Phase II DORA Study of Olaparib with or without Durvalumab as a Chemotherapy-Free Maintenance Strategy in Platinum-Pretreated Advanced Triple-Negative Breast Cancer

PURPOSE

We explored the efficacy of PARP inhibition with or without programmed death ligand-1 (PD-L1) blockade as chemotherapy-free maintenance therapy for advanced triple-negative breast cancer (aTNBC) sensitive to platinum-based chemotherapy.

PATIENTS AND METHODS

In the phase II non-comparative DORA trial (NCT03167619), patients with ongoing stable disease (SD) or complete/partial response (CR/PR) to first- or second-line platinum-based chemotherapy for TNBC (≤10% estrogen/progesterone receptor expression) were randomized 1:1 to receive olaparib 300 mg twice daily with or without durvalumab 1,500 mg on day 1 every 4 weeks. The primary objective was to compare progression-free survival (PFS) versus a historical control of continued platinum-based therapy.

RESULTS

45 patients were randomized (23 to olaparib alone, 22 to the combination; 3 with estrogen/progesterone receptor expression 1%-10%). At 9.8 months' median follow-up, median PFS from randomization was 4.0 [95% confidence interval (CI), 2.6-6.1] months with olaparib and 6.1 (95% CI, 3.7-10.1) months with the combination, both significantly longer than the historical control (P = 0.0023 and P < 0.0001, respectively). Clinical benefit rates (SD ≥24 weeks or CR/PR) were 44% (95% CI, 23%-66%) and 36% (95% CI, 17%-59%) in the monotherapy and combination arms, respectively. Sustained clinical benefit was seen irrespective of germline BRCA mutation or PD-L1 status, but tended to be associated with CR/PR to prior platinum, particularly in the olaparib-alone arm. No new safety signals were reported.

CONCLUSIONS

PFS was longer than expected with both regimens. A patient subset with wild-type BRCA platinum-sensitive aTNBC had durable disease control with chemotherapy-free maintenance.

Selection of appropriate biomarkers to monitor effectiveness of ovarian function suppression in pre-menopausal patients with ER+ breast cancer

Use of gonadotropin-releasing hormone (GnRH) agonists has been widely adopted to provide reversible ovarian function suppression for pre-menopausal breast cancer patients who are also receiving aromatase inhibitor or tamoxifen therapy based on results of 25 randomized trials representing almost 15,000 women demonstrating a survival benefit with this approach. Past clinical trials designed to establish the efficacy of GnRH agonists have monitored testosterone in the prostate cancer setting and estradiol in the breast cancer setting. We explore the merits of various biomarkers including estradiol, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) and their utility for informing GnRH agonist treatment decisions in breast cancer. Estradiol remains our biomarker of choice in ensuring adequate ovarian function suppression with GnRH agonist therapy among pre-menopausal women with breast cancer. We recommend future trials to continue to focus on estradiol levels as the primary endpoint, as they have in the past.

Timing of exercise therapy when initiating adjuvant chemotherapy for breast cancer: a randomized trial

AIMS

The most appropriate timing of exercise therapy to improve cardiorespiratory fitness (CRF) among patients initiating chemotherapy is not known. The effects of exercise therapy administered during, following, or during and following chemotherapy were examined in patients with breast cancer.

METHODS AND RESULTS

Using a parallel-group randomized trial design, 158 inactive women with breast cancer initiating (neo)adjuvant chemotherapy were allocated to receive (1:1 ratio): usual care or one of three exercise regimens-concurrent (during chemotherapy only), sequential (after chemotherapy only), or concurrent and sequential (continuous) (n = 39/40 per group). Exercise consisted of treadmill walking three sessions/week, 20-50 min at 55%-100% of peak oxygen consumption (VO2peak) for ≈16 (concurrent, sequential) or ≈32 (continuous) consecutive weeks. VO2peak was evaluated at baseline (pre-treatment), immediately post-chemotherapy, and ≈16 weeks after chemotherapy. In intention-to-treat analysis, there was no difference in the primary endpoint of VO2peak change between concurrent exercise and usual care during chemotherapy vs. VO2peak change between sequential exercise and usual care after chemotherapy [overall difference, -0.88 mL O2·kg-1·min-1; 95% confidence interval (CI): -3.36, 1.59, P = 0.48]. In secondary analysis, continuous exercise, approximately equal to twice the length of the other regimens, was well-tolerated and the only strategy associated with significant improvements in VO2peak from baseline to post-intervention (1.74 mL O2·kg-1·min-1, P < 0.001).

CONCLUSION

There was no statistical difference in CRF improvement between concurrent vs. sequential exercise therapy relative to usual care in women with primary breast cancer. The promising tolerability and CRF benefit of ≈32 weeks of continuous exercise therapy warrant further evaluation in larger trials.

TROPION-Breast02: Datopotamab deruxtecan for locally recurrent inoperable or metastatic triple-negative breast cancer

Despite recent treatment advances, the prognosis for patients with locally recurrent inoperable or metastatic triple-negative breast cancer (TNBC) remains poor. The antibody-drug conjugate datopotamab deruxtecan (Dato-DXd) is composed of a humanized anti-TROP2 IgG1 monoclonal antibody linked to a topoisomerase I inhibitor payload via a stable, cleavable linker. The phase III TROPION-Breast02 trial in patients previously untreated for locally recurrent inoperable or metastatic TNBC, who are not candidates for PD-1/PD-L1 inhibitors is evaluating efficacy and safety of Dato-DXd versus investigator's choice of chemotherapy (ICC). Approximately 600 patients will be randomized 1:1 to Dato-DXd 6 mg/kg iv. every 3 weeks or ICC (paclitaxel, nab-paclitaxel, carboplatin, capecitabine or eribulin mesylate). Dual primary end points are progression-free survival by blinded independent central review and overall survival.

Circulating tumor DNA association with residual cancer burden after neoadjuvant chemotherapy in triple-negative breast cancer in TBCRC 030

BACKGROUND

We aimed to examine circulating tumor DNA (ctDNA) and its association with residual cancer burden (RCB) using an ultrasensitive assay in patients with triple-negative breast cancer (TNBC) receiving neoadjuvant chemotherapy.

PATIENTS AND METHODS

We identified responders (RCB 0/1) and matched non-responders (RCB 2/3) from the phase II TBCRC 030 prospective study of neoadjuvant paclitaxel versus cisplatin in TNBC. We collected plasma samples at baseline, 3 weeks and 12 weeks (end of therapy). We created personalized ctDNA assays utilizing MAESTRO mutation enrichment sequencing. We explored associations between ctDNA and RCB status and disease recurrence.

RESULTS

Of 139 patients, 68 had complete samples and no additional neoadjuvant chemotherapy. Twenty-two were responders and 19 of those had sufficient tissue for whole-genome sequencing. We identified an additional 19 non-responders for a matched case-control analysis of 38 patients using a MAESTRO ctDNA assay tracking 319-1000 variants (median 1000 variants) to 114 plasma samples from 3 timepoints. Overall, ctDNA positivity was 100% at baseline, 79% at week 3 and 55% at week 12. Median tumor fraction (TFx) was 3.7 × 10-4 (range 7.9 × 10-7-4.9 × 10-1). TFx decreased 285-fold from baseline to week 3 in responders and 24-fold in non-responders. Week 12 ctDNA clearance correlated with RCB: clearance was observed in 10 of 11 patients with RCB 0, 3 of 8 with RCB 1, 4 of 15 with RCB 2 and 0 of 4 with RCB 3. Among six patients with known recurrence, five had persistent ctDNA at week 12.

CONCLUSIONS

Neoadjuvant chemotherapy for TNBC reduced ctDNA TFx by 285-fold in responders and 24-fold in non-responders. In 58% (22/38) of patients, ctDNA TFx dropped below the detection level of a commercially available test, emphasizing the need for sensitive tests. Additional studies will determine whether ctDNA-guided approaches can improve outcomes.

Circulating tumor DNA association with residual cancer burden after neoadjuvant chemotherapy in triple-negative breast cancer in TBCRC 030

Purpose

To examine circulating tumor DNA (ctDNA) and its association with residual cancer burden (RCB) using an ultrasensitive assay in patients with triple-negative breast cancer (TNBC) receiving neoadjuvant chemotherapy (NAT).

Patients and Methods

We identified responders (RCB-0/1) and matched non-responders (RCB-2/3) from the phase II TBCRC 030 prospective study of neoadjuvant paclitaxel vs. cisplatin in TNBC. We collected plasma samples at baseline, three weeks, and twelve weeks (end of therapy). We created personalized ctDNA assays utilizing MAESTRO mutation enrichment sequencing. We explored associations between ctDNA and RCB status and disease recurrence.

Results

Of 139 patients, 68 had complete samples and no additional NAT. Twenty-two were responders and 19 of those had sufficient tissue for whole-genome sequencing. We identified an additional 19 non-responders for a matched case-control analysis of 38 patients using a MAESTRO ctDNA assay tracking 319-1000 variants (median 1000) to 114 plasma samples from 3 timepoints. Overall, ctDNA positivity was 100% at baseline, 79% at week 3, and 55% at week 12. Median tumor fraction (TFx) was 3.7 × 10 -4 (range: 7.9 × 10 -7 to 4.9 × 10 -1 ). TFx decreased 285-fold from baseline to week 3 in responders and 24-fold in non-responders. Week 12 ctDNA clearance correlated with RCB: clearance was observed in 10/11 patients with RCB-0, 3/8 with RCB-1, 4/15 with RCB-2, and 0/4 with RCB-3. Among 6 patients with known recurrence five had persistent ctDNA at week 12.

Conclusion

NAT for TNBC reduced ctDNA TFx by 285-fold in responders and 24-fold in non-responders. In 58% (22/38) of patients, ctDNA TFx dropped below the detection level of a commercially available test, emphasizing the need for sensitive tests. Additional studies will determine if ctDNA-guided approaches can improve outcomes.

Abstract OT3-15-01: TBCRC-053: P-RAD: A Randomized Study of Preoperative Chemotherapy, Pembrolizumab and No, Low or High Dose RADiation in Node-Positive, HER2-Negative Breast Cancer

Background: The introduction of immune checkpoint inhibitors (ICI) to standard neoadjuvant chemotherapy regimens has been shown to significantly improve outcomes in patients with triple negative breast cancer and is being investigated for high-risk hormone receptor-positive (HR+)/human epidermal growth factor-2 negative (HER2-) breast cancer. Preclinical evidence suggests radiation therapy (RT) can stimulate intra-tumoral T cell infiltration and enhance the expression and immune detection of tumor-specific neoantigens. This phase II pilot randomized study (NCT04443348) aims to evaluate the safety and efficacy of two different doses of preoperative primary tumor RT boost when combined with neoadjuvant pembrolizumab, then followed by standard neoadjuvant chemotherapy. Dual co-primary endpoints include determining the pathologic complete response (pCR) rate in the non-irradiated and pathologically confirmed metastatic axillary lymph node(s) in each treatment arm and quantifying tumor-infiltrating T lymphocytes in on-treatment (C1D14) tumor biopsies. We hypothesize that high-dose RT will increase the proportion of tumors with high T cell infiltration (i.e., top quartile) from 25% to 55%. Secondary endpoints include measuring residual cancer burden, evaluating tolerability of the regimen, and assessing quality of life. Exploratory endpoints include evaluation of treatment-associated changes in the tumor immune microenvironment, circulating immune cell analyses, and circulating tumor DNA kinetics. Methods: The study plans to enroll 128 participants with either triple negative (n=80) or high-risk HR=/HER2- (n=48) breast cancer who will be randomized to receive no, low (9 Gy), or high (24 Gy) dose of preoperative RT boost, after which 24 participants of either breast cancer subtype will be enrolled to an exploratory high dose proton therapy boost cohort. The eligibility criteria include patients who have biopsy-proven, axillary lymph node-positive breast cancer that is either triple negative (defined as ER&lt; 10%, PR&lt; 10%, and HER2-negative) or high-risk HR+/HER2- (grade III or having a high-risk genomic assay score). Study treatment is given in 6-week cycles, with 400 mg Pembrolizumab given on day 1 of each cycle. For those participants randomized to receive a preoperative RT boost, treatment is delivered in 3 fractions (3 × 3 Gy or 3 × 8 Gy) over consecutive business days, where one of the fractions is given on the same day as C1D1 Pembrolizumab. Standard neoadjuvant chemotherapy begins on C1D15 with paclitaxel (plus carboplatin for triple negative) administered weekly for 12 weeks, and then starting on C3D15, dose-dense doxorubicin/cyclophosphamide is administered every 2 weeks for 8 weeks. Following neoadjuvant treatment, participants will receive standard breast surgery (including removal of the pathologically confirmed metastatic lymph node) followed by adjuvant pembrolizumab, radiation therapy, and standard-of-care systemic therapy as clinically indicated. Tissue samples from the primary tumor and biopsy-proven lymph node are taken at baseline, C1D14, and at the time of surgery. There are eleven blood collection timepoints throughout the neoadjuvant and adjuvant settings. Participants will be followed for 2 years after surgery to assess safety and durability of responses. Results: This study has accrued 12 participants to date, including 10 with triple negative breast cancer and 2 with high-risk HR+/HER2- breast cancer. Formal results for this study are forthcoming, as the trial is actively accruing at 6 institutions, with plans to open at 3 more within the year. For persons with a specific interest in this trial, please contact Joseph Connolly, Multi-Center Coordinator, at jconnolly28@mgh.harvard.edu.

