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Importance: Adjuvant ovarian function suppression (OFS) with oral endocrine therapy improves outcomes for premenopausal patients with hormone receptor-positive (HR+) breast cancer but adds adverse effects. A genomic biomarker for selecting patients most likely to benefit from OFS-based treatment is lacking., Objective: To assess the predictive and prognostic performance of the Breast Cancer Index (BCI) for OFS benefit in premenopausal women with HR+ breast cancer., Design, Setting, and Participants: This prospective-retrospective translational study used all available tumor tissue samples from female patients from the Suppression of Ovarian Function Trial (SOFT). These individuals were randomized to receive 5 years of adjuvant tamoxifen alone, tamoxifen plus OFS, or exemestane plus OFS. BCI testing was performed blinded to clinical data and outcome. The a priori hypothesis was that BCI HOXB13/IL17BR ratio (BCI[H/I])-high tumors would benefit more from OFS and high BCI portended poorer prognosis in this population. Settings spanned multiple centers internationally. Participants included premenopausal female patients with HR+ early breast cancer with specimens in the International Breast Cancer Study Group tumor repository available for RNA extraction. Data were collected from December 2003 to April 2021 and were analyzed from May 2022 to October 2022., Main Outcomes and Measures: Primary end points were breast cancer-free interval (BCFI) for the predictive analysis and distant recurrence-free interval (DRFI) for the prognostic analyses., Results: Tumor specimens were available for 1718 of the 3047 female patients in the SOFT intention-to-treat population. The 1687 patients (98.2%) who had specimens that yielded sufficient RNA for BCI testing represented the parent trial population. The median (IQR) follow-up time was 12 (10.5-13.4) years, and 512 patients (30.3%) were younger than 40 years. Tumors were BCI(H/I)-low for 972 patients (57.6%) and BCI(H/I)-high for 715 patients (42.4%). Patients with tumors classified as BCI(H/I)-low exhibited a 12-year absolute benefit in BCFI of 11.6% from exemestane plus OFS (hazard ratio [HR], 0.48 [95% CI, 0.33-0.71]) and an absolute benefit of 7.3% from tamoxifen plus OFS (HR, 0.69 [95% CI, 0.48-0.97]) relative to tamoxifen alone. In contrast, patients with BCI(H/I)-high tumors did not benefit from either exemestane plus OFS (absolute benefit, -0.4%; HR, 1.03 [95% CI, 0.70-1.53]; P for interaction = .006) or tamoxifen plus OFS (absolute benefit, -1.2%; HR, 1.05 [95% CI, 0.72-1.54]; P for interaction = .11) compared with tamoxifen alone. BCI continuous index was significantly prognostic in the N0 subgroup for DRFI (n = 1110; P = .004), with 12-year DRFI of 95.9%, 90.8%, and 86.3% in BCI low-risk, intermediate-risk, and high-risk N0 cancers, respectively., Conclusions and Relevance: In this prospective-retrospective translational study of patients enrolled in SOFT, BCI was confirmed as prognostic in premenopausal women with HR+ breast cancer. The benefit from OFS-containing adjuvant endocrine therapy was greater for patients with BCI(H/I)-low tumors than BCI(H/I)-high tumors. BCI(H/I)-low status may identify premenopausal patients who are likely to benefit from this more intensive endocrine therapy.

