Colon cancer screening programs prevent cancer

Abstract

In this article we comment on the article by Agatsuma et al. Our article focuses on the use of screening for colon cancer increases the likelihood of early diagnosis of colorectal cancer compared to those presenting after symptoms develop. Patients with symptoms were more likely to have left-sided lesions with resultant hematochezia and/or changes in bowel habits. In this study almost all patients in the screen group were first screened with immunochemical fecal occult blood testing. Colonoscopy was used either if it was thought to be the more appropriate initial screening modality or if the non-invasive test was positive. The exact timing when an initial screening colonoscopy should be performed is not totally clear from this study. However, early screening for colon cancer does reduce the risk of cancer diagnosis and more advanced cancer diagnoses.

Core Tip: Colon cancer is rising in incidence and prevalence worldwide. Colon cancer screening programs are associated with reduction in cancer diagnoses and in advanced stages of cancer diagnoses. The ideal screening test remains unclear but both fecal immunochemical test (FIT) testing and colonoscopy are both appropriate modalities. Ultimately, if a patient has risk factors or if the FIT test is positive, then colonoscopy should be used to evaluate for colon cancer.

TO THE EDITOR

In this trial, Agatsuma et al[1] use a colorectal cancer (CRC) registry to comment on both the clinical circumstances of CRC diagnosis as well as the effect of those circumstances on stage of diagnosis. Their study relies on prior work that has shown early-stage diagnosis of CRC correlates with better outcomes and improved patient survival. The main result supported by the study is that patients who undergo testing for CRC-related symptoms have a lower likelihood of early-stage diagnosis than either patients presenting for CRC screening or those who visit the hospital due to other, non-CRC-related comorbidities (hypertension, diabetes, heart disease, etc.).

Symptomatic patients trended towards less right-sided lesions than either the screening or follow-up populations. Left-sided lesions may be more likely to demonstrate symptoms (e.g. hematochezia, change in bowel habits, etc.) to explain this trend. It is interesting that despite a trend toward more left-sided lesions, which have been shown previously to have better prognostic outcomes[2], the symptomatic population demonstrated less likelihood of early-stage diagnoses. The importance of screening patients prior to symptomatic development has been noted in other studies, but is certainly highlighted here[3].

Unsurprisingly, the population tested for screening purposes trended younger than either the symptomatic or follow-up groups. This speaks to the importance of screening earlier, in younger populations, to prevent later-stage diagnoses[4]. Recent studies have identified an increasing incidence of CRC, and particularly rectal cancer, in younger populations[4]. Concern regarding these data have resulted in a decrease in the age of recommended CRC screening initiation by groups such as the United States Preventive Service Task Force, the American Cancer Society, and others[5,6]. The ideal role of colonoscopy and non-invasive testing in CRC screening is not well defined; it is noted that in this study, almost all patients in the screening group underwent immunochemical fecal occult blood testing. It remains to be established if the ideal CRC screening modality should be a non-invasive test followed by an invasive procedure if positive, or if colonoscopy should be the initial screening modality.

There are some limitations to the study that the authors identify and address. The limitations include the retrospective design and generalizability. The effect of the specific mechanisms and practices of the Japanese healthcare system, and any differences from other regions, is unclear. Furthermore, whether there is bias from a surveillance hypothesis or crossover between groups is uncertain; we do not know whether the patients in the symptomatic group were being screened previously. However, the underlying message remains the same: CRC screening prior to symptom development is an important measure for identifying early-stage CRC.

Agatsuma et al[1] include in their discussion a call for CRC screening, with a comment on the difficulties of effective CRC screening promotion. The introduction of a CRC screening protocol to national guidelines has repeatedly demonstrated a benefit to early diagnosis and prognosis of CRC. Further study on outreach techniques and efficacy is required to ensure that more patients are appropriately screened prior to symptom onset.