Uterine malignancies: Promptly evaluate abnormal vaginal bleeding in a woman with current or past tamoxifen use. Thromboembolic events: Risk increases with coadministered chemotherapy. For treatment of breast cancer, consider risks and benefits in patients with a history of thromboembolic events. Embryo-fetal toxicity: Can cause fetal harm. Advise females of reproductive potential of the potential risk to a fetus and to use effective contraception. ( 5.3 , 8.1 , 8.3 ) Effects on the liver: Liver cancer and liver abnormalities, some fatal, have occurred. Perform periodic liver function testing. 5.1 Endometrial Cancer, Uterine Sarcoma, and Other Effects on the Uterus Endometrial Cancer and Uterine Sarcoma An increased incidence of uterine malignancies (endometrial adenocarcinoma and uterine sarcoma), including fatal cases, has been reported with tamoxifen treatment. The underlying mechanism is unknown, but may be related to the estrogen-like effect of tamoxifen. Most uterine malignancies seen with tamoxifen are classified as adenocarcinoma of the endometrium; however, uterine sarcomas, including malignant mixed mullerian tumors (MMMT), have also been reported. Uterine sarcoma was generally associated with a higher FIGO stage (III/IV) at diagnosis, poor prognosis, and short survival. Uterine sarcoma has been reported to occur more frequently among long-term users (≥2 years) of tamoxifen than non-users. Promptly evaluate any patient receiving or who has previously received tamoxifen who reports abnormal vaginal bleeding. Patients receiving or who have previously received tamoxifen should have annual gynecological examinations. Advise patients to promptly inform a healthcare provider if they experience any abnormal gynecological symptoms (e.g., menstrual irregularities, abnormal vaginal bleeding, changes in vaginal discharge, or pelvic pain or pressure). There are no data to suggest that routine endometrial sampling in asymptomatic women taking tamoxifen is beneficial. In a review of long-term data (median length of total follow-up was 6.9 years, including blinded follow-up) on 8,306 women with an intact uterus at randomization in the NSABP P-1 risk reduction trial, the incidence of both adenocarcinomas and uterine sarcomas was increased in women taking tamoxifen. During blinded follow-up, there were 36 cases of FIGO Stage I endometrial adenocarcinoma (22 were FIGO Stage IA, 13 IB, and 1 IC) in women receiving tamoxifen and 15 cases in women receiving placebo [14 were FIGO Stage I (9 IA and 5 IB), and 1 case was FIGO Stage IV]. During total follow-up, endometrial adenocarcinoma was reported in 53 women randomized to tamoxifen (30 cases of FIGO Stage IA, 20 were Stage IB, 1 was Stage IC, and 2 were Stage IIIC), and 17 women randomized to placebo (9 cases were FIGO Stage IA, 6 were Stage IB, 1 was Stage IIIC, and 1 was Stage IVB) (incidence per 1,000 women-years of 2.20 and 0.71, respectively). Uterine sarcomas were reported in 4 women randomized to tamoxifen (1 was FIGO IA, 1 was FIGO IB, 1 was FIGO IIA, and 1 was FIGO IIIC) and 1 patient randomized to placebo (FIGO IA); incidence per 1,000 women-years of 0.17 and 0.04, respectively. Of the patients randomized to tamoxifen, the FIGO IA and IB cases were a MMMT and sarcoma, respectively; the FIGO II was a MMMT; and the FIGO III was a sarcoma; and the 1 patient randomized to placebo had a MMMT. A similar increased incidence in endometrial adenocarcinoma and uterine sarcoma was observed among women receiving tamoxifen in 5 other NSABP clinical trials. In the NSABP P-1 trial, endometrial sampling did not alter the endometrial cancer detection rate compared to women who did not undergo endometrial sampling (0.6% with sampling, 0.5% without sampling) for women who had not undergone hysterectomy. Non-Malignant Effects on the Uterus An increased incidence of endometrial changes including hyperplasia and polyps has been reported with tamoxifen treatment. The incidence and pattern of this increase suggest that the underlying mechanism is related to the partial estrogenic effect of tamoxifen. There have been reports of endometriosis and uterine fibroids in women receiving tamoxifen. Ovarian cysts have also been observed in premenopausal patients with advanced breast cancer who have been treated with tamoxifen. Tamoxifen has been reported to cause menstrual irregularity or amenorrhea
