Cancer following breast reduction surgery in Denmark

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Abstract
Intuitively, breast tissue mass should be directly related to a woman'srisk of breast cancer, simply because having more cells at risk would seem toincrease the potential for malignant transformation. However, studiesattempting to link breast size with breast cancer risk have beeninconsistent. Limitations include crude measures of breast size, theinability to distinguish glandular from adipose tissue, and the confoundinginfluence of co-factors such as obesity. A nationwide study in Denmark wasundertaken to investigate the effect of breast reduction surgery on thesubsequent risk of breast cancer, including an evaluation of the patterns ofrisk by age and time since surgery. The Danish Hospital Discharge Registrywas used to identify women who underwent reduction mammaplasty between 1977and 1992. Linkage based on personal identification numbers with the DanishCancer Registry provided information on cancer incidence. Expected numbers ofcancers were calculated from rates in the general population. Among 7,720women whose breasts were surgically reduced, 182 cancers were subsequentlyobserved cf 209 expected (standardized incidence ratio [SIR] = 0.9; 95percent confidence interval [CI] = 0.7-1.0). Breast cancer was significantlyreduced by nearly 50 percent (29 observed cf 53.9 expected, SIR = 0.5, CI =0.4-0.8), and accounted for the overall deficit in cancer. The riskreductions were related inversely to age at surgery, with significantdeficits apparent only among women 40 years of age and older at surgery andespecially among those over age 50 (SIR = 0.3). No clear trend was apparentwith increasing years post-surgery. The findings indicate that breastreduction surgery among women over age 40 is associated with a lowersubsequent risk of breast cancer, but the surgery and presumably glandularmass appear less closely related to breast cancer risk among youngerwomen.

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