title: Lower incidence but more aggressive behavior of right sided breast cancer in Pakistani women: does right deserve more respect?
abstract: BACKGROUND
  The aim of this epidemiological study was to establish the laterality of breast cancer (BC) and its association with size, receptor status of the primary tumor and bone metastasis (BM) in a local population.
  
  
  METHODS
  This retrospective study included cases of BC from Jan-2009 to Dec-2011 who were referred for metastatic work up or follow up survey with Technetium-99m MDP bone scan (BS) to the Nuclear Medicine Department of Karachi Institute of Radiotherapy and Nuclear Medicine (KIRAN). A total of 384 patients out of 521 were included and all reviewed for age, primary tumor size (PTS), laterality, receptor status like estrogen receptor (ER) progesterone receptor (PR) and Her-2-Neu receptor, presence or absence of BM with sites of involvement and time interval between diagnosis of BC and appearance of BM.
  
  
  RESULTS
  The left to right sided BC proportion was significantly higher than unity (59%:41%; p<0.001). The right sided BC was observed 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 predominance of 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 side with log rank value of 5.579; p<0.05. The Kaplan Meier survival plot for event free survival of BM in left sided BC was significantly higher than for the right side (log rank value=4.155, p<0.05), with an earlier appearance of BM in right BC.
  
  
  CONCLUSIONS
  1) A left sided predominance of BC was seen in local population; 2) right sided BC had a more aggressive behavior with extensive and earlier appearance of BM at relatively younger age, smaller PTS and receptor (s) negativity.
authors.affiliation: Karachi Institute of Radiotherapy and Nuclear Medicine, Karachi, Pakistan.
authors.forename: Nosheen
authors.initials: N
authors.lastname: Fatima
authors.forename: Maseeh Uz
authors.initials: MU
authors.lastname: Zaman
authors.forename: Aamir
authors.initials: A
authors.lastname: Maqbool
authors.forename: Shaista H
authors.initials: SH
authors.lastname: Khan
authors.forename: Nazia
authors.initials: N
authors.lastname: Riaz
mesh_terms: D000328:Adult; D000367:Age Factors; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000556:secondary*; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D015994:Incidence; D053208:Kaplan-Meier Estimate; D008875:Middle Aged; D010154:Pakistan / Q000453:epidemiology; D011877:Radionuclide Imaging; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone