title: 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.
abstract: OBJECTIVE
  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.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Biostatistics and Epidemiology, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Zahra Fazeli
authors.initials: ZF
authors.lastname: Dehkordi
authors.affiliation: Department of Biostatistics and Epidemiology, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Tazhibi
authors.affiliation: Department of Radiation Oncology of Breast Cancer of Seyed-al-Shohada, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Shadi
authors.initials: S
authors.lastname: Babazade
keywords: Age; breast cancer; incidence; joinpoint regression; tumor characteristics