Masterclass: Colorectal Screening Plus (Virtual) | September 2025-Paine - Stool and Blood Testing for CRC screening

Paine - Stool and Blood Testing for CRC screening

Pdf Summary

This presentation by Dr. Elizabeth R. Paine provides a comprehensive overview of non-invasive colorectal cancer (CRC) screening methods, focusing on stool and blood tests, as well as CT colonography and capsule colonoscopy.<br /><br />Stool-based tests include the guaiac-based fecal occult blood test (gFOBT), fecal immunochemical test (FIT), multitarget stool DNA-FIT tests, and multitarget stool RNA tests. The gFOBT, once common, requires annual testing of three consecutive stools with dietary restrictions and has lower sensitivity, especially for advanced adenomas. FIT, done annually on a single stool sample without diet restrictions, shows improved sensitivity (~74-79%) and specificity (~94-96%), but lower detection rates for advanced precancerous lesions. Multitarget stool DNA-FIT tests detect DNA mutations and methylation markers alongside hemoglobin, done every 1-3 years, with higher sensitivity (~92% for CRC) but lower specificity than FIT, leading to more false positives and higher costs. Next-generation stool DNA-FIT tests use advanced molecular panels to improve detection. Multitarget stool RNA tests, incorporating RNA markers and smoking status, are emerging but not yet standard recommended screening.<br /><br />Blood-based tests include cell-free DNA ("liquid biopsy") and methylated Septin 9 DNA tests. Cell-free DNA testing detects tumor DNA released into blood, showing high CRC sensitivity (~83%) but low sensitivity for precancerous lesions (~13%), and is not yet USPSTF recommended. The Septin 9 test, FDA-approved, detects hypermethylated DNA but has lower sensitivity and is reserved for patients refusing other screenings.<br /><br />CT colonography offers a radiologic screening option requiring bowel prep but no sedation or radiation exposure, with sensitivities varying by adenoma size. Capsule colonoscopy is an option for incomplete colonoscopies but is not FDA approved for average-risk screening and involves extensive prep.<br /><br />Each non-invasive test has benefits such as no sedation or bowel prep, but limitations include cost, need for follow-up colonoscopy after positives, and varying sensitivity/specificity. While non-invasive tests improve screening accessibility, colonoscopy remains the definitive diagnostic and therapeutic procedure. Overall, these options impact CRC mortality and incidence positively by increasing screening uptake and early detection.

Keywords

colorectal cancer screening

non-invasive tests

stool-based tests

blood-based tests

CT colonography

capsule colonoscopy

fecal immunochemical test (FIT)

multitarget stool DNA-FIT test

cell-free DNA liquid biopsy

sensitivity and specificity