Current usage of pembrolizumab in triple negative breast cancer (TNBC)

INTRODUCTION

The use of immune checkpoint inhibitors (ICI) targeting the PD-1/PD-L1 pathway has changed the landscape in the treatment of triple negative breast cancer (TNBC). The ICI pembrolizumab in combination with chemotherapy now forms a standard of care for the treatment of advanced PD-L1 positive TNBC and as part of neoadjuvant therapy for high-risk early-stage disease. Evidence in this space is rapidly advancing.

AREAS COVERED

This review aims to highlight the evolving role of immunotherapy in TNBC management and to discuss current challenges. The studies in this review were searched from PubMed and ClinicalTrials.gov.

EXPERT OPINION

The KEYNOTE-522 trial demonstrated that the addition of peri-operative pembrolizumab to neoadjuvant chemotherapy improves patient outcomes in early-stage TNBC. However, critical questions remain including how to select which patients truly gain benefit from the addition of pembrolizumab; the optimal duration of therapy, and the optimal adjuvant therapy depending on pathologic response.

Addition of endocrine therapy to dual anti-HER2 targeted therapy in initial treatment of HER2+/HR+ metastatic breast cancer

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Background: The combination of dual anti-HER2 targeted therapy and chemotherapy is the current first line standard of care for HER2+ metastatic breast cancer. Endocrine therapy (ET) is the backbone of treatment in hormone receptor positive (HR+) disease, but the role of the addition of endocrine therapy following chemotherapy in HER2+/HR+ disease remains unclear as pivotal first line clinical trials excluded endocrine therapy use. Methods: Data from a multi-site community cohort of consecutive HER2+ metastatic breast cancer patients diagnosed between 1 January 2012 and 31 August 2019 was examined. Patients were treated at clinician discretion. The subset of patients eligible for this analysis were those that were HR+ and had received first line dual anti-HER2 targeted therapy. Results: Of 132 eligible patients included in the analysis, 78 (59.1%) received endocrine therapy and 54 (40.9%) did not. Median follow up was 25.9 months. There were no significant differences between the two groups based on age, performance status, previous therapy or de novo disease (Table), however, patients with bone metastases were more likely to receive ET in conjunction with first line dual anti-HER2 therapy (71% vs 52%, p= .043). The addition of ET was associated with improved progression free (HR 2.1, 95% CI 1.2-3.5, p = 0.007) and overall survival (HR 2.7, 95% CI 1.2-5.5, p = 0.007) in multivariate analysis. No increase in serious adverse events was noted although endocrine therapy related toxicities were not specifically collected. Conclusions: In this real-world series, the addition of ET to first line dual anti-HER2 therapy in HER2+/HR+ metastatic breast cancer was associated with improved progression free and overall survival. Further research is required to validate these findings and examine the role of CDK4/6 inhibitors in this disease, but may provide reassurance to clinicians considering ET in this clinical context. [Table: see text]

Spotlight on the utility of the Oncotype DX® breast cancer assay

The Oncotype DX^® assay was developed to address the need for optimizing the selection of adjuvant systemic therapy for patients with estrogen receptor (ER)-positive, lymph node-negative breast cancer. It has ushered in the era of genomic-based personalized cancer care for ER-positive primary breast cancer and is now widely utilized in various parts of the world. Together with several other genomic assays, Oncotype DX has been incorporated into clinical practice guidelines on biomarker use to guide treatment decisions. The Oncotype DX result is presented as the recurrence score which is a continuous score that predicts the risk of distant disease recurrence. The assay, which provides information on clinicopathological factors, has been validated for use in the prognostication and prediction of degree of adjuvant chemotherapy benefit in both lymph node-positive and lymph node-negative early breast cancers. Clinical studies have consistently shown that the Oncotype DX has a significant impact on decision making in adjuvant therapy recommendations and appears to be cost-effective in diverse health care settings. In this article, we provide an overview of the validation and clinical impact studies for the Oncotype DX assay. We also discuss its potential use in the neoadjuvant setting, as well as the more recent prospective validation trials, and the economic and utility implications of studies that use a lower cutoff score to define low-risk disease.

