Ademuyiwa, Foluso O.

Abstract Purpose To determine if the COVID‐19 pandemic has further exacerbated racial disparities in late‐stage presentation of breast, colorectal, lung, and prostate cancers. Methods We conducted a registry‐based retrospective study of patients with newly reported diagnoses of breast, colorectal, lung, and prostate cancers between March 2019–June 2019 (pre‐COVID‐19) and March 2020–June 2020 (early‐COVID‐19). We compared the volume of new diagnoses and stage at presentation according to race between both periods. Results During the study period, a total of 3528 patients had newly diagnosed cancer; 3304 of which had known disease stages and were included in the formal analyses. 467 (14.1%) were Blacks, and 2743 were (83%) Whites. 1216 (36.8%) had breast, 415 (12.6%) had colorectal, 827 (25%) had lung, and 846 (25.6%) had prostate cancers, respectively. The pre‐COVID‐19 period included 2120 (64.2%), and the early‐COVID‐19 period included 1184 (35.8%), representing a proportional 44.2% decline in the volume of new cases of breast, colorectal, lung, and prostate cancers, p < 0.0001. Pre‐COVID‐19, 16.8% were diagnosed with metastatic disease, versus 20.4% early‐COVID‐19, representing a proportional increase of 21.4% in the numbers of new cases with metastatic disease, p = 0.01. There was a non‐significant proportional decline of 1.9% in Black patients diagnosed with non‐metastatic breast, colorectal, lung, and prostate cancers early‐COVID‐19 ( p = 0.71) and a non‐significant proportional increase of 7% in Black patients diagnosed with metastatic disease ( p = 0.71). Difference‐in‐difference analyses showed no statistically significant differences in metastatic presentation comparing Black to White patients. Conclusion While we identified substantial reductions in the volume of new cancer diagnoses and increases in metastatic presentations due to the COVID‐19 pandemic, the impact was similar for White and Black patients.

Abstract Background: Cyclin-dependent kinase 4/6 inhibitors (CKD4/6i) have demonstrated clinical utility extending progression-free survival (PFS) and overall survival (OS) for advanced hormone receptor positive and HER2 negative (HR+/HER2-) breast cancer patients. The efficacy in early-stage breast cancer (eBC) is unclear, with conflicting results from adjuvant CDK4/6i trials on invasive disease-free survival. Thus, there is a critical need to identify biomarkers of response (BoR) to determine which, if any, eBC patients could benefit from this treatment. This BoR could also stratify advanced BC patients for likelihood to respond to CDK4/6i. Metabolism is influenced by both genome and environment, and changes in the metabolome can be correlated with drug responsiveness. Thus, metabolite BoRs may serve to identify eBC patients for which CDK4/6i would offer a therapeutic benefit.Methods: Plasma and serum samples from 50 early-stage ER+/HER2- breast cancer patients, treated with neoadjuvant CDK4/6 inhibitor palbociclib (palbo) and aromatase inhibitor (AI) anastrozole on NeoPalAna trial (ClinicalTrials.gov identifier NCT01723774), were collected from treatment-naïve patients (BL) and 3 consecutive time points: anastrozole,1 mg daily for 4 weeks (C1D1), anastrozole plus palbo,125 mg daily, for 15 days (C1D15), and for 4-5 months before surgery (SURG). Metabolites were extracted from all samples via methanol and chloroform precipitation and quantified using an unbiased, non-destructive, nuclear magnetic resonance (NMR)-based profiling platform (Olaris®, Inc., Waltham, MA). Statistical analysis and machine learning was used to identify differential metabolites and generate predictive models. A separate validation set of samples was collected from a subset of patients (N=6) who received an additional cycle of palbo treatment prior to surgery to assess model accuracy. Results: Non-parametric differential expression analysis of BL/C1D1, BL/C1D15, and C1D1/C1D15 identified 53 ,97, and 90 differential NMR resonances in plasma (p&lt;0.05) and 36, 34, and 25 differential NMR resonances in serum (p&lt;0.05), respectively. Based on the proliferative marker Ki67 levels at C1D15, 37 patients were classified as responders (Ki67≤2.7%) and 6 patients as non-responders (Ki67&gt;2.7%). Analysis