Colon Cancer: Improved Screening and Chemotherapy Contribute To Improved Survival

MedicalResearch.com Interview with:
Xianglin L. Du, MB, MS, Ph.D. 

Professor of Epidemiology,
Department of Epidemiology, Human Genetics, and Environmental Sciences,
The University of Texas School of Public Health,
Houston, TX 77030, USA.

Medical Research: What is the background for this study?

Dr. Du: Widespread use of screening and advances in screening strategies played a key role in colorectal cancer survival improvement. With the increasing evidence on the benefit of fecal occult blood test and sigmoidoscopy during 1990s, the U.S. Preventive Service Task Force for the first time in 1996 recommended the annual use of fecal occult blood test, periodic use of sigmoidoscopy, or routine use of both modalities for all persons aged 50 or older. Because colonoscopy is able to detect lesions in the entire colon and has a high sensitivity for lesions of over 10mm in size, Medicare began to cover colonoscopy since 2001 for individuals with average-risk of colorectal cancer. Advances in chemotherapy, particularly some new therapeutic regimens approved by Food and Drug Administration (FDA) over the past decades also played a key role in survival improvement for patients with colorectal cancer. However, the overall impact of newly approved chemotherapy regimens on survival in population-based elderly patients remains unclear. It is also unknown what proportion of survival improvement was attributable to changes in tumor stage and size due to screening, and what proportion was attributable to more effective chemotherapy regimens. Hence, we studied a large nationwide and population-based cohort of elderly colorectal cancer patients to examine the changes in tumor stage and tumor size from 1992 to 2009, and to further quantify the effects of changes in stage/size and chemotherapy regimens on improved survival over the two decades.

Medical Research: What are the main findings?

Dr. Du: Study periods were categorized into three periods according to the major changes or advances in screening and chemotherapy regimens:
1) Period-1 (1992-1995), during which there was no evidence-based recommendation for routine colorectal cancer screening and 5-fluorouracil was the mainstay for chemotherapy; 2) Period-2 (1996-2000), during which evidences and guidelines supported the use of fecal occult blood test and sigmoidoscopy for routine colorectal cancer screening; and
3) Period-3 (2001-2009), during which Medicare Program added the full coverage for colonoscopy screening to average-risk individuals, and several newly developed chemotherapy regimens were approved.

Compared to Period-1 (1992-1995), the likelihood of being diagnosed with early stage colorectal cancer increased by 20% in Period-2 (1996-2000) and 30% in Period-3 (2001-2009); and the likelihood of being diagnosed with small-size colorectal cancer increased by 60% in period-2 and 110% in period-3. Similarly, 5-year overall relative survival increased from 51% in period-1 to 56% in period-2 and 60% in period-3. Increase in survival attributable to migration in stage/size was 9% in period-2 and 20% in period-3, while the remaining survival improvement during period-2 and period-3 were largely attributable to more effective chemotherapy regimens (≥71.6%) and about 25% of improvement in overall survival were explained by treatment factors other than chemotherapy, including improved management in chronic diseases among elderly colorectal cancer patients.

Medical Research: What should clinicians and patients take away from your report?

Dr. Du: Overall, improvements in early detection or screening for colorectal cancer and chemotherapy regimens over the past two decades have had led to the real world effectiveness in prolonging survival for elderly patients. Improvements in colorectal cancer screening resulted in a change of colorectal cancer towards earlier tumor stage and smaller size, which contributed to 20% or less of survival increase. Survival improvement over the past 2 decades was largely explained by more effective chemotherapy regimens and other treatment factors, including improved management in chronic diseases. Therefore, strategies to improve both cancer screening and chemotherapy regimens will continue to be of great importance and guidelines to minimize the underuse of chemotherapy in elderly patients is also important.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Du:  Future studies may need to take into consideration of changes in stage and size affected by misclassification bias because of advances in screening technology and changes in stage definition over time. Studies also need to incorporate the information on early detection rates and screening-detected tumors when possible, and to obtain the data that may allow researchers to better quantify the contribution of specific treatment modalities and other helpful strategies from providers and patients to survival improvement.

Citation:

Tong L, Ahn C, Symanski E, Lai D, Du XL. Relative impact of earlier diagnosis and improved treatment on survival for colorectal cancer: A US database study among elderly patients. Cancer Epidemiology. 2014 Nov 7. [Epub ahead of print]. http://dx.doi.org/10.1016/j.canep.2014.10.004.)..