Colon cancer blood in stool
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Blood in Stool as an Indicator of Colon Cancer
Introduction to Colon Cancer and Blood in Stool
Colon cancer, also known as colorectal cancer (CRC), is a significant health concern worldwide. One of the early signs of colon cancer is the presence of blood in the stool, which can be detected through various screening methods. This article synthesizes research findings on the effectiveness of different screening tests for detecting blood in stool and their impact on colon cancer detection and mortality.
Fecal Occult Blood Testing (FOBT) for Colon Cancer Screening
Annual and Biennial Screening
Fecal occult blood testing (FOBT) is a widely used method for screening colorectal cancer. The Minnesota Colon Cancer Control Study demonstrated that annual FOBT significantly reduces mortality from colorectal cancer. In this study, participants aged 50 to 80 were screened either annually or biennially, with those testing positive undergoing further diagnostic evaluations, including colonoscopy. The results showed a 33% reduction in 13-year cumulative mortality from colorectal cancer in the annually screened group compared to the control group. Additionally, both annual and biennial screenings were found to reduce the incidence of colorectal cancer over an 18-year follow-up period.
Detection Rates and Cancer Stages
FOBT has been effective in detecting colorectal cancers at earlier stages. A study involving 48,000 asymptomatic participants found that 113 patients had invasive carcinomas, with a significant proportion detected at early stages (Dukes' A and B). Another study highlighted that 1% of routine adult patients tested with FOBT had asymptomatic colon cancer, emphasizing the importance of regular screening.
Stool DNA Testing: A Promising Alternative
Sensitivity and Specificity
Stool DNA testing (SDT) is emerging as a more sensitive alternative to FOBT. Research comparing first- and second-generation stool DNA tests (SDT-1 and SDT-2) with Hemoccult and HemoccultSensa found that SDT-2 had a sensitivity of 40% for screen-relevant neoplasms, significantly higher than the 21% sensitivity of HemoccultSensa. This higher sensitivity is due to the continuous shedding of cancer-related DNA markers in the stool, unlike the intermittent bleeding detected by FOBT .
Molecular Markers and Non-Invasiveness
Stool DNA tests leverage molecular markers, such as mutations in the APC, K-ras genes, and vimentin methylation, to detect colorectal cancer. These tests are non-invasive, do not require dietary restrictions, and can be easily administered via mail, making them a convenient option for patients. The development of these tests has been driven by advances in understanding the genetic and epigenetic changes in colorectal cancer .
Conclusion
Detecting blood in stool is a critical component of colorectal cancer screening. While FOBT has been effective in reducing mortality and detecting cancers at earlier stages, stool DNA testing offers a more sensitive and non-invasive alternative. Both methods play a vital role in early detection and prevention, ultimately improving patient outcomes. Regular screening, whether through FOBT or stool DNA tests, is essential for reducing the incidence and mortality of colorectal cancer.
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