Breast cancer in Iraq is associated with a unimodally distributed predominance of luminal type B over luminal type A surrogates from young to old age

Runnak A Majid, Hemin A Hassan, Dana N Muhealdeen, Hazha A Mohammed, Michael D Hughson

Breast cancer has recently increased in post-menopausal Iraqi women. In Western countries at high-risk for breast cancer, there is a bimodal increase in estrogen receptor (ER) positive tumors with a peak of low proliferation rate luminal A over higher proliferation rate luminal B tumors after 60 years of age. The aim of this study was to analyze in Iraqi women whether shifts are occurring in immunohistochemical (IHC) surrogates of molecular breast cancer subtypes toward a high-risk profile. Age specific and age standardized womens breast cancer incidence was estimated for the years 2006 through 2012. IHC results of ER, PR, HER2, and Ki67 testing were analyzed on the breast cancers of 125 Arabic and 725 Kurdish women by frequency of distribution and by age. Between 2006 and 2012, age standardized incidence of breast cancer in Iraq increased from 30 to 40/100,000 women with the increase specifically occurring in women ≥ 60 years old (P < 0.001). Breast cancers in Kurdish women ≥ 60 years old may also have increased (P = 0.047) with urban exceeding rural rates by 2:1. For both Kurdish and Arabic women, there was a marked predominance of luminal B tumors at all ages in which luminal B and luminal A tumors were asymmetric skewed toward older age but with no late luminal A age peak. Older Iraqi women do not show the bimodal shift toward higher rates of luminal A breast cancers seen in the West. The modest increase in age standardized incidence of breast cancer in Iraqi is being seen specifically in older women and may be better attributed to a trend for care in urban cancer centers rather than changing tumor characteristics.