Case-control, cohort and cross-sectional studies which included women with a diagnosis of breast cancer after previous cosmetic augmentation mammaplasty were eligible. Comparison groups could be women with a breast cancer diagnosis who had previous common elective cosmetic surgical procedures, or women from the general population of breast cancer patients.
Studies that assessed association of breast implants with stage distribution needed to report data for both exposed and non-exposed women at each breast cancer stage, for nodal status or metastases status, or a combination of these. Studies that assessed survival needed to provide hazard ratios for exposed and non-exposed women, or to show Kaplan-Meier curves for both groups.
Included studies used three different staging systems. Data on breast cancer were obtained mainly from cancer registries or medical records, data on augmentation surgeries from hospital/surgeons records or medical records. Most comparison groups were women from the general population; a minority had other cosmetic surgical procedures. A minority of studies reported adjusted analyses.
Two authors were involved in selecting the studies for the review.