Breast cancer laterality among Egyptian patients and its association with treatments and survival

Abstract

Background and aim: Breast cancers (BCs) involve the left side (LS) more than the right side (RS). Among the Egyptians, neither BC laterality nor its association with demographic factors, tumor locations, treatments and outcomes were previously reported.

Patients and methods: Laterality was analyzed among 5459 BCs from the Gharbiah population-based cancer registry covering >5% of the Egyptian population. Cox proportional model was used to assess the independent effect of stage, ER, and laterality on overall survival (OS).

Results: In Egypt, BCs involve LS more than RS with LS-to-RS ratio (LRR) of 1.16. LS predominance was evident among men and women and both younger (< 45 years) and older patients. HER2 over-expression and ductal cancers were significantly more in RSBCs while lobular cancers were significantly more in LSBCs. There were no significant differences in localization within the breast between LSBCs and RSBCs (p = 0.51). LS predominance was noticed across all subgroups except in patients with HER2 positive tumors (LRR = 0.63; p = 0.02). OS was significantly better in stage II and ER positive tumors than stage III and ER negative tumors. Despite OS of LSBCs being generally lower than RSBCs, this was not statistically significant. The significant impact of stage on OS was lost in LSBCs.

Conclusions: Among Egyptian patients, the left breast is at greater risk of cancer than the right one. Despite right-sided tumors seemed more aggressive, Left-sided ones tend to confer worse survival than right-sided tumors.

Keywords: Breast cancer; Egypt; Laterality; Survival; Therapy.