A real-world registry to evaluate HER2-directed therapy in Australian patients with metastatic breast cancer (MBC)

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Background: The management and outcomes of HER2 positive MBC have dramatically evolved with the introduction of HER2-targeted therapies. However, limited data regarding the uptake, impact and safety of these treatments in the real-world context, prompted us to initiate a comprehensive registry across multiple settings in Australia. Methods: We examined the multisite electronic registry TABITHA (Treatment of Advanced Breast Cancer in the HER2 positive Australian Patient) to capture clinical data of consecutive patients diagnosed with HER2 positive MBC between Jan 2016-Jan 2017. Patient demographics, use and outcomes of treatment were explored. Results: An initial cohort of 74 patients was identified, 28 (38%) with de novo metastatic and 46 (62%) with relapsed disease. The median age at presentation with MBC was 57 years (range 27-83), with main metastatic sites being bone (n = 41, 55%), major organs (n = 40, 54%), locoregional (N = 26, 35%) and central nervous system (n = 13, 18%). In total, 64 (86%) patients had received first-line HER2 therapy, including trastuzumab plus pertuzumab (n = 48, 75%), trastuzumab alone (n = 10, 16%) and trastuzumab-emtansine (n = 6, 9%). Ten patients had not received any HER2 therapy, of which 8 received best supportive care alone, 1 received endocrine therapy, and 1 received anti-resorptive therapy. The median age of non-HER2 treated patients was 61 (range 44-81) and 40% were ECOG 2+ compared to 25% of patients receiving HER2 therapy (p = NS). First-line HER2 therapy had been discontinued in 20/63 (32%) patients, due to progressive disease (n = 18, 90%) or toxicity (n = 2, 10%). Median time to progression was 12.7+ months (range 2.0-81.9+). Conclusions: Whilst trials of HER2 directed therapies have demonstrated a substantial impact on survival outcomes for MBC with modest toxicity, a proportion of HER2 positive patients in routine care may not receive these agents. Poor performance status contributes to non-HER2 therapy use, however data collection is ongoing and other potential drivers will be further examined. Where HER2 directed therapies are used, the preliminary data indicates good activity with the majority of patients still currently on treatment.

Abstract OT3-1-03: An open-label, multicentre, phase IIIb study with intravenous administration of pertuzumab, subcutaneous trastuzumab, and a taxane in patients with HER2-positive metastatic breast cancer (SAPPHIRE)

Background: The primary goals of treatment for patients (pts) with metastatic breast cancer (mBC) are maximising survival and preserving the quality of life. Intravenous (IV) trastuzumab has proven clinical benefits in pts with human epidermal growth factor receptor 2 (HER2)-positive mBC. Pertuzumab also targets HER2 through an independent epitope to that of trastuzumab. Addition of pertuzumab to the established combination of trastuzumab and docetaxel has shown improved efficacy with acceptable toxicity in mBC (Swain et al. Lancet Oncol 2013;14:461-71); they are considered standard of care. Subcutaneous (SC) and IV trastuzumab formulations have shown comparable efficacy but SC administration is preferred by pts for reducing duration of clinic visits (Pivot, et al. Lancet Oncol 2013;14: 962–970). The combination of IV pertuzumab and SC trastuzumab has not been studied. The aim is to assess safety, tolerability, and efficacy of combining IV pertuzumab with SC trastuzumab and a taxane, as first-line therapy in pts with HER2-positive mBC.

Trial Design: SAPPHIRE is an open-label, multicentre, Phase IIIb study. Pts will receive IV pertuzumab every 3 weeks with a loading dose of 840 mg and subsequent doses at 420 mg combined with SC trastuzumab at 600 mg/5 mL every 3 weeks and a taxane (docetaxel, paclitaxel, or nab-paclitaxel; regimen determined by the investigator). Treatment will continue until disease progression, unacceptable toxicity, or pts withdraw consent, whichever occurs first. The study is expected to run for 42 months.

Eligibility: Pts aged ≥18 years old with histologically or cytologically confirmed HER2-positive [immunohistochemistry (IHC) positive at 3+ or in situ hybridisation-positive (ISH+)] mBC with at least one measurable lesion and/or non-measurable disease according RECIST version 1.1 and ECOG performance status (PS) 0-2 are eligible.

Specific Aims: The primary objective is to assess the safety and tolerability of combining IV pertuzumab with SC trastuzumab and investigator’s choice taxane chemotherapy. The secondary objectives are to assess the efficacy of the first-line combination of pertuzumab, trastuzumab, and taxane chemotherapy and second-line treatments for mBC after disease progression.

Statistical Methods: Primary safety analyses will report incidence and severity of adverse events (AEs)/serious AEs, AEs leading to premature discontinuation of study treatment and evidence of cardiac dysfunction. Secondary safety analyses will include exposure and duration of study treatment, ECOG PS and laboratory data. Secondary efficacy analyses will report the overall response rate, progression-free survival, event-free survival and overall survival. Continuous data will be summarised using mean, median, range, standard deviation, and standard error. Discrete data will be summarised using frequency counts and percentages. Time-to-event analyses will be based on Kaplan-Meier methodology.

