RESUMO
Fecal immunochemical test (FIT) followed by colonoscopy in positive cases is commonly used for population-based colorectal cancer (CRC) screening. However, specificity of FIT for CRC is not ideal, and has poor performance for advanced adenoma detection. Fecal Fusobacterium nucleatum (Fn) detection has been proposed as a potential non-invasive biomarker for CRC and advanced adenoma detection. We aimed to evaluate the diagnostic performance of Fn detection using droplet digital PCR (ddPCR) in FIT samples from individuals enrolled in a CRC screening program with colorectal adenoma or cancer. We evaluated Fn presence in DNA isolated from FIT leftover material of 300 participants in a CRC Screening Program using ddPCR. The Fn DNA amount was classified as Fn-low/negative and Fn-high, and the association with patients clinicopathological features and accuracy measurements was calculated. Fn high levels were more prevalent in FIT-positive (47.2%n=34 of72) than FIT-negative samples (28.9%, n=66 of 228) (p<0.04). Among FIT-positive samples, high Fn levels were significantly more frequent in cancer patients (CA, n=8) when compared to normal (NT, n=16) (p=0.02), non-advanced adenomas (NAA, n=36) (p=0.01), and advanced adenomas (AA, n=12) (p=0.01). Performance analysis of Fn in FIT-positive samples for colorectal cancer detection yielded an AUC of 0.8203 (CI: 0.6464-0.9942), with high sensitivity (100%) and specificity of 50%%. Concluding, we showed the feasibility of detecting Fn in FIT leftovers using the ultrasensitive ddPCR technique. Furthermore, we highlighted the potential use of Fn levels in fecal samples to ameliorate CRC detection.
RESUMO
BACKGROUND: Colorectal cancer (CRC) screening can help to reduce its incidence and mortality. Noninvasive strategies, such as plasma analysis of epigenetic alterations, can constitute important biomarkers of CRC detection. OBJECTIVE: This study aimed to evaluate the plasma methylation status of SEPT9 and BMP3 promoters as biomarkers for detection of CRC and its precursor lesions in a Brazilian population. METHODS: Plasma samples from 262 participants of the CRC screening program of Barretos Cancer Hospital who had a positive fecal occult blood test and underwent colonoscopy and cancer patients were analyzed. Participants were grouped according to the worst lesion detected in the colonoscopy. Cell-free circulating DNA (cfDNA) was bisulfite treated followed by the analysis of SEPT9 and BMP3 methylation status using a droplet digital PCR system (ddPCR). The best methylation cutoff value for group discrimination was calculated by receiver operating characteristic (ROC) curve analysis. RESULTS: Among the 262 participants, 38 were diagnosed with CRC, 46 with advanced adenomas 119 with nonadvanced adenomas, three with sessile serrated lesions, and 13 with hyperplastic polyps. In 43 participants, no lesion was detected in the colonoscopy and were used as controls. The CRC group showed the highest cfDNA concentration (10.4 ng/mL). For the SEPT9 gene, a cutoff of 2.5% (AUC = 0.681) that discriminates between CRC and the control group resulted in CRC sensitivity and specificity of 50% and 90%, respectively. Concerning the BMP3 gene, a cutoff of 2.3% (AUC = 0.576) showed 40% and 90% of sensitivity and specificity for CRC detection, respectively. Combining SEPT9, BMP3 status, and age over 60 years resulted in a better performance for detecting CRC (AUC = 0.845) than the individual gene models, yielding 80% and 81% of sensitivity and specificity, respectively. CONCLUSION: The present study suggests that a combination of SEPT9 and BMP3 plasma methylation, along with age over 60 years, showed the highest performance in detecting CRC in a Brazilian population. These noninvasive biomarkers can potentially serve as useful tools for CRC screening programs.
