Differences Observed in the Site Incidence of Cancer, Between the Parsi Community and the Total Population of Greater Bombay: A Critical Appraisal

The Bombay Cancer Registry has been in operation since June 1963 and reliable morbidity data on cancer have since been obtained for the first time in India, from a precisely outlined population base delineated by residential qualifications within strict geographicalboundaries. An attempt has been made to examine the differences noticed in the site-specific cancer risks, between 2 groups of people living in this area—the Parsi community and the total Bombay population. The over-all age adjusted rates for the Parsis were found to be lower than those for the total population and more noticeably, their site-specific risks seem to differ radically from the Greater Bombay pattern. Thus, cancers of the buccal cavity, pharynx, larynx, oesophagus and cervix uteri, which are frequently seen in the total Bombay population, are less commonly observed in the Parsi community. On the other hand the Parsi rates are higher at sites such as the female breast, body of uterus, ovary, prostate and skin and for all leukaemias. Even though the population pyramid of the Parsi community is very different from that of the total population of Bombay, age correction does not change the basic outline of risk patterns noted in the 2 groups. Such site-specific contrasts are believed to be due to differences present in the habits, customs and economic status of the two groups. (A study of the probable aetiological factors of epidemiological importance involved in this segment of the population, is already under way in Bombay, in an effort to identify the reasons for the differences noted in cancer risks at different sites.)