Thromboembolic Events There is an increased incidence of thromboembolic events, including deep vein thrombosis and pulmonary embolism, during tamoxifen therapy. When tamoxifen is coadministered with chemotherapy, there is a further increase in the risk of thromboembolic events. For treatment of breast cancer, carefully consider the risks and benefits of tamoxifen in women with a history of thromboembolic events. For women with DCIS and for the reduction in breast cancer incidence in women at high risk, tamoxifen is contraindicated in women who require concomitant warfarin-type anticoagulant therapy or in women with a history of deep vein thrombosis or pulmonary embolus. Advise patients to seek medical attention immediately if signs or symptoms of a thromboembolic event occur. Data from the NSABP P-1 trial in women at high risk for breast cancer show that participants receiving tamoxifen without a history of pulmonary emboli (PE) had a statistically significant increase in pulmonary emboli (events: 18 tamoxifen, 6 placebo; incidence rate per 1,000 women-years: 0.75 tamoxifen versus 0.25 placebo; RR = 3.01, 95% CI: 1.15 to 9.27) . Three of the pulmonary emboli, all in the tamoxifen arm, were fatal. Eighty-seven percent of the cases of pulmonary embolism occurred in women at least 50 years of age at randomization. Among women receiving tamoxifen, PE events occurred between 2 and 60 months (average = 27 months) from the start of treatment. In this same population, a non-statistically significant increase in deep vein thrombosis (DVT) was seen in the tamoxifen group (30 tamoxifen, 19 placebo; relative risk (RR) = 1.59, 95% CI: 0.86 to 2.98). The same increase in relative risk was seen in women ≤49 and in women ≥50, although fewer events occurred in younger women. Women with thromboembolic events were at risk for a second related event (7 out of 25 women on placebo, 5 out of 48 women on tamoxifen) and were at risk for thromboembolic event and treatment related complications (0/25 on placebo, 4/48 on tamoxifen). Among women receiving tamoxifen, DVT events occurred between 2 and 57 months (average = 19 months) from the start of treatment. In a small substudy (N = 81) of the NSABP-1 trial, there appeared to be no benefit to screening women for Factor V Leiden and Prothrombin mutations G20210A as a means to identify those who may not be appropriate candidates for tamoxifen therapy. In the NSABP P-1 trial, there was an increase in stroke among women randomized to tamoxifen compared to women randomized to placebo (events: 24 placebo; 34 tamoxifen; incidence rate per 1,000 women-years: 1.43 tamoxifen versus 1.00 placebo; RR = 1.42, 95% CI: 0.82 to 2.51). Six of the 24 strokes in the placebo group were considered hemorrhagic in origin and 10 of the 34 strokes in the tamoxifen group were categorized as hemorrhagic. Seventeen of the 34 strokes in the tamoxifen group were considered occlusive and 7 were considered to be of unknown etiology. Fourteen of the 24 strokes on the placebo arm were reported to be occlusive and 4 of unknown etiology. Three strokes in the placebo group and 4 strokes in the tamoxifen group were fatal. Eighty-eight percent of the strokes occurred in women at least 50 years of age at the time of randomization. Among women receiving tamoxifen, the stroke events occurred between 1 and 63 months (average = 30 months) from the start of treatment
Embryo-Fetal Toxicity Tamoxifen can cause fetal harm when administered to a pregnant woman. There are postmarketing reports of vaginal bleeding, spontaneous abortions, birth defects, and fetal deaths in pregnant women taking tamoxifen. In a primate model, administration of tamoxifen at doses 2 times the maximum recommended human dose resulted in spontaneous abortion. In rat and rabbit studies, doses of tamoxifen less than or equal to human doses resulted in increased embryotoxicity, abortions, and altered learning behaviors in the offspring. Additionally, rodent models showed reproductive tract changes often associated with diethylstilbestrol (DES) in offspring of both sexes. Advise pregnant women of the potential risks to a fetus, including the potential long-term risk of a DES-like syndrome. Advise females of reproductive potential to use effective non-hormonal contraception during treatment with tamoxifen and for 2 months following the last dose