Accrual: The planned 50 pts will be recruited from 13 Australian Centres. The study started in December 2013 with 24 pts now enrolled. Clinicaltrials.gov#NCT02019277.

Citation Format: Natasha Woodward, Richard H De Boer, Andrew Redfern, Vita Von Neumann-Cosel, Ronelle M Heath, Jane Beith. An open-label, multicentre, phase IIIb study with intravenous administration of pertuzumab, subcutaneous trastuzumab, and a taxane in patients with HER2-positive metastatic breast cancer (SAPPHIRE) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr OT3-1-03.

Ph IB study of LEE011 and BYL719 in combination with letrozole in ER+, HER2- breast cancer

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Background: Activation of the PI3K/AKT/mTOR and cyclin D–CDK4/6–INK4–Rb pathways has been implicated in endocrine therapy resistance in pts with advanced HR+ breast cancer (BC). BYL719 (BYL), an α-isoform selective PI3K inhibitor and LEE011 (LEE), a CDK4/6 inhibitor have demonstrated clinical activity in pts with advanced HR+ BC and advanced solid tumors, respectively. In preclinical HR+ BC models, the combination of LEE, BYL, and letrozole (LET) had enhanced antitumor activity vs either agent alone. Here we report results from Arm (A)1 (LEE + LET) and A2 (BYL + LET) of the Ph Ib part of a Ph Ib/II, 3-arm study of LEE, BYL, and LET in pts with advanced ER+ BC (CLEE011X2107/NCT01872260). Methods: Postmenopausal women with advanced ER+, HER2− BC receive daily oral doses of LEE (3-wks on/1-wk off; A1) or BYL (continuous; A2), plus fixed, daily LET (2.5 mg, continuous), as part of a 28-day cycle. Primary objective: determine the MTD and/or RP2D of A1 and A2. Dose escalation is guided by a Bayesian Logistic Regression Model using the escalation with overdose control principle and real-time PK. Safety and preliminary efficacy are also assessed. Results: As of March 28, 2014, 10 pts have been treated with 600 mg LEE + LET (A1), and 7 pts with 300 mg BYL + LET (A2). One DLT was observed (A1: Grade [G]4 neutropenia; data cut-off: May 15). Common (all grade >30%) study drug-related AEs (all grade/G3–4) were: A1: neutropenia (90%/50%) and nausea (40%/0%); A2: hyperglycemia (57%/14%), decreased appetite, diarrhea, and nausea (43%/0% each). PK for LEE and BYL on Days 1 and 21, and LET on Day 1, are comparable to historic single-agent data. PK of LET at steady state is being evaluated. In A1, 6 pts had known responses: 1 PR, 2 SD, 1 NCRNPD, and 2 PD. In A2 5 pts had known responses: 2 SD, and 3 NCRNPD. Conclusions: LET plus LEE or BYL had an acceptable safety profile and preliminary signs of clinical activity have been observed. Upon determination of the MTD/RP2D in A1 and A2, enrollment into A3 (LEE + BYL + LET) will commence. The randomized Ph II part of the trial will compare LET + LEE or BYL with LET + LEE + BYL. MONALEESA-2 (CLEE011A2301/NCT01958021), a Ph III, randomized, double-blind, placebo-controlled study of LEE + LET in untreated advanced HR+ BC is currently recruiting pts. Clinical trial information: NCT01872260.

