng/ml, and post-treatment was 1.2 ng/ml, both significantly higher than in controls (0.4 ng/ml and 0.5 ng/ml, respectively). Vaginal bleeding was the most common symptom (94.7%), and 68% presented with locally advanced disease. SCC histology was confirmed in 94.7% of cases, and 61% showed either complete or partial treatment response. Median SCC-Ag levels were significantly associated with disease stage (P<0.001) but not with tumor grade (P=0.159). Logistic regression identified tumor size as a significant predictor of treatment response, while pre-treatment SCC-Ag and SCC-Ag reduction rate were not.Conclusion: Serum SCC-Ag levels were normal among all healthy controls and some patients with prior treatment. SCC-Ag correlated with disease stage but was not predictive of treatment response in patients undergoing chemoradiation. Tumor size was the only significant predictor of treatment response.