EFFECT OF AGE AT DIAGNOSIS ON THE PROGNOSES IN FEMALE BREAST CANCER PATIENTS IN GEORGIA

The aim of the study was to describe prognostic factors of Breast Cancer (BC) survival in relation to patient's age at diagnosis. Cox proportional hazard regression model was constructed. All women aged ≤80 years, diagnosed from 2006 to 2015 with invasive breast cancer, and included in the national cancer registry database, were eligible for inclusion in the analysis. We estimated hazard (mortality) ratio (HR) and 95% of confidence interval (95%CI). The patients under 41 years were selected as a reference group. High risk of death was defined as a mortality of BC patients within 5 years after diagnosis. Total number of BC cases enrolled in the study is 3852, about 10% of patients was under 41 years (a young group), 50% - 41-59 years (a middle age group), and 40% - 60 years and over (an elderly group). There were some age-specific differences in almost all the variables of interest: for example, 53.3% of patients aged under 41 years were detected at early stages (the first and second) compared with 46% in patients aged 41-59 years, and 45% in patients aged ≥60 years old. Younger women were more likely to have histologically poorly differentiated tumor; it was 42%, 35%, and 31% in young, middle, and elderly age group of patients accordingly. Utilization of radio and chemotherapy decreased with age. Application of radio and chemotherapy among young group of patients in comparison with older counterparts were about twice and 1.2 times higher accordingly. The HR for cancer cases detected at any stage, except of the first stage, was increasing with age and it was the highest and statistically significant for older patients, diagnosed at the second (HR=2.84; 95%CI=1.02-7.95) and fourth stages (HR=2.71; 95%CI=1.64-4.49). Poorly differentiated cancer has the worst outcome among elderly - aged ≥60 years old (HR=2.78; 95%CI=1.61-4.80), while moderately differentiated cancer survival is not related with patients' age during detection of cancer. In addition, absence of a radio or chemotherapy treatment is associated with increased hazard of mortality. In conclusion, the relatively low risk of mortality among young women diagnosed with BC in Georgia can be explained by the higher proportion of cases in the early stages and the high level of use of chemotherapy and radiotherapy.