Here are the main results of the study:
The NCI researchers found no association between breast implants and the subsequent risk of breast cancer
In addition, they found no link between breast cancer risk and number of years of follow-up, nor with any particular type of implant. They did, however, see a shift toward somewhat later detection of breast cancers among the implant patients compared to the controls. Even though the differences were not statistically significant, there were consistently smaller percentages of in situ (early-stage) cancers among the implant patients. However, there was no significant difference in breast cancer mortality between the implant and comparison patients.
Reference: Brinton LA, Lubin JH, Burich MC, et al. Breast Cancer Following Augmentation Mammoplasty (United States). Cancer Causes & Control 2000; 11(9):819-827.
Women with implants were not at increased risk for most cancers with the exception of respiratory and brain cancers. The significance of the increased risks is not clear.
NCI researchers did not find increased risks for cancers of the stomach, large intestine, cervix, uterus, ovary, bladder or thyroid. Likewise, neither connective tissue nor immune system cancers such as soft tissue sarcomas, lymphoma, and multiple myeloma, developed at higher rates. These cancers were previously linked to implants in smaller studies. The cancer rates for brain and respiratory cancers, however, were two to three times greater in the implant patients compared to other plastic surgery patients; only the rates of respiratory cancers reached statistical significance. The significance of the findings is not clear. It is possible that the higher risks observed for respiratory and brain cancers are not related to exposure to silicone, but are due to either chance findings or to factors common to women who choose to have implants.
Reference: Brinton LA, Lubin JH, Burich MC, et al. Cancer Risk at Sites Other than Breast Following Augmentation Mammoplasty. Annals of Epidemiology May 2001; 11(4):248-256.