Should We Embrace or Ablate Our Urge to (Ovarian) Suppress?

Abstract

The quest to define optimal endocrine therapy for premenopausal women with early-stage breast cancer began more than 50 years ago but is still unfulfilled. Multiple strategies have emerged, including tamoxifen, ovarian function suppression (OFS) by surgery, luteinizing hormone–releasing hormone agonist or radiation, and combination strategies such as tamoxifen plus OFS or aromatase inhibitor plus OFS. An added confounder is that these strategies have frequently been assessed in the context of adjuvant chemotherapy, which is commonly used in premenopausal women and may have indirect endocrine effects because of chemotherapy-induced menopause. This complex landscape was reviewed in a 2011 American Society of Clinical Oncology (ASCO) endorsement of the 2010 Cancer Care Ontario guideline recommending against the routine use of OFS in addition to tamoxifen or chemotherapy and a 2014 ASCO guideline endorsing consideration of 10 years of tamoxifen for these young women with hormone-responsive disease. Against this backdrop, in the article that accompanies this editorial, Tevaarwerk et al report the final results of a phase III Eastern Cooperative Oncology Group trial (E-3193, INT-0142) in which 345 premenopausal women with lymph node–negative, hormone receptor–positive breast cancer measuring 3 cm were randomly assigned from 1994-1997 to receive 5 years of tamoxifen alone or 5 years of tamoxifen plus OFS; no chemotherapy was permitted. With a median follow-up of almost 10 years, there were no significant differences in the primary end points of disease-free survival (DFS; 87.9% v 89.7% P .62) or overall survival (95.2% v 97.6%; P .67). Secondary end points included toxicity and several patient-reported outcomes (PROs) including menopausal symptoms, sexual function, and health-related quality of life. These results suggest that tamoxifen plus OFS leads to increased toxicity, more menopausal symptoms, and reduced sexual function, peaking around year 3 and then diminishing over time. The strengths of this study include the importance of the question, the clean design that enabled the testing of hormone therapies in the absence of chemotherapy, the focus on hormone-responsive tumors, the balance between the arms, the long follow-up, and the assessment of PROs. The major limitation is, of course, that the study’s early closure as a result of poor accrual left it vastly underpowered for its primary end points; this trial fell victim to the 1997 report of National Surgical Adjuvant Breast and Bowel Project (NSABP) B20, which recommended the use of chemotherapy in addition to tamoxifen for women with axillary lymph node–negative, hormoneresponsive breast cancer, especially women younger than 50 years of age. However, E-3193 was a success in its collection of detailed PROs, and it is noteworthy that it met the prespecified target accrual for these secondary end points. Given the exceptional outcomes for patients enrolled onto this trial, which had greater than 95% overall survival in the absence of chemotherapy, such patient-reported data are valuable contributions to the discussion between physicians and patients about the risks and benefits of individual therapies. Several crucial questions remain. Given the statistical limitations of this trial, might the combination of OFS plus tamoxifen actually be better than tamoxifen? What about the combination of OFS plus an aromatase inhibitor, given the efficacy of aromatase inhibitors in postmenopausal hormone receptor–positive breast cancer? Three large trials are helping to address these two questions: ABCSG-12 (Austrian Breast and Colorectal Cancer Study Group trial 12), SOFT (Suppression of Ovarian Function Trial), and TEXT (Tamoxifen and Exemestane Trial). A lingering concern is how we can integrate the results of all of these trials that use 3 to 5 years of adjuvant endocrine therapy with the findings of the ATLAS (Adjuvant Tamoxifen: Longer Against Shorter) and aTTom (Adjuvant Tamoxifen—To Offer More?) trials, which support the use of 10 years of tamoxifen. In the SOFT trial, 3,066 premenopausal women with hormoneresponsive breast cancer were randomly assigned to 5 years of tamoxifen, tamoxifen plus OFS, or exemestane plus OFS; (neo)adjuvant chemotherapy was permitted as long as patients remained premenopausal at its completion. In the TEXT trial, 2,672 premenopausal patients with hormone-responsive breast cancer were randomly assigned to receive 5 years of tamoxifen plus OFS or exemestane plus OFS; endocrine therapy was started concurrently with chemotherapy if chemotherapy was planned. Because of lower than expected event rates, the statistical plans for these two trials were revised some years ago to enable a joint analysis of 4,690 women receiving tamoxifen plus OFS versus exemestane plus OFS. In contrast to E-3193, 42% of these women were lymph node positive, and 57% received some type of chemotherapy. At a median follow-up of 68 months, a significantly improved DFS was seen with exemestane plus OFS (91.1% v 87.3%; HR, 0.72; 95% CI, JOURNAL OF CLINICAL ONCOLOGY E D I T O R I A L VOLUME 32 NUMBER 35 DECEMBER 1