title: Familial transmission of prostate, breast and colorectal cancer in adoptees is related to cancer in biological but not in adoptive parents: a nationwide family study.
abstract: OBJECTIVE
  Familial clustering of prostate, breast and colorectal cancer is well established, but the familial risk of these cancers has not been determined among adoptees. The aim was to disentangle the contributions of genetic and environmental factors to the familial transmission of prostate, breast and colorectal cancer.
  
  
  METHODS
  The Swedish Multi-Generation Register was used to follow all adoptees born between 1932 and 1969 (n=70,965) for prostate, breast and colorectal cancer from January 1958 up to December 2010. The risk of prostate, breast and colorectal cancer was estimated in adoptees with at least one biological parent with the same cancer type compared with adoptees without a biological parent with the same cancer type. The risk of cancer was also determined in adoptees with at least one adoptive parent with cancer compared with adoptees with an adoptive parent without cancer.
  
  
  RESULTS
  Adoptees with at least one biological parent with prostate, breast or colorectal cancer were more likely to have cancer of the same type than adoptees with biological parents not affected by these respective cancer types (standardised incidence ratio=SIR: 1.8 [95% confidence interval 1.2-2.7], 2.0 [1.6-2.5] and 1.9 [1.2-2.9], respectively). In contrast, adoptees with at least one adoptive parent with prostate, breast or colorectal cancer were not at an increased risk of these respective cancer types (SIR=1.2 [0.94-1.6], 0.97 [0.71-1.3], and 1.1 [0.71-1.5], respectively).
  
  
  CONCLUSIONS
  The findings of the study support the importance of genetic/biological factors in the familial transmission of prostate, breast and colorectal cancer.
authors: Center for Primary Health Care Research, Lund University, Malmö, Sweden. Electronic address: bengt.zoller@med.lu.se.
authors: Bengt
authors: B
authors: Zöller
authors: Center for Primary Health Care Research, Lund University, Malmö, Sweden.
authors: Xinjun
authors: X
authors: Li
authors: Center for Primary Health Care Research, Lund University, Malmö, Sweden; Stanford Prevention Research Centre, Stanford University School of Medicine, Stanford, CA, USA.
authors: Jan
authors: J
authors: Sundquist
authors: Center for Primary Health Care Research, Lund University, Malmö, Sweden.
authors: Kristina
authors: K
authors: Sundquist
mesh_terms: D000300:Adoption; D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000235:genetics; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000235:genetics; D004777:Environment; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000453:epidemiology* / Q000235:genetics; D012042:Registries; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology
keywords: Adoption; Breast neoplasms; Colorectal neoplasms; Epidemiology; Family; Genetics; Prostatic neoplasms