Hahn, Olwen

504 Background: For PM patients (pts) with locally advanced ER+ HER2- BC, NET improves breast conservation surgery (BCS) rates, and modified preoperative endocrine prognostic index (mPEPI) 0, defined as pT1-2 pN0 Ki67< 2.7%, or pathologic complete response (pCR: no invasive disease in breast or lymph node) is associated with low risk of recurrence without adjuvant chemotherapy (CT). The ALTERNATE trial was initiated to assess if the endocrine-sensitive disease rate (ESDR: number of mPEPI 0 pts/number of eligible pts initiating NET) with fulvestrant (F) or F+anastrozole (A) is improved relative to A alone (reported here) and if the 5-year (yr) recurrence-free survival (RFS) rate for pts with mPEPI 0 on A alone without CT is ≥ 95% (awaits further follow-up). Methods: PM pts with clinical stage II/III ER+ HER2- BC were randomized 1:1:1 to 1 mg A po daily, 500 mg F IM every 4 week (wk)s after loading dose, or A+F for 6 months. Ki67 was tested centrally on biopsies acquired prior to NET, wk 4, wk 12 and at surgery. Pts with Ki67 >10% at wk 4 or 12 were recommended to go off protocol-directed ET and switch to CT. Pts with mPEPI 0 at surgery were recommended to continue assigned ET for 1.5 yrs followed by A for a total of 5 yrs ET (and not to receive CT). The primary endpoint of the neoadjuvant phase was ESDR. ESDR of each F arm was compared to that of the A alone arm. With 425 pts per arm, a one-tailed alpha = 0.025 chi-square test of two independent proportions has 84% power to detect an increase of ≥10% in ESDR for F or F+A compared to the A arm, assuming ESDR ≤30% in A. Results: 1362 pts (A 452; F 454; A+F 456) were enrolled Feb 2014 to Nov 2018. 63 pts were excluded (did not start NET). Of the remaining 1299 pts (A 434; F 431, A+F 434), 42% were cN1-3 and 73% were considered candidates for BCS. ESDR was 18.6% (95%CI: 15.1-22.7%) with A, 22.7% (95%CI: 18.9-27.0%) with F, and 20.5% (95%CI: 16.8-24.6%) with A+F. No significant difference in ESDR was found between A and F (p=0.15) or A and A+F (p=0.55). Among the 825 pts with wk 4 Ki67 < 10% who completed NET and surgery, ESDR and the BCS rate were 27.7% and 70.3% with A; 29.6% and 68.1% with F, and 26.8% and 69.9% with A+F, respectively. Conclusion: Neither F nor F+A significantly improved ESDR compared to A alone in PM pts with locally advanced ER+ HER2- BC. RFS data are awaited. Support: U10CA180821, U10CA180882, U24CA196171, https://acknowledgments.alliancefound.org ; NCI BIQSFP, BCRF, Genentech, AstraZeneca. Clinical trial information: NCT01953588 .

5079 Background: Neoadjuvant CHT followed by RP did not increase 3-year biochemical progression free-survival (bPFS) compared to RP alone in men with CLHRPC. However, there is evidence that bPFS and overall survival over time was improved. In the current analysis we assessed whether CHT followed by RP improved pathological specimen features compared to RP alone. Methods: CALGB 90203 (Alliance) is a Phase III study which randomly assigned, in a 1:1 fashion, men with CLHRPC [biopsy Gleason Grade Group (GGG) 4 or 5 or Kattan pre-op nomogram bPFS < 60%] to RP alone or RP plus neoadjuvant CHT [androgen deprivation plus docetaxel (75 mg/m2 every 3 weeks for 6 cycles)]. We conducted an exploratory analysis comparing histologic findings, determined at the treating center, in the RP specimens of men receiving CHT plus RP and men treated with RP alone. We used the Chi-square test, with P-values adjusted by the Holm method for multiple comparisons. Results: A total of 788 men (median age, 62; range: 32-83 years) were randomized, with 738 ultimately undergoing RP. There was no difference in pathologic GGG (Table). Men treated with neoadjuvant CHT had a lower pathologic T-stage and lower likelihood of having seminal vesicle invasion (SVI), positive pelvic lymph nodes, or positive surgical margins (SM) (Table). Conclusions: Most pathologic features in the RP specimen were improved in men receiving neoadjuvant CHT compared to RP alone. The relationship between pathologic changes and the development of metastasis and survival require further analysis. RP pathologic outcomes. Summary statistics are calculated for the number of patients with non-missing data for each characteristic. Clinical trial information: NCT00430183. [Table: see text]