Citation Format: Joseph J. Connolly, Laura M. Spring, Alphonse G. Taghian, Michele Gadd, Laura Warren, Ana C. Garrido-Castro, Tari King, Elizabeth A. Mittendorf, Jose P. Leone, Dana L. Casey, Lisa Carey, Tiffany A. Traina, Yara Abdou, Atif Khan, George Plitas, Jean Wright, Cesar Augusto Santa-Maria, Lisa Jacobs, Rachel Blitzblau, E Shelley Hwang, Carey Anders, Ian Krop, Antonio C. Wolff, Alastair M. Thompson, Elyssa Denault, Gaorav Gupta, Alice Ho. TBCRC-053: P-RAD: A Randomized Study of Preoperative Chemotherapy, Pembrolizumab and No, Low or High Dose RADiation in Node-Positive, HER2-Negative Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-15-01.

Abstract PD11-06: PD11-06 Circulating tumor DNA association with residual cancer burden after neoadjuvant therapy in triple negative breast cancer in TBCRC 030

Background. Patients (pts) with early triple negative breast cancer (eTNBC) are at increased risk of breast cancer recurrence and death. Recent studies have focused on escalation of therapy, with current treatment standard of at least five drugs – and associated toxicities - for eTNBC. Though presence of residual disease after neoadjuvant therapy (NAT) as measured by residual cancer burden (RCB) helps guide addition of adjuvant treatment, more effective tools to tailor therapy are limited. Persistence of circulating tumor DNA (ctDNA) in the setting of residual disease is associated with high risk of distant recurrence. However, more sensitive minimal residual disease (MRD) assays are needed to potentially guide optimization of systemic therapy.

Methods. TBCRC 030 is a phase II randomized study of 12 weeks of NAT single agent cisplatin or paclitaxel for stage II-III TNBC, followed by surgery. The primary objective of the parent study was to correlate baseline biomarker for homologous recombination deficiency and RCB by study arm. From this group, responders (RCB 0/1) and non-responders (RCB 2/3) from both study arms who did not receive additional NAT prior to surgery were selected for analysis from the study cohort, matched on baseline nodal status and tumor size. As a post hoc study amendment, available pts were followed for event free survival (EFS). Plasma samples were collected prior to treatment initiation (W0), at three weeks (W3), and at twelve weeks, prior to surgery (W12). Whole genome sequencing (WGS) was performed on primary tumor tissue to identify somatic mutations and design for each pt a tumor-informed, ctDNA assay tracking up to 1000 mutations to detect MRD. Detection limit was computed for each tested sample as previously described. For each sample assayed, we report tumor fraction (TFx) when MRD was detected and the detection limit at 90% power when MRD was not detected.

Results. Of 139 study pts, 68 had complete tissue and plasma samples and no receipt of additional NAT. Of these, 22 were responders. These responders, and 22 matched non-responders were identified for analysis. Data from 22 pts – 11 responders, 11 non-responders - are described here; full analysis on all 44 pts will be presented at the meeting. Personalized ctDNA assays were designed targeting 434 to 1000 variants (median 1000) and applied to 66 plasma samples. At W0, 100% (22/22) were positive for ctDNA; 73% (16/22) and 55% (12/22) were positive at W3, and W12, respectively. In pts with T1-T2 tumors median TFx was 4.1e-3(7.8e-6, 3.4e-2) and 4.7e-1(4.3e-2, 9.0e-1) in pts with T3-T4 tumors. TFx decreased from W0 to W3 and from W0 to W12 in responders (Table 1). By W12, ctDNA had cleared in 7/8 pts with RCB 0, 1/3 with RCB 1, 2/8 with RCB 2, and 0/3 with RCB 3. Overall, ctDNA levels were broad with median TFx of 1.5e-3 (range 2.9e-6 to 0.90). Detection limit at 90% power for all tested samples was a median of 8.8e-6 (range 9.9e-7 to 6.8e-3).

To investigate whether ctDNA persistence after NAT was associated with BC recurrence, we analyzed a separate group of all 8 pts with known recurrence and with complete data and samples. All pts had persistent ctDNA at W12 (median TFx 6.8e-3, [2.9e-6 to 6.6e-2]).

Conclusions. After 3 weeks of NAT for eTNBC, ctDNA TFx decreased, with a 3900-fold change in responders and 18-fold change in non-responders. By W3, TFx for most pts with RCB 0/1 were below the 1 in 10,000 limit of detection for many currently available assays, emphasizing the need for sensitive tests to potentially guide therapy. Additional studies will determine if ctDNA-guided approaches in eTNBC can improve pt outcomes.

Table 1: Tumer Fraction and Tumer Fraction Fold Change by Response to Neoadjuvant Therapy

Citation Format: Heather A. Parsons, Timothy Blewett, Xiangying Chu, Sainetra Sridhar, Katheryn Santos, Kan Xiong, Vandana Abramson, Ashka Patel, Ju Cheng, Adam M. Brufsky, Justin Rhoades, Jeremy Force, Ruolin Liu, Tiffany A. Traina, Lisa Carey, Mothaffar Rimawi, Ahmed Elkhanany, Vered Stearns, Jennifer M. Specht, Harold Burstein, Antonio C. Wolff, Eric Winer, Nabihah Tayob, Ian Krop, Todd Golub, Erica L. Mayer, Viktor Adalsteinsson. PD11-06 Circulating tumor DNA association with residual cancer burden after neoadjuvant therapy in triple negative breast cancer in TBCRC 030 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD11-06.

Abstract PD11-12: PD11-12 DORA: A Phase II, Multicenter, International, Non-Comparator Study of Olaparib (O) +/- Durvalumab (D) as a chemotherapy-free maintenance strategy in Platinum tReated Advanced Triple-Negative Breast Cancer (aTNBC)

Introduction: A significant proportion of aTNBC patients carry homologous recombination defects associated with platinum sensitivity. Olaparib is an approved PARP inhibitor (PARPi) for germline BRCA (gBRCA) associated early and metastatic breast cancer as well as maintenance therapy in platinum-sensitive ovarian cancer irrespective of gBRCA status. PARPi enhances immune response via cGAS/STING activation and is synergistic with anti-PD-1 blockade in preclinical models without overlapping toxicities. Here, the efficacy of maintenance olaparib (O) +/- durvalumab (D) in aTNBC patients following clinical benefit from platinum chemotherapy is investigated (NCT03167619). Methods: Eligible pts had aTNBC with investigator-assessed clinical benefit (SD, PR, CR) after a minimum of 3 q3-weekly or 6 q1-weekly cycles of platinum-based chemotherapy in the 1st or 2nd line treatment setting. Patients were randomized 1:1 to receive O 300 mg BID daily or O 300mg BID daily + D 1.5g IV q4 wks. The study was a non-comparator trial; randomization aimed to reduce bias. Tumors were evaluated by RECIST1.1 at baseline and q8 wks. Known gBRCA carriers were limited to 10. The primary endpoint was progression-free survival (PFS). Secondary endpoints were disease control rate (DCR), clinical benefit rate (CBR), and overall survival (OS). Results: From 2/4/2019-12/24/2020, 45 pts were randomized (23 pts in O arm; 22 in O+D arm). 82.2% received platinum as 1st line therapy and 82% received a platinum-doublet. As of data cutoff (6/30/2021), median follow-up of 9.8m (7.2-15.1), the median PFS was 3.95m (p= 0.0023; 95% CI 2.55-6.13) with O monotherapy. The median PFS was 6.1 mos (p= &lt;.0001; 95% CI 3.68-10.11) in the O+D arm. CBR (CR, PR or SD ≥ 24 wks) was 39.1% (19.7%-61.5%) and 36.4% (17.2%-59.3%) in the O and O+D arms, respectively. DCR was 52.2% (30.6%, 73.2%) and 68.2% (45.1%, 86.1%) in the O and O + D arms, respectively. Currently, 7 pts (15.6%) remain on study treatment, only 2 have gBRCA alterations. No new safety signals were reported. Correlative analysis including germline/somatic BRCA, HRR genes, BRCA methylation, TMB and PDL-1 in association with clinical outcomes will be presented. Conclusions: A subset of non-gBRCA altered aTNBC pts who derived clinical benefit from platinum-based chemotherapy had a durable disease control with a chemotherapy-free maintenance strategy of olaparib +/- durvalumab.

Citation Format: Sarah L. Sammons, Tira J. Tan, Young Hyunk Im, Tiffany A. Traina, Carey Anders, Ezekiel Renzulli, Sung-Bae Kim, Rebecca Dent. PD11-12 DORA: A Phase II, Multicenter, International, Non-Comparator Study of Olaparib (O) +/- Durvalumab (D) as a chemotherapy-free maintenance strategy in Platinum tReated Advanced Triple-Negative Breast Cancer (aTNBC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD11-12.

Adjuvant palbociclib for ER+ breast cancer (PALLAS Trial (ABCSG-42/AFT-05/PrE0109/BIG-14-13): A preplanned analysis of the stage IIA cohort

390216

Background: CDK4/6 inhibitors have become standard of care for advanced hormone receptor positive, HER2-negative (HR+/HER2-) breast cancer in combination with endocrine therapy (ET), with one approved for high-risk patients (pts) in the adjuvant setting. The PALLAS Trial investigated the addition of palbociclib to adjuvant ET in pts with stage II-III breast cancer. Stage IIA patients were specifically enrolled to evaluate the potential benefit of using palbociclib with adjuvant ET pts diagnosed at lower risk who may have more indolent disease. Methods: In the prospective, randomized, phase III PALLAS trial, pts with HR+/HER2- early breast cancer were randomly assigned to receive adjuvant ET for at least 5 years with or without 2 years of palbociclib (125 mg orally once daily, days 1-21 of a 28-day cycle). ET was of provider’s choice. Stage IIA enrollment was capped at 1,000 patients. While the primary end point of the overall study was invasive disease-free survival (iDFS) for the entire cohort, there was a preplanned analysis of recurrence and survival endpoints in the stage IIA cohort. Outcomes were compared between arms using stratified log-rank tests and Cox models (stratification factors: chemotherapy and age ≤ 50). Results: Among 5,796 pts enrolled at 406 centers in 21 countries worldwide between 9/1/2015 and 11/30/2018, a total of 1,010 stage IIA pts were enrolled. The protocol-defined number of events occurred at a median follow-up of 50 months for this subgroup (43.1 months for the overall study). Median age within this subgroup was 54 (range 29-85 yrs), and 410 (40.6%) were pre/perimenopausal, 506 (50.1%) T2/N0 (vs T0-1/N1), 272 (26.9%) grade 3 (vs. grade1/2), and 561 (55.5%) received chemotherapy. iDFS events occurred in 31 of 503 (6.2%) pts who received palbociclib plus ET and in 45 of 507 (8.9%) pts who received ET alone, resulting in a statistically nonsignificant difference in iDFS at 4 years (92.9% vs. 92.1%; hazard ratio, 0.75; CI, 0.48 to 1.19; P = .23). Nonsignificant differences were also observed for invasive breast cancer-free, distant recurrence-free, and locoregional cancer-free survival. No significant differences in iDFS were observed in subgroups including age group, receipt of chemotherapy, tumor grade, and clinical risk (T1/N1 vs. T2/N0).Conclusions: In this preplanned analysis of the stage IIA cohort of the PALLAS trial, the addition of adjuvant palbociclib to standard ET did not improve outcomes over ET alone, suggesting no benefit from the agent in reducing the incidence of early relapse in pts with lower-stage HR+/HER2- breast cancer. Future analyses will incorporate genomic risk and other molecular patterns from the extensive transPALLAS correlative program. Additional follow-up (10-year minimum) is also underway to assess the impact of palbociclib exposure on late recurrence in HR+ disease. Clinical trial information: NCT02513394.

Adjuvant enzalutamide for the treatment of early-stage androgen-receptor positive, triple-negative breast cancer: a feasibility study

PURPOSE

Chemotherapy with or without immunotherapy remains the mainstay of treatment for triple-negative breast cancer (TNBC). A subset of TNBCs express the androgen receptor (AR), representing a potential new therapeutic target. This study assessed the feasibility of adjuvant enzalutamide, an AR antagonist, in early-stage, AR-positive (AR +) TNBC.

