Impact of screening on presentation and survival of colorectal cancer

Abstract

1535 Background: There is an increasing emphasis and utilization of colorectal cancer (CRC) screening. We evaluated the effect of screening on CRC presentation and outcome. Methods: We reviewed all the invasive CRC cases diagnosed between Jan 1995-Dec 2005 at the Cincinnati Veteran’s Affairs hospital. Individual case records were reviewed and the data collected including patient demographics, treatment, outcome, mode of presentation as well as whether CRC was detected as a result of screening. Results: Altogether 288 patients were diagnosed with CRC during the study period. The median age at presentation was 69.3 years and 18.8% were African-Americans. Early stage CRC was diagnosed in 63.4% cases (stage 1: 32.7%, stage 2: 30.8%) and 33.3% were diagnosed at advanced stage (stage 3: 18.1% and stage 4: 15.3%). Seventy seven (26.7%) CRCs were asymptomatic at presentation and were diagnosed as a result of screening. Predominant screening modalities included fecal occult blood testing (46.8%) and flexible sigmoidoscopy (22.1%). The proportion of screen- detected cases increased from 19% in 1995–1999 to 32% in 2000–05 (p = 0.047). Demographics, including age and race, as well as the site of CRC were similar to symptomatic cases. Screen-detected cancers presented early, with 77.9% presenting at early stage (stage 1: 55.8%, stage 2: 22.1%), compared to 51.5% (stage 1: 21.0%, stage 2: 30.5%) of symptomatic cancers (p <0.01). Only 1.3% of screen-detected CRC was found to be metastatic as compared to 21.0% of the symptomatic cases. The screen-detected cancers had significant survival advantage compared to symptomatic cases; with median survival being 81 months vs. 43 months in the latter (p =0.018). A proportional hazard regression analysis indicated that this improvement in survival was related to the fact that screening resulted in earlier stage at diagnosis. Only 20.3% of screen-detected CRC received adjuvant chemotherapy compared to 41.4% of symptomatic cases (p=0.002). Conclusions: An increasing proportion of CRC is being diagnosed as a result of screening. These cancers present at an earlier stage and are associated with a significantly improved survival. However, most CRC still presents symptomatically and more effective population screening is needed. No significant financial relationships to disclose.