Tamoxifen is an effective treatment for breast cancer but an undesirable side-effect is an increased risk of endometrial cancer, particularly rare tumor types associated with poor prognosis. We investigated whether tamoxifen therapy increases mortality among breast cancer patients subsequently diagnosed with endometrial cancer. We pooled case-patient data from the three largest case-control studies of tamoxifen in relation to endometrial cancer after breast cancer (1,875 patients: Netherlands, 765; United Kingdom, 786; United States, 324) and collected follow-up information on vital status. Breast cancers were diagnosed in 1972 to 2005 with endometrial cancers diagnosed in 1978 to 2006. We used Cox proportional hazards survival analysis to estimate hazard ratios (HRs) and 95% confidence intervals (CI). A total of 1,104 deaths occurred during, on average, 5.8 years following endometrial cancer (32% attributed to breast cancer, 25% to endometrial cancer). Mortality from endometrial cancer increased significantly with unfavorable non-endometrioid morphologies ( Patients with endometrial cancer after breast cancer who received tamoxifen treatment for five years for breast cancer have greater endometrial cancer mortality risk than those who did not receive tamoxifen. For some women with breast cancer, taking adjuvant tamoxifen (Nolvadex®) for 10 years after primary treatment leads to a greater reduction in breast cancer recurrences and deaths than taking the drug for only 5 years, according to the results of a large international clinical trial. The findings from the ATLAS trial—presented at the San Antonio Breast Cancer Symposium (SABCS) and published in on December 5, 2012—are likely to change clinical practice, several researchers said. Nearly 7,000 women with early-stage, estrogen receptor-positive breast cancer were enrolled in the trial between 19. After taking tamoxifen for 5 years, participants were randomly assigned to continue taking tamoxifen for another 5 years or to stop taking it. From 5 to 9 years after the women began tamoxifen therapy, there was little difference in outcomes between the two treatment groups. This finding is consistent with those from other trials of adjuvant tamoxifen therapy, which showed that 5 years of tamoxifen can substantially reduce the risk of the cancer returning and of cancer death in the next few years, what one of the trial investigators, Richard Gray, MSc, of Oxford University, UK, called a "carryover effect." The improved outcomes with longer tamoxifen use emerged only after the 10-year mark, Gray explained during an SABCS press briefing. Among the women who took tamoxifen for 10 years, the risk of breast cancer returning between 10 and 14 years after starting tamoxifen was 25 percent lower than it was among women who took it for 5 years, and the risk of dying from breast cancer was nearly 30 percent lower.
Women who’ve had breast cancer can still get other cancers, although most don’t get cancer again. Breast cancer survivors are at higher risk for getting another breast cancer, as well as some other types of cancer. Steps for staying as healthy as possible include eating right, getting regular exercise, staying away from tobacco, and getting recommended screening tests. Breast cancer survivors can be affected by a number of health problems, but often a major concern is facing cancer again. Cancer that comes back after treatment is called a The most common second cancer in survivors of breast cancer is another breast cancer. The new cancer can occur in the opposite breast, as well as in the same breast for women who were treated with breast-conserving surgery (such as a lumpectomy). For some second cancers, shared genetic risk factors may play a role. Tamoxifen and raloxifene have been shown to reduce the risk breast cancer, but they can have their own risks and side effects. Tamoxifen and raloxifene are the only drugs that are approved in the US to help lower the risk of breast cancer, although for some women, drugs called aromatase inhibitors might be an option as well. This means that they act against (or block) estrogen (a female hormone) in some tissues of the body, but act like estrogen in others. Estrogen can fuel the growth of breast cancer cells. Tamoxifen can be taken whether or not you have gone through menopause, but raloxifene is only approved for post-menopausal women. Both of these drugs block estrogen in breast cells, which is why they can be useful in lowering breast cancer risk. To lower the risk of breast cancer, these drugs are taken for 5 years. The effect of these drugs on breast cancer risk has varied in different studies. When the results of all the studies are taken together, the overall reduction in risk for these drugs is about 40% (more than a third). These drugs lower the risk of both invasive breast cancer and ductal carcinoma in situ (DCIS). Although a medicine that cuts your risk by about 40% sounds like it must be a good thing, what it would really mean for you depends on how high your risk is in the first place (your baseline risk).
A risk factor is anything that affects your chance of getting a disease such as cancer. Although certain factors increase a woman's risk for developing endometrial cancer, they do not always cause the disease. Others, like a person’s age or family history, can’t be changed. Many women with one or more risk factors never develop endometrial cancer. Some women with endometrial cancer do not have any known risk factors. Even if a woman with endometrial cancer has one or more risk factors, there is no way to know which, if any, of these factors was responsible for her cancer. Several factors influence the risk of developing endometrial cancer, including: Some of these, like pregnancy, birth control pills, and the use of an intrauterine device are linked to a lower risk of endometrial cancer, while many are linked to a higher risk. These factors and how they affect endometrial cancer risk are discussed in more detail below. There was a twofold increase in the risk of endometrial cancer following extended versus standard adjuvant tamoxifen therapy in patients with breast cancer, a meta-analysis found. The systematic review of four randomized controlled trials showed that the absolute risk of endometrial cancer in patients receiving adjuvant tamoxifen for 10 years was 3.2% compared with 1.5% in patients receiving 5-year standard therapy (cumulative risk ratio [RR] 2.29, 1.60 to 3.28, Most tamoxifen-related uterine cancers occurred in patients who were postmenopausal and symptomatic, but diagnosed at an early stage and with a low grade, and carried a mortality risk of less than 1%, the authors wrote in the "There is a paucity of clear evidence on how we should best manage endometrial cancer risk in extended tamoxifen therapy," said Fleming in a statement. "This is a research area that requires immediate focus with expansion of extended tamoxifen therapy regimes." Few studies have data on endometrial surveillance in patients on adjuvant tamoxifen, the most recent of which (2003) was part of this review and did not find any benefit for routine endometrial surveillance in patients receiving tamoxifen for 5 years. Guidelines published by the American College of Obstetricians and Gynecologists, plus those from the Australian and New Zealand group do not recommend routine surveillance in asymptomatic patients receiving tamoxifen. "Although it is difficult to make clear evidence-based recommendations on endometrial surveillance in the setting of extended therapy because of the sparsity of robust results, a practical approach may be to screen all patients using endometrial ultrasonography after 5 years on tamoxifen," they wrote. "The validity of this approach should be assessed prospectively." Regarding breast cancer outcomes, Fleming's group observed a non-significant reduction in breast cancer-specific mortality in patients receiving tamoxifen for 10 years, from 11.6% to 10.1% (RR 0.94, He added that there are "many factors to consider in choosing endocrine therapy," including menopausal status, risk of breast cancer recurrence, bone health, other comorbid conditions, and tolerance of estrogen deprivation. Soliman, who was not affiliated with the study, noted that the absolute increase in endometrial cancer rates was very small.
Tamoxifen. Risk of blood clots, especially in the. Forbes JF, et al. Anastrozole for prevention of breast cancer in high-risk postmenopausal women. Feb 29, 2016. Different cancers have different risk factors. The risk of developing endometrial cancer from tamoxifen is low less than 1% per year. Women.