5008 Background: Androgen receptor (AR) signaling is an important growth mechanism in mCRPC, providing the rationale for treatment with AR axis inhibitors such as ENZ and AAP. Targeting AR with anti-androgens such as ENZ can result in compensatory autocrine and paracrine androgenic stimulation. Therefore, using ENZ with the androgen biosynthesis inhibitor AAP to dampen these resistance mechanisms could improve clinical outcomes relative to ENZ alone. Methods: Men with progressive mCRPC by Prostate Cancer Working Group 2 criteria were eligible. Prior treatment with taxanes for mCRPC and any prior treatment with ENZ or AAP was exclusionary. Patients (pts) were randomized 1:1 to ENZ or ENZ/AAP at standard FDA-approved doses. Randomization was stratified by prior chemotherapy and Halabi prognostic three risk groups. Castrating therapy was maintained. The primary endpoint was overall survival (OS) defined as the date of randomization from date of death or last follow-up. The log-rank test had 90% power to detect a hazard ratio for OS of 0.77 with a one-sided type I error rate of 0.025. Secondary endpoints included radiographic progression free survival (rPFS) and on-treatment PSA declines. Exploratory endpoints included imaging changes, and changes in serum biomarkers such as androgens, angiokines, and circulating microRNA and RNA. The primary analysis was based on the stratified log-rank test adjusting on the stratification factors. Results: Between January 2014 and August 2016, 1311 men were randomized: 657 to ENZ and 654 to ENZ/AAP. Groups were well balanced between arms, including stratification variables. 15.6% of pts were high risk, 35.3% intermediate, and 48.1% low. Median OS was 33.6 mo (95% CI 30.5-36.4) and 32.7 mo (29.9-35.4) respectively, two-sided p = 0.53. Fifty percent PSA decline rate was 80% vs. 76.5%. Grade 3-5 adverse events (AE) (all attributions) were 55.6% and 68.8% respectively. Treatment discontinuation due to AEs occurred in 5% and 12%, pt withdrawal in 5% and 13%, and progression or death in 57% and 48% of pts respectively. Conclusions: Addition of abiraterone acetate to enzalutamide did not prolong survival in men with mCRPC. The combination resulted in more AEs than enzalutamide alone. Support: U10CA180821, U10CA180882, U24CA196171; https://acknowledgments.alliancefound.org . Clinical trial information: NCT01949337.

591 Background: Both Cb and Bev demonstrate activity when combined with standard chemotherapy in TNBC. CALGB 40603 is a 2x2 randomized trial that previously demonstrated that adding Cb to NACT significantly increased pathologic complete responses in the breast/axilla (pCR), while adding Bev did not (Sikov, JCO 2015). Here we report 5-year LTOs and assess factors that influenced them. Methods: 443 patients with clinical stage II-III previously untreated TNBC received 12 weeks of paclitaxel (wP) +/- Cb then dose-dense AC, +/- Bev before surgery. The primary endpoint was pCR. Analyses of LTOs (event-free survival (EFS), distant recurrence-free interval (DRFI) and overall survival (OS)), impact of residual cancer burden and other variables were secondary. Results: Median follow-up was 5.7 years (y); 5y EFS was 70.9% (95% CI; 66.7%-75.4%), DRFI 76.3% (72.3%-80.5%) and OS 76.9% (72.9%-81.2%). Pretreatment clinical stage and achieving pCR correlated with LTOs, while age, race, subtype (basal-like vs. not) and tumor grade did not. Among pCR 5y EFS was 86.4% vs. 57.5% for non-pCR (HR 0.28, 0.19-0.43), OS was 88.7% vs 66.5% (HR = 0.28, 0.17-0.44). This relationship was similar in all trial arms. Any residual disease conferred poorer outcome; compared with pCR/Residual Cancer Burden (RCB) 0, EFS HRs were 2.29 (1.32-3.97), 3.01 (1.90-4.74), and 9.67 (5.66-16.51) for RCBI, II and III, respectively. There were no improvements in LTOs with Cb (EFS HR 0.99, 0.70-1.40) or Bev (EFS HR 0.91, 0.64-1.29). In an exploratory analysis, receipt of ≥11 doses of wP was associated with better EFS (HR 1.92, 1.33-2.77); this was particularly notable in Cb-treated arms. Conclusions: As expected, regardless of treatment arm pCR was associated with markedly better LTOs, and pts with any residual disease had significantly worse outcomes. The addition of Cb or Bev to standard NACT for TNBC did not improve LTOs in this trial, although it should be noted that the trial was not powered for this endpoint. Omission of chemotherapy doses may result in poorer outcomes, especially among Cb-treated pts, which may warrant further evaluation. Support: U10CA180821; U10CA180882; Genentech; https://acknowledgments.alliancefound.org ; NCT00861705 Clinical trial information: NCT00861705.

