Our controlled trial of screening for colorectal cancer has now been in progress for almost five years. Screening is accomplished by rigid sigmoidoscopy in control and study groups and, in addition, by fecal occult blood testing in the study group. Patients screened are men and women age 40 and older, mostly at average risk. Fecal occult blood testing is with Hemoccult slides with patients on a meat-free, highbulk diet without hydration, and with a four-day storage interval between slide preparation and testing. Patients with positive slides undergo diagnostic investigation that includes both colonoseopy and doublecontrast barium enema and, in some, an upper gastrointestinal series. Preliminary results to date include: patient baseline statistics and subgroup comparability, rate of positive slides of 1-4%, predictive value for neoplasia of 44-50%, false-positives of 0.5-2.1%, favorable Dukes' staging of cancers in the study group, and high patient compliance. Considerably more follow-up is needed in our study and control population, and issues such as mortality and cost need to be addressed. Additional time will be necessary to provide firm conclusions.
Cancer 4529 59 -2964, 19 80.
LINICAL TRIALS have been initiated recently in this C country to address the issue of screening for colorectal ~a n c e r . " ~~" ~ Interest in such trials has evolved over the past few years with the advent of fecal occult blood testing as a potential new approach to screening at this anatomic site. Previous techniques with fecal occult blood testing in combination with unrestricted diets and testing of single specimens were discarded as ineffective screening methods. l9 Introduction of the impregnated guaiac slide [Hemoccult@* (HO)] and the demonstration of its potential usefulness in asymptomatic patients on restricted diets with testing of multiple specimens stimulated a new interest in this a p p r ~a c h . ~
The justification for a renewed effort in screening for colorectal cancer in the United States is based on the high annual incidence of cancer