METHODS

This study was a single-arm, open-label, multicenter trial in which patients with stage I-III, AR ≥ 1% TNBC who had completed standard-of-care therapy were treated with enzalutamide 160 mg/day orally for 1 year. The primary objective of this study was to evaluate the feasibility of 1 year of adjuvant enzalutamide, defined as the treatment discontinuation rate of enzalutamide due to toxicity, withdrawal of consent, or other events related to tolerability. Secondary endpoints included disease-free survival (DFS), overall survival (OS), safety, and genomic features of recurrent tumors.

RESULTS

Fifty patients were enrolled in this study. Thirty-five patients completed 1 year of therapy, thereby meeting the prespecified trial endpoint for feasibility. Thirty-two patients elected to continue with an optional second year of treatment. Grade ≥ 3 treatment-related adverse events were uncommon. The 1-year, 2-year, and 3-year DFS were 94%, 92% , and 80%, respectively. Median OS has not been reached.

CONCLUSION

This clinical trial demonstrates that adjuvant enzalutamide is a feasible and well-tolerated regimen in patients with an early-stage AR + TNBC. Randomized trials in the metastatic setting may inform patient selection through biomarker development; longer follow-up is needed to determine the effect of anti-androgens on DFS and OS in this patient population.

Homologous recombination-deficient mutation cluster in tumor suppressor RAD51C identified by comprehensive analysis of cancer variants

Mutations in homologous recombination (HR) genes, including BRCA1, BRCA2, and the RAD51 paralog RAD51C, predispose to tumorigenesis and sensitize cancers to DNA-damaging agents and poly(ADP ribose) polymerase inhibitors. However, ∼800 missense variants of unknown significance have been identified for RAD51C alone, impairing cancer risk assessment and therapeutic strategies. Here, we interrogated >50 RAD51C missense variants, finding that mutations in residues conserved with RAD51 strongly predicted HR deficiency and disrupted interactions with other RAD51 paralogs. A cluster of mutations was identified in and around the Walker A box that led to impairments in HR, interactions with three other RAD51 paralogs, binding to single-stranded DNA, and ATP hydrolysis. We generated structural models of the two RAD51 paralog complexes containing RAD51C, RAD51B-RAD51C-RAD51D-XRCC2 and RAD51C-XRCC3. Together with our functional and biochemical analyses, the structural models predict ATP binding at the interface of RAD51C interactions with other RAD51 paralogs, similar to interactions between monomers in RAD51 filaments, and explain the failure of RAD51C variants in binding multiple paralogs. Ovarian cancer patients with variants in this cluster showed exceptionally long survival, which may be relevant to the reversion potential of the variants. This comprehensive analysis provides a framework for RAD51C variant classification. Importantly, it also provides insight into the functioning of the RAD51 paralog complexes.

Oral minoxidil for the treatment of late alopecia in cancer survivors

12022

Background: Late alopecia is defined as incomplete hair regrowth > 6 months following cytotoxic chemotherapy or from initiation of endocrine therapy. It has been reported in up to 25-30% of cancer survivors and is associated with decreased quality of life and reduced dose intensity of cancer therapies. Minoxidil is an aminopyridine potassium channel opener, resulting in vasodilation and premature entry of resting hair follicles into the anagen (growth) phase and increase in hair follicle size. This study aims to assess clinical outcomes and adverse events of oral minoxidil for the treatment of cancer therapy-related late alopecia. Methods: We retrospectively assessed all women with late alopecia treated with oral minoxidil (1.25 mg daily) evaluated at an oncodermatology referral program between 1/2018-5/2021. Outcomes were assessed by standardized photography (4 views) and trichoscopy (HairMetrix, Canfield Scientific, Inc.). Trichoscopy recorded hair density (hair count/cm2) and hair thickness (shaft diameter) at uniform frontal and occipital target areas (12 and 36 cm midline from the glabella, respectively). Adverse events were recorded and graded using CTCAE v5.0. Descriptive statistics were used to summarize the patient demographics and clinical characteristics. Changes in trichoscopy measurements from baseline to follow-up were estimated using paired t-tests. Results: Two hundred and sixteen patients (mean age 57.8±13.7) were included for analysis. Thirty-one (14%) received chemotherapy alone, 65 (30%) endocrine monotherapy, and 120 (56%) chemotherapy followed by endocrine therapy. The majority of patients (n = 170, 79.1%) had a history of breast cancer. Standardized photography assessments (n = 119) after a median of 105 days (IQR = 70) on oral minoxidil revealed clinical improvement in 88 (74%). Trichoscopy assessments (n = 42) after a median of 91 days (IQR = 126) demonstrated increased frontal hair density (124.2 vs 153.2 hairs/cm2, p = 0.008) and occipital hair density (100.3 vs 123.5 hairs/cm2, p = 0.004). There was no statistically significant difference in average frontal or occipital hair thickness (69.3 vs 67.3 μm, p = 0.22, and 70.3 vs 69.9 μm, p = 0.84, respectively). No patients reported discontinuation of oral minoxidil due to adverse effects. Conclusions: Oral minoxidil may benefit both frontal and occipital late alopecia in cancer survivors treated with cytotoxic and/or endocrine therapy. This regimen was well tolerated by patients. Prospective, controlled studies are needed to confirm these observations.

Androgen receptor splice variant-7 in breast cancer: clinical and pathologic correlations

Androgen receptor (AR) inhibitor therapy is a developing treatment for AR-positive breast cancer (BC) with ongoing clinical trials. AR splice variant-7 (AR-V7) is a truncated variant of AR that leads to AR inhibitor therapy resistance in prostate cancer; recent studies have identified AR-V7 in BC and theorized that AR-V7 can have a similar impact. This study assessed the prevalence and clinicopathologic features associated with AR-V7 in a large BC cohort. BC samples were evaluated by MSK-Fusion targeted RNAseq for AR-V7 detection and MSK-IMPACT targeted DNAseq, including triple-negative tumors with no driver alteration and estrogen receptor-positive/ESR1 wildtype tumors progressing on therapy. Among 196 primary and metastatic/recurrent cases (196 RNAseq, 194DNAseq), 9.7% (19/196) were AR-V7 positive and 90.3% (177/196) AR-V7 negative. All AR-V7 positive BC were AR-positive by immunohistochemistry (19/19). The prevalence of AR-V7 by receptor subtype (N = 189) was: 18% (12/67) in ER-/PgR-/HER2-negative BC, 3.7% (4/109) in ER-positive/HER2-negative BC, and 15.4% (2/13) in HER2-positive BC; AR-V7 was detected in one ER-positive/HER2-unknown BC. Apocrine morphology was observed in 42.1% (8/19) of AR-V7 positive BC and 3.4% (6/177) AR-V7 negative BC (P < 0.00001). Notably, AR-V7 was detected in 2 primary BC and 7 metastatic/recurrent BC patients with no prior endocrine therapy. We conclude that positive AR IHC and apocrine morphology are pathologic features that may indicate testing for AR-V7 is warranted in both primary and metastatic BC in the appropriate clinical context. The study findings further encourage the assessment of AR-V7 as a predictive biomarker for AR antagonist benefit in ongoing clinical BC trials.

Abstract P1-14-03: Adjuvant enzalutamide for the treatment of early-stage androgen-receptor positive, triple negative breast cancer: A feasibility study

Background: Chemotherapy remains the mainstay of treatment for early-stage triple negative breast cancer (TNBC), yet targetable drivers of interest are under investigation. A subset of TNBCs express the androgen receptor (AR) and exhibit androgen-dependent growth. The AR-antagonist enzalutamide (ENZA) has shown activity in patients with metastatic AR+ TNBC. In this study, the feasibility of adjuvant ENZA in early-stage, AR+ TNBC was assessed (NCT02750358). As reported previously, this study met its primary endpoint of feasibility (Traina et al., ASCO 2019). Here we report secondary survival endpoints. Methods: In this single-arm, open-label, multi-center trial, patients with stage I-III, AR≥1% TNBC (ER/PR &lt;1%, HER2 negative) who had completed standard of care therapy were treated with ENZA 160 mg/day orally for 1 year. Patients who completed 1 year had an option to remain on adjuvant ENZA for another year. Toxicity was graded using National Cancer Institute Common Toxicity Criteria (NCI CTCAE) v4. The primary endpoint of this study was to evaluate feasibility of adjuvant ENZA, defined as the discontinuation rate due to toxicity, withdrawal of consent, other events related to tolerability or patient preference. The study was designed to discriminate between feasibility rates of 50% and 70% and was considered feasible if ≥29 out of 46 patients received ENZA for one year without discontinuation. Secondary endpoints included DFS, OS, safety, patient reported outcomes and correlative science. Patients who had disease progression (PD) during year 1 of ENZA without treatment discontinuation due to the above reasons were not included in the primary feasibility analysis but were included in secondary endpoint analyses for survival. Results: 50 patients enrolled on study from 05/2016 - 06/2018. The median age was 58 years (range 34-81 years); 8% had a germline BRCA1/2 (n=3) or PALB2 (n=1) mutation. 38% had stage I disease at diagnosis, 48% stage II and 14% stage III. 74% had grade 3 tumors. 94% of all patients received prior systemic chemotherapy, 81% of whom received prior anthracycline-taxane. 38% (n=19) were treated with prior neoadjuvant chemotherapy and 32% of those patients (n=6) achieved a pCR. Of those who did not achieve a pCR, 69% received adjuvant capecitabine. 47 patients were evaluable for the study endpoint and 35 patients completed 1 year of ENZA thereby meeting the prespecified trial endpoint for feasibility. 32 patients elected to continue into a second year of treatment. After a median follow-up of 140 weeks (range 4 - 236 weeks), 8 patients had a DFS event: 7 TNBC recurrences and 1 new primary breast cancer. The 1-year DFS was 94% (95% CI: 87 - 100%), 2-year DFS was 92% (95% CI: 84 - 99.8%) and the 3-year DFS was 80% (95% CI: 67 - 94%). The median DFS and OS have not yet been reached. Two patients died of TNBC recurrence after 55 and 59 weeks. There were no new or unexpected toxicities observed at study completion. Conclusion: This single-arm trial previously met its primary endpoint of feasibility in patients with early-stage AR+ TNBC. In this relatively high-risk, albeit highly selected patient population, the 3-year DFS measured 80% (95% CI: 67 - 94%) with an adjuvant endocrine therapy approach. Efforts to determine the optimal biomarker for AR+ TNBC are ongoing, so that patients most likely to respond to AR-antagonists in both the early and metastatic setting may be identified. Biomarker data from this study including PD-L1 status and tumor sequencing will be reported at the time of presentation.Funding and drug support for this study was provided by Astellas Pharma Global Development Inc./Pfizer Inc.

Citation Format: Elaine M Walsh, Ayca Gucalp, Sujata Patil, Marcia Edelweiss, Dara S Ross, Pedram Razavi, Shanu Modi, Neil M Iyengar, Rachel Sanford, Tiffany Troso-Sandoval, Mila Gorsky, Jackie Bromberg, Pamela Drullinsky, Diana Lake, Serena Wong, Patricia DeFusco, Nicholas Lamparella, Ranja Gupta, Tasmila Tabassum, Leigh Ann Boyle, Artavazd Arumov, Tiffany A Traina. Adjuvant enzalutamide for the treatment of early-stage androgen-receptor positive, triple negative breast cancer: A feasibility study [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 P1-14-03.

Abstract OT1-18-04: A phase II study of dual immune checkpoint blockade (ICB) plus bicalutamide to enhance thymic T-cell production and immunotherapy response in metastatic breast cancer (MBC)

Background: The addition of anti-programmed death 1/ligand 1 (anti-PD-1/L1) improves progression-free survival when combined with chemotherapy in PD-L1-positive triple-negative MBC. However, novel combination therapies are needed to improve efficacy in hormone receptor positive (HR+) MBC, or in patients with PD-L1-negative disease. Dual ICB with nivolumab (anti-PD-1) and ipilimumab (anti-CTLA-4) has not been studied in depth in MBC despite its success in other solid tumors. Furthermore, MBCs often express the androgen receptor (AR), which can be targeted therapeutically. AR blockade agents have been shown to stimulate thymic production of naïve T-cell clones. It is proposed that ICB in conjunction with AR blockade may facilitate thymopoeisis and subsequent activation of novel, tumor-reactive T-cell clones. Trial design: This is a phase II, open-label trial investigating the combination of ICB (nivolumab 240mg IV q2w; ipilimumab 1mg/kg IV q6w) and AR blockade (bicalutamide, 150mg PO daily) in MBC. Two cohorts will be studied: AR-positive TNBC [ &gt; 1% by IHC, constituting ~50% of TNBCs]; and HR+ MBC (of which the great majority are AR-positive). Eligibility: Patients must have RECIST1.1 measurable disease, ECOG performance score 0-1, and adequate hematological and hepatic function. Subjects may have received no more than 1 prior non-curative chemotherapy. Specific aims: Subjects will be assessed for clinical benefit by iRECIST criteria and safety by CTCAE v4.0, with clinical efficacy defined as &gt;20% improvement in week 24 clinical benefit rate, over historical control (30% per EMBRACE clinical trial). Statistical analysis will be performed by a Simon 2-stage design to minimize futility (n = 46/cohort, stage I: n = 15). As exploratory aims, thymic generation of T-cells will be measured via quantitative deep sequencing of T-cell receptors (TcR, ImmunoSEQ assay), TcR excision circles (TRECs), and flow cytometry using markers of recent thymic emigration. Present accrual: As of 7/8/2021, n=19 subjects are enrolled (4 TNBC, 15 HR+). The trial is open at Providence Cancer Institute (Portland, OR) and Memorial Sloan Kettering Cancer Center (New York, NY). Target accrual: stage I: n=15 per arm; a maximum of 138 patients (46 per cohort) may be enrolled in expansion cohorts. Contact: Dr. David Page (David.page2@providence.org) Clinicaltrials.gov#: NCT03650894

Citation Format: David B Page, Krystle L Collins, Brie Chun, Zhaoyu Sun, William L Redmond, Maritza Martel, Yaping Wu, Nicole Moxon, Staci L Mellinger, Walter J Urba, Tiffany A Traina, Ayca Gucalp. A phase II study of dual immune checkpoint blockade (ICB) plus bicalutamide to enhance thymic T-cell production and immunotherapy response in metastatic breast cancer (MBC) [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 OT1-18-04.

