Rural-urban residence and cancer survival in high-income countries: A systematic review.

There is some evidence that place of residence is associated with cancer survival, but the findings are inconsistent, and the underlying mechanisms by which residential location might affect survival are not well understood. We conducted a systematic review of observational studies investigating the association of rural versus urban residence with cancer survival in high-income countries. We searched the Ovid Medline, EMBASE, and CINAHL (Cumulative Index to Nursing and Allied Health Literature) databases up to May 31, 2016. Forty-five studies published between 1984 and 2016 were included. We extracted unadjusted and adjusted relative risk estimates with the corresponding 95% confidence intervals. Most studies reported worse survival for cancer patients living in rural areas than those in urban regions. The most consistent evidence, observed across several studies, was for colorectal, lung, and prostate cancer. Of the included studies, 18 did not account for socio-economic position. Lower survival for more disadvantaged patients is well documented; therefore, it could be beneficial for future research to take socio-economic factors into consideration when assessing rural/urban differences in cancer survival. Some studies cited differential stage at diagnosis and treatment modalities as major contributing factors to regional inequalities in cancer survival. Further research is needed to disentangle the mediating effects of these factors, which may help to establish effective interventions to improve survival for patients living outside major cities.