of the responder (R) and non-responder (NR) groups identified that 13 plasma and 14 serum resonances (21 unique resonances and 6 overlapping) were differentially expressed (p&lt;0.05) at C1D1. Many of the differential resonances could be mapped back to amino acid metabolites including several branched chain amino acids such as leucine, valine, and isoleucine, and positively charged amino acids such as lysine. A Olaris® BoR score was generated using 5 differential resonances that had an AUC of 0.931 (training set) and 100% accuracy when predicting palbo-response in a blinded test set (N=6).Conclusion: The differential metabolites identified from matching plasma and serum samples suggest that, compared to serum, plasma has a better representation of the metabolic changes associated with palbo treatment-response. While comparing samples from R and NR patients, amino acids were found to be consistently altered in both serum and plasma before palbo treatment. In addition, a BoR model based on select metabolites could precisely stratify palbo-response in a blinded dataset. A larger independent validation cohort is ongoing. Citation Format: Chen Dong, Shana Thomas, Chandrashekhar Honrao, Leonardo O. Rodrigues, Nathalie Tessier, Bo Zhang, Souzan Sanati, Kiran Vij, Brenda J. Ernst, Karen S. Anderson, Mateusz Opyrchal, Foluso Ademuyiwa, Lindsay L. Peterson, Matthew P. Goetz, Donald Northfelt, Elizabeth O'Day, Cynthia Ma. Identifying a metabolite signature that correlates with tumor proliferation in early-stage breast cancer patients treated with CDK4/6 inhibitors from matched plasma and serum samples [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-20.

Abstract Background Patients (pts) with ER+ HER2+ breast cancer (BC) are less likely to achieve pathological complete response (pCR) after neoadjuvant chemotherapy with dual HER2 blockade than pts with ER- HER2+ BC. Endocrine therapy (ET) plus trastuzumab is effective in advanced ER+ HER2+ BC, but pCR rate is low in the neoadjuvant setting. Inhibition of CDK4/6 and HER2 results in synergistic reduction in cell proliferation in preclinical studies. We therefore combined ET with CDK4/6 inhibition and trastuzumab in ER+ HER2+ BC as a chemotherapy-sparing regimen. Methods We evaluated the efficacy of palbociclib, letrozole, trastuzumab (PLT) in the neoadjuvant setting for pts with stages II or III ER+ HER2+ BC. Primary endpoint was pCR after 16 weeks of therapy. We assumed null of 15% pCR and pCR ≥ 30% warrants further investigation. To achieve 80% power at 1-sided 0.05 significance, 48 pts were to be enrolled. Evaluable population included pts who completed Cycle (C) 1 unless discontinued due to treatment-emergent adverse events (TEAEs) prior to completing C1. All who received one dose on study were considered evaluable for toxicity. Biopsies were collected at baseline (BL), C1 day 15 (C1D15), and surgery for RNA sequencing and central Ki67 assessment, for PAM50 subtype distribution, complete cell cycle arrest (CCCA: Ki67 ≤2.7%) at C1D15 and surgery, and treatment induced signaling changes. Results Accrual stopped early due to futility. 26 pts accrued were evaluable for efficacy and toxicity. pCR (residual cancer burden- [RCB] 0) was 7.7% (95% CI 0.9 - 25.1%) and RCB 0/I was 38.5% (95% CI 20.2 - 59.4%). TEAEs (n= 337) were seen in all pts (71.5% grade [G] 1, 19.3% G2, 8.6% G3, 0.6% G4); the most common were leukopenia (7.7%), neutropenia (7.1%), anemia (5.9%). G3/4 TEAEs occurred in 19 pts (73.1%). Among the 19, incidence of G3/4 neutropenia was 50%, hypertension 26.9%, leucopenia 7.7%. TEAEs (hypertension, ventricular tachycardia, pulmonary edema) leading to treatment discontinuation were reported in 1 pt. Two pts had at least one SAE. No treatment-related deaths occurred. Pt reported outcomes using NCI PRO-CTCAE revealed no differences in appetite, nausea, respiratory symptoms, edema, palpitations, rashes and dry skin, or concentration from BL to end of C4. Pts had worsening hair loss from BL to end of C4. Ki67 analysis indicated CCCA in 78% at C1D15, compared to 18% at surgery after only P had been discontinued approximately 4 weeks prior to surgery. RNA sequencing was performed on available biopsies collected at BL (N=16), C1D15 (N=5), and surgery (N=2) from 16 pts. Among 16 BL samples, PAM50 subtyping identified 5 (31.3%) basal-like, 2 (12.5%) HER2-E, 6 (37.5%) Lum B, and 3 (18.8%) normal. Subtype switching to Lum A at C1D15 (N=3, 1 each with HER2-E, Lum B, and normal at BL) or normal (N=2, 1 basal and 1 HER2-E at BL) was observed. 