It has long been thought that there is a link between thyroid cancer and breast cancer, especially with iodine 131 treatment after total thyroidectomy, and many suspect that it may increase the risk of breast cancer development. A recent study in Korea found that iodine 131 internal radiation therapy did not increase the risk of breast cancer development. Researchers at Seoul National University Hospital in Korea, a region with a high incidence of thyroid cancer, recently conducted a retrospective analysis of their 3,631 female patients treated with spot 131 after total thyroid cancer from 1973 to 2009, and found that 99 of these more than 3,000 patients had concomitant breast cancer after long-term follow-up. A statistical risk model analysis showed that patients who received iodine 131 internal radiation therapy had similar incidence rates compared to those who did not receive iodine 131 therapy and did not have an increased incidence of breast cancer. Dr. Harold Burstein of the Harvard Medical School noted that this study is the first to demonstrate that radioactive iodine 131 therapy is a safe treatment and does not lead to an increased incidence of other cancers.