Application of joinpoint regression in determining breast cancer incidence rate change points by age and tumor characteristics in women aged 30–69 (years) and in Isfahan city from 2001 to 2010
Volume 4, Issue 5, Autumn 2014, Pages 1-10
. Zahra Fazeli Dehkordi, . Mehdi Tazhibi, . Shadi Babazade
Abstract Background and Objectives: Breast cancer is a major threat to women’s health. Evaluation
of the changes in trend of the incidence rate provides valuable information for the assessment
and planning of development indicators of each country. The aim of the present study was to
apply the JoinPoint regression model for determining changes in the trend of the breast cancer
incidence rate in Isfahan. Materials and Methods: In this cross‑sectional study, 3640 women
with breast cancer referring to oncology and radiotherapy departments of Seyed‑al‑Shohada
and Milad cancer treatment centers of Isfahan during 2001–2010 were studied and sampling
was not done. Joinpoint regression model was used to investigate the pattern of breast
cancer incidence rate. Response and independent variables were the natural logarithm of the
age‑standardized incidence rates and year of diagnosis of breast cancer, respectively, in which
various levels of cancer tumor characteristics (P < 0.05) were analyzed. Results: The incidence
rates increased annually in the age groups of 40–44 years (6.2%), 45–49 years (5.3%), and
55–59 years (5.3%). The trend of incidence rates in women with tumor size ≤2 cm (18.2%),
well (moderately) differentiated tumor grade [8% (10.2%)], positive estrogen (progesterone)
hormone receptor status [10.5% (6.9%)], and the proportion of positive lymph node to surgery
node ≤25% (nonsignificant) was upward. Conclusion: The trend of incidence rates with tumor
size ≤2 cm, well‑differentiated tumor grade, moderately differentiated tumor grade, and positive
estrogen and progesterone hormone receptors was upward. The pattern of breast cancer can
help in cancer prevention and prognosis, and in selecting the best type of surgery.