Background: The use of adjuvant chemotherapy in patients with breast cancer may be guided by clinicopathological factors and a score based on a 21-gene assay to determine the risk of recurrence. Whether the level of clinical risk of breast cancer recurrence adds prognostic information to the recurrence score is not known., Methods: We performed a prospective trial involving 9427 women with hormone-receptor-positive, human epidermal growth factor receptor 2-negative, axillary node-negative breast cancer, in whom an assay of 21 genes had been performed, and we classified the clinical risk of recurrence of breast cancer as low or high on the basis of the tumor size and histologic grade. The effect of clinical risk was evaluated by calculating hazard ratios for distant recurrence with the use of Cox proportional-hazards models. The initial endocrine therapy was tamoxifen alone in the majority of the premenopausal women who were 50 years of age or younger., Results: The level of clinical risk was prognostic of distant recurrence in women with an intermediate 21-gene recurrence score of 11 to 25 (on a scale of 0 to 100, with higher scores indicating a worse prognosis or a greater potential benefit from chemotherapy) who were randomly assigned to endocrine therapy (hazard ratio for the comparison of high vs. low clinical risk, 2.73; 95% confidence interval [CI], 1.93 to 3.87) or to chemotherapy plus endocrine (chemoendocrine) therapy (hazard ratio, 2.41; 95% CI, 1.66 to 3.48) and in women with a high recurrence score (a score of 26 to 100), all of whom were assigned to chemoendocrine therapy (hazard ratio, 3.17; 95% CI, 1.94 to 5.19). Among women who were 50 years of age or younger who had received endocrine therapy alone, the estimated (±SE) rate of distant recurrence at 9 years was less than 5% (≤1.8±0.9%) with a low recurrence score (a score of 0 to 10), irrespective of clinical risk, and 4.7±1.0% with an intermediate recurrence score and low clinical risk. In this age group, the estimated distant recurrence at 9 years exceeded 10% among women with a high clinical risk and an intermediate recurrence score who received endocrine therapy alone (12.3±2.4%) and among those with a high recurrence score who received chemoendocrine therapy (15.2±3.3%)., Conclusions: Clinical-risk stratification provided prognostic information that, when added to the 21-gene recurrence score, could be used to identify premenopausal women who could benefit from more effective therapy. (Funded by the National Cancer Institute and others; ClinicalTrials.gov number, NCT00310180.)., (Copyright © 2019 Massachusetts Medical Society.)

Background: In the Suppression of Ovarian Function Trial (SOFT) and the Tamoxifen and Exemestane Trial (TEXT), the 5-year rates of recurrence of breast cancer were significantly lower among premenopausal women who received the aromatase inhibitor exemestane plus ovarian suppression than among those who received tamoxifen plus ovarian suppression. The addition of ovarian suppression to tamoxifen did not result in significantly lower recurrence rates than those with tamoxifen alone. Here, we report the updated results from the two trials., Methods: Premenopausal women were randomly assigned to receive 5 years of tamoxifen, tamoxifen plus ovarian suppression, or exemestane plus ovarian suppression in SOFT and to receive tamoxifen plus ovarian suppression or exemestane plus ovarian suppression in TEXT. Randomization was stratified according to the receipt of chemotherapy., Results: In SOFT, the 8-year disease-free survival rate was 78.9% with tamoxifen alone, 83.2% with tamoxifen plus ovarian suppression, and 85.9% with exemestane plus ovarian suppression (P=0.009 for tamoxifen alone vs. tamoxifen plus ovarian suppression). The 8-year rate of overall survival was 91.5% with tamoxifen alone, 93.3% with tamoxifen plus ovarian suppression, and 92.1% with exemestane plus ovarian suppression (P=0.01 for tamoxifen alone vs. tamoxifen plus ovarian suppression); among the women who remained premenopausal after chemotherapy, the rates were 85.1%, 89.4%, and 87.2%, respectively. Among the women with cancers that were negative for HER2 who received chemotherapy, the 8-year rate of distant recurrence with exemestane plus ovarian suppression was lower than the rate with tamoxifen plus ovarian suppression (by 7.0 percentage points in SOFT and by 5.0 percentage points in TEXT). Grade 3 or higher adverse events were reported in 24.6% of the tamoxifen-alone group, 31.0% of the tamoxifen-ovarian suppression group, and 32.3% of the exemestane-ovarian suppression group., Conclusions: Among premenopausal women with breast cancer, the addition of ovarian suppression to tamoxifen resulted in significantly higher 8-year rates of both disease-free and overall survival than tamoxifen alone. The use of exemestane plus ovarian suppression resulted in even higher rates of freedom from recurrence. The frequency of adverse events was higher in the two groups that received ovarian suppression than in the tamoxifen-alone group. (Funded by Pfizer and others; SOFT and TEXT ClinicalTrials.gov numbers, NCT00066690 and NCT00066703 , respectively.).

