The available epidemiologic evidence does not support a carcinogenic effect of
silicone breast implants on breast or other
cancers. Data on
cancer risk other than
breast cancer are limited and few studies have assessed
cancer risk beyond 10-15 years after
breast implantation. We extended follow-up of our earlier cohort study of Danish women with cosmetic
breast implants by 7 years, yielding 30 years of follow-up for women with longest implant duration. The study population consisted of women who underwent cosmetic
breast implant surgery at private clinics of plastic surgery (n = 1,653) or public hospitals (n = 1,110), and a control group of women who attended private clinics for other plastic surgery (n = 1,736), between 1973-95.
Cancer incidence through 2002 was ascertained using the Danish
Cancer Registry. Risk evaluation was based on computation of standardized incidence ratios (SIR) and Cox proportional hazards models, adjusting for age, calendar period and reproductive history. We observed 163
cancers among women with
breast implants compared to 136.7 expected based on general population rates (SIR = 1.2; 95% confidence interval [CI] = 1.0-1.4), during a mean follow-up period of 14.4 years (range = 0-30 years). Women with
breast implants experienced a reduced risk of
breast cancer (SIR = 0.7; 95% CI = 0.5-1.0), and an increased risk of non-
melanoma skin cancer (SIR = 2.1; 95% CI = 1.5-2.7). Stratification by age at implantation, calendar year at implantation and time since implantation showed no clear trends, however, the statistical precision was limited in these analyses. When excluding non-
melanoma skin cancer, the SIR for
cancer overall was 1.0 (95% CI = 0.8-1.2). With respect to other site-specific
cancers, no significantly increased or decreased SIR were observed. Similar results were found when directly comparing women who had implants at private clinics with women who attended private clinics for other plastic surgery, with rate ratios for
cancer overall,
breast cancer and non-
melanoma skin cancer of 1.1 (95% CI = 0.8-1.6), 0.7 (95% CI = 0.4-1.3) and 1.5 (95% CI = 0.8-2.7), respectively. In conclusion, our study lends further support to the accumulating evidence that
silicone breast implants are not carcinogenic. Reasons for the consistently reported deficit of
breast cancer among women with
breast implants remain unclear, whereas increased exposure to sunlight may explain the excess occurrence of non-
melanoma skin cancer. We found no indication of delayed diagnosis of
breast cancer due to the presence of
breast implants.