Subnational trends and provincial disparities in mortality-to-incidence ratios for six major cancers in Iran, 1990-2019.

Background

Cancer incidence and mortality vary substantially across regions, whereas direct population-based survival data remain limited in many settings, including Iran. The mortality-to-incidence ratio (MIR) is increasingly used as a population-level proxy for cancer survival and health system performance where survival registries are incomplete. This study examined long-term subnational trends and geographic disparities in MIR for six major cancers across 31 Iranian provinces from 1990 to 2019.

Methods

This ecological study used Global Burden of Disease 2019 estimates. Age-standardized incidence rates (ASIRs) and mortality rates (ASMRs) were extracted for prostate, stomach, and colorectal cancers in men, and breast, stomach, and colorectal cancers in women. MIR was calculated annually as ASMR divided by ASIR for each province, cancer type, sex, and year. Joinpoint regression estimated annual percent change (APC) and average annual percent change (AAPC) with 95% confidence intervals.

Results

ASIRs increased for prostate and colorectal cancers in men and for breast and colorectal cancers in women, while stomach cancer incidence declined modestly in both sexes. MIR declined significantly for all cancers studied. The greatest reductions were observed for prostate cancer in men (AAPC = -1.77%, p < 0.001) and breast cancer in women (AAPC = -1.54%, p < 0.001). Colorectal cancer MIR also declined in men (AAPC = -1.02%, p < 0.001) and women (AAPC = -0.56%, p < 0.001). Stomach cancer showed smaller reductions in men (AAPC = -0.32%, p < 0.001) and women (AAPC = -0.30%, p < 0.001), with high MIRs across most provinces. Sistan and Baluchistan remained a high-MIR province for several cancers.

Conclusions

MIR-based cancer outcomes improved in Iran, but marked cancer-specific and provincial disparities remained. High MIRs for stomach cancer and in underserved provinces highlight the need for targeted early diagnosis, timely treatment, and equitable cancer control strategies.