MedWire News: Repeat screening by flexible sigmoidoscopy (FSG) after 3 to 5 years increases the detection of colorectal cancer or advanced adenoma by a quarter in women and by a third in men, show results of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial.
Joel Weissfeld (University of Pittsburg Cancer Institute, Philadelphia, USA) and colleagues explain that endoscopic methods detect colorectal cancer and adenoma with greater sensitivity than fecal occult blood testing.
However, "because the cost-effectiveness of endoscopic colorectal cancer screening depends strongly on the age groups screened and on the frequency of screening, it is important to determine whether repeated screenings are beneficial and at what time interval they should be conducted."
This was one of the aims of the PLCO trial. Participants were screened by 60-cm FSG in 10 regional screening centers at study entry and 3 or 5 years later, depending on the time of random assignment.
Of 77,447 enrollees, 67,073 (86.6%) had at least one FSG and 39,443 (50.9%) had two FSGs.
The researchers found that the second FSG increased the screening yield by 32% overall: colorectal cancer or advanced adenoma was detected in 37.8 per 1000 individuals after first screening and in 49.8 per 1000 persons after all screenings.
The impact of a second screening was greater in men than in women, with respective yield increases of 34% and 26%. More specifically, the first FSG detected advanced colorectal neoplasia in 26 of every 1000 women and 49 of every 1000 men screened, while the second FSG detected advanced colorectal neoplasia in 13 of every 1000 women and 27 of every 1000 men screened.
The gender-related differences in yield were partly due to the fact that more men than women had at least one sigmoidoscopy (adjusted difference=3.9) and more males also screened positive for polyp or mass than women (39.4% vs 26.1%).
Cumulatively, 22.9% of participants had a diagnostic intervention. The intervention rate was 74.9% among individuals who were screen positive at the first screen and 78.7% among those who were screen positive at the repeat screen.
The similar rates of intervention after first and second screening "suggest that PLCO screening and intervention procedures, instead of producing participant fatigue, sustained participants' willingness to undergo screening and diagnostic intervention for FSG-detected abnormalities."
The researchers note that 82.1% of screen-detected carcinomas were early stage (stage I or II).
"Subsequent analyses that compare the PLCO intervention group and control group (usual care) will determine whether screening works to reduce incidence or mortality, from colorectal cancer overall and from cancer in the rectum, distal colon, and proximal colon specifically," conclude Weissfeld and co-authors in the Journal of the National Cancer Institute.
MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2012
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