FOBT Colorectal Cancer Screening Only Effective in Men

Liam Davenport

November 26, 2018

Colorectal cancer (CRC) screening with fecal occult blood tests (FOBTs) improves outcomes in men moreso than women, and especially in men with left-sided tumors, say Finnish researchers. Their conclusion comes from a reanalysis of data from a large screening study.

The Finnish FOBT screening program (2004–2011) was conducted in more than 320,000 men and women aged 60 to 69 years. Participants were randomly assigned into screening and control arms. Results from this trial, published in 2015, found no difference in CRC mortality between the two arms, in contrast to findings from several previous randomized screening trials.

Now, a team of researchers led by Laura Koskenvuo, MD, PhD, a gastrointestinal surgeon at Helsinki University Hospital, Finland, has reexamined the data to assess "outcomes beyond mortality."

They found that biennial FOBT screening "seems to be effective in terms of improving several different outcomes in men, but not in women."

It was particularly beneficial in men with left-sided tumors. In this subgroup, FOBT screening was associated with better overall survival, lower rates of nonradical resections, and a reduced need for postoperative chemotherapy.

However, these benefits were not seen in women, nor in men or women with right-sided tumors.

The research was published online November 21 in the British Journal of Surgery.

The team suggests that, given that FOBT screening did not appear to be associated with improved survival in women, "screening by different methods or at different intervals or ages should be considered in women."

Details of the Findings

The Finish FOBT study covered approximately 41% of Finnish men and women who were in the target age group (60-69 years) by the end 2011.

Although it found no significant difference in CRC mortality between the screening arm and the control arm, the results did suggest that there was a reduction in CRC-related mortality with screening in men and an increase among women. Such a finding has also been seen in other studies of biennial FOBT, the researchers comment.

"Practically no cancer screenings have been found to have an impact on overall mortality," Koskenvuo commented in a press statement.

"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," she explained.

The team therefore collected data on CRC diagnoses from the Finnish Cancer Registry and examined the patients' medical records to identify clinical and pathologic TNM stage; symptoms and extent of surgery; the patients' need for emergency surgery, stoma, or chemotherapy; and histopathologic diagnoses.

From the 321,311 people in the study, 743 CRC cases were detected in the screening arm, and 617 were detected in the control arm.

Patients in the screening group were more likely to experience successful removal of the entire tumor, less likely to require chemotherapy, and less likely to undergo emergency surgery.

"The control group had 50% more emergency surgeries, 40% more incomplete tumor removals, and 20% more chemotherapy treatments than patients in the screening group," explained coauthor Ville Sallinen, MD, PhD, an adjunct professor at the University of Helsinki.

CRC was less common in women than in men, at a rate of 0.34% vs 0.50% (risk ratio [RR], 0.82).

Women were less likely to be asymptomatic than men, at 16.7% vs 22.0 (RR, 0.76). Abdominal pain was the only symptom that was significantly more prevalent in women than men (RR, 1.36).

Women were substantially more likely to have right-sided tumors than men, at 32.0% vs 21.3% (RR, 1.51).

Cancers among patients in the screening arm were of lower T category (RR, 1.25), N category (RR, 1.14), and M category (RR, 1.33) in comparison with cancers in the control arm.

Among men with left-sided tumors, in patients in the screening arm, cancers were of lower N category (RR, 1.23) and M category (RR, 1.57) than in patients in the control arm.

Among men with left-sided tumors, those in the control arm were more likely to undergo nonradical resections than those in the screening arm, at 26.2% vs 15.7% (RR, 1.67), and were more likely to receive postoperative chemotherapy, at 61.6% vs 48.2% or (RR, 1.28).

Survival was worse in the control arm than in the screening arm in men with CRC (hazard ratio [HR], 1.31), but it was no different in women [HR, 1.07].

Among men, 5-year overall survival rates were 68.8% in the screening arm vs 61.5% in the control arm. Among women, the rates were 70.7% and 71.5%, respectively.

With respect to tumor sidedness, among men with left-sided tumors, survival was better in the screening arm than in the control arm (HR,1.37).

This survival benefit was not seen in men with right-sided tumors, however (HR, 1.19]. Survival rates were unaffected by tumor sidedness in women.

Coauthor Nea Malila, MD, PhD, director of the Finnish Cancer Registry, Helsinki, said that the large sample size is a strength of the study.

"It randomized an enormous number of people in the public healthcare system, which meant that we could objectively evaluate the benefits of the screening," she noted.

"Similar studies have not been available anywhere else," she said.

"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 conclude.

The study was supported financially by Vatsatautien Tutkimussäätiö, Helsinki University Hospital research funds, the Mary and Georg Ehrnrooth's Foundation, and Cancer Foundation Finland. The authors have disclosed no relevant financial relationships.

Br J Surg. Published online November 21, 2018. Full text

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