Abstract Neoadjuvant endocrine therapy (ET) in patients (pts) with locally advanced estrogen receptor positive (ER+) breast cancer (BC) improves breast conservation rate, and importantly offers an opportunity for individualized assessment of tumor responsiveness to ET to guide subsequent treatment. Previous neoadjuvant ET trials demonstrated that pathologic tumor size (pT), axillary lymph node status (N), and tumor Ki67 value at surgery predicted risk of relapse. Preoperative endocrine prognostic index (PEPI) was therefore developed to assign risk scores based on these factors. Modified PEPI 0, defined by pT1-2 N0 Ki67&lt; 2.7%, was associated with extremely low risk of recurrence without adjuvant chemotherapy. In addition, high Ki67 post 2-4 weeks (wks) of neoadjuvant ET identified resistant tumors with poor outcome. ALTERNATE trial is a three-arm phase III neoadjuvant/adjuvant ET trial designed to achieve two primary objectives. The first is to prospectively validate that modified PEPI 0 predicts &gt; 95% relapse-free survival (RFS). The second is to determine whether fulvestrant (F), or fulvestrant (F) plus anastrozole (A), is superior to A in inducing a higher rate of modified PEPI 0. Secondary objectives include assessing RFS for pts with endocrine resistant tumor, defined by Ki67 &gt; 10% at 4 or 12 wk, disease progression, or modified PEPI non-0, and pathologic responses of resistant tumors to neoadjuvant chemotherapy. Correlative studies include degrees of Ki67 suppression and ER level post treatment. In addition, ongoing research sequencing studies of DNA and RNA will be performed to contrast sensitive vs resistant tumors. During the first phase of the trial, 1200 pts are randomized 1:1:1 to the F, A or F/A. This provides an 82% chance, 1-sided alpha 0.025 chi-square test to detect at least 10% difference in modified PEPI 0 rate comparing F or F/A with A. While waiting for result of analysis, the A arm will continue for the 2nd phase enrollment. Only the F-containing arm(s) superior over A will be continued to the 2nd phase. During the 2nd phase, an additional 540 pts in each arm is estimated to obtain 317 pts with PEPI score 0. This will have a 90% chance, with a one-sided alpha=0.025 nonparametric Brookmeyer-Crowley type one sample survival test, rejecting that 5 year RFS rate is 95%. The maximum sample size is 2820 pts. Eligible pts include postmenopausal women with newly diagnosed clinical stage II or III ER+ (Allred score 6-8) HER2- BC. Tumor biopsy is required at baseline, 4 wk, and surgery for central Ki67 analysis. Treatment decision is individualized based on 4 wk Ki67 and modified PEPI score. Pts with Ki67 &gt; 10% at 4 wk are switched to chemotherapy. Pts with a modified PEPI score of 0 are recommended not to receive chemotherapy, but continue the assigned ET for 1.5 years followed by 3 years of A. This trial is currently accruing pts through CTSU. This research is supported in part by NCI BIQSFP, and grants from Breast Cancer Research Foundation, Genentech, and the Investigator-Sponsored Study Program of AstraZeneca. The Clinical Trials.gov Identifier: NCT01953588. Citation Format: Cynthia X Ma, Vera Suman, A Marilyn Leitch, Souzan Sanati, Katherine DeSchryver, Gary W Unzeitig, Paul Haluska, Mark Watson, Olwen Hahn, Jo Anne Zujewski, Kelly Hunt, Eric P Winer, Cliff A Hudis, Matthew J Ellis. Alliance A011106: ALTernate approaches for clinical stage II or III Estrogen Receptor positive breast cancer NeoAdjuvant TrEatment (ALTERNATE) in postmenopausal women: A phase III study [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr OT2-1-04.