Stage at Diagnosis and Relative Differences in Breast and Prostate Cancer Incidence in India : Comparison with the United States


Purpose: To examine and reconcile differences in incidence rates and stage-at-initial-presentation of prostate andbreast cancers in India, a country in epidemiologic transition.
Methods: Age-adjusted prostate and female breastcancer incidence rates and proportion of cases by stage-at-diagnosis were compared. Data were derived from theNational Cancer Registry Program of India, other Indian registries, the International Agency for Research on Cancer,and the US/ NCI Surveillance, Epidemiology, and End Results (SEER) Program.
Results: Average annual cancerincidence rates in India ranged from 5.0 to 9.1 per 100,000/year for prostate and 7.2 to 31.3 per 100,000/year forfemale breast. Comparative rates in the US for prostate cancer are 110.4 for Whites and 180.9 for Blacks; for femalebreast, the rates are 86.6 for Blacks and 96.4 for Whites. Notable differences were observed between rural and urbanareas in India, while such differences by rurality appear to be much smaller in the US. Overall, about 50-55% ofbreast cancer cases and about 85% of prostate cancers were detected at late (III and IV) stage; in contrast to the USwhere 15% of either cancer is diagnosed at late stage.
Conclusions: Differences in stage-at-diagnosis help explainvariations in incidence rates among cancer registries in India and rate differences between India and the US. Thesefindings indicate that erroneous inferences will result from incidence-rate comparisons that do not take into accountstage-at-diagnosis. Results also point to epidemiologic studies that could be conducted to deepen understanding ofthe etiology of these cancers. By enhancing data on staging, the Indian cancer registries could widen the scope ofcollaborative, cross-national research.