Optimal cutoff level of serum squamous cell carcinoma antigen to detect recurrent cervical squamous cell carcinoma during post-treatment surveillance

OBJECTIVE: The objective of this study was to determine the optimal cutoff level of serum squamous cell carcinoma antigen (SCC-Ag) to detect recurrent cervical squamous cell carcinoma during post-treatment surveillance. METHODS: Between January 2000 and July 2014, a total of 158 women with cervical squamous cell carcinoma were treated with radiotherapy with or without concurrent chemotherapy at our department. A total of 1,550 serum SCC-Ag tests performed during post-treatment surveillance of the 158 patients were included in this retrospective study. RESULTS: During post-treatment surveillance, 53 patients were diagnosed as having recurrent cervical cancer based on biopsy or a radiological test showing progression of a lesion. Receiver operating characteristic (ROC) curve for serum SCC-Ag to diagnose recurrent cervical squamous cell carcinoma showed that the area under the ROC curve was 0.914 (95% confidence interval, 0.887–0.942; P<0.001). The best cutoff value for serum SCC-Ag to obtain the highest Youden's index was ≥2 ng/mL (sensitivity, 80.2%; specificity, 94.6%). CONCLUSION: Serum SCC-Ag test was helpful in detecting recurrent cervical squamous cell carcinoma during post-treatment surveillance, and the optimal cutoff value was ≥2 ng/mL. The researchers recommend active imaging studies, when serum SCC-Ag level ≥2 ng/mL during post-treatment surveillance.