Treatment Exposure and Discontinuation in the PALbociclib CoLlaborative Adjuvant Study of Palbociclib With Adjuvant Endocrine Therapy for Hormone Receptor-Positive/Human Epidermal Growth Factor Receptor 2-Negative Early Breast Cancer (PALLAS/AFT-05/ABCSG-42/BIG-14-03)

PURPOSE

The PALLAS study investigated whether the addition of palbociclib, an oral CDK4/6 inhibitor, to adjuvant endocrine therapy (ET) improves invasive disease-free survival (iDFS) in early hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) breast cancer. In this analysis, we evaluated palbociclib exposure and discontinuation in PALLAS.

METHODS

Patients with stage II-III HR+, HER2- disease were randomly assigned to 2 years of palbociclib with adjuvant ET versus ET alone. The primary objective was to compare iDFS between arms. Continuous monitoring of toxicity, dose modifications, and early discontinuation was performed. Association of baseline covariates with time to palbociclib reduction and discontinuation was analyzed with multivariable competing risk models. Landmark and inverse probability weighted per-protocol analyses were performed to assess the impact of drug persistence and exposure on iDFS.

RESULTS

Of the 5,743 patient analysis population (2,840 initiating palbociclib), 1,199 (42.2%) stopped palbociclib before 2 years, the majority (772, 27.2%) for adverse effects, most commonly neutropenia and fatigue. Discontinuation of ET did not differ between arms. Discontinuations for non-protocol-defined reasons were greater in the first 3 months of palbociclib, and in the first calendar year of accrual, and declined over time. No significant relationship was seen between longer palbociclib duration or ≥ 70% exposure intensity and improved iDFS. In the weighted per-protocol analysis, no improvement in iDFS was observed in patients receiving palbociclib versus not (hazard ratio 0.89; 95% CI, 0.72 to 1.11).

CONCLUSION

Despite observed rates of discontinuation in PALLAS, analyses suggest that the lack of significant iDFS difference between arms was not directly related to inadequate palbociclib exposure. However, the discontinuation rate illustrates the challenge of introducing novel adjuvant treatments, and the need for interventions to improve persistence with oral cancer therapies.

RASAL2 Confers Collateral MEK/EGFR Dependency in Chemoresistant Triple-Negative Breast Cancer

PURPOSE

While chemotherapy remains the standard treatment for triple-negative breast cancer (TNBC), identifying and managing chemoresistant tumors has proven elusive. We sought to discover hallmarks and therapeutically actionable features of refractory TNBC through molecular analysis of primary chemoresistant TNBC specimens.

EXPERIMENTAL DESIGN

We performed transcriptional profiling of tumors from a phase II clinical trial of platinum chemotherapy for advanced TNBC (TBCRC-009), revealing a gene expression signature that identified de novo chemorefractory tumors. We then employed pharmacogenomic data mining, proteomic and other molecular studies to define the therapeutic vulnerabilities of these tumors.

RESULTS

We reveal the RAS-GTPase-activating protein (RAS-GAP) RASAL2 as an upregulated factor that mediates chemotherapy resistance but also an exquisite collateral sensitivity to combination MAP kinase kinase (MEK1/2) and EGFR inhibitors in TNBC. Mechanistically, RASAL2 GAP activity is required to confer kinase inhibitor sensitivity, as RASAL2-high TNBCs sustain basal RAS activity through suppression of negative feedback regulators SPRY1/2, together with EGFR upregulation. Consequently, RASAL2 expression results in failed feedback compensation upon co-inhibition of MEK1/2 and EGFR that induces synergistic apoptosis in vitro and in vivo. In patients with TNBC, high RASAL2 levels predict clinical chemotherapy response and long-term outcomes, and are associated via direct transcriptional regulation with activated oncogenic Yes-Associated Protein (YAP). Accordingly, chemorefractory patient-derived TNBC models exhibit YAP activation, high RASAL2 expression, and tumor regression in response to MEK/EGFR inhibitor combinations despite well-tolerated intermittent dosing.

CONCLUSIONS

These findings identify RASAL2 as a mediator of TNBC chemoresistance that rewires MAPK feedback and cross-talk to confer profound collateral sensitivity to combination MEK1/2 and EGFR inhibitors.

Outcomes in patients (pts) aged ≥65 years in the phase 3 ASCENT study of sacituzumab govitecan (SG) in metastatic triple-negative breast cancer (mTNBC)

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Background: Approximately 20% of pts diagnosed with TNBC are aged ≥65 y. Often, older pts are less fit for chemotherapy due to a greater rate of comorbidities, increased use of medications, and pre-existing frailty or functional loss. SG is an antibody-drug conjugate composed of an anti–Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. The landmark phase 3 ASCENT study (NCT02574455) showed improved outcomes with SG vs single-agent chemotherapy of physician’s choice (TPC) in pts with relapsed/refractory mTNBC (median progression-free survival [PFS], 5.6 vs 1.7 mo; median overall survival [OS], 12.1 vs 6.7 mo). Here we assess the impact of age on the efficacy and safety of SG in ASCENT. Methods: Pts with mTNBC refractory/relapsing after ≥2 prior chemotherapies were randomized 1:1 to receive SG (10 mg/kg IV on days 1 and 8, every 21 days) or TPC (capecitabine, eribulin, vinorelbine, or gemcitabine) until disease progression/unacceptable toxicity. Primary endpoint was PFS per RECIST 1.1 by independent review in brain metastases-negative (BMNeg) pts. Safety outcomes were assessed in all treated pts. This prespecified subgroup analysis assessed the impact of age (pts ≥65 y) on PFS, OS, and safety. Results: Of 529 pts enrolled, 468 were BMNeg (median age, 54 y); of these, 44/235 pts (19%) who received SG and 46/233 pts (20%) who received TPC were aged ≥65 y. SG treatment improved median PFS vs TPC in pts ≥65 y (7.1 vs 2.4 mo; HR, 0.22; 95% CI, 0.12-0.40). SG vs TPC treatment also improved median OS in pts ≥65 y (15.3 vs 8.2 mo; HR, 0.37; 95% CI, 0.22-0.64). Treatment with SG vs TPC resulted in higher ORR (50% vs 0%) and clinical benefit rate (CBR, 61% vs 9%) in pts ≥65 y. Of the 7 pts ≥75 y who received SG, 2 had partial response, 4 had stable disease [SD], and 1 had SD > 6 mo as best response. In pts < 65 y, median PFS for SG vs TPC was 4.6 vs 1.7 mo (HR, 0.46; 95% CI, 0.35-0.59), and median OS was 11.2 vs 6.6 mo (HR, 0.50; 95% CI, 0.40-0.64), respectively; the ORR and CBR were 31% vs 6% and 41% vs 9%, respectively. Pts ≥65 y treated with SG vs TPC had similar rates of all grade and grade ≥3 treatment-emergent adverse events (TEAEs). TEAEs leading to dose reduction were similar in pts ≥65 y in the SG vs TPC arms (35% vs 33%) and were lower in pts < 65 y (19% vs 24%). Key treatment-related TEAEs leading to dose reduction in pts ≥65 y in the SG vs TPC arms were neutropenia (including febrile neutropenia; 14% vs 25%), fatigue (10% vs 4%), diarrhea (6% vs 0%), and nausea (4% vs 0%). TEAEs leading to treatment discontinuation with SG vs TPC were low in pts ≥65 y (2% vs 2%) and < 65 y (5% vs 6%). There were no treatment-related AEs leading to death in any SG-treated age group. Conclusions: Irrespective of age, pts who received SG had a significant survival benefit vs TPC, with a tolerable safety profile. Proactive AE monitoring and management will allow optimal therapeutic exposure to SG in older pts. Clinical trial information: NCT02574455 .

Phase Ib/II study of capecitabine 7/7 schedule with neratinib in patients with HER2-positive metastatic breast cancer (MBC)

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Background: Neratinib (N) is a potent irreversible inhibitor of HER1, HER2, and HER4. Capecitabine (X) at optimal dose of 7 days on and 7 days off schedule (7/7) is well-tolerated with low rates of ≥ grade (G3) diarrhea. Methods: We conducted phase Ib/II study of N with X (7/7) with loperamide and colestipol prophylaxis in patients (pts) with pretreated HER2+ MBC (NCT03377387). Eligible pts had normal left ventricular ejection fraction (≥ 50%), any and < 4 prior chemotherapy-based treatments in phase Ib and II, respectively. Primary endpoint of phase Ib is maximum tolerated dose (MTD) and phase II is response rate. Secondary endpoints are safety, tolerability, and progression-free survival. Exploratory endpoint is to quantify cell-free DNA (cfDNA), correlating with response. Phase Ib follows traditional 3+3 design with 4 dose levels. In phase II, if > 3/9 respond, study is expanded to 24. If > 10/24 respond, study is deemed successful. Results: As of 2-4-2021, 10 pts were enrolled in phase Ib. 4 pts were treated at dose level 1 (X at 1500 mg BID at 7/7 and N at 240 mg daily); 2/4 pts experienced with G3 diarrhea during cycle 1. Six pts were treated at dose level -1 (X at 1000 mg BID 7/7 and N at 240 mg daily); 1 (17%) developed G3 diarrhea. The MTD is X at 1000 mg BID 7/7 and N at 240 mg daily. Twenty-two of 24 pts have been enrolled in phase II. Of 22 pts, data show 6 with partial response, 8 with stable disease, 3 with progressive disease, and 5 have not been assessed radiographically. Overall, 6/22 (27.3%) and 1/22 (4.5%) had all G and G3 diarrhea, respectively. Other significant toxicities at MTD included G2 hand foot syndrome (n = 1, 4.5%), G1 fatigue (n = 1, 4.5%) and G1 nausea (n = 4, 18%). Conclusions: The MTD is X at 1000 mg BID at 7/7 and N at 240 mg daily. This combination is safe and well tolerated with G3 diarrhea rate of 4.5%, which is significantly lower than the X 14/7 schedule in NALA study. The phase II portion of the study is near completion and updated result will be presented. Analysis of cfDNA, to correlate with response for phase II portion, is ongoing. Clinical trial information: NCT03377387.

Provision of subspecialized expert oncology (SEO) opinions using Navya Cancer Data Model (NCDM), a technology-based platform: Prospective study to facilitate access to care

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Background: Outcomes for patients (pts) with cancer may vary widely based on accessibility and quality of care. Subspecialized expert care is associated with improved outcomes yet access to this scarce resource is limited. Providing SEO opinions in legacy ways is time-consuming and difficult to scale. We hypothesized that summarizing comprehensive pt records could enhance efficiency of a remote opinion process. In this prospective pilot, oncologists (MDs) at Memorial Sloan Kettering (MSK) tested the NCDM, a clinically-validated, semi-automated system which abstracts pertinent data elements from medical records into a structured summary to support SEO decision making for remote opinions. Methods: From July to December 2020, 12 MSK MDs provided remote opinions to consecutive pts from an international second opinion service who were specifically seeking MSK expertise. NCDM summaries, with relevant DICOM imaging, were provided to MDs via web and mobile app. MDs answered a brief survey about their experience after each opinion. Time spent to read and respond to an NCDM summary was tracked electronically. Pt feedback was collected by prospective phone follow up. Results: N = 101 remote opinions. Cancer type (N): breast (24), gastrointestinal (15), heme malignancy (14), prostate (12), renal (8), gynecologic (7), head & neck (11), lung (9) and skin (1). 92% MD response rate. Pt characteristics: median age (60 years, range 17-83); stage of disease (early stage 41%, advanced 59%); 86% of pts had received prior treatment. MDs survey responses: median time to complete record review and render opinion = 4.8 min (IQR 2.7 – 7.9 min); NCDM provided adequate information needed to make a decision in this case = 95.7% (89/93); Decision making was easy in this case with data presented in the NCDM format = 96.8% (90/93). Pt survey responses (71/88): 92% shared recommendation with local MD; 87% received the recommended treatment; 99% stated they would recommend a NCDM enabled remote opinion service to others. Conclusions: NCDM summaries enabled subspecialized MSK cancer experts to provide oncology remote opinions with ease. Patients reported high satisfaction with the experience. Technology assisted abstraction and case summary can facilitate access to subspecialized expert opinions at a global scale.

