title: Postmenopausal cancer risk after self-reported endometriosis diagnosis in the Iowa Women's Health Study.
abstract: BACKGROUND
  Endometriosis, the presence of endometrial tissue outside the uterus, has an estimated prevalence between 4% and 10%. A recent study reported that women with a hospital discharge diagnosis of endometriosis were at increased risk of cancer at any site, breast cancer, ovarian cancer, and hematopoietic malignancies, especially non-Hodgkin lymphoma (NHL).
  
  
  METHODS
  The authors examined whether self-reported diagnosis of endometriosis was associated with increased risk of various cancers in the Iowa Women's Health Study. Incident cancer cases were identified from 1986 through 1998. Cox proportional hazards regression models were used to calculate relative risks and 95% confidence intervals for the particular cancers of interest.
  
  
  RESULTS
  Of 37,434 participants in this analysis, 3.8% reported a history of endometriosis at baseline in 1986. After 13 years of follow-up, 1795 breast, 188 ovarian, and 243 NHL cases were detected in the cohort. Endometriosis was not associated with risk of all cancers combined (age-adjusted relative risk [RR], 0.9; 95% confidence interval [CI], 0.7-1.2), breast carcinoma (RR, 1.0; 95% CI, 0.8-1.3), or ovarian carcinoma (RR, 0.8; 95% CI, 0.2-2.4). However, endometriosis was significantly associated with risk of NHL (age-adjusted RR, 1.8; 95% CI, 1.0-3.0), especially diffuse NHL (RR, 3.2; 95% CI, 1.8-5.6). Multivariate adjustment had minimal effect on the point estimates of risk (NHL RR, 1.7; 95% CI, 0.97-2.7; diffuse NHL RR, 3.3; 95% CI, 1.9-5.9). Endometriosis was not associated with elevated risk of lung, urinary tract, endometrial, melanoma, or colorectal carcinomas (RRs, 1.2, 0.8, 1.2, 0.7, and 0.7, respectively).
  
  
  CONCLUSIONS
  These results corroborate a previously reported association between endometriosis and increased risk of NHL but not cancer at other sites.
authors.affiliation: Mayo Foundation, Health Sciences Research, Rochester, Minnesota 55905, USA.
authors.forename: Janet E
authors.initials: JE
authors.lastname: Olson
authors.forename: James R
authors.initials: JR
authors.lastname: Cerhan
authors.forename: Carol A
authors.initials: CA
authors.lastname: Janney
authors.forename: Kristin E
authors.initials: KE
authors.lastname: Anderson
authors.forename: Celine M
authors.initials: CM
authors.lastname: Vachon
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Sellers
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology; D015331:Cohort Studies; D004715:Endometriosis / Q000150:complications*; D005260:Female; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008228:Lymphoma, Non-Hodgkin / Q000453:epidemiology / Q000209:etiology*; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000453:epidemiology / Q000209:etiology; D017698:Postmenopause; D018570:Risk Assessment