Background: Suppression of ovarian estrogen production reduces the recurrence of hormone-receptor-positive early breast cancer in premenopausal women, but its value when added to tamoxifen is uncertain., Methods: We randomly assigned 3066 premenopausal women, stratified according to prior receipt or nonreceipt of chemotherapy, to receive 5 years of tamoxifen, tamoxifen plus ovarian suppression, or exemestane plus ovarian suppression. The primary analysis tested the hypothesis that tamoxifen plus ovarian suppression would improve disease-free survival, as compared with tamoxifen alone. In the primary analysis, 46.7% of the patients had not received chemotherapy previously, and 53.3% had received chemotherapy and remained premenopausal., Results: After a median follow-up of 67 months, the estimated disease-free survival rate at 5 years was 86.6% in the tamoxifen-ovarian suppression group and 84.7% in the tamoxifen group (hazard ratio for disease recurrence, second invasive cancer, or death, 0.83; 95% confidence interval [CI], 0.66 to 1.04; P=0.10). Multivariable allowance for prognostic factors suggested a greater treatment effect with tamoxifen plus ovarian suppression than with tamoxifen alone (hazard ratio, 0.78; 95% CI, 0.62 to 0.98). Most recurrences occurred in patients who had received prior chemotherapy, among whom the rate of freedom from breast cancer at 5 years was 82.5% in the tamoxifen-ovarian suppression group and 78.0% in the tamoxifen group (hazard ratio for recurrence, 0.78; 95% CI, 0.60 to 1.02). At 5 years, the rate of freedom from breast cancer was 85.7% in the exemestane-ovarian suppression group (hazard ratio for recurrence vs. tamoxifen, 0.65; 95% CI, 0.49 to 0.87)., Conclusions: Adding ovarian suppression to tamoxifen did not provide a significant benefit in the overall study population. However, for women who were at sufficient risk for recurrence to warrant adjuvant chemotherapy and who remained premenopausal, the addition of ovarian suppression improved disease outcomes. Further improvement was seen with the use of exemestane plus ovarian suppression. (Funded by Pfizer and others; SOFT ClinicalTrials.gov number, NCT00066690.).

Background: Adjuvant therapy with an aromatase inhibitor improves outcomes, as compared with tamoxifen, in postmenopausal women with hormone-receptor-positive breast cancer., Methods: In two phase 3 trials, we randomly assigned premenopausal women with hormone-receptor-positive early breast cancer to the aromatase inhibitor exemestane plus ovarian suppression or tamoxifen plus ovarian suppression for a period of 5 years. Suppression of ovarian estrogen production was achieved with the use of the gonadotropin-releasing-hormone agonist triptorelin, oophorectomy, or ovarian irradiation. The primary analysis combined data from 4690 patients in the two trials., Results: After a median follow-up of 68 months, disease-free survival at 5 years was 91.1% in the exemestane-ovarian suppression group and 87.3% in the tamoxifen-ovarian suppression group (hazard ratio for disease recurrence, second invasive cancer, or death, 0.72; 95% confidence interval [CI], 0.60 to 0.85; P<0.001). The rate of freedom from breast cancer at 5 years was 92.8% in the exemestane-ovarian suppression group, as compared with 88.8% in the tamoxifen-ovarian suppression group (hazard ratio for recurrence, 0.66; 95% CI, 0.55 to 0.80; P<0.001). With 194 deaths (4.1% of the patients), overall survival did not differ significantly between the two groups (hazard ratio for death in the exemestane-ovarian suppression group, 1.14; 95% CI, 0.86 to 1.51; P=0.37). Selected adverse events of grade 3 or 4 were reported for 30.6% of the patients in the exemestane-ovarian suppression group and 29.4% of those in the tamoxifen-ovarian suppression group, with profiles similar to those for postmenopausal women., Conclusions: In premenopausal women with hormone-receptor-positive early breast cancer, adjuvant treatment with exemestane plus ovarian suppression, as compared with tamoxifen plus ovarian suppression, significantly reduced recurrence. (Funded by Pfizer and others; TEXT and SOFT ClinicalTrials.gov numbers, NCT00066703 and NCT00066690, respectively.).