PARP (Poly ADP-Ribose Polymerase) inhibitors for locally advanced or metastatic breast cancer

BACKGROUND

Locally advanced and metastatic breast cancer remains a challenge to treat. With emerging study results, it is important to interpret the available clinical data and apply the evidence offering the most effective treatment to the right patient. Poly(ADP Ribose) Polymerase (PARP) inhibitors are a new class of drug and their role in the treatment of locally advanced and metastatic breast cancer is being established.

OBJECTIVES

To determine the efficacy, safety profile, and potential harms of Poly(ADP-Ribose) Polymerase (PARP) inhibitors in the treatment of patients with locally advanced or metastatic breast cancer. The primary outcome of interest was overall survival; secondary outcomes included progression-free survival, tumour response rate, quality of life, and adverse events.

SEARCH METHODS

On 8 June 2020, we searched the Cochrane Breast Cancer Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE via OvidSP, Embase via OvidSP, World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) search portal and ClinicalTrials.gov. We also searched proceedings from the major oncology conferences as well as scanned reference lists from eligible publications and contacted corresponding authors of trials for further information, where needed.

SELECTION CRITERIA

We included randomised controlled trials on participants with locally advanced or metastatic breast cancer comparing 1) chemotherapy in combination with PARP inhibitors, compared to the same chemotherapy without PARP inhibitors or 2) treatment with PARP inhibitors, compared to treatment with other chemotherapy. We included studies that reported on our primary outcome of overall survival and secondary outcomes including progression-free survival, tumour response rate, quality of life, and adverse events.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures defined by Cochrane. Summary statistics for the endpoints used hazard ratios (HR) with 95% confidence intervals (CI) for overall survival and progression-free survival, and odds ratios (OR) for response rate (RR) and toxicity.

MAIN RESULTS

We identified 49 articles for qualitative synthesis, describing five randomised controlled trials that were included in the quantitative synthesis (meta-analysis). A sixth trial was assessed as eligible but had ended prematurely and no data were available for inclusion in our meta-analysis. Risk of bias was predominately low to unclear across all studies except in regards to performance bias (3/5 high risk) and detection bias for the outcomes of quality of life (2/2 high risk) and reporting of adverse events (3/5 high risk). High-certainty evidence shows there may be a small advantage in overall survival (HR 0.87, 95% CI 0.76 to 1.00; 4 studies; 1435 patients). High-certainty evidence shows that PARP inhibitors offer an improvement in PFS in locally advanced/metastatic HER2-negative, BRCA germline mutated breast cancer patients (HR 0.63, 95% CI 0.56 to 0.71; 5 studies; 1474 patients). There was no statistical heterogeneity for these outcomes. Subgroup analyses for PFS outcomes based on trial level data were performed for triple-negative breast cancer, hormone-positive and/or HER2-positive breast cancer, BRCA1 and BRCA2 germline mutations, and patients who had received prior chemotherapy for advanced breast cancer or not. The subgroup analyses showed a persistent PFS benefit regardless of the subgroup chosen. Pooled analysis shows PARP inhibitors likely result in a moderate improvement in tumour response rate compared to other treatment arms (66.9% vs 48.9%; RR 1.39, 95% CI 1.24 to 1.54; 5 studies; 1185 participants; moderate-certainty evidence). The most common adverse events reported across all five studies included neutropenia, anaemia and fatigue. Grade 3 or higher adverse events probably occur no less frequently in patients receiving PARP inhibitors (59.4% for PARP arm versus 64.5% for non-PARP arm, RR 0.98, 95% CI 0.91 to 1.04; 5 studies; 1443 participants; moderate-certainty evidence). Only two studies reported quality of life outcomes so this was not amenable to meta-analysis. However, both studies that did assess quality of life showed PARP inhibitors were superior compared to physician's choice of chemotherapy in terms of participant-reported outcomes.

AUTHORS' CONCLUSIONS

In people with locally advanced or metastatic HER2-negative, BRCA germline mutated breast cancer, PARP inhibitors offer an improvement in progression-free survival, and likely improve overall survival and tumour response rates. This systematic review provides evidence supporting the use of PARP inhibitors as part of the therapeutic strategy for breast cancer patients in this subgroup. The toxicity profile for PARP inhibitors is probably no worse than chemotherapy but more information is required regarding quality of life outcomes, highlighting the importance of collecting such data in future studies. Future studies should also be powered to detect clinically important differences in overall survival and could focus on the role of PARP inhibitors in other relevant breast cancer populations, including HER2-positive, BRCA-negative/homologous recombination repair-deficient and Programmed Death-Ligand 1 (PDL1) positive.

Abstract OT-29-01: Tenacity: A phase 2, multicenter, open-label, single-arm study of AL101 monotherapy in patients with notch-activated triple negative breast cancer

Background: There is an urgent need to identify new therapeutic strategies for triple-negative breast cancer (TNBC), a sub-type associated with poor prognosis. The Notch pathway is activated during mammary gland development and has been implicated as a key driver in breast cancer (Collu, 2007). The frequency of Notch mutations or gene rearrangements was reported at 5 to 16% in TNBC tumors and over-expression of Notch was associated with worse overall survival (Robinson, 2011; Stoeck, 2014; Wang, 2015). AL101 is a potent and selective inhibitor of gamma secretase-mediated Notch signaling. In preclinical models, AL101 exerts its antitumor activity through direct inhibition of cell proliferation and indirectly via inhibition of tumor angiogenesis. In TNBC patient-derived xenograft (PDX) tumor models, the presence of activating Notch mutations/fusions correlated with robust response to AL101 monotherapy (ASCO 2019, Abstr 1064). AL101 has been studied in three Phase 1 studies in more than 200 subjects with various cancers (ASCO 2018, Abstr 2515) and is currently being studied in a Phase 2 study for patients with Adenoid Cystic Carcinoma with Notch activating mutations (ACCURACY- NCT03691207). Preliminary data reported from this trial showed clear signs of clinical activity along with a favorable safety profile (ESMO 2019, Abstr 3568). Trial design: The TENACITY study is an open-label, international, multicenter, single arm Phase 2, Simon two-stage optimal design for targeted therapy study of AL101 monotherapy in subjects with Notch-activated recurrent or metastatic TNBC who have received ≤ 3 lines of prior therapy. Patients with stable, asymptomatic CNS metastases are eligible. Notch activation will be determined by Next Generation Sequencing (NGS) of tumor DNA/RNA to detect somatic mutations and gene rearrangements. Target enrollment is 67 subjects. The design will include a lead-in cohort of 6 subjects to ascertain safety of AL101, 6 mg weekly (QW). After the 6th subject completes 4 weeks of therapy, safety will be assessed and subsequent dosage of AL101 will be determined (continue at 6 mg QW versus reduction to 4 mg QW). The primary endpoint is overall response rate (ORR), based on RECIST v1.1 as assessed by the treating investigator. The study design has 80% power with type I error level of 5% to detect an ORR of 23%. Key Secondary endpoints include progression free survival, clinical benefit rate, duration of response, overall survival and quality of life. Study will open to enrollment in July 2020. For further information on this trial, email chen.d@ayalapharma.com or visit clinicaltrials.gov (NCT04461600).

Citation Format: Tiffany A Traina, Erin F Cobain, Ella Evron, Chen Duksin, Gary Gordon. Tenacity: A phase 2, multicenter, open-label, single-arm study of AL101 monotherapy in patients with notch-activated triple negative breast cancer [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 OT-29-01.

American Society of Clinical Oncology Road to Recovery Report: Learning From the COVID-19 Experience to Improve Clinical Research and Cancer Care

This report presents the American Society of Clinical Oncology's (ASCO's) evaluation of the adaptations in care delivery, research operations, and regulatory oversight made in response to the coronavirus pandemic and presents recommendations for moving forward as the pandemic recedes. ASCO organized its recommendations for clinical research around five goals to ensure lessons learned from the COVID-19 experience are used to craft a more equitable, accessible, and efficient clinical research system that protects patient safety, ensures scientific integrity, and maintains data quality. The specific goals are: (1) ensure that clinical research is accessible, affordable, and equitable; (2) design more pragmatic and efficient clinical trials; (3) minimize administrative and regulatory burdens on research sites; (4) recruit, retain, and support a well-trained clinical research workforce; and (5) promote appropriate oversight and review of clinical trial conduct and results. Similarly, ASCO also organized its recommendations regarding cancer care delivery around five goals: (1) promote and protect equitable access to high-quality cancer care; (2) support safe delivery of high-quality cancer care; (3) advance policies to ensure oncology providers have sufficient resources to provide high-quality patient care; (4) recognize and address threats to clinician, provider, and patient well-being; and (5) improve patient access to high-quality cancer care via telemedicine. ASCO will work at all levels to advance the recommendations made in this report.

Phase II trial of bicalutamide in combination with palbociclib for the treatment of androgen receptor (+) metastatic breast cancer

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Background: Genome-wide transcriptional analysis has identified a unique subset of androgen receptor (AR) +, estrogen receptor (ER)/progesterone receptor (PR)- breast cancer (BC). The functional role of AR was confirmed initially in preclinical models demonstrating that androgen-driven growth could be abrogated by antiandrogen therapy. TBCRC011 established the safety and efficacy of inhibiting AR with bicalutamide (B) in patients (pts) with AR+/ER/PR- metastatic BC (MBC) with a median progression free survival (PFS) of 12 weeks (wks) (95% CI, 11–22 wks). In preclinical data, palbociclib (P) has been shown to reduce growth of AR+/ER/PR- MDA-MB-453 BC cells. It has been shown that AR+ triple negative BC (TNBC) expresses a luminal profile and has intact Rb protein, the target of P activity. We conducted this Phase I/II trial of the AR inhibitor B in combination with the CDK4/6 inhibitor P in pts with AR+/ER/PR/HER2- BC (NCT02605486) to test the hypothesis that androgen blockade, paired with CDK4/6 inhibition would have increased efficacy in pts with androgen-dependent BC. Methods: Postmenopausal pts with AR+ TN MBC defined as IHC ≥ 1% nuclear staining (DAKO, Clone AR441 (5/2016-11/2016) then Ventana AR SP107 (11/2016-6/2018), ECOG ≤2, measurable/non-measurable disease were eligible for enrollment. Any number of prior regimens was permitted. Pts received B 150 mg daily and P 125 mg daily 3 wks on 1 wk off. Pts were evaluated for toxicity every 2-4 wks and for response every 8-12 wks. Primary endpoint: 6 month (mo) PFS. Secondary endpoints: clinical benefit rate, toxicity, correlative studies to better characterize AR+ TNBC. A Simon 2-stage minimax design that discriminates between 6 mo PFS rates of 20% and 40% was used. If ≥ 11/33 pts were PF at 6 mo then B+P would warrant further study. Results: As of 1.1.20 33 pts were enrolled on study with median (med) age 67 (42-79), performance status 0 (0-1). Number of pts with visceral metastases: 20, measurable disease: 22. AR% 1-9: 3, 10-50: 6; 51-100: 24. Med prior lines for MBC: 3 (0-9). Best response: (31 evaluable pts): 11 pts PF at 6mo: 10 SD > 6mo, 1 PR. Med wks on study: 14 (2-101). Toxicity > 10% grade >3 related: Number of pts with leukopenia: 21, neutropenia: 21, lymphocytopenia: 6, thrombocytopenia: 3. One pt with febrile neutropenia. One death due to disease progression within 30 days off study. Conclusions: In this selected subset of pts with AR+ TN MBC, this study met its prespecified endpoint with 11 pts PF at 6 mo on B 150 mg + P 125 mg. B+P has been well tolerated with no unexpected toxicity observed. Clinical trial information: NCT02605486 .

