Summary of Key Points
This article focuses on “Interval Colorectal Cancer (I-CRC),” explaining its definition (colon cancer detected between two colonoscopy screenings), the four main causes (missed diagnoses, inadequate examinations, incomplete removals, and new cancers), and pointing out that nearly 90% of cases are related to human error (such as differences in doctors’ expertise). It also emphasizes that despite the small probability of missed diagnoses during colonoscopies, the overall effectiveness in reducing colon cancer mortality is significant. If you are diagnosed with I-CRC, there is no need to panic, as it is often in a treatable stage; regular treatment should be pursued.
Detailed Explanation
1. What is “Interval Colorectal Cancer”?
Simply put, it refers to the situation where you are told everything is normal after a colonoscopy, but shortly thereafter (usually within 3-5 years), colon cancer is detected. The “interval” refers to the time between two colonoscopies:
- If the first colonoscopy shows no abnormalities and the doctor recommends a follow-up in 10 years, but cancer is found within 5 years, it is considered I-CRC.
- If polyps are detected and removed during the first colonoscopy, and the doctor suggests a follow-up in 3 years, but cancer is discovered before that time, it is also classified as I-CRC.
- The exact duration of this “interval” has not been universally agreed upon by the scientific community, but cases found within 3 years are generally included.
The proportion of I-CRC is not high (5%-8% of all colon cancers), but due to the high incidence of colon cancer, the total number is still significant.
2. Why Does I-CRC Occur?
There are mainly four reasons:
- Missed Diagnoses: The intestines are complex and curved, with lesions potentially hidden in shaded areas or bends, or obscured by intestinal spasms, making them difficult to detect.
- Inadequate Examinations: Either the laxatives used do not thoroughly clean the intestines (covering the lesions), or the colonoscope does not reach the end of the large intestine (the cecum), leading to missed detections.
- Incomplete Removals: If polyps are not completely removed during a previous colonoscopy, the remaining parts may develop into cancer over time.
- New Cancers: In some cases, new cancers grow between two screenings (usually detected after 3 years).
The first three reasons are largely due to human error and account for nearly 90% of I-CRC cases.
3. Human Factors Play a Crucial Role: Who Performs the Colonoscopy Matters?
Research in the Netherlands found that among 147 cases of I-CRC, missed diagnoses (57.8%), inadequate examinations (19.8%), and incomplete removals (8.8%) together accounted for 86.4% of the issues. The main difference lies in the expertise of the performing doctor:
- Gastroenterologists Are More Reliable: Studies in the United States have shown that colonoscopies performed by gastroenterologists can reduce the risk of colon cancer death by 65%, compared to 57% for general practitioners and only 45% for surgeons, due to their more extensive and systematic training.
- The Importance of Non-Specialized Doctors: In many places, there is a shortage of gastroenterologists, so surgeons, general practitioners, or even nurse assistants perform colonoscopies as a backup. While the quality may be slightly lower, it is still better than not having any screening at all (for example, surgeries performed by surgeons in Canada can still reduce mortality rates).
- Exception with VA Systems: In some Veterans Affairs hospitals, the quality of colonoscopies performed by nurses and assistants is even better than that of gastroenterologists, but this practice has not yet become widespread.
4. What to Do If You Are Diagnosed with I-CRC?
Don’t panic!
- Early Stages: Most cases of I-CRC are detected at an early stage and are treatable.
- Standard Treatment: Treatment is similar to that for regular colon cancer, requiring a multidisciplinary approach involving surgery, internal medicine, and oncology.
- Do Not Deny Standard Medical Care: Don’t distrust the hospital just because you think a doctor made a mistake; seeking alternative treatments can be more dangerous.
I-CRC is simply an example of the imperfections in medical technology. Acknowledging these issues allows for improvements, but regular treatment remains the best approach.
5. Colonoscopy Screening Remains Effective: Don’t Give Up on It Due to Small Risks
Despite the existence of I-CRC, the overall effectiveness of colonoscopy screening is undeniable:
- In developed countries, the incidence and mortality rates of colon cancer have been declining for many years, largely due to effective screening.
- Even screenings performed by non-specialized doctors can significantly reduce the risk of death.
- The core value of early screening is prevention: Most colon cancers develop from polyps, and colonoscopies can remove them, preventing cancer before it progresses.
Therefore, continue with the necessary screenings; don’t let a small risk deter you from getting checked.
Final Reminder
Colon cancer is one of the cancers for which early detection and treatment are most effective. Starting colonoscopy screenings at age 45 (or earlier if you have a family history) is still the best way to protect yourself. If you encounter any issues, seek care at a reputable hospital. Don’t let the possibility of I-CRC affect your trust in scientific medical practices.