161 genes were differentially expressed (FDR p&lt;0.05); 145 downregulated and 16 upregulated comparing C1D15 to BL. MKI67, TK1, CCNB1, AURKB, PLK1 were among the downregulated genes, consistent with CCCA for majority of the samples at C1D15 by Ki67. Analysis of the Molecular Signatures Database Hallmark gene-sets comparing C1D15 and BL samples demonstrated downregulated biological processes involved in proliferation (E2F targets, G2M checkpoint, MYC targets, mitotic spindle), signaling (Estrogen response, mTORC1 signaling), and DNA damage (DNA repair) at C1D15, consistent with the mechanisms of action of the study drugs. E2F targets were higher in BL samples of RCB II/III, compared to RCB I (FDR p=0.042). Conclusions PALTAN did not meet its primary endpoint of pCR. Neoadjuvant PLT showed a pCR of 7.7% but was well tolerated. RNA sequencing and Ki67 data indicated potent anti-proliferative effects of study treatments, despite significant heterogeneity of intrinsic subtypes. Clinical trial information: NCT02907918. Citation Format: Foluso O Ademuyiwa, Donald Northfelt, Tracey O'Connor, Ellis Levine, Jingqin Luo, Yu Tao, Jeremy Hoog, Marie Laury, Tracy Summa, Trish Hammerschmidt, Zhanfang Guo, Ashley Frith, Katherine Weilbaecher, Mateusz Opyrchal, Rebecca Aft, Katherine Clifton, Rama Suresh, Nusayba Bagegni, Ian S Hagemann, Cynthia X Ma. Phase 2 study of neoadjuvant palbociclib, letrozole, and trastuzumab in patients with ER+ HER2+ breast cancer (PALTAN) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-01.

10525 Background: Several groups have described disparities in genetic test results for inherited breast cancer predisposition, with a disproportionate number of variants of unknown significance (VUS) reported in non-Caucasian individuals. These disparities are due in part to the underrepresentation of non-Caucasians in reference databases and clinical genetic testing cohorts. Over the past few years, diversification efforts have been made however, little data exists on how ethnicity- and gene-specific VUS rates have changed over time and whether such disparities have improved or worsened. Methods: We retrospectively reviewed demographic information and test results for individuals who underwent hereditary cancer multigene panel testing between March 2012 and September 2020 at a single laboratory. Individuals who self-reported as African American, Asian, Caucasian, or Hispanic on the test requisition form and whose testing included ATM, BRCA1, BRCA2, CHEK2 and PALB2 (five commonly tested breast cancer predisposition genes with management guidelines) were included in the study (n = 284,130). The frequency of germline variants of unknown significance (VUS) in the five genes was assessed in September 2015 and September 2020. Results: Amongst patients tested between March 2012 and September 2015, 82.8% of the study cohort self-reported as Caucasian and 17.2% were not Caucasian (6.5% African American, 6.0% Hispanic, and 4.6% Asian). The proportion of non-Caucasian individuals in the study cohort increased slightly by September 2020 to 22.8% (77.2% Caucasian, 9.2% African American, 8.4% Hispanic, and 5.3% Asian). Consistent with previous reports, Caucasians had the lowest VUS rate overall in both 2015 and 2020. This was also true at the individual gene level, with the exception of CHEK2. Over time, we observed a relative decrease in VUS rates across all ethnicities. Between 2015 and 2020, the overall VUS rate for the five included genes in non-Caucasian individuals was reduced by 32.0% in non-Caucasians compared to 23.6% in Caucasians. The absolute difference in VUS rate between non-Caucasians and Caucasians decreased from 7.9% in 2015 to 4.5% in 2020. Conclusions: While VUS rates for commonly tested breast cancer predisposition genes remain higher in non-Caucasians relative to Caucasians, our results demonstrate that this gap has been reduced over a five-year time period. These findings may be indicative of efforts by clinicians and laboratories to reduce these disparities. Further studies are necessary to improve the clinical utility of genetic testing in under-represented populations.[Table: see text]

