Trends in 'cure' fraction from colorectal cancer by age and tumour stage between 1975 and 2000, using population-based data, Osaka, Japan.

Since the 1960s, Japan has experienced a striking increase in the incidence of colorectal cancer, now the second most common cancer in the country. Meanwhile, the management of colorectal cancer has changed dramatically with the implementation of, for example, screening, endoscopy and adjuvant chemotherapy. It is therefore of interest to monitor the long-term trends in population 'cure' in Japan. We analysed 33 885 colorectal cancer cases diagnosed between 1975 and 2000 in Osaka. We applied the multivariable mixture cure model to estimate cure fraction and median survival time (MST) for 'uncured' patients, by sex, age, stage, period at diagnosis and subsite. For colon cancer, the cure fraction increased by about 25%, while MST for the uncured was prolonged from 8 to 12 months. The cure fraction was 5% higher in men than in women, while MST was similar in both. The cure fraction also increased for localized and regional tumours. For rectal cancer, the cure fraction increased by about 25-30%, but remained lower than for colon cancer. From the late 1970s, the cure fraction for colorectal cancer increased dramatically due to better management of detection and care for colorectal cancer. This improvement was obtained at the cost of shorter MST for uncured patients.