Cancer survival in Khon Kaen, Thailand, 1993-1997.

The Khon Kaen cancer registry was established in 1984 as a hospital-based cancer registry, and population-based cancer registration started in 1988 with retrospective data collection from 1985. Cancer registration is done by passive and active methods. Data on survival for 13 cancer sites or types registered during 1993-1997 were reported. Follow-up was done by active methods, with median follow-up ranging between 8-32 months for different cancers. The proportion with histologically verified diagnosis for various cancers ranged between 54-100%; death certificates only (DCOs) comprised 0-5%; 85-97% of total registered cases were included for survival analysis. Five-year follow-up ranged from 40-83%. Five-year age-standardized relative survival rates for common cancers were cervix (58%), breast (61%), colon (39%), ovary (43%), non-Hodgkin lymphoma (42%) and rectum (43%). Five-year relative survival by age group portrayed an inverse relationship or was fluctuating. Five-year survival was the highest for localized disease, followed by the regional and distant metastasis categories. Trends in 5-year relative survival in 1993-1997 compared to 1985-1992 showed a marked increase for cancers of the rectum, breast, ovary, Hodgkin and non-Hodgkin lymphomas and decrease for cancers of the lip and larynx.

Loss-adjusted survival of cervix cancer in Khon Kaen, Northeast Thailand.

For incident cancers of the cervix uteri (601 cases) registered in the population-based cancer registry of Khon Kaen province, Northeast Thailand, in 1985-1990 loss-adjusted survival probabilities were estimated by a logistic regression model with four prognostic factors (age at diagnosis, stage of disease, place of residence and treatment), and compared with observed survival, estimated by the actuarial method. All patients were followed up for a minimum of 5 years, using both passive and active methods. In all, 27.6% of patients were lost to follow-up within 5 years of the index date. The overall observed survival at 5 years was 56.8% and loss-adjusted survival was 54.7%. The difference between the loss-adjusted and observed survival at 5 years was small: 2.1% overall, varying between 0.8 and 3.5 percent units for any prognostic group. The assumption of independence of loss to follow-up and death in the calculation of survival by the actuarial method in this, and probably in other, population-based series, is reasonable and leads to no material bias in the estimates.

Prevalence of Opisthorchis viverrini infection and incidence of cholangiocarcinoma in Khon Kaen, Northeast Thailand.

Liver cancer is the most common cancer in Khon Kaen, Northeast Thailand, because of the high incidence of cholangiocarcinoma (CHCA). Opisthorchis viverrini (OV), a liver fluke, is endemic in the area, and has been evaluated as a cause of CHCA by International Agency for Research on Cancer. Residents of 20 districts in the province were invited to attend a mobile screening programme between 1990 and 2001. Of 24 723 participants, 18 393 aged 35-69 years were tested for OV infection, by examining stools for the presence of eggs. Prevalence of infection in each district was estimated from the sample of the population who had been tested. The incidence of liver cancer in 1990-2001 was obtained for each district from the cancer registry. The average crude prevalence of OV infection in the sample subjects was 24.5%, ranging from 2.1% to 70.8% in different districts. Truncated age-standardized incidence of CHCA at ages >35 years varied threefold between districts, from 93.8 to 317.6 per 100,000 person-years. After adjustment for age group, sex and period of sampling, there was a positive association between prevalence of OV infection and incidence of CHCA at the population level. Associations between CHCA and active OV infection in individuals have become hard to demonstrate, because of effective anti-OV treatment. The relationship may, however, be clear in comparisons between populations, which, for infectious diseases, take into account the contextual effects of group exposure in determining individual outcome. The cancer registry is an appropriate tool for disease monitoring in small areas.