Purpose: The NSABP (National Surgical Adjuvant Breast and Bowel Project) B-24 study demonstrated significant benefit with adjuvant tamoxifen in patients with ductal carcinoma in situ (DCIS) after lumpectomy and radiation. Patients were enrolled without knowledge of hormone receptor status. The current study retrospectively evaluated the relationship between receptors and response to tamoxifen., Patients and Methods: Estrogen (ER) and progesterone receptors (PgR) were evaluated in 732 patients with DCIS (41% of original study population). An experienced central laboratory determined receptor status in all patient cases with available paraffin blocks (n = 449) by immunohistochemistry (IHC) using comprehensively validated assays. Results for additional patients (n = 283) determined by various methods (primarily IHC) were available from enrolling institutions. Combined results were evaluated for benefit of tamoxifen by receptor status at 10 years and overall follow-up (median, 14.5 years)., Results: ER was positive in 76% of patients. Patients with ER-positive DCIS treated with tamoxifen (v placebo) showed significant decreases in subsequent breast cancer at 10 years (hazard ratio [HR], 0.49; P < .001) and overall follow-up (HR, 0.60; P = .003), which remained significant in multivariable analysis (overall HR, 0.64; P = .003). Results were similar, but less significant, when subsequent ipsilateral and contralateral, invasive and noninvasive, breast cancers were considered separately. No significant benefit was observed in ER-negative DCIS. PgR and either receptor were positive in 66% and 79% of patients, respectively, and in general, neither was more predictive than ER alone., Conclusion: Patients in NSABP B-24 with ER-positive DCIS receiving adjuvant tamoxifen after standard therapy showed significant reductions in subsequent breast cancer. The use of adjuvant tamoxifen should be considered for patients with DCIS.

Purpose: Several mechanisms have been proposed to explain tamoxifen resistance of estrogen receptor (ER) -positive tumors, but a clinically useful explanation for such resistance has not been described. Because the ER is the treatment target for tamoxifen, a linear association between ER expression levels and the degree of benefit from tamoxifen might be expected. However, such an association has never been demonstrated with conventional clinical ER assays, and the ER is currently used clinically as a dichotomous marker. We used gene expression profiling and ER protein assays to help elucidate molecular mechanism(s) responsible for tamoxifen resistance in breast tumors., Patients and Methods: We performed gene expression profiling of paraffin-embedded tumors from National Surgical Adjuvant Breast and Bowel Project (NSABP) trials that tested the worth of tamoxifen as an adjuvant systemic therapy (B-14) and as a preventive agent (P-1). This was a retrospective subset analysis based on available materials., Results: In B-14, ESR1 was the strongest linear predictor of tamoxifen benefit among 16 genes examined, including PGR and ERBB2. On the basis of these data, we hypothesized that, in the P-1 trial, a lower level of ESR1 mRNA in the tamoxifen arm was the main difference between the two study arms. Only ESR1 was downregulated by more than two-fold in ER-positive cancer events in the tamoxifen arm (P < .001). Tamoxifen did not prevent ER-positive tumors with low levels of ESR1 expression., Conclusion: These data suggest that low-level expression of ESR1 is a determinant of tamoxifen resistance in ER-positive breast cancer. Strategies should be developed to identify, treat, and prevent such tumors.