Hypocalcemia in patients with metastatic bone disease receiving denosumab

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Background: Patients (pts) with metastatic bone disease (MBD) are at risk of skeletal-related events (SREs). Potent antiresorptives reduce the risk of SREs, by inhibiting cancer-induced bone destruction, which also reduces release of skeletal calcium (Ca) into the bloodstream. Hypocalcemia (hypoCa) may occur if Ca and vit D intake is inadequate while taking antiresorptive agents. A combined analysis of 3 phase III trials in pts with MBD showed denosumab (DMAb) was superior to zoledronic acid (ZA) in preventing SREs. The overall safety profiles were similar; hypoCa was more common with DMAb (9.6%) than ZA (5.0%). Characteristics of hypoCa events in DMAb pts in these clinical trials and from post marketing adverse event (AE) reports are presented. Methods: Pts with solid tumors or multiple myeloma and MBD were randomized (1:1) to DMAb 120 mg SC or ZA 4 mg IV (adjusted for renal function) every 4 weeks (Q4W). Pts were advised to take daily Ca (≥ 500 mg) and vit D (≥ 400 IU); intake was collected by pt report. Albumin-corrected serum Ca was measured Q4W by central lab. HypoCa events were collected as decreases in serum Ca per central lab and investigator-reported AEs. Post marketing data from spontaneous reports of hypoCa to the sponsor's global safety department (AGS) were reviewed. Results: In the 3 trials, 2841 pts received DMAb and 2836 pts received ZA. The median Ca levels for both treatment groups were similar over time. Among DMAb pts, hypoCa was most common within 6 months of starting treatment and was more common in pts who did not report use of Ca and vit D vs those who did (15.8% vs 8.7%). Grade 3 or 4 (< 7 mg/dL; < 1.75 mmol/L) decreases in serum Ca were reported in 3.1% of DMAb pts and 1.3% of ZA pts. No fatal cases of hypoCa were reported in the trials. From May to Nov 2012, 37 cases of severe symptomatic hypoCa (seizures, tetany, prolonged QTc, altered mental state) were reported to AGS; fatal outcomes were reported for 3 other pts with advanced cancers and various comorbidities. Conclusions: HypoCa is a known risk with antiresorptive therapy, including DMAb 120 mg. HypoCa occurred less often in pts who reported taking Ca and vit D. HypoCa should be corrected prior to starting DMAb and Ca monitored during treatment. Pts should take adequate Ca and vit D while receiving DMAb. Clinical trial information: NCT00321464, NCT00321620, and NCT00330759.

Retrospective evaluation of RET biomarker status and outcome to vandetanib in four phase III randomized NSCLC trials

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Background: The prevalence of the tumorigenic KIF5B:RET fusion gene in NSCLC tumors has been estimated at 0.2–6% (Jiu et al 2012; Lipson et al 2012). We retrospectively analyzed tumor samples from 4 Phase III NSCLC trials of vandetanib, a TKI that selectively targets RET, VEGFR and EGFR signaling, to determine the prevalence of RET fusions and other RET biomarkers, and any potential association with outcome to vandetanib (V). Methods: The studies evaluated were ZODIAC (NCT00312377; docetaxel ± V 100mg), ZEAL (NCT00418886; pemetrexed ± V 100mg), ZEPHYR (NCT00404924; V 300mg vs placebo) and ZEST (NCT00364351; V 300mg vs erlotinib). RET biomarkers evaluated included RET fusions (including KIF5B:RET) and RET gene copy number (assessed by a 4-probe FISH assay), as well as RET protein expression (by IHC). Results: Of 4089 patients randomized across the 4 studies, 1291 and 1234 had tumor samples available for FISH and IHC analysis, respectively, with evaluable data obtained for 944 and 1102. RET fusions (in >10% of tumor cells) were detected in 7 of 944 samples (vandetanib, n=3; comparator, n=4), at a prevalence of 0.7% (95% CI, 0.3–1.5%). None of the 3 vandetanib-treated RET fusion-positive patients had an objective RECIST response, although there was radiologic evidence of tumor shrinkage in 2. Overall, 2.8% (n=26) of samples had RET amplification (innumerable RET clusters, or ≥7 copies in >10% tumor cells), 8.1% (n=76) had lower RET gene copy number gain (4–6 copies in ≥40% tumor cells) and 8.3% (n=92) were RET expression positive (signal intensity ++ or +++ in >10% of tumor cells). There was no difference in ORR between vandetanib and comparator for the RET amplification-positive subset (both 8.3% [1/12]), the RET copy number gain subset (9.8% [4/41] vs 9.1% [3/33], respectively) or the RET protein expression-positive subset (15.2% [7/46] and 13.6% [6/44], respectively). Conclusions: The prevalence of RET fusions was estimated at 0.7%. There were too few vandetanib-treated patients with RET fusions to make any firm conclusion regarding association with efficacy. Evidence from the other RET biomarkers tested suggested that these do not infer a differential advantage in patients treated with vandetanib. Clinical trial information: NCT00312377; NCT00418886; NCT00404924.

Incidence of osteonecrosis of the jaw in patients receiving denosumab or zoledronic acid for bone metastases from solid tumors or multiple myeloma: Results from three phase III trials

