Identifying hormone receptor–positive breast cancer subtypes with recurrence scores derived from pathological data without Ki-67 indices: a clinicopathological study of breast cancer survival in West Asia

Breast cancer (BC) consists of several subtypes that vary regionally by incidence and mortality rates. The study population consisted of 1411 incident BCs diagnosed in Sulaimania, Iraq, in the years 2009-2014. Based upon positive (p) or negative (n) reactions, hormone receptor (HR)pHER2n tumors were divided into low recurrence risk (HRp low-risk) and high recurrence risk (HRp high-risk) subtypes with the Magee 2 equation that uses pathological data, without a Ki67 index. The 5-, 10-, and 13-year distant disease-free survival (DDFS) rates for the subtypes were estimated using proportional hazards models. The median age of patients for all subtypes was < 50 years. The proportion of subtypes was 29.6% for HRp low-risk, 36.2% for HRp high-risk, 11.8% for HRpHER2p, 11.7% for HRnHERp, and 10.6% for triple-negative (TN) BC. The 5-, 10-, and 13-year DDFS rates were as follows: HRp low-risk (n = 418, 85.5%, 74.4%, 71.7%), HRp high-risk (n = 511, 76.2%, 62.8%, 58.7%), HRpHER2p (n = 167; 77.7%, 58.6%, not reached), HRnHER2p (n = 165; 60.4%, 46.6%, not reached), and TNBC (n = 150; 61.4%, 54.2%, not reached). The difference in DDFS between HRp low-risk vs HRp high-risk was significant, p < 0.001, as were the differences between HRp high-risk vs HRnHER2p and HRp high-risk vs TNBC, both p < 0.001. The difference in DDFS between HRp high-risk vs HRpHER2p BC was not significant, p = 0.83, nor was the difference between HRnHER2p vs TNBC, p = 0.91. Distant disease or death from breast cancer was identified for 395 patients, 86 with HRp low-risk, 137 with HRp high-risk, 50 with HRpHERp, 69 with HRnHER2p, and 53 with TNBC. Iraqi HRpHER2n BCs can be separated into low and high risk using the Magee 2 risk assessment equation. The HRp low-risk BC has a favorable outcome. HRp high-risk was the most common subtype and the major cause of recurrent distant disease.