Prevalence and characterization of dermatologic adverse events related to alpelisib (BYL719) in breast cancer patients

1063

Background: Rash develops in approximately 50% of breast cancer patients receiving alpelisib, often requiring dose modifications. Herein, we describe the characteristics of alpelisib-related dermatologic adverse events (dAEs). Methods: A single center retrospective analysis was conducted via review of electronic medical records. We collected clinical, laboratory and management data relevant to patients treated with alpelisib for advanced breast cancer under four different randomized clinical trials or post approval by regulatory agencies from 6/1/2013 to 7/31/2019. Type and severity of dAEs was recorded using the Common Terminology Criteria for Adverse Events version 5.0 (CTCAE v5.0). Results: A total of 102 patients (mean age 56 years, range 27-83) receiving alpelisib from 200 to 350 mg daily, most frequently in combination with endocrine therapy (79, 77.5%) were included. We identified 41 (40.2%) patients with all-grade rash [CTCAE grade 1/2 = 22 (21.6%); CTCAE grade 3 = 19, (18.6%)] distributed primarily along the trunk (18, 78%) and developing, on average, within 12.8 +/- 1.5 days of treatment initiation (n = 38). Mean duration of rash was 7.1 +/- 3.8 days; and no grade 4 dAEs were observed. Of 29 patients with documented morphology of alpelisib-related dAEs, the majority (26, 89.7%) had maculopapular rash. Thirteen (68%) of 19 patients with any-grade rash and report of any associated symptoms had pruritus (7, 36%) or burning pain (6, 32%). All-grade dAEs correlated with an increase in serum eosinophils from 2.7% to 4.4% (p < 0.05), and prophylaxis with non-sedating antihistamines (n = 43) was correlated with a reduction of grade 1/2 rash onset (OR 0.39, p = 0.09). Sixteen (84.2%) of 19 patients with grade 3 dAEs had interruption of alpelisib, followed by management with antihistamines, topical and/or systemic corticosteroids. We did not observe rash recurrence in 12 (75%) of these 16 patients who re-initiated therapy; and the majority (9, 56.3%) were re-challenged without a dose reduction. Conclusions: Pruritus and increased blood eosinophils occur with maculopapular rash within the first two weeks of initiating alpelisib and persists for approximately seven days. To reduce onset of grade 1/2 rash, non-sedating antihistamines (i.e. cetirizine) are recommended during the first eight weeks. While grade 3 rash leads to interruption of alpelisib, dermatologic improvement is evident with systemic corticosteroids; and most patients can resume therapy at a maintained or reduced dose upon re-challenge.

Abstract P4-14-07: Treatment patterns for metastatic hormone receptor-positive breast cancer: Comparing expert and community practice

Background Endocrine therapies and CDK4/6 inhibitors have dramatically improved outcomes for patients with hormone receptor-positive (HR+) metastatic breast cancer (MBC). To help inform treatment decisions among healthcare providers (HCPs) caring for patients with MBC, we have developed and regularly updated an online treatment decision support tool that provides recommendations from multiple breast cancer experts for specifically defined patient scenarios. Here we report data for HR+/HER2- MBC cases entered into the tool since 2016, capturing self-reported practice trends from HCPs compared with matched treatment recommendations from experts. Methods For the most recent MBC treatment tool (published October 2018), 5 breast cancer experts provided treatment consultation for 549 unique MBC case scenarios based on a simplified set of variables: disease phenotype, previous systemic therapy, visceral crisis (yes/no), rate of disease progression, and the presence or absence of germline BRCA1/2 mutations. HCPs used selection menus to enter patient and disease factors based on these variables along with their intended treatment plan. When completed, the experts’ treatment recommendations for that specific patient case were shown to the HCPs at which time they were asked to indicate if the expert recommendations changed their planned treatment. Results From October 2018 through June 2019, 603 HCPs entered 1127 patient case scenarios, including 581 HR+/HER2- MBC cases, in the most recent online tool. A comparison of expert and HCP treatment choices for select HR+/HER2- MBC case scenarios from the October 2016 and October 2018 tool is shown in the Table. In the setting of HR+/HER2- MBC, among those HCPs whose planned treatment differed from the consensus expert recommendation, 55% indicated that they would change their original choice of treatment. Conclusions CDK4/6 inhibitors have had a large impact on expert treatment recommendations for patients with HR+/HER2- MBC. However, data from this online treatment decision support tool suggest ongoing differences in practice between experts and community HCPs in this setting. For many cases entered into the tool, the practice of the majority of HCPs differed from expert consensus (Table). Consensus expert recommendations in this online tool changed the intended treatment plan of many using it and, therefore, can help optimize the care of patients with MBC. A detailed analysis of overall community practice trends for HR+/HER2- MBC along with a comparison of expert and HCP practice for different case scenarios will be presented.

HR+/HER2- MBC Case Scenarios (no visceral crisis)Expert Consensus Recommendation (%)Expert Consensus Recommendation (%)HCP Practice Matched Expert Consensus Recommendation, % (n)HCP Practice Matched Expert Consensus Recommendation, % (n)2016201820162018de novoCDK4/6i + AI (100)CDK4/6i + AI (100)23 (111)32 (188)Previous (neo)adjuvant AICDK4/6i + FULV (92)CDK4/6i + FULV (90)22 (54)17 (77)Previous CDK4/6i + AIFULV (82)FULV ± EVE (92)0 (14)18 (40)Previous AI and CDK4/6i + FulvEVE + EXE (87)EVE + EXE (73)63 (19)28 (18)

Citation Format: Timothy Quill, Sara Hurvitz, Kathy D. Miller, Ruth O'Regan, Tiffany A. Traina, Rachael Andrie, Kevin L. Obholz, Mohammad Jahanzeb. Treatment patterns for metastatic hormone receptor-positive breast cancer: Comparing expert and community practice [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-14-07.

Abstract P4-17-01: Genomic profiling of primary and metastatic breast cancer in men

Background: Male breast cancer is rare, with approximately 2,600 cases diagnosed annually in the United States. Data are scant regarding the genomics and pathophysiology of male breast cancer, especially in the metastatic setting, requiring most treatment recommendations in male breast cancer to be made by inference from breast cancer in women.

Methods: We performed prospective genomic profiling of primary and metastatic tumor samples from men with breast cancer treated at Memorial Sloan Kettering Cancer Center using the MSK-IMPACT targeted-DNA-sequencing panel for somatic mutations. Comprehensive demographic, clinical, and pathologic data were collected on all included patients. Statistics are descriptive.

Results: Genomic sequencing was performed on 45 samples from 41 men (31 primary samples and 14 from metastatic sites). Median age at time of sample collection was 61 years, with a range of 27-92 years. Thirty-seven (90.2%) men had ER+/HER2- breast cancer, 3 (7.3%) had ER+/HER2+ breast cancer and 1 (2.4%) had triple negative disease. Thirty-nine (95.1%) had ductal carcinoma, and no cases of lobular carcinoma were identified. Forty patients underwent germline testing, and 12 (30%) were found to have pathogenic germline mutations (6 BRCA2 mutations, 2 BRCA1 mutations [one of whom had a concurrent CHEK2 mutation], and one mutation each in PALB2, MUTYH, and MSH6).

Overall, the pattern of genomic alterations in male breast cancer was similar that in women. Twelve (29.3%) patients had PIK3CA mutations, 9 (22%) had GATA3 mutations, 3 (7.3%) had TP53 mutations, 3 (7.3%) had ARID1A mutations, 3 (7.3%) had KMT2C mutations, 2 (4.9%) had FOX1A mutations, 2 (4.9%) had RB1 mutations, and 2 (4.9%) had TERT promoter hotspot mutations. Eleven (26.8%) patients had CCND1 amplification, 8 (19.5%) had MYC amplification, 6 (14.6%) had FGFR1 amplification, and 5 (12.2%) had MDM2 amplification. All other findings were present in ≤ 1 patient. All included patients had normal mutational burden, and all samples were microsatellite stable. PIK3CA mutations occurred in 33% of primary samples vs. 15% of metastatic samples, CCND1 amplification occurred in 23% of primary samples vs. 38% of metastatic samples, and TERT hotspot promoter mutations were found only in metastatic samples.

Of note, we observed a single ESR1 D538G mutation in the metastatic sample of a patient with significant prior exposure to aromatase inhibitors in the adjuvant and metastatic settings. We further found concurrent ERBB2 mutation and amplification in the post-treatment metastatic samples of an ER+/HER2- patient, who was treated with neratinib for 14 weeks with clinical response. Lastly, we report a heavily pretreated patient with metastatic secretory breast carcinoma who was found to have an ETV6-NTRK3 fusion gene. This patient was treated with a first-generation TRK inhibitor and continues to exhibit an ongoing clinical response at 8.6 months.

Conclusions: Based on our data, the overall genomic landscape of male breast cancer appears comparable to that of breast cancer in women, as has been previously reported. However, despite the small number of metastatic cases examined, several previously unreported and treatment-informing signatures were discovered, especially in those patients with less common male breast cancer variants. Further study is warranted to confirm these findings in a larger cohort.

Citation Format: Joshua Z Drago, Cristian Serna-Tamayo, Carlos H Dos Anjos, David N Brown, Shanu Modi, Komal Jhaveri, David B Solit, Tiffany A Traina, Sarat Chandarlapaty, Jorge S Reis-Filho, Mark E Robson, Ayca Gucalp, Pedram Razavi. Genomic profiling of primary and metastatic breast cancer in men [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-17-01.

Efficacy and Safety of Gemcitabine With Trastuzumab and Pertuzumab After Prior Pertuzumab-Based Therapy Among Patients With Human Epidermal Growth Factor Receptor 2-Positive Metastatic Breast Cancer: A Phase 2 Clinical Trial

IMPORTANCE

Taxanes with trastuzumab and pertuzumab for initial treatment of human epidermal growth factor receptor 2 (ERBB2, formerly HER2)-positive metastatic breast cancer is associated with improved progression-free survival (PFS) and overall survival. While continued use of trastuzumab in therapeutic combinations after disease progression is standard, the efficacy of continuing pertuzumab is unknown.

OBJECTIVE

To evaluate the efficacy and safety of pertuzumab in combination with gemcitabine and trastuzumab after prior treatment with pertuzumab for ERBB2-positive metastatic breast cancer.

DESIGN, SETTING, AND PARTICIPANTS

This is a phase 2 single-arm clinical trial of dual anti-ERBB2 therapy after prior treatment with pertuzumab. The study took place at a single academic center from March 2015 to April 2017 among women with ERBB2-positive metastatic breast cancer, prior pertuzumab-based treatment, and 3 or fewer prior chemotherapy regimens. Data were analyzed between January 2019 and March 2019.

INTERVENTION

Treatment consisted of gemcitabine, 1200 mg/m2 (later amended to 1000 mg/m2) on days 1 and 8 every 3 weeks, plus trastuzumab (8-mg/kg loading dose, then 6 mg/kg) and pertuzumab (840-mg loading dose, then 420 mg) once every 3 weeks.

MAIN OUTCOMES AND MEASURES

The primary end point was 3-month PFS. Based on prior trials, a target rate of 70% or higher was selected as the promising progression-free rate at 3 months. Secondary outcomes included safety, tolerability, and overall survival.

RESULTS

A total of 45 patients (median [range] age, 57.1 [31.7-77.2] years) were enrolled; 22 (49%) were treated in the second-line setting, and 23 (51%) were treated in the third-line setting or beyond. Of these, 22 (49%) received prior trastuzumab emtansine (T-DM1). At a median (range) follow-up of 27.6 (8.3-36.0) months, 3-month PFS was 73.3% (95% CI, 61.5%-87.5%). Overall, median PFS was 5.5 months (95% CI, 5.4-8.2 months). Treatment was well tolerated, with no occurrences of febrile neutropenia or symptomatic left ventricular systolic dysfunction.

CONCLUSIONS AND RELEVANCE

In this phase 2 trial, treatment with gemcitabine, trastuzumab, and pertuzumab after prior pertuzumab-based therapy for ERBB2-positive metastatic breast cancer was associated with a 3-month PFS rate of 73.3% and was well tolerated. Continuation of pertuzumab beyond progression was associated with apparent clinical benefit.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02252887.

Adjuvant enzalutamide for the treatment of early-stage androgen receptor-positive (AR+) TNBC

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Background: A subset of TNBC is dependent on AR signaling. Enzalutamide (ENZA), an AR-antagonist, has activity in patients (pts) with metastatic AR+ TNBC, with a clinical benefit rate of 33%. This study tests the feasibility of adjuvant ENZA for the treatment (tx) of early stage, AR+ TNBC. We now report the primary endpoint (endpt) and safety. Methods: Eligible pts have centrally confirmed, Stage I-III, ER/PR < 1%, HER2(-), AR ≥1% BC and completed all planned surgery, chemotx and radiation (RT) < 6 months of tx start. AR testing by IHC per MSK methods. Tx consists of ENZA 160mg daily for 1 year (y) with the option to extend tx to 2y. Toxicity per NCI CTCAEv4 every (q) 4 weeks (wk) for 12 wk, then q3 months. Primary endpt: feasibility of 1y ENZA defined as the discontinuation rate due to toxicity, consent withdrawal or tolerability. 50 pts are enrolled to have 46 evaluable pts required to discriminate between feasibility of 50% and 70%, with type I error 5% and 88% power. Pts who have disease progression (PD) or die during 1st y of ENZA and do not have tx discontinuation due to the above will not be included in the primary analysis. If 29 pts complete 1y, adjuvant ENZA will be deemed feasible. Secondary endpts: safety and 3y DFS and OS. Exploratory endpts: PROs and biomarker development. Results: Between 5/2016-6/2018, 50 pts were enrolled. Pt and tumor characteristics (N = 50): Median age 55y (33-81); Stage: I 20 (40%), II 23 (46%), III 7 (14%); Grade (gr): 2 = 26%, 3 = 74%. AR > 10% = 35 (70%), AR ≤10% = 15 (30%). Chemotx 47/50 (94%): Neoadjuvant (neo) 40%, Adjuvant (adj) 60%; Anthracycline/Taxane-based 38/47 (81%), Platinum 1/47 (2%), Docetaxel/Cyclophosphamide 3/47 (6%), other 5/47 (11%). 13/19 who received neo tx failed pCR; 9/13 (69.2%) received adj capecitabine. RT: 38/50 (76%). 27 pts completed 1y of tx. 7 pts will be evaluable by 6/1/19. 1 pt to complete 1y 6/21/19. 15 pts are off tx: PD (3), toxicity (5), noncompliance (4), withdrawal of consent (3). Tx-related AEs, any gr, > 10% (N = 50): fatigue (48%), hot flashes (22%), headache (18%), hyperglycemia (18%), nausea (18%), WBC decreased (16%), dizziness (14%), arthralgia (12%), dyspnea (12%). Tx-related, gr 3 AEs: fatigue (6%), hyperglycemia (2%), hypertension (2%). No gr 4/5 AEs or seizures. 11 pts had dose reduction. Conclusions: Feasibility of adjuvant ENZA will be fully evaluable in 4/2019 and is anticipated to meet the prespecified statistical expectations for primary endpt. ENZA is well tolerated following locoregional tx and standard of care systemic tx. Secondary analyses and correlatives are ongoing to define the role of AR in TNBC. Clinical trial information: NCT02750358.

