Lower Incidence but More Aggressive Behavior of Right Sided Breast Cancer in Pakistani Women: Does Right Deserve More Respect?

Background: The aim of this epidemiological study was to establish the laterality of breast cancer (BC) andits association with size, receptor status of the primary tumor and bone metastasis (BM) in a local population.Materials and
Methods: This retrospective study included cases of BC from Jan-2009 to Dec-2011 who werereferred for metastatic work up or follow up survey with Technetium-99m MDP bone scan (BS) to the NuclearMedicine Department of Karachi Institute of Radiotherapy and Nuclear Medicine (KIRAN). A total of 384patients out of 521 were included and all reviewed for age, primary tumor size (PTS), laterality, receptor statuslike estrogen receptor (ER) progesterone receptor (PR) and Her-2-Neu receptor, presence or absence of BMwith sites of involvement and time interval between diagnosis of BC and appearance of BM.
Results: The leftto right sided BC proportion was significantly higher than unity (59%:41%; p<0.001). The right sided BC wasobserved in younger age group (46:52 years; p<0.0001) and with a smaller PTS than the left sided (3.43:4.15 cm;p<0.0001). The patients with BM had relatively higher negative receptor status with a significant predominanceof right sided BC. The overall incidence of BM on BS was 28% and relatively higher in right than left breast(33%:24% p=0.068). The average number of BM sites was also significantly greater for the right side (6:4,P<0.0001). The % cumulative risk of BM in right breast was noted at significantly smaller PTS than left sidewith log rank value of 5.579; p<0.05. The Kaplan Meier survival plot for event free survival of BM in left sidedBC was significantly higher than for the right side (log rank value=4.155, p<0.05), with an earlier appearance ofBM in right BC.
Conclusions: 1) A left sided predominance of BC was seen in local population; 2) right sided BChad a more aggressive behavior with extensive and earlier appearance of BM at relatively younger age, smallerPTS and receptor (s) negativity.