Answer: B. Offer all premenopausal females antiestrogen therapy after they complete breast cancer treatment.
The patient is a premenopausal female who has completed breast surgery, radiation therapy and adjuvant chemotherapy for her cancer. Because she is premenopausal she should be treated with antiestrogen therapy. Additionally, her breast cancer was estrogen receptor positive, which also is an indication for antiestrogen therapy.
The recommended adjuvant endocrine therapy following breast cancer treatment for a premenopausal patient is tamoxifen for at least 5 years, but preferably for 10 years to reduce her risk of recurrence. Tamoxifen has been the standard treatment in premenopausal women for a long time. Especially in cases where breast cancer is estrogen receptor positive, adjuvant antiestrogen therapy will reduce her risk of distant recurrence by 40% to 50%. Premenopausal women with hormone receptor–positive early-stage breast cancer should be advised to use tamoxifen for at least 5 years at a minimum but preferably 10 years based on the results of the Adjuvant Tamoxifen: Longer Against Shorter (ATLAS) and Adjuvant Tamoxifen Treatment Offers More (aTTom) trials.
Exemestane is an aromatase inhibitor. Aromatase inhibitors act by blocking the peripheral conversion of androgens to estrogens. Aromatase inhibitors are used only in postmenopausal women where the primary source of estrogen comes from the peripheral conversion of adrenal androgens. This patient would not benefit from exemestane alone because she is premenopausal and has ovarian function. Exemestane has recently been compared with tamoxifen in conjunction with ovarian suppression in premenopausal women. The Tamoxifen and Exemestane Trial (TEXT) and Suppression of Ovarian Function Trial (SOFT) trials showed improved disease free survival at 5 years for exemestane with ovarian suppression compared to tamoxifen with ovarian suppression, and this is now an option that can be discussed with premenopausal patients, particularly those at high risk of recurrence. But there is at present no difference in breast cancer mortality between these two treatments and the toxicity analysis of these treatments with ovarian suppression compared to tamoxifen alone has not yet been done. Another recent study has demonstrated that extending aromatase therapy for 10 years resulted in higher disease free survival and reduced cancer in the contralateral breast.
Currently, there is no evidence that maintenance chemotherapy is effective in early stage breast cancer and it has not been used outside of a clinical trial.
Pembrolizumab is an IgG4 isotype antibody that targets the PD-1 (programmed cell death 1) receptor of lymphocytes. It is used to treat metastatic melanoma and metastatic non small cell lung cancer. It is also used second line for head and neck carcinomas and refractory classic non-Hodgkin's Lymphoma. It is not used to treat breast cancer.
Without antiestrogen adjuvant therapy, this patient's risk of distant recurrence will increase. As above, antiestrogen therapy reduces the risk of breast cancer distant recurrence by 40 to 50% and also decreases the risk of contralateral breast cancers by 50%. Its use should be recommended in this patient with hormone receptor–positive early-stage breast cancer.
Reference:
Burstein HJ, Temin S, Anderson H, et al. Adjuvant endocrine therapy for women with hormone receptor-positive breast cancer: american society of clinical oncology clinical practice guideline focused update. J Clin Oncol. 2014 Jul 20;32(21):2255-69. PMID: 24868023