Dora: A randomized phase II multicenter maintenance study of olaparib alone or olaparib in combination with durvalumab in platinum responsive advanced triple-negative breast cancer (aTNBC)

TPS1113

Background: PARP inhibition (PARPi) with olaparib is approved in HER2-negative germline BRCA mutant (g BRCAm) metastatic breast cancer. Maintenance PARPi in relapsed platinum-sensitive ovarian cancer improves median PFS regardless of gBRCA mutation status. Preclinical work has shown that platinum response strongly correlates with olaparib response in breast cancer models; hence, maintenance therapy trials are underway in aTNBC. PARPi modulates immune responses and enhances immunogenicity in many preclinical models. We hypothesize that olaparib either alone or in combination with the PD-L1 inhibitor durvalumab will have clinical efficacy as maintenance therapy in aTNBC subjects who have responded to platinum-based chemotherapy. Methods: DORA is a randomized, international, multicenter, phase II study designed to explore the efficacy of olaparib or olaparib in combination with durvalumab as maintenance therapy in platinum-sensitive aTNBC. 60 subjects will be enrolled following a minimum of 3 cycles of treatment with platinum-based (cisplatin or carboplatin) chemotherapy as a single agent or combination therapy in the first or second-line setting. Subjects deriving clinical benefit (CR / PR / SD) from platinum-based therapy will be eligible and randomized in a 1:1 ratio. Patients in arm 1 will receive olaparib orally 300mg BID continuously and in arm 2 will receive olaparib orally 300mg BID continuously in combination with durvalumab 1500mg IV every 4 weeks. Assessment of tumor response will be done every 8 weeks. Primary endpoint: progression-free survival. Secondary endpoints: overall survival, clinical benefit rate, safety. Correlative analyses: pre-treatment archival/fresh biopsy samples are mandated. Post-treatment tissue biopsy is requested. Serial ctDNA will be collected at baseline, staging, and progression to correlate with response and track emerging genomic alterations in a platinum sensitive cohort under the pressure of PARP inhibition. Whole exome DNA sequencing, IHC for PDL-1 and TILs will be performed on tissue samples. ClincalTrials.gov Identifier: NCT03167619. (Moore K, et al "SOLO-1: Phase III trial of maintenance olaparib following platinum-based chemotherapy in newly diagnosed patients with advanced ovarian cancer and a BRCA1/2 mutation" ESMO 2018; Abstract LBA7-PR). Clinical trial information: NCT03167619.

A phase II study of dual immune checkpoint blockade (ICB) plus androgen receptor (AR) blockade to enhance thymic T-cell production and immunotherapy response in metastatic breast cancer (MBC)

TPS1106

Background: ICB (atezolizumab, anti-PD-L1) is known to improve survival when added to chemo, however only in PD-L1-positive, triple-negative MBC. ICB is less effective in hormone receptor positive (HR+) MBC, or when administered following palliative chemo. Novel approaches are required to broaden clinical benefit of ICB, particularly in PD-L1-negative, HR+, or chemo-experienced MBC. Dual ICB with anti-PD-1 (nivolumab) and anti-CTLA-4 (ipilimumab) is associated with enhanced activity in melanoma other malignancies, but has not been explored extensively in MBC. Androgen receptor (AR) blockade, in addition to known direct cytostatic effects in AR-expressing MBCs (50% of TNBC, > 75% of HR+ MBC), may also modulate immune response. AR blockade has been shown experimentally to stimulate thymic production of naïve T-cell clones, which in turn can facilitate de novo anti-tumor immune responses. Concurrent ICB can enhance the activity of these T-cell clones by interfering with PD-1-mediated peripheral tolerance. This combination approach is promising in MBC in light of known AR positivity, and the routine use of lymphodepleting chemo regimens in the curative-intent setting. Methods: This is a phase II trial of dual immune checkpoint blockade (nivolumab 240mg IV q2w; ipilimumab 1mg/kg IV q6w) plus AR blockade (bicalutamide, 150mg PO daily, dose reduction allowed) in triple-negative MBC (cohort A: AR-positive [ > 1% by IHC]; cohort B: AR-negative) or HR+ MBC (cohort C) in subjects who received 0/1 prior chemotherapies in the non-curative setting. Objectives include 24-week clinical benefit rate by iRECIST (primary), safety (CTCAE v4.0), and other response measures (RECIST1.1, PFS, OS). Efficacy for each cohort is defined as > 20% improvement in response over historical control (30% per EMBRACE clinical trial) employing a Simon 2-stage design to minimize futility (n = 46/cohort, stage I n = 15). Thymic generation of T-cells will be measured via quantitative deep sequencing of T-cell receptors (TcR, ImmunoSEQ assay) and TcR excision circles (TRECs), as well as real-time flow cytometry using surrogate cell surface markers of recent thymic emigration. Enrollment has commenced, sites: Earle A. Chiles Research Institute (Portland, OR), Memorial Sloan Kettering Cancer Center (New York, NY). Clinical trial information: NCT03650894.

TBCRC 030: A randomized phase II study of preoperative cisplatin versus paclitaxel in TNBC—Evaluating the homologous recombination deficiency (HRD) biomarker

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Background: Cisplatin (C) and paclitaxel (T) have activity in TNBC, however predictive biomarkers are lacking. The HRD assay detects impaired dsDNA break repair and may identify BRCA1/2-proficient tumors for treatment with DNA targeting therapies. TBCRC 030 was designed to determine the association between HRD and response to preoperative chemotherapy (CT) in TNBC. Methods: This phase II study randomized patients (pts) with BRCA1/2-proficient/unknown stage I-III TNBC to 12 weeks (wks) of preoperative C or T, followed by surgery. HRD was performed on baseline tissue, with positive scores > 33. Non-responders at 12 wks could crossover to alternative CT. The co-primary objectives were to detect a positive association of HRD with pathologic response (RCB 0-1) vs not (RCB 2-3) to C and a negative association to T. Target accrual of 160 pts was planned to yield 140 evaluable specimens for HRD, providing 90% power for the primary objectives. Analyses used logistic models and likelihood ratio tests with one-sided Type I errors of alpha = 0.05. Results: 140 pts initiated treatment, (72 Arm C, 68 Arm T; 81% T1-2, 62% node negative); 138 were evaluable for response at 12 wks. Post-enrollment testing showed 8 pts (5.8%) with germline DNA-repair pathway mutations. HRD results were available for 95 pts (68.8%, 23 inadequate tissue, 22 pending); 68 (71.6%) were HRD positive: 38 in Arm C, 30 in Arm T. In response-evaluable pts, 87 (63.0%) had surgery at 12 wks, and 51 (37.0%) crossed over. Response outcomes are shown in the Table. No association was seen between HRD score and RCB response to either neoadjuvant C (OR 2.78, [CI 0.61, 17.74]) or T (OR 0.98, CI [0.20, 5.06]). There was no evidence of an interaction between HRD and CT arms. Similarly, no association was observed between HRD score and pCR to either C (OR 1.47, CI [0.40, 5.59]) or T (OR 0.61, CI [0.14, 2.52]). There were no new safety signals. Conclusions: In this mostly BRCA1/2 proficient TNBC cohort, 12 wks of preoperative C or T led to a similar response rate of about 40%; baseline HRD was not predictive of response to preoperative CT, defined either by RCB 0-1 or pCR. Further data will be presented. Correlative analyses of research tissues for markers predictive of response to specific CT in TNBC is ongoing. Clinical trial information: NCT01982448. [Table: see text]

Emerging Novel Therapeutics in Triple-Negative Breast Cancer

The mortality from breast cancer has steadily decreased due in part to early detection and advances in therapy. The treatment options for breast cancer vary considerably depending on the histological subtype. There are a number of very effective targeted therapies available for estrogen receptor-positive disease and for human epidermal growth factor receptor 2-positive disease. However, triple-negative breast cancer is a particularly aggressive subtype. This subtype represents an unmet need for improved therapies. TNBC is a heterogenous subtype of breast cancer that is beginning to be refined by its molecular characteristics and clinical response to a targeted therapeutic approach. Here we review the recent advances in the treatment of TNBC with emphasis on the many emerging novel targeted therapies.

Phase 2 Study of Dose-Dense Doxorubicin and Cyclophosphamide Followed by Eribulin Mesylate With or Without Prophylactic Growth Factor for Adjuvant Treatment of Early-Stage Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer

BACKGROUND

Eribulin has significantly improved overall survival for patients with metastatic breast cancer who received ≥ 2 prior chemotherapy regimens for advanced disease. This trial assessed eribulin as adjuvant therapy for patients with early-stage breast cancer.

PATIENTS AND METHODS

Patients with human epidermal growth factor receptor 2-negative, stage I to III breast cancer received doxorubicin 60 mg/m2 and cyclophosphamide 600 mg/m2 provided intravenously on day 1 of each 14-day cycle for 4 cycles, with pegfilgrastim on day 2, followed by 4 cycles of eribulin mesylate 1.4 mg/m2 provided intravenously on days 1 and 8 every 21 days. There were 2 cohorts, as follows: cohort 1: no prophylactic growth factor with eribulin (allowed at physician's discretion only); cohort 2: prophylactic filgrastim with eribulin. The primary end point was feasibility, defined as the percentage of patients who completed the eribulin portion of the regimen without a dose omission, delay, or reduction due to an eribulin-related adverse event. Relative dose intensity of eribulin and toxicities are summarized by cohort. Exploratory end points included 3-year disease-free survival and overall survival.

RESULTS

Eighty-one patients (cohort 1, n = 55; cohort 2, n = 26) entered the treatment phase; 88% completed treatment. Feasibility was 72.9 % (90% confidence interval, 60.4, 83.2) in cohort 1 and 60.0% (90% confidence interval, 41.7, 76.4) in cohort 2. The most frequent eribulin-related adverse events (all grades) were fatigue (75.9%), peripheral neuropathy (54.4%), nausea (39.2%), neutropenia (35.4% [31.5% of patients in cohort 1; 44.0% in cohort 2]), and arthralgia (26.6%).

CONCLUSION

The primary end point of > 80% feasibility was not met. No unexpected adverse events were observed, and 62% of patients received full dosing with no dose delay or reduction. Further investigation of this regimen with alternative dosing schedules or use of growth factors could be considered.

The Genomic Landscape of Endocrine-Resistant Advanced Breast Cancers

We integrated the genomic sequencing of 1,918 breast cancers, including 1,501 hormone receptor-positive tumors, with detailed clinical information and treatment outcomes. In 692 tumors previously exposed to hormonal therapy, we identified an increased number of alterations in genes involved in the mitogen-activated protein kinase (MAPK) pathway and in the estrogen receptor transcriptional machinery. Activating ERBB2 mutations and NF1 loss-of-function mutations were more than twice as common in endocrine resistant tumors. Alterations in other MAPK pathway genes (EGFR, KRAS, among others) and estrogen receptor transcriptional regulators (MYC, CTCF, FOXA1, and TBX3) were also enriched. Altogether, these alterations were present in 22% of tumors, mutually exclusive with ESR1 mutations, and associated with a shorter duration of response to subsequent hormonal therapies.