Abstract Background Inhibition of PD-L1 with atezolizumab combined with chemotherapy has shown acceptable safety and improved survival in patients with metastatic PD-L1 positive triple negative breast cancer (TNBC). Patients with TNBC who do not achieve a pathological complete response (pCR) to neoadjuvant chemotherapy have a high risk of disease recurrence and death. This randomized, open-label, phase 2 trial evaluates neoadjuvant carboplatin and paclitaxel with or without atezolizumab in patients with previously untreated clinical stages II and III TNBC. Methods Women aged ≥18 years with clinical stage T2-T4c, any N, M0 primary tumor by AJCC 7th edition staging TNBC; ECOG PS 0-2; and no prior systemic therapy for the indexed breast cancer were eligible. Patients were randomized in a 1:2 ratio to carboplatin AUC5 q 3 weeks x 4 + paclitaxel 80 mg/m2 q week x 12 (Arm A), or carboplatin AUC5 q 3 weeks x 4 + paclitaxel 80 mg/m2 q week x 12 + atezolizumab 1200 mg q3 weeks x 4 (Arm B). Surgery was 3-6 weeks following neoadjuvant chemotherapy. Adjuvant dose-dense doxorubicin and cyclophosphamide was administered q2 weeks with growth factor support to all patients as per routine care. pCR and tumor infiltrating lymphocyte (TIL) percentages are the co-primary endpoints. pCR-evaluable population includes all eligible women who have been randomized and received at least one dose of combination therapy, while the TIL-evaluable population includes all eligible women who have evaluable TIL percentage after one cycle of therapy. A sample size of 67 (22 in Arm A, and 45 in Arm B) provided 80% power at 1-sided alpha = 0.10 to detect a minimum of 15% difference in TIL and 29% improvement (40% vs. 69%) in pCR, respectively. Herein, we report pCR results in the per protocol modified intent-to-treat population (mITT), which includes all eligible patients who were randomized and received at least one dose of combination therapy. Results Sixty-seven patients were randomized between 8/2017 and 9/2019. Six patients randomized to Arm A withdrew consent; 2 of these received protocol therapy but are excluded from the mITT analyses as they are not evaluable because definitive pathology reports are not available. Median follow up is 6 months (range 0.3 - 12.6 months). Median age is 52 years (range 25 - 78). Forty-three (64.2%) were Caucasian and thirteen (19.4%) were African American. Twenty-five (37.3%) were pre-menopausal. 67.2% and 32.8% had stages II and III disease respectively. Nine (13.4%) had a germline mutation in either BRCA1 or BRCA2. In the mITT population, 3 of 16 patients achieved pCR in Arm A - 18.8% (95% CI 4.0%- 45.6%), versus 25 of 45 patients in Arm B - 55.6% (95% CI 40.0%-70.4%); p value 0.018. pCR in those with BRCA mutations was 50% and 80% in Arm A and Arm B, respectively. Treatment delays were observed in 9 patients (40.9%) in Arm A, and 20 (44.4%) in Arm B; dose reductions occurred in 4 patients (18.1%) in Arm A, and in 6 (13.3%) in Arm B. There were 4 SAEs in Arm A and 10 in Arm B. One patient in Arm B had grade 3 adrenal insufficiency. One patient in Arm B died from recurrent disease during the follow-up period. Conclusions: The addition of atezolizumab to neoadjuvant carboplatin and paclitaxel resulted in an increased pCR rate in patients with clinical stages II and III TNBC. However, the pCR in the control Arm A was lower than expected, possibly due to the absence of neoadjuvant anthracyclines. The high pCR rate observed in the experimental arm of this study is similar to that observed in other neoadjuvant trials utilizing anthracyclines, taxanes, and carboplatin in TNBC. Clinical trial information: NCT02883062. Citation Format: Foluso O Ademuyiwa, Feng Gao, Ina Chen, Donald W Northfelt, Robert Wesolowski, Mili Arora, Adam Brufsky, Claire Dees, Cesar A Santa-Maria, Roisin M Connolly, Jeremy Force, Alvaro Moreno-Aspitia, Sarah Larson, Elad Sharon, William Gillanders. Nci 10013 - A randomized phase 2 study of neoadjuvant carboplatin and paclitaxel, with or without atezolizumab in triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD14-09.