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Background: In patients with metastatic bone disease (MBD), the use of antiresorptive therapies such as denosumab or zoledronic acid (ZA) reduces the risk of skeletal-related events but is associated with a small risk of osteonecrosis of the jaw (ONJ). Two phase 3 clinical trials of denosumab vs ZA in patients with MBD showed overall cumulative ONJ incidences to be 3.8% to 4.7% at approximately 5 years of treatment with denosumab across blinded and open-label extension phases. ONJ associated with ZA was only assessed in the blinded treatment phases, as patients switched to denosumab once superior efficacy was demonstrated. Here we report incidence rates of ONJ by first vs subsequent years of exposure for the blinded treatment phase of all three phase III clinical trials. Methods: Patients (n = 5,677) with bone metastases from solid tumors or multiple myeloma received either SC denosumab 120 mg and IV placebo or IV ZA 4 mg (adjusted for renal function) and SC placebo Q4W in the double-blinded treatment phase of each trial. Patients who received ≥ 1 active dose during the blinded treatment phase were included in this analysis for up to 44.5 months of denosumab exposure and 41.3 months of ZA exposure. Oral assessments were conducted at baseline and every 6 months thereafter by the investigator or other qualified examiner. Potential ONJ events were independently adjudicated by a blinded committee of experts. Results: The median (Q1, Q3) time to onset of ONJ was similar in both treatment groups (15.6 [9.5, 20.0] months for denosumab, 15.8 [11.0, 23.6] months for ZA). Cumulative incidence rates of ONJ during the blinded treatment phases for all three trials by patient-years of follow-up are shown below (Table). Conclusions: The incidence of ONJ increased with longer duration of antiresorptive exposure. There were no significant differences between treatment groups in ONJ incidence at year 1 or beyond. Clinical trial information: NCT00321464; NCT00330759; NCT00321620. [Table: see text]

BOLERO-6: Phase II study of everolimus plus exemestane versus everolimus or capecitabine monotherapy in HR+, HER2- advanced breast cancer

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Background: Everolimus (EVE), an orally bioavailable inhibitor of the mammalian target of rapamycin (mTOR), has shown clinical activity as monotherapy and in combination with endocrine therapy (ET) in hormone-receptor–positive (HR+; estrogen and/or progesterone receptors) advanced breast cancer (ABC). In a pivotal phase 3 trial in patients with HR+ ABC progressing on ET, EVE + exemestane (EXE) significantly prolonged median progression-free survival (PFS) vs EXE alone per local (7.8 vs 3.2 months; log-rank P<.0001) or central (11.0 months for EVE+EXE vs 4.1 months for EXE alone; log-rank P<.0001) assessment. Capecitabine, an orally administered fluoropyrimidine carbamate indicated as monotherapy in paclitaxel and/or anthracycline-refractory ABC, has shown clinical benefit in patients with HR+, human epidermal growth factor receptor 2-negative (HER2-) ABC. The BOLERO-6 study in patients with HR+, HER2- ABC progressing on prior anastrozole or letrozole will compare PFS following EVE+EXE combination therapy vs EVE or capecitabine monotherapy. Methods: In this multicenter, open-label, randomized, 3-arm, phase 2 study, 300 patients will be randomized to receive either EVE (10 mg/d) + EXE (25 mg/d) combination therapy, or EVE (10 mg/d) alone, or capecitabine (1,250 mg/m2twice daily for 14 d/3-wk cycle) alone, until disease progression. Patients will be stratified based on the presence of visceral disease. Key eligibility criteria include age ≥18 years, postmenopausal status; histologic or cytologic confirmation of estrogen-receptor–positive, HER2- ABC; radiologic or objective evidence of recurrence or progression on prior aromatase inhibitors; Eastern Cooperative Oncology Group (ECOG) performance status ≤2. The primary endpoint is PFS with EVE+EXE vs EVE, based on local radiologic assessment (Response Evaluation Criteria in Solid Tumors [RECIST] 1.1). The key secondary endpoint is PFS with EVE+EXE vs capecitabine. Other secondary endpoints include overall survival, objective response rate, clinical benefit rate, safety, quality of life, and patient satisfaction with treatment. Enrollment will start in Q1 2013. Estimated study completion in Q1 2015. Clinical trial information: NCT01783444.

Profile of cabozantinib and its potential in the treatment of advanced medullary thyroid cancer

Medullary thyroid cancer is an uncommon malignancy for which until recently little effective treatment existed. It is often characterized by mutation and overexpression of the receptor tyrosine kinases RET (rearranged during transfection), VEGFR2 (vascular endothelial growth factor receptor 2) and MET (mesenchymal-epithelial transition factor), which make attractive targets for drug development. Cabozantinib is an orally bioavailable tyrosine kinase inhibitor which blocks MET, VEGRF2 and RET, and has shown considerable activity in medullary thyroid cancer in a Phase III trial, including in heavily pretreated patients. Its novel combination of vascular endothelial growth factor and MET inhibition is believed to address the MET escape pathway, which is thought to be the cause of nonsustained tumor responses resulting from inhibition of vascular endothelial growth factor alone.

Phase 1b dose-finding study of motesanib with docetaxel or paclitaxel in patients with metastatic breast cancer

The purpose of this study was to investigate the safety