First international TNBC conference meeting report

Recently, Georgia State University's Centennial Hall was the premier location for the 2017 International Conference on Triple Negative Breast Cancer (TNBC): Illuminating Actionable Biology, which was held from Sept. 18 to 20, 2017, in Atlanta, USA. The conference featured a stellar line-up of domestic and international speakers and diverse participants including TNBC survivors, luminaries in breast cancer research, medical students and fellows, clinicians, translational researchers, epidemiologists, biostatisticians, bioinformaticians, and representatives from the industry. This report distills the burning questions that spiked the event and summarizes key themes, findings, unique opportunities and future directions that emerged from this confluence of thought leaders.

Phase 1 study of seviteronel, a selective CYP17 lyase and androgen receptor inhibitor, in women with estrogen receptor-positive or triple-negative breast cancer

PURPOSE

Seviteronel (INO-464) is an oral, selective cytochrome P450c17a (CYP17) 17,20-lyase (lyase) and androgen receptor inhibitor with in vitro and in vivo anti-tumor activity. This open-label phase 1 clinical study evaluated safety, tolerability, pharmacokinetics (PK), and activity of once-daily (QD) seviteronel in women with locally advanced or metastatic TNBC or ER+ breast cancer.

METHODS

Seviteronel was administered in de-escalating 750, 600, and 450 mg QD 6-subject cohorts. The 750 mg QD start dose was a phase 2 dose determined for men with castration-resistant prostate cancer in (Shore et al. J Clin Oncol 34, 2016). Enrollment at lower doses was initiated in the presence of dose-limiting toxicities (DLTs). The primary objective of this study was to determine seviteronel safety, tolerability, and MTD. The secondary objectives included description of its PK in women and its initial activity, including clinical benefit rate at 4 (CBR16) and 6 months (CBR24).

RESULTS

Nineteen women were enrolled. A majority of adverse events (AEs) were Grade (Gr) 1/2, independent of relationship; the most common were tremor (42%), nausea (42%), vomiting (37%), and fatigue (37%). Four Gr 3/4 AEs (anemia, delirium, mental status change, and confusional state) deemed possibly related to seviteronel occurred in four subjects. DLTs were observed at 750 mg (Gr 3 confusional state with paranoia) and 600 mg (Gr 3 mental status change and Gr 3 delirium) QD, with none at 450 mg QD. The recommended phase 2 dose (RP2D) was 450 mg QD, and at the RP2D, 4 of 7 subjects reached at least CBR16 (2 TNBC subjects and 2 ER+ subjects achieved CBR16 and CBR24, respectively); no objective tumor responses were reported.

CONCLUSIONS

Once-daily seviteronel was generally well tolerated in women with and 450 mg QD was chosen as the RP2D.

Enzalutamide for the Treatment of Androgen Receptor-Expressing Triple-Negative Breast Cancer

Purpose Studies suggest that a subset of patients with triple-negative breast cancer (TNBC) have tumors that express the androgen receptor (AR) and may benefit from an AR inhibitor. This phase II study evaluated the antitumor activity and safety of enzalutamide in patients with locally advanced or metastatic AR-positive TNBC. Patients and Methods Tumors were tested for AR with an immunohistochemistry assay optimized for breast cancer; nuclear AR staining > 0% was considered positive. Patients received enzalutamide 160 mg once per day until disease progression. The primary end point was clinical benefit rate (CBR) at 16 weeks. Secondary end points included CBR at 24 weeks, progression-free survival, and safety. End points were analyzed in all enrolled patients (the intent-to-treat [ITT] population) and in patients with one or more postbaseline assessment whose tumor expressed ≥ 10% nuclear AR (the evaluable subgroup). Results Of 118 patients enrolled, 78 were evaluable. CBR at 16 weeks was 25% (95% CI, 17% to 33%) in the ITT population and 33% (95% CI, 23% to 45%) in the evaluable subgroup. Median progression-free survival was 2.9 months (95% CI, 1.9 to 3.7 months) in the ITT population and 3.3 months (95% CI, 1.9 to 4.1 months) in the evaluable subgroup. Median overall survival was 12.7 months (95% CI, 8.5 months to not yet reached) in the ITT population and 17.6 months (95% CI, 11.6 months to not yet reached) in the evaluable subgroup. Fatigue was the only treatment-related grade 3 or higher adverse event with an incidence of > 2%. Conclusion Enzalutamide demonstrated clinical activity and was well tolerated in patients with advanced AR-positive TNBC. Adverse events related to enzalutamide were consistent with its known safety profile. This study supports additional development of enzalutamide in advanced TNBC.

OncoKB: A Precision Oncology Knowledge Base

PURPOSE

With prospective clinical sequencing of tumors emerging as a mainstay in cancer care, there is an urgent need for a clinical support tool that distills the clinical implications associated with specific mutation events into a standardized and easily interpretable format. To this end, we developed OncoKB, an expert-guided precision oncology knowledge base.

METHODS

OncoKB annotates the biological and oncogenic effect and the prognostic and predictive significance of somatic molecular alterations. Potential treatment implications are stratified by the level of evidence that a specific molecular alteration is predictive of drug response based on US Food and Drug Administration (FDA) labeling, National Comprehensive Cancer Network (NCCN) guidelines, disease-focused expert group recommendations and the scientific literature.

RESULTS

To date, over 3000 unique mutations, fusions, and copy number alterations in 418 cancer-associated genes have been annotated. To test the utility of OncoKB, we annotated all genomic events in 5983 primary tumor samples in 19 cancer types. Forty-one percent of samples harbored at least one potentially actionable alteration, of which 7.5% were predictive of clinical benefit from a standard treatment. OncoKB annotations are available through a public web resource (http://oncokb.org/) and are also incorporated into the cBioPortal for Cancer Genomics to facilitate the interpretation of genomic alterations by physicians and researchers.

CONCLUSION

OncoKB, a comprehensive and curated precision oncology knowledge base, offers oncologists detailed, evidence-based information about individual somatic mutations and structural alterations present in patient tumors with the goal of supporting optimal treatment decisions.

Phase (Ph) 2 stage 1 clinical activity of seviteronel, a selective CYP17-lyase and androgen receptor (AR) inhibitor, in women with advanced AR+ triple-negative breast cancer (TNBC) or estrogen receptor (ER)+ BC: CLARITY-01

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Background: Seviteronel (Sevi), an oral selective CYP17-lyase and AR inhibitor that blocks testosterone and estradiol production and competitively antagonizes the AR, is in Ph 2 clinical development for BC and prostate cancer. The primary objective of this ongoing Ph 2 study (NCT02580448) is to estimate the activity of once daily Sevi in women with AR+ TNBC and ER+ BC as measured by clinical benefit rate (CBR) at 16 and 24 weeks (wk), respectively. Methods: Patients (pts) with ER+/HER2-normal metastatic BC following progression of ≥1 prior line of endocrine therapy or TNBC were enrolled with no limit of prior therapies in either cohort. Evaluable pts had AR ≥10% via central IHC staining (TNBC only) and 1 post-baseline scan. Sevi was administered at 450 mg oral daily. Scans were performed every 8 wk. Circulating tumor cell (CTC) enumeration was performed by EPIC CTC analysis. A Simon’s 2-stage design was employed to determine activity (≥2 of 13 CBR16 in TNBC and ≥2 of 12 CBR24 in ER+ BC allow for accrual to Stage 2). Results: As of 4 Oct, 2016, 16 pts with AR+ TNBC (6 evaluable) and 14 pts with ER+ BC (11 evaluable) were enrolled. 67% had visceral metastases; 10% had stable brain metastases. 60% had ≥2 lines of prior therapy for advanced disease. 13 of 14 (93%) TNBC pts who underwent central AR testing had AR ≥10%. Four pts in the TNBC cohort and 8 pts in the ER+ cohort remain on therapy. CBR16 (TNBC) and CBR24 (ER+) was 2 of 6 (33%) and 2 of 11 (18%) allowing Stage 2 accrual in both cohorts. 7 of 10 evaluable pts with CTCs present at baseline had a CTC decline at C2D1, including all that met CBR (-94.3% [-27.5, -100] median [range]). The most common adverse events (≥ 25%) were fatigue (50%), nausea (43%) and decreased appetite (33%); all Grade 1/2. Updated CBR data will be presented at the time of presentation. Conclusions: Sevi Stage 1 activity is suggested by CBRs, along with associated CTC declines in heavily pre-treated pts with high disease burden. The observed safety profile is consistent with on-target pharmacology. Stage 2 enrollment is ongoing. Sevi may provide a novel treatment option for women with AR+ TNBC or ER+ BC. Clinical trial information: NCT02580448.

Overall survival (OS) in patients (Pts) with diagnostic positive (Dx+) breast cancer: Subgroup analysis from a phase 2 study of enzalutamide (ENZA), an androgen receptor (AR) inhibitor, in AR+ triple-negative breast cancer (TNBC) treated with 0-1 prior lines of therapy

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Background: The AR may be a novel therapeutic target for pts with AR-driven TNBC. ENZA, a potent AR inhibitor approved in men with metastatic prostate cancer, was evaluated in this phase 2 study of pts with AR+ TNBC. A genomic signature associated with AR-driven biology was identified; updated OS results in pts treated with 0-1 prior lines of therapy are presented. Methods: This is an open-label, Simon two-stage study (NCT01889238) of ENZA monotherapy in advanced AR+ TNBC (AR > 0% by IHC). Bone-only disease and unlimited prior regimens were allowed; CNS metastases or seizure history were exclusionary. The primary endpoint was clinical benefit rate at 16 weeks (CBR16) in evaluable pts (AR > 10% and ≥1 postbaseline assessment). OS was an exploratory endpoint. Results in intent-to-treat (ITT) and evaluable pts were presented previously (Traina TA et al. J Clin Oncol. 2015;33:1003). Results: 118 pts were enrolled (ITT). CBR16 in 78 evaluable pts was 33.3%. Of the 118 ITT pts, 56 were Dx+ and 62 were Dx–; ≥50% received 0-1 prior lines of therapy (28 Dx+, 37 Dx–). As of 26 Nov 2016 there were 83 deaths (median follow-up 28 mo); median OS (mOS) was 13 mo (95% CI; 8-18). In the Dx+ subgroup there were 32 deaths (mOS 20 mo [95% CI; 13-29]) vs 51 deaths in the Dx– subgroup (mOS 8 mo [95% CI; 5-11]). In pts with 0-1 prior lines of therapy, there were 13 deaths in the Dx+ subgroup (mOS 29 mo [95% CI; 19-not reached] vs 28 in the Dx– subgroup (mOS 10 mo [95% CI; 7-15]). The most common adverse events (AEs) were fatigue and nausea; fatigue was the only grade 3 related AE in > 5% of pts. A multi-covariate Cox analysis identified Dx status (+ vs –) and line of therapy (0-1 vs ≥2) as the only variables significantly associated with OS. Conclusions: In this study, the mOS of pts with Dx+ TNBC who received 0-1 prior lines of therapy appears longer than that of unselected historic controls. ENZA may represent a therapeutic option in pts with AR+ TNBC who would otherwise receive cytotoxic chemotherapy and is currently being evaluated in ENDEAR, a phase 3 study in pts with Dx+ advanced TNBC and 0-1 prior lines of therapy. Clinical trial information: NCT01889238.

Phase II study of gemcitabine (G), trastuzumab (H), and pertuzumab (P) for HER2-positive metastatic breast cancer (MBC) after prior pertuzumab-based therapy

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Background: The combination of taxanes with HP for first line treatment of HER2-positive MBC is associated with improved progression-free (PFS) and overall survival (OS). Treatment per physician’s choice with anti-HER2 therapy after second line therapy is associated with a median PFS of 3 months. While continued use of H in therapeutic combinations after progression on H-based therapy is standard, the efficacy of continuing HP-based treatment after progression on P-based therapy is unknown. Methods: This is a single arm phase II trial of G with HP. Eligible patients (pts) had HER2-positive (IHC 3+ or FISH > 2.0) MBC with prior HP-based treatment and ≤ 3 prior chemotherapies. Pts received G (1200 mg/m2) on days 1 and 8 of a q 3 week (w) cycle, and H (8 mg/kg load → 6 mg/kg) and P (840 mg load → 420 mg) q3w. The primary endpoint is PFS at 3 months. Secondary endpoints include OS, safety and tolerability. An exploratory endpoint is to compare PFS by RECIST criteria versus 18-F FDG-PET response criteria. The study therapy will be considered successful if at least 27/45 (60%) patients are progression free at 3 months. Results: As of 1-27-17, 41 of 45 pts are enrolled; 34 are evaluable at 3 months and 7 have not had 3-month evaluation. At 3 months, 26/34 (76%) are progression free (1 CR, 8 PR, 17 SD); 8 pts progressed. There are no cardiac or febrile neutropenic events to date. 4 pts required G dose reduction (3 grade 3 neutropenia and 1 grade 3 vomiting) and the study was amended to lower initial G dose to 1000 mg/m2. Conclusions: The preliminary 3 month-PFS is 76% in evaluable pts (95% CI 60% to 88%). The updated 3 month-PFS results will be presented. Continuation of P beyond progression is associated with apparent clinical benefit. A randomized trial is justified to confirm this clinically important observation. Clinical trial information: NCT02252887.