Colorectal cancer (CRC) is the third most common form of cancer in the world.
In Finland, a country with approximately 5.5 million people (compare the United States population in 2017 was 325.70 million), approximately 3,000 new patient cases are diagnosed every year, and roughly 1,200 patients die of the disease.
Between 2004 and 2016, an extensive screening program was conducted in Finland, intending to study the potential benefits and downsides of a nation-wide screening for colorectal cancer. Results of the program were published in the British Journal of Surgery.
The study targeted people aged 60-69 years, and just under a half of the age group, or a 321.311 people, were randomized by late 2011. Half of the population in the study were invited for screening, while the other half of the age cohort served as a control group. Fecal occult blood tests (FOBT) were used in the screening, and patients who tested positive for blood were referred for a colonoscopy.
While screening for colorectal cancer did not, so far, reduce mortality, it did reduce the need for chemotherapy and emergency surgeries among male patients…
No decrease in mortality
The first study based on the screening results indicated no significant decrease in mortality, so the screenings were discontinued after 2016. However, researchers from the Helsinki University Hospital and the Finnish Cancer Registry wanted to examine whether the screening had offered benefits to patients with colorectal cancer.
“Practically no cancer screenings have been found to have an impact on overall mortality. However, they may still be useful in other ways. We wanted to study whether the patients could avoid the more intense treatments if they participated in screening for colorectal cancer,” noted Laura Koskenvuo, MD, Ph.D, a gastrointestinal surgeon.
The study examined the data of 1,360 patients diagnosed with colorectal cancer, including 743 patients with screening-detected tumors and 617 control patients with CRC were analyzed.
The researchers observed that CRC was less common in women than in men (0·34 vs 0·50%; risk ratio (RR) 0·82, 95% c.i. 0·74 to 0·91) and women were less often asymptomatic (16·7 vs. 22·0%; RR 0·76, 0·61 to 0·93).
The researchers also noted that women more often had right-sided tumors (32·0 versus 21·3%; RR 1·51, 1·26 to 1·80). Among men with left-sided tumors, those in the screening arm had lower N (RR 1·23, 1·02 to 1·48) and M (RR 1·57, 1·14 to 2·17) categories, as well as a higher overall survival rate than those in the control arm.
Furthermore among men with left-sided tumors, non-radical resections (26·2 versus 15·7%; RR 1·67, 1·22 to 2·30) and postoperative chemotherapy sessions (61·6 vs. 48·2%; RR 1·28, 1·10 to 1·48) were more frequent in the control arm. Similar benefits of screening were not detected in men with right-sided tumors or in women.
The results indicated that among patients from the screening group, the surgical removal of the entire tumor was more commonly successful than it was among the control group patients, and they were less likely to require chemotherapy. The patients from the screening group were also less likely to undergo emergency surgery because of their tumor than the control group patients.
“The control group had 50% more emergency surgeries, 40% more incomplete tumor removals and 20% more chemotherapy treatments than patients in the screening group,” said Adjunct Professor Ville Sallinen, MD, Ph.D, a gastrointestinal surgeon.
Closer inspection of the results showed that these benefits were particularly prevalent among male patients. Similar benefits were not seen among women. Additionally, the researchers found that the screening was most efficient at detecting left-sided colorectal cancer and the screening was found to have no benefit for patients with cancer on the right side, possibly because blood seeping from tumors on the right side becomes so diluted as it travels through the colon that the gFOBT can no longer detect it.
Given the difference in incidence, symptoms and tumor location, the researchers conclude that biennial FOBT screening may be more effective improving outcomes in men, but not in women.
“The strength of this Finnish study is that it randomized an enormous number of people in the public health care system, which meant that we could objectively evaluate the benefits of the screening. Similar studies have not been available anywhere else,” said Professor Nea Malila, director of the Finnish Cancer Registry.
“In the future, we must examine whether different screening techniques could improve the situation of female patients and facilitate the diagnosis of right-sided colorectal cancer,” the researchers state.
 Koskenvuo L, Malila N, Pitkäniemi J, Miettinen J, Heikkinen S, Sallinen V. Sex differences in faecal occult blood test screening for colorectal cancer. Br J Surg. 2018 Nov 21. doi: 10.1002/bjs.11011. [Epub ahead of print][Pubmed]
Last Editorial Review: November 23, 2018
Featured Image: Gastrointestinal surgeons Laura Koskenvuo (left) and Ville Sallinen at work. Courtesy: 2018 © University of Helsinki, Helsinki, Finland. Used with permission.
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