Patho-epidemiology of breast cancer in Karachi '1995-1997'.

OBJECTIVE Provide an overview of the demographics and pathology of breast cancer in the female population of Karachi South during a 3 year period, 1995-1997. METHODS Epidemiological data for 709 incident breast cancer cases, ICD-10 category C50 registered at Karachi Cancer Registry during 1st January 1995 to 31st December 1997 were reviewed. RESULTS Breast cancer accounted for approximately one-third of the cancers in females. The age standardized incidence rate (ASR) world per 100,000 was 53.8, the crude incidence rate was 30.9. In KS 60% of the newly diagnosed breast cancers were observed in women below 50 years. The age-specific curves showed a gradual increase in risk from the third up till the seventh decade, followed by an actual/apparent decrease in risk. The socio-economic distribution was 24.9% in category I the financially deprived class, 38.9% in category II the middle class and 35.9% in category III, the affluent class. Microscopic confirmation of malignancies was 99%. Invasive breast cancers predominated with 99.4%, with in-situ cancers contributing to 0.6% of the malignancies. The morphology of cancers was tilted towards duct cell carcinoma (DCC), pure DCC (92%), combinations of DCC /Paget's disease (0.6%) and lobular carcinoma (0.4%). Approximately 45% of duct cell carcinoma were seen in the premenopausal age group (<45 years). All bilateral breast cancers were duct cell carcinoma with a family history of first degree relative with breast cancer. The majority of the cases presented as moderately differentiated or grade 2 lesions (59.0%). Approximately 56% cancers had spread to the regional lymph nodes and 8.3% to a distant site at the time of diagnosis. A family history of first degree relative with breast cancer was present in 3% and second degree relatives in 7% of the cases. Odds ratio (OR) for 680 breast cancer cases with complete demographic information was calculated with 675 gender matched controls. A slightly higher risk was observed in non-Muslims and migrant ethnicities: two to three fold elevation in the Indian migrants (Gujrati speaking Mohajirs OR 3.86 (95% CI 2.51; 5.92) Urdu speaking Mohajirs OR 2.85 (95% CI 2.05; 3.96), Memon Mohajirs OR 2.21 (95% CI 1.48; 3.29) and Afghan migrants [OR 2.99 (95% CI 11.20; 7.44)]. The risk was also high in the females of Punjabi ethnicity settled in KS [OR 2.73 (95% CI 1.87; 3.99)]. The risk seems much less for the ethnicities belonging to North Western Pakistan i.e. Pathans [OR 1.684 (95% CI 0.89; 3.17)] and Baluchs [OR 0.90 (95% CI 0.58; 1.39)]. A marginally higher risk was observed in the higher socio-economic categories. The risk of developing breast cancer increased gradually for each age category from illiterate [OR 1.2 (95% CI 0.94; 1.55)] to college graduates [OR 13.12 (95% CI 7.31; 23.73)]. CONCLUSIONS The incidence of breast cancer in Karachi South (KS) for the period 1995-1997 was the third highest in Asia. The hallmarks were a high reproductive age malignancy involving a higher socio-economic class, an invasive duct cell carcinoma diagnosed at an advanced stage, in younger more educated females and a low in-situ malignancy. More studies are required to obtain a deeper insight into this breast cancer epidemic in Karachi. Implementation of breast cancer screening with stress on public health education is today a major responsibility of the government.