Temporal changes in regional variations in cancer survival rates in Osaka, Japan (1997-2015).

The variation in survival rates among patients with cancer based on residential areas has become a significant concern globally. Japan's Basic Plan to Promote Cancer Control Programs (BPPCCP), implemented in 2007, aimed to reduce this variation by designating cancer care hospitals in each cancer medical area (CMA) where patients resided. From the Osaka Cancer Registry data, we extracted 407,489 patients aged 15-74 years with cancer who received treatment in Osaka Prefecture between 1997 and 2015 and analyzed regional variations in survival rates for each patient's residential CMA before and after the implementation of the BPPCCP. By standardizing the distribution of the patients' background factors (sex, age, stage, and socioeconomic status) to the distribution of the whole prefecture, 5-year relative survival rates for each CMA were calculated, and regional variations were assessed. Before BPPCCP, survival variation reached 2.00 percentage points (p-values < 0.05); post-BPPCCP, it decreased to 0.98 percentage points and was no longer significant. In conclusion, the introduction of the BPPCCP in 2007 may have reduced regional variation in the survival rate of patients with cancer in Osaka Prefecture. Measures such as the BPPCCP could potentially equalize the cancer care delivery system.