ASYMPTOMATIC COLORECTAL-CANCER DETECTED BY SCREENING

PURPOSE: Colorectal cancer screening has become prevalent. To discuss the efficacy of screening, ave studied the characteristics of asymptom atic colorectal cancer detected by screening. METHODS: This is a retro spective review of patients with colorectal cancer treated at our inst itution. During the past 20 years, 96 of 1,046 cases of colorectal can cer were asymptomatic and detected by screening. Sixty-one of these ca ses were detected in the recent five years. The initial screening proc edures were fecal occult blood test in 51 cases, sigmoidoscopy or colo noscopy in 18, barium enema in 51, and other tests in 18. RESULTS: Thi rteen lesions (14 percent) were smaller than 1.0 cm and 32 (33 percent ) were 1-2 cm in size. There were 34 Tis, 21 T1, and 8 T2 tumors. Of t he 55 Tis or T1 lesions, 14 showed nonpolypoid growth (5 flat-elevated , 7 flat-elevated with depression, 1 flat, 1 depressed), and 12 of the se were detected on endoscopy. Thirty-four cases were TNM Stage 0, 25 were Stage I, 16 were Stage II, 12 were Stage III and 9 were Stage IV. Sixty-one percent of those detected by screening were in either Stage 0 or Stage I compared with 16 percent in the symptomatic group. Cumul ative five-year disease-free survival rates were 100 percent for both Stage 0 and Stage I, 94 percent for Stage II, and 52 percent for Stage III. Overall cumulative five year survival rate was 87 percent for th ose detected by screening, compared with 57 percent in symptomatic pat ients. CONCLUSIONS: Asymptomatic cancers detected by screening were at a less advanced stage. In particular, many nonpolypoid early cancers were detected by endoscopic screening.