Evaluation of effectiveness of mass screening for colorectal cancer.

As the first step in the epidemiological evaluation of the effectiveness of mass screening for colorectal cancer, we compared clinicopathological features and survival rates of patients with cancer detected by mass screening (screened group) with those for patients treated in our outpatient clinic in the same period (outpatient group). The screened group consisted of 53 patients with colorectal cancer detected by 2-day or 3-day screening for fecal occult blood by guaiac slides. Their background factors were comparable to those of 120 patients of the outpatient group in regard to age, sex ratio, location of cancer, and histological type of cancer. In the screened group, 90% of patients had no complaints, and positive occult blood tests led to the detection of cancers. More than 60% of the patients had Dukes' A and B1 early cancers while only about 30% had advanced cancers. In the outpatient group, nearly 90% of patients were symptomatic, most commonly from rectal bleeding. Early-stage cancers made up only 20%, and large, advanced-stage cancers accounted for 80%. The 5-year survival rate of the screened group was 91.5%, being significantly higher than the 60% survival rate for the outpatient group. It is anticipated that mass screening for colorectal cancer by guaiac fecal occult blood testing will significantly reduce the mortality due to this neoplasm.

Mass screening for colorectal cancer by testing for occult blood under restricted diet and a questionnaire in Osaka.

Because of the recent increase in the incidence of colorectal cancer in Japan, attempts were made to find an effective method for screening asymptomatic patients with this cancer. A total of 12,520 participants in Osaka were screened in a 2-year program from April 1982 by a test of fecal occult blood under a restricted diet, and a medical questionnaire. Occult blood in feces was examined for 3 consecutive days using one guaiac-impregnated slide (Shionogi B) each day. This slide was about twice as sensitive as the Hemoccult slide. Further diagnostic workups were required in 3,452 individuals, of which 2,602 (75.7%) were due to positive occult blood. Proctosigmoidoscopy was performed in 2,214 (64.4%) of these persons, barium enema in 1,397 persons, and flexible colonoscopy in 187 persons. Colorectal cancers were detected in 18 patients (0.14% of the total screened); ten of these cancers were in an early stage. Thus this screening method is reliable for detecting asymptomatic cancer of the colon and rectum.

[Occult blood screening for colorectal cancer].

Because of the recent increase in the incidence of colorectal cancer in Japan, attempts were made to find an effective method for screening asymptomatic patients with this cancer. In current mass screening, guaiac-impregnated slides such as the Shionogi and Hemoccult types are widely used. A screening system consisting of examination with Shionogi B slides for 3 consecutive days under mild restricted diet and a medical questionnaire, followed by re-examination under a restricted diet for persons showing a partially positive result is accepted as the most reliable screening method. As these slide tests are based on peroxidase-like activity in hemoglobin, dietary fiber, meat, peroxidase-containing foods and drugs influence the sensitivity and specificity of the test. Recently, immunological fecal occult blood tests with high sensitivity and specificity such as RPHA or Feca-EIA have been developed. We have evaluated the RPHA method and compared it with the Shionogi B slide. The positive rate of the RPHA method was rather lower than that of the Shionogi test and the detection rate of Colorectal cancer was equivalent to that of Shionogi. We are now applying the RPHA method to mass screening, and the Feca-EIA Test is also under consideration for practical use.

[Mass screening for breast cancer--the results for 15 years].

Mass screening for breast cancer has been carried out in 13 cities in Osaka Prefecture for the past 15 years. The screening method was inspection and palpation by the physician, and examination by mammography was performed for the women with abnormal findings as the second screening. Among the total of 73,488 examinees (actual number was 44,835 examinees) 3,022 (4.1%) were examined by mammography and 106 (0.14%) patients with breast cancer were detected. Seventy-two of them were found at the first screening, 15 at the subsequent screening, and 19 were interval cases. Sixty-two cases of breast cancer (63.9%) were without lymph node metastasis, and cancer in Stage I and TIS reached 37.8% in this series. These results show that our screening method is valid for detecting the earlier stages of breast cancer.

[Mass screening for colorectal cancer by occult blood testing under restricted diet].

We conducted a mass screening survey for colorectal cancer by the combination of fecal occult blood tests under a restricted diet and a medical questionnaire in 7,392 healthy volunteers. Further diagnostic work-up was needed in 1,934 (26.2%) individuals. Of these, 1,409 (72.9%) showed occult blood in at least one slide, 245 (12.7%) had symptoms and 306 (15.8%) had a positive family history. Proctosigmoidoscopy, barium enema and flexible colonoscopy were performed in 1,251, 779 and 95 persons, respectively. Colorectal cancers were detected in 10 individuals (0.14%); 5 of these were in the early stage.