Abstract Background LIV-1, a transmembrane protein and downstream target of STAT3, is highly expressed in breast cancer cells. It is associated with lymph node involvement and metastatic progression. SGN-LIV1A is an anti-LIV-1 antibody conjugated via a protease-cleavable linker to monomethyl auristatin E (MMAE). Upon binding to cell-surface LIV-1, SGN-LIV1A is internalized and releases MMAE, which disrupts microtubulin and induces apoptosis. Methods This ongoing, phase 1 study evaluates safety, tolerability, pharmacokinetics, and antitumor activity of SGN-LIV1A (q3wks IV) in women with LIV-1-positive, unresectable, locally advanced or metastatic breast cancer (LA/MBC) (NCT01969643). Patients (pts) with measurable disease and ≥2 prior cytotoxic regimens for LA/MBC are eligible. Pts with ≥ Grade 2 neuropathy are excluded. Response is assessed per RECIST v1.1; pts with stable disease (SD) or better can continue treatment until disease progression or intolerable toxicity. At completion of dose escalation in hormone receptor-positive/HER2-negative (HR+/HER2–) and triple-negative (TN) pts, expansion cohorts were opened to further evaluate safety and antitumor activity of monotherapy in TN pts. Tumor biopsies are evaluated for LIV-1 expression. Results To date, 69 pts (18 HR+/HER2–, 51 TN) have received a median of 3 cycles (range, 1–12) of SGN-LIV1A at doses of 0.5–2.8 mg/kg. Median age was 56 yrs. Pts had a median of 3 prior cytotoxic regimens for LA/MBC; 58 had visceral disease and 37 had bone metastases. No dose-limiting toxicities (DLTs) occurred in 19 DLT-evaluable pts; maximum tolerated dose was not exceeded at 2.8 mg/kg. Expansion cohorts of TN pts were opened at 2.0 and 2.5 mg/kg. Treatment-emergent adverse events (AEs) reported in ≥25% of pts were fatigue (59%), nausea (51%), peripheral neuropathy (44%), alopecia (36%), decreased appetite (33%), constipation (30%), abdominal pain, diarrhea, and neutropenia (25% each). Most AEs were Grade 1/2; AEs ≥ Grade 3 included neutropenia (25%) and anemia (15%). Febrile neutropenia occurred in 2 pts whose total dose exceeded 200 mg per cycle, including 1 treatment-related death due to sepsis. No other treatment-related deaths occurred on-study. Seven pts discontinued treatment due to AEs. In dose escalation, activity was observed in 17 efficacy evaluable (EE) HR+/HER2- pts, with a disease control rate (DCR= CR+PR+SD) of 59% (10 SD), including 1 pt with SD ≥24 wks. Among the 44 EE TN pts (dose escalation plus expansion cohorts), the objective response rate (ORR) was 32% (14 PR) with a confirmed PR rate of 21%, DCR was 64% (14 PR, 14 SD), and clinical benefit rate (CBR=CR+PR+SD ≥24 wks) was 36% (16 pts). For TN pts, median PFS was 11.3 wks (95% CI: 6.1, 17.1); 10 pts remain on treatment. Of 631 MBC tumor samples of all clinical subtypes evaluated for LIV-1, 91% were positive; 75% had moderate-to-high expression (H-score ≥100). Conclusions LIV-1 is expressed in almost all MBC tumors. SGN-LIV1A monotherapy was generally well tolerated and showed encouraging antitumor activity in heavily pretreated TN MBC, with a PR rate of 32%, confirmed PR rate of 21%, and CBR (≥24 wks) of 36%. Response duration data continue to evolve. Enrollment continues in the TN monotherapy expansion cohort. Citation Format: Modi S, Pusztai L, Forero A, Mita M, Miller KD, Weise A, Krop I, Burris III H, Kalinsky K, Tsai M, Liu MC, Hurvitz SA, Wilks S, Ademuyiwa F, Diab S, Han HS, Kato G, Nanda R, O'Shaughnessy J, Kostic A, Li M, Specht J. Phase 1 study of the antibody-drug conjugate SGN-LIV1A in patients with heavily pretreated triple-negative metastatic breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD3-14.

