From the current work it is evident that
From the current work, it is evident that MM incidence in India exhibits considerable variation across sex, age and geographical regions of the country. A male preponderance was noticed. The MM rates (both crude and age-adjusted) in men exceeded those in women (at zonal as well as national levels), which concurs with reports from other world regions [12,35,36]. With respect to age, some hospital-based studies have previously reported a lower age of MM onset in Indian patients (median: ∼55 years) [13,15,16,18,19,37]. This is nearly a decade earlier than that in the USA (median: ∼67 yrs in Blacks, ∼66 yrs in Hispanics, and ∼71 yrs in Whites) [16,36,37]. The reported median MM onset age of around 55 years in Indians is also quite early than that in other Asian patients, viz. Thai (59 yrs), Chinese (59 yrs), Koreans (61 yrs), Singaporean (62 yrs), Taiwanese (63 yrs), Hong Kongese (65 years) and Japanese (66 yrs) , and patients from Latin America (61 yrs)  and Africa (62 yrs) . However, the current study found that most MM patients from India overall were aged between 60 and 69 yrs at the time of diagnosis. Exceptions to this trend were seen in the Northern and Central zones where 50–59 yrs was the most common age category for MM detection, and also in the Eastern zone where the majority of the new MM patients were aged 70 yrs or older. In addition to these variations, stark differences in age-adjusted incidence existed across the different zones of India. For example, the AARs for the Northern and Southern zones were at par or higher than the global average, whereas the AAR for the Northeastern zone matched those for world regions with the lowest AAR values. This remarkable heterogeneity in MM incidence across different zones of India may be due to the differences in environmental and lifestyle factors. This may partly explain the lesser incidence of MM in the remote Northeastern zone as compared to the MM incidence in the PBCRs located in the relatively more industrial and developed Northern and Southern zones. Urban areas are usually associated with greater environmental and occupational exposure to air pollutants, chemical carcinogens and ionizing Loxapine Succinate and also with lifestyle factors (viz. Westernized diet and greater presence of overweight/ obesity) that are known to predispose to MM [10,12,34,, , , , ]. Further, quality of health care resources may affect myeloma diagnosis. In general, MM incidence in urban/metropolitan areas is higher than that in rural areas [45,46]. Since MM is a rare disease and its diagnosis is lab-intensive requiring sensitive investigations, hence it may be under-reported if the available healthcare facilities for myeloma detection are inadequate. Urban and industrialized areas with better health facilities are more likely to have improved myeloma detection than their rural and less developed counterparts; and this may partly account for the higher incidence of myeloma in urban localities. In general, the healthcare resources in northeast India are modest as compared to other parts of the country . However, it deserves mention that the states in the Northeastern zone otherwise have a very high burden of overall cancer in general. In fact, unlike for MM, the highest AAR values for cancer in general for both males and females in India are reported from PBCRs of the Northeastern zone (Aizawl district under Mizoram PBCR for males, Papumpare district under Naharlagun PBCR for females) . In addition to environmental factors, genetic susceptibility to MM is suggested to vary by the racial background [, , , ,11]. The Indian population is heterogeneous and multiracial with diverse ethnic affiliations. Thus, it is plausible that both genetic and environmental factors are collectively responsible for the heterogeneity in MM incidence noticed among the different zones in India. The urban versus rural disparities in MM incidence in India could not be explored in details in the current analyses. That was because most PBCRs in the country (listed in Supplementary material 1) cater to populations from entire state or district(s), i.e. both rural and urban areas fall under the geographical area of the PBCR. Cancer data from the rural and the urban areas under such PBCRs are not provided separately in the NCRP reports . Only the Barshi (rural) registry covered an exclusively rural population in the 2012-14 period, where the crude and age-adjusted MM rates in men as well as women were considerably lower than those in the exclusively urban registries [namely: Chennai, Delhi, Bangalore, Ahmedabad (urban), Kolkata, Kamrup (urban), Mumbai, Pune, Nagpur, Aurangabad, and Bhopal].