Liver Cancer and Other Effects on the Liver Liver Cancer In the Swedish Breast Cancer Cooperative Group trial using adjuvant tamoxifen 40 mg per day (two times the recommended dosage) for 2 to 5 years, 3 cases of liver cancer were reported in the tamoxifen-treated group versus 1 case in the observation group . One case of liver cancer was reported in NSABP P-1 (women at high risk for breast cancer) in a participant randomized to tamoxifen . Hepatocellular carcinoma has been observed in animals receiving tamoxifen . Non-Malignant Effects on the Liver Tamoxifen has been associated with changes in liver enzyme levels, and on rare occasions, a spectrum of more severe liver abnormalities including fatty liver, cholestasis, hepatitis and hepatic necrosis. Some of these serious cases included fatalities. In most reported cases, the relationship to tamoxifen is uncertain. However, some positive rechallenges and dechallenges have been reported. Monitor liver function periodically. In the NSABP P-1 trial, grade 3 to 4 changes in liver function (SGOT, SGPT, bilirubin, alkaline phosphatase) were observed (10 on placebo and 6 on tamoxifen). Serum lipids were not systematically collected
Other Cancers A number of second primary tumors occurring at sites other than the endometrium have been reported following the treatment of breast cancer with tamoxifen in clinical trials. Data from the NSABP B-14 (adjuvant breast cancer study in women with axillary node-negative breast cancer) and P-1 studies show no increase in other (non-uterine) cancers among patients receiving tamoxifen . Whether an increased risk for other (non-uterine) cancers is associated with tamoxifen is still unknown
Hypercalcemia in Patients with Metastatic Breast Cancer As with other additive hormonal therapy (estrogens and androgens), hypercalcemia has been reported in some breast cancer patients with bone metastases within a few weeks of starting treatment with tamoxifen. If hypercalcemia occurs, treat as appropriate; if the hypercalcemia is severe, discontinue tamoxifen
Hematologic Effects Decreases in platelet counts, usually to 50,000-100,000/mm 3 , infrequently lower, have been reported in patients taking tamoxifen for breast cancer. In the NSABP P-1 trial, 6 women on tamoxifen and 2 on placebo experienced grade 3 to 4 decreases in platelet counts (≤50,000/mm 3 ). In patients with significant thrombocytopenia, hemorrhagic episodes have occurred, but it is uncertain if these episodes were due to tamoxifen therapy. Leukopenia has been observed, sometimes in association with anemia and/or thrombocytopenia. There have been reports of neutropenia and pancytopenia, including some severe cases, in patients receiving tamoxifen. Perform periodic complete blood counts, including platelet counts
Effects on the Eye Ocular disturbances, including corneal changes, decrement in color vision perception, retinal vein thrombosis, and retinopathy have been reported in patients receiving tamoxifen. An increased incidence of cataracts and the need for cataract surgery have also been reported. Patients should be advised to seek medical attention if they experience any visual disturbance. In the NSABP P-1 trial, an increased risk of borderline significance of developing cataracts among those women without cataracts at baseline (540 tamoxifen; 483 placebo; RR = 1.13, 95% CI: 1.00 to 1.28) was observed. Among these same women, tamoxifen was associated with an increased risk of having cataract surgery (101 tamoxifen; 63 placebo; RR = 1.62, 95% CI: 1.18 to 2.22) . Among all women on the trial (with or without cataracts at baseline), tamoxifen was associated with an increased risk of having cataract surgery (201 tamoxifen; 129 placebo; RR = 1.58, 95% CI: 1.26 to 1.97)
Laboratory Monitoring Perform periodic complete blood counts, including platelet counts, and periodic liver function tests during therapy with SOLTAMOX. Periodic monitoring of plasma triglycerides and cholesterol may be indicated in patients with preexisting hyperlipidemias.