Abstract Purpose: Hyperactivation of AKT is common and associated with endocrine resistance in estrogen receptor–positive (ER+) breast cancer. The allosteric pan-AKT inhibitor MK-2206 induced apoptosis in PIK3CA-mutant ER+ breast cancer under estrogen-deprived condition in preclinical studies. This neoadjuvant phase II trial was therefore conducted to test the hypothesis that adding MK-2206 to anastrozole induces pathologic complete response (pCR) in PIK3CA mutant ER+ breast cancer. Experimental Design: Potential eligible patients with clinical stage II/III ER+/HER2− breast cancer were preregistered and received anastrozole (goserelin if premenopausal) for 28 days in cycle 0 pending tumor PIK3CA sequencing. Patients positive for PIK3CA mutation in the tumor were eligible to start MK-2206 (150 mg orally weekly, with prophylactic prednisone) on cycle 1 day 2 (C1D2) and to receive a maximum of four 28-day cycles of combination therapy before surgery. Serial biopsies were collected at preregistration, C1D1 and C1D17. Results: Fifty-one patients preregistered and 16 of 22 with PIK3CA-mutant tumors received study drug. Three patients went off study due to C1D17 Ki67 &gt;10% (n = 2) and toxicity (n = 1). Thirteen patients completed neoadjuvant therapy followed by surgery. No pCRs were observed. Rash was common. MK-2206 did not further suppress cell proliferation and did not induce apoptosis on C1D17 biopsies. Although AKT phosphorylation was reduced, PRAS40 phosphorylation at C1D17 after MK-2206 persisted. One patient acquired an ESR1 mutation at surgery. Conclusions: MK-2206 is unlikely to add to the efficacy of anastrozole alone in PIK3CA-mutant ER+ breast cancer and should not be studied further in the target patient population. Clin Cancer Res; 23(22); 6823–32. ©2017 AACR.

Abstract Purpose: Cyclin-dependent kinase (CDK) 4/6 drives cell proliferation in estrogen receptor–positive (ER+) breast cancer. This single-arm phase II neoadjuvant trial (NeoPalAna) assessed the antiproliferative activity of the CDK4/6 inhibitor palbociclib in primary breast cancer as a prelude to adjuvant studies. Experimental Design: Eligible patients with clinical stage II/III ER+/HER2− breast cancer received anastrozole 1 mg daily for 4 weeks (cycle 0; with goserelin if premenopausal), followed by adding palbociclib (125 mg daily on days 1–21) on cycle 1 day 1 (C1D1) for four 28-day cycles unless C1D15 Ki67 &gt; 10%, in which case patients went off study due to inadequate response. Anastrozole was continued until surgery, which occurred 3 to 5 weeks after palbociclib exposure. Later patients received additional 10 to 12 days of palbociclib (Cycle 5) immediately before surgery. Serial biopsies at baseline, C1D1, C1D15, and surgery were analyzed for Ki67, gene expression, and mutation profiles. The primary endpoint was complete cell cycle arrest (CCCA: central Ki67 ≤ 2.7%). Results: Fifty patients enrolled. The CCCA rate was significantly higher after adding palbociclib to anastrozole (C1D15 87% vs. C1D1 26%, P &lt; 0.001). Palbociclib enhanced cell-cycle control over anastrozole monotherapy regardless of luminal subtype (A vs. B) and PIK3CA status with activity observed across a broad range of clinicopathologic and mutation profiles. Ki67 recovery at surgery following palbociclib washout was suppressed by cycle 5 palbociclib. Resistance was associated with nonluminal subtypes and persistent E2F-target gene expression. Conclusions: Palbociclib is an active antiproliferative agent for early-stage breast cancer resistant to anastrozole; however, prolonged administration may be necessary to maintain its effect. Clin Cancer Res; 23(15); 4055–65. ©2017 AACR.