Purpose: Patients with early-stage, hormone receptor-positive breast cancer have considerable residual risk for recurrence after completing 5 years of adjuvant tamoxifen. In May 2001, the National Surgical Adjuvant Breast and Bowel Project (NSABP) initiated accrual to a randomized, placebo-controlled, double-blind clinical trial to evaluate the steroidal aromatase inhibitor exemestane as extended adjuvant therapy in this setting., Patients and Methods: Postmenopausal patients with clinical T(1-3)N(1)M(0) breast cancer who were disease free after 5 years of tamoxifen were randomly assigned to 5 years of exemestane (25 mg/d orally) or 5 years of placebo. Our primary aim was to test whether exemestane prolongs disease-free survival (DFS). In October 2003, results of National Cancer Institute of Canada (NCIC) MA.17 showing benefit from adjuvant letrozole in this setting necessitated termination of accrual to B-33, unblinding, and offering of exemestane to patients in the placebo group., Results: At the time of unblinding, 1,598 patients had been randomly assigned; 72% in the exemestane group continued on exemestane and 44% in the placebo group elected to receive exemestane. With 30 months of median follow-up, original exemestane assignment resulted in a borderline statistically significant improvement in 4-year DFS (91% v 89%; relative risk [RR] = 0.68; P = .07) and in a statistically significant improvement in 4-year relapse-free survival (RFS; 96% v 94%; RR = 0.44; P = .004). Toxicity, assessed up to time of unblinding, was acceptable for the adjuvant setting., Conclusion: Despite premature closure and crossover to exemestane by a substantial proportion of patients, original exemestane assignment resulted in non-statistically significant improvement in DFS and in statistically significant improvement in RFS.

Background: The optimal duration of extended therapy with aromatase inhibitors in patients with postmenopausal breast cancer is unknown. In the NSABP B-42 study, we aimed to determine whether extended letrozole treatment improves disease-free survival after 5 years of aromatase inhibitor-based therapy in women with postmenopausal breast cancer.Methods: This randomised, double-blind, placebo-controlled, phase 3 trial was done in 158 centres in the USA, Canada, and Ireland. Postmenopausal women with stage I-IIIA hormone receptor-positive breast cancer, who were disease-free after about 5 years of treatment with an aromatase inhibitor or tamoxifen followed by an aromatase inhibitor, were randomly assigned (1:1) to receive 5 years of letrozole (2·5 mg orally per day) or placebo. Randomisation was stratified by pathological node status, previous tamoxifen use, and lowest bone mineral density T score in the lumbosacral spine, total hip, or femoral neck. The primary endpoint was disease-free survival, defined as time from randomisation to breast cancer recurrence, second primary malignancy, or death, and was analysed by intention to treat. To adjust for previous interim analyses, the two-sided statistical significance level for disease-free survival was set at 0·0418. This study is registered with ClinicalTrials.gov, number NCT00382070, is active, and is no longer enrolling patients.Findings: Between Sept 28, 2006, and Jan 6, 2010, 3966 patients were randomly assigned to receive letrozole (n=1983) or placebo (n=1983). Follow-up information was available for 3903 patients for the analyses of disease-free survival. Median follow-up was 6·9 years (IQR 6·1-7·5). Letrozole treatment did not significantly improve disease-free survival (339 disease-free survival events were reported in the placebo group and 292 disease-free survival events were reported in the letrozole group; hazard ratio 0·85, 95% CI 0·73-0·999; p=0·048). 7-year disease-free survival estimate was 81·3% (95% CI 79·3-83·1) in the placebo group and 84·7% (82·9-86·4) in the letrozole group. The most common grade 3 adverse events were arthralgia (47 [2%] of 1933 patients in the placebo group vs 50 [3%] of 1941 patients in the letrozole group) and back pain (44 [2%] vs 38 [2%]). The most common grade 4 adverse event in the placebo group was thromboembolic event (eight [<1%]) and the most common grade 4 adverse events in the letrozole group were urinary tract infection, hypokalaemia, and left ventricular systolic dysfunction (four [<1%] each).Interpretation: After 5 years of aromatase inhibitor-based therapy, 5 years of letrozole therapy did not significantly prolong disease-free survival compared with placebo. Careful assessment of potential risks and benefits is required before recommending extended letrozole therapy to patients with early-stage breast cancer.Funding: National Cancer Institute, Korea Health Technology R&D Project, Novartis. [ABSTRACT FROM AUTHOR]