Diverging breast and stomach cancer incidence and survival in migrants in The Netherlands, 1996-2009.

BACKGROUND: Migrant populations usually experience a health transition with respect to their cancer risk as a result from environmental changes and acculturation processes. We investigated potentially contrasting experiences with breast and stomach cancer risk and survival in migrants to the Netherlands in a retrospective cohort study.
METHODS: Invasive breast (n = 96 126) and stomach cancer cases (n = 24 496) diagnosed 1996-2009 were selected from the population-based Netherlands Cancer Registry. Standardized Incidence Ratios (SIRs) were computed as the ratio of observed and expected cancers. Differences in survival were expressed as relative excess risk of mortality (RER).
RESULTS: Women from Morocco, Suriname and Turkey exhibited a significantly lower risk for breast cancer than native Dutch women (SIR range 0.5-0.9). Relative excess mortality was significantly increased in Surinamese (RER = 1.2, 95% CI 1.0-1.5) patients. The incidence of non-cardia stomach cancer was significantly elevated in all migrants, except in Indonesians, being highest in Turkish males (SIR = 2.2, 1.9-2.6). Cardia stomach cancer appeared to be less frequent in all migrants, being lowest in Surinamese males (SIR = 0.3, 0.2-0.5). Relative excess mortality was significantly lower in patients from the Antilles (RER = 0.7, 0.5-1.0), Suriname (0.8, 0.6-0.9) and Turkey (0.7, 0.6-0.9).
CONCLUSION: The lower incidence rates of breast and cardia stomach cancer in migrants as well as their higher non-cardia stomach cancer rates reflect most likely early life exposures including pregnancy and/or dietary patterns during life-course. While higher relative excess mortality from breast cancer in migrant women might point toward inadequate access and treatment in this group, lower excess mortality from (especially non-cardia) stomach cancer remains to be explained.