Abstract Background ER+ BC is associated with activated CDK4/6. The CDK4/6 inhibitor palbociclib (P) markedly improves time to progression in advanced ER+HER2- BC. We conducted a neoadjuvant phase II trial to determine the activity of P in primary breast cancer as a prelude to adjuvant studies. Methods To assess molecular changes induced by anastrozole (A) or P+A, patients (pts) were treated initially with A alone (1mg PO daily) for 28 days in cycle 0 (C0) before the addition of P (125mg PO daily on D1-21 each cycle) on C1D1. P+A was administered for 4 28-day cycles followed by C5 with A alone for 2-4 weeks (wks) before surgery. P was added in C5 for 10-12 days immediately prior to surgery in the last 20 pts enrolled to assess molecular changes induced by A, either alone or in combination with P immediately prior to surgery, in resected tumor. Goserelin was added in premenopausal pts. Research tumor biopsies were obtained at baseline, C1D1, and C1D15. Central Ki67 analysis was performed at all timepoints, those with Ki67 &gt;10% at C1D15 went off study treatment. The primary endpoint was complete cell cycle arrest (CCA), defined as Ki67 &lt;2.7%, at C1D15. Patient stratification was based on PIK3CA mutation status with an initial focus on PIK3CA wild type (WT) disease. Pts with PIK3CA mutant (Mut) tumors enrolled to a separate cohort. A sample size of 33 pts in the PIK3CA WT cohort was chosen based on the Fleming's single-stage phase II design to test the hypothesis that P+A leads to &gt; 50% improvement over A in CCA rate on C1D15 biopsy (44% with A alone based on historical data, vs 66% with P+A, power = 0.8, alpha=0.05). The primary endpoint is met if &gt;20 pts achieved CCA in this cohort. Correlative endpoints included assessment of markers of proliferation, apoptosis, senescence, Rb, gene expression microarray, intrinsic subtype, and next generation sequencing of 83-gene panels, which will be reported at the meeting. Results Between 4/23/2013 and 4/24/2015, 50 pts (33 PIK3CA WT, 11 PIK3CA Mut, 2 pending, 4 tissue quantity or quality not sufficient for sequencing (QNS)) were enrolled to the study. Median age was 57.5 (range: 34.1–79.6) years. Four pts, all with WT PIK3CA, went off study due to Ki67 &gt;10% on C1D15 biopsy, 26 pts completed treatment and surgery, 1 refused surgery, 3 withdrew study treatment in C1, and 16 continued to receive study drug (2 in C0, 3 in C1, 4 in C2, 5 in C3, 1 in C4, and 1 in C5). Among the 40 pts currently evaluable for the primary endpoint (C1D15 Ki67), CCA occurred in 34 (85%) pts, including 9 of 9 (100%) PIK3CA Mut, 22 of 28 (78.5%) WT, and 3 of 3 QNS pts. Preliminary analysis of available data indicated a significantly lower Ki67 value after 2 wks of P+A (C1D15) compared to that on A alone (C1D1) (p=0.034, n=18). Conclusion This study met the primary endpoint demonstrating that P+A is a highly effective anti-proliferative combination. The sequential biopsy design clearly demonstrated that P+A increased cell cycle control over A alone. P+A was effective regardless of PIK3CA mutation status and these results support the evaluation of this combination in the adjuvant setting for ER+HER2- BC. Citation Format: Ma CX, Gao F, Northfelt D, Goetz M, Forero A, Naughton M, Ademuyiwa F, Suresh R, Anderson KS, Margenthaler J, Aft R, Hobday T, Moynihan T, Gillanders W, Cyr A, Eberlein TJ, Hieken T, Krontiras H, Hoog J, Han J, Guo Z, Vij K, Mardis E, Al-Kateb H, Sanati S, Ellis MJ. A phase II trial of neoadjuvant palbociclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, in combination with anastrozole for clinical stage 2 or 3 estrogen receptor positive HER2 negative (ER+HER2-) breast cancer (BC). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr S6-05.

