BREAST CANCER IN WESTERN KAZAKHSTAN: INCIDENCE, MORTALITY AND FACTORS ASSOCIATED WITH SURVIVAL

Marzhan A. Aitmagambetova, Yerbol Bekmukhambetov, Gaziza Smagulova, Anar Balkashevna Tulyayeva, Arip K. Koyshybaev, A M Grjibovski

2021

Full text Open access: Gold Metadata (CSL-JSON)
DOI 10.33396/1728-0869-2021-7-51-57
Data confidence 70 medium
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Abstract

Background: Breast cancer is the most common cancer among women. Incidence of and mortality from breast cancer varies considerably between countries. The evidence from Kazakhstan, however, is almost non-existent in international peer-reviewed literature. Aim: To study incidence of and mortality from breast cancer in Western Kazakhstan and assesse selected determinants of survival among breast cancer patients. Methods: A registry-based historical cohort study. Data on all primary cases of breast cancer in the Aktobe region in 2014-2018 and their follow-up data were obtained from the regional cancer registry. Standardized incidence and mortality data were calculated using Segi world reference population. One- and five-years survival was calculated using actuarial analysis. Factors associated with survival were assessed using multivariable Cox regression. Crude and adjusted hazard ratios (HR) were calculated with 9 5 % confidence intervals (CI). Results: From 2014 to 2018, 891 new cases and 251 deaths from breast cancer were registered in the Aktobe region. Standardized incidence of breast cancer increased from 40.8 to 44.6 per 100,000 while standardized mortality decreased from 12.4 to 8.8 per 100,000 during the study period. Only 16.4 % of cases were diagnosed at stage I, while 21.6 % of cancer cases were detected at stage III or IV. One- and five-year survival estimates based on the registry data was 94.5 % (95 % CI: 92.5-96.5) and 90.2 % (95 % CI: 88.2-92.2), respectively. Patients with stage III (HR = 7.4, 95 % CI: 1.7-31.6) and stage IV (HR = 29.7, 95 % CI: 6.7-131.8) had shorter survival than patients with stage I. Conclusions: Both incidence and mortality of breast cancer in Western Kazakhstan are lower than in most European countries. The incidence has been gradually increasing while no clear pattern on mortality was observed. Surprisingly high level of five-year survival in the study area requires further investigation. The results should be interpreted with caution assuming valid data on cancer-specific mortality and non-differential reporting of deaths across the studied characteristics.