8 July 2019
Patients who have been diagnosed with atypical ductal hyperplasia (ADH) and lobular carcinoma in-situ (LCIS) have a much higher risk of developing breast cancer compared with the average population, usually well over the “high risk” threshold of 20%. Tamoxifen is recommended for these patients to reduce help reduce subsequent breast cancer risk, but a relatively low percentage of patients actually take it, often due to concerns about side effects.
In December 2018, the TAM-01 study was presented at the San Antonio Breast Cancer Symposium. This study used a reduced dose (5 mg instead of the usual 20 mg daily) of tamoxifen in women who had ADH, LCIS or ductal carcinoma in situ (DCIS) to see if a lower than standard dose could effectively reduce breast cancer risk.
The full manuscript* has recently been published. 500 women with a history of ADH, LCIS or DCIS were randomized to receive 3 years of either low dose tamoxifen or placebo. The study was performed in Italy. Mean patient age was 54, and 55% of the patients were post-menopausal. 20% had ADH, 11% had LCIS, and 69% had DCIS.
With a median follow up of 5.1 years, there were 14 cancers (invasive or DCIS) in the tamoxifen group and 28 in the placebo group (11.6 versus 23.9 per 1000 person-years). Tamoxifen decreased the number of contralateral (opposite side) events by 75% but numbers were low (3 versus 12). Daily hot flashes in patients receiving tamoxifen were more frequent (2 versus 1.5 per day) than in patients receiving placebo. There were no differences in patient-reported hot flash score (combination of hot flash frequency and intensity), vaginal dryness, pain during sexual intercourse, or joint / muscle pains between the 2 groups. There were fewer serious adverse events (blood clot, pulmonary embolus, uterine cancer) in the patients receiving tamoxifen versus placebo (12 versus 16). 65% of patients in the tamoxifen arm and 61% in the placebo arm took ≥85% of pills for the first 2 ½ years of the study. The authors concluded that low dose tamoxifen for 3 years can reduce the risk of invasive or non-invasive breast cancer, with similar side effects to placebo.
It is important to stress that this is one study, with a relatively small number of patients – 195 of the 253 in the tamoxifen arm completed the study. An important finding is that the authors found risk-reducing effects after only 3 years of therapy. However, current guidelines do still recommend standard (20mg) tamoxifen for 5 years for high risk patients as well as those with a history of estrogen-receptor positive (ER+) DCIS. There is no data on the use of low dose tamoxifen for invasive breast cancer treatment. However, for patients who are reluctant to take the full dose of tamoxifen, or who have significant side effects, it may be reasonable to consider a reduced dose – taking into account the patient’s individual risk, side effects of the standard 20mg dose, and the limitations of this study.
*Journal of Clinical Oncology Editorial: Will a low-dose option improve uptake of tamoxifen for breast cancer risk reduction?
*If you are not able to access the full study and would like a copy, please email me: contact at drattai dot com