Incidence and Current Trends of Colorectal Malignancies in an Unscreened, Low Risk Population

Introduction: Karachi falls into a low risk region for colorectal (CRC). The incidence rate is known butdetailed epidemiology and pathology data regarding the disease are not available. The aim of this study is todescribe CRC with reference to incidence, gender; topographic sub-site, tumor morphology, grade and stage atdiagnosis and to determine the trends of incidence. Materials and
Methods: Four hundred and seventy threecases of colorectal cancer submitted to the Karachi Cancer Registry for Karachi South, years 1995-2002 werereviewed. Cases were analyzed in two time periods (1995-7 and 1998-2002) to facilitate the study of time trends.
Results: A total of 151 CRC cases were registered during period one [86 (57%) males; 65 (43%) females] and322 cases [210 (65%) males; 112 (35%) females] in period two. Age standardized rate (ASR) world per 100,000,crude incidence rate (CIR) and relative frequency in period one were 5.3, 3.2 and 4.1% in males and 5.5, 3.2and 3.2% in females respectively. Corresponding figures for period two were 7.1, 4.5 and 4.7% for males and5.2, 2.8 and 2.7% in females. The male, female ratio was equal for colon (1:1). Men had more rectal cancers(2:1) and overall CRC (1.7:1). The mean age of the patients varied with sub-site and gender from 43.7 years to51.2 years. Cancers of the rectum presented at a relatively earlier age. Less then 5% of the cases were diagnosedin adolescents, 50% above 50 years of age and only 30% above 60 years. The ratio under-40 to above-40 forCRC patients was 0.3, which is much higher than the international average, indicating a younger age group atrisk. The first cases were observed in adolescents (15-19 years) and a peak was observed in the seventh decade.Colon to rectum ratio was 1:1 in males and 2:1 in females. Most cases presented with advanced disease, thoughsome down staging was observed in period 2 (1998-2002).
Conclusion: The current low but increasing incidence(especially in men), the younger age and advanced stage of CRC at diagnosis reflects a low risk, unscreenedpopulation. With existing prevalence of high risk factors in Pakistan, the low CRC incidence may be an artifact.There are concerns that an aging population over the next decade and changing lifestyle patterns may translateinto a higher CRC incidence. Screening must be considered as part of the health sector planning for the futureand include the high risk younger age groups.