title: Risk of second cancer among women with breast cancer.
abstract: A large number of women survive a diagnosis of breast cancer. Knowledge of their risk of developing a new primary cancer is important not only in relation to potential side effects of their cancer treatment, but also in relation to the possibility of shared etiology with other types of cancer. A cohort of 525,527 women with primary breast cancer was identified from 13 population-based cancer registries in Europe, Canada, Australia and Singapore, and followed for second primary cancers within the period 1943-2000. We used cancer incidence rates of first primary cancer for the calculation of standardized incidence ratios (SIRs) of second primary cancer. Risk of second primary breast cancer after various types of nonbreast cancer was also computed. For all second cancer sites combined, except contralateral breast cancer, we found a SIR of 1.25 (95% CI = 1.24-1.26) on the basis of 31,399 observed cases after first primary breast cancer. The overall risk increased with increasing time since breast cancer diagnosis and decreased by increasing age at breast cancer diagnosis. There were significant excesses of many different cancer sites; among these the excess was larger than 150 cases for stomach (SIR = 1.35), colorectal (SIR = 1.22), lung (SIR = 1.24), soft tissue sarcoma (SIR = 2.25), melanoma (SIR = 1.29), non-melanoma skin (SIR = 1.58), endometrium (SIR = 1.52), ovary (SIR = 1.48), kidney (SIR = 1.27), thyroid gland (SIR = 1.62) and leukaemia (SIR = 1.52). The excess of cancer after a breast cancer diagnosis is likely to be explained by treatment for breast cancer and by shared genetic or environmental risk factors, although the general excess of cancer suggests that there may be additional explanations such as increased surveillance and general cancer susceptibility.
authors.affiliation: Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark. lene@cancer.dk
authors.forename: Lene
authors.initials: L
authors.lastname: Mellemkjaer
authors.forename: Søren
authors.initials: S
authors.lastname: Friis
authors.forename: Jørgen H
authors.initials: JH
authors.lastname: Olsen
authors.forename: Ghislaine
authors.initials: G
authors.lastname: Scélo
authors.forename: Kari
authors.initials: K
authors.lastname: Hemminki
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Tracey
authors.forename: Aage
authors.initials: A
authors.lastname: Andersen
authors.forename: David H
authors.initials: DH
authors.lastname: Brewster
authors.forename: Eero
authors.initials: E
authors.lastname: Pukkala
authors.forename: Mary L
authors.initials: ML
authors.lastname: McBride
authors.forename: Erich V
authors.initials: EV
authors.lastname: Kliewer
authors.forename: Jon M
authors.initials: JM
authors.lastname: Tonita
authors.forename: Chia
authors.initials: C
authors.lastname: Kee-Seng
authors.forename: Vera
authors.initials: V
authors.lastname: Pompe-Kirn
authors.forename: Carmen
authors.initials: C
authors.lastname: Martos
authors.forename: Jon G
authors.initials: JG
authors.lastname: Jonasson
authors.forename: Paolo
authors.initials: P
authors.lastname: Boffetta
authors.forename: Paul
authors.initials: P
authors.lastname: Brennan
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000473:pathology*; D015331:Cohort Studies; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009378:Neoplasms, Multiple Primary / Q000453:epidemiology* / Q000209:etiology*; D016017:Odds Ratio; D012307:Risk Factors