Abstract Background Activating mutations in PIK3CA occur in approximately 40% ER+BC. MK-2206 (M), a pan-AKT inhibitor, induced apoptosis of ER+ BC under estrogen deprivation in preclinical studies. We conducted this neoadjuvant trial to determine the pathologic complete response (pCR) rate of M plus anastrozole (A) for PIK3CA mutant (Mut) ER+ BC. Methods This single arm open label study of M+A used a 2-stage Simon phase II design (stage 1, n=16; stage 2, n=13, alpha=0.10, power=0.90) to test whether pCR rate &lt;1% (based on historical data with A alone), against the alternative that pCR rate ≥15% in PIK3CA Mut ER+ BC. At least 1 pCR in stage 1 was required to proceed to stage 2. Eligible patients (pts) with clinical stage II or III ER+HER2- BC were pre-registered and proceeded to a research tumor biopsy for PIK3CA sequencing, followed by treatment with daily A monotherapy for 28 days (cycle 0). Pts with PIK3CA Mut BC were subsequently registered, underwent a second biopsy, and started M (150mg PO weekly) with daily A on cycle 1 day 1 (C1D1) for a maximum of four 28-day cycles followed by surgery. Goserelin was added for premenopausal pts. A tumor biopsy on C1D17, 17 days post the start of M, was performed. Those with C1D17 Ki67 &gt;10% discontinued study treatment. pCR was defined as no invasive cancer in the breast and the lymph nodes. Tumor specimens collected at all timepoints are being analyzed for markers of proliferation, apoptosis, and PI3K pathway activity, gene expression microarray, intrinsic subtypes, and next generation sequencing of 83 genes. Results Of the 51 pts pre-registered, 35 pts did not register due to no PIK3CA mutation (n=22), inadequate specimen for testing (n=6), physician/pt decision (n=7). The remaining 16 pts (median age: 58, range: 40-77 years) received combination therapy. Three pts did not complete 4 cycles due to C1D17 Ki67 &gt;10% (n=2) and intolerability (grade (Gr) 4 transaminase elevation in C1, n=1). Other severe toxicities possibly related to M included Gr 3 rash (25%) and pruritus (12.5%). Of the 13 pts completed study therapy and underwent surgery, all had residual disease in the breast and 7 also had positive nodes. Table 1 summarized changes in Ki67 during treatment. ComparisonsnAbsolute changes in Ki67 median (range)Wilcoxon signed rank p-valueC1D1 relative to pre-registration11-17.0% (-49.8 to 4.1%)0.0020C1D17 relative to pre-registration14-16.4% (-51.4 to 4.1%)0.0004C1D17 relative to C1D112-1.5% (-18.6 to 15.8%)0.9697C1D1, biopsy post 28 days of A alone; C1D17 biopsy post 17 days on combination therapy Although Ki67 levels post A monotherapy (C1D1) or M+A (C1D17) were significantly lower than that of pre-registration samples, Ki67 did not differ between C1D17 and C1D1 samples. Other correlative studies are ongoing and results will be presented. Conclusion Despite the small sample size, biomarker analysis on serial biopsy specimens demonstrated that M+A is unlikely to be more effective than A alone in PIK3CA Mut ER+ BC. This trial demonstrated the feasibility of genomic sequencing for pt selection and the value of a small, well-designed proof-of-principle neoadjuvant trial for the evaluation of targeted agents. Citation Format: Ma CX, Suman VJ, Goetz M, Northfelt D, Burkard M, Ademuyiwa F, Naughton M, Margenthaler J, Aft R, Gray R, Tavaarwerk A, Wilke L, Haddad T, Moynihan T, Loprinzi C, Hieken T, Hoog J, Guo Z, Han J, Vij K, Mardis E, Sanati S, Al-Kateb H, Doyle L, Erlichman C, Ellis MJ. A phase II neoadjuvant trial of MK-2206, an AKT inhibitor, in combination with anastrozole for clinical stage 2 or 3 PIK3CA mutant estrogen receptor positive HER2 negative (ER+HER2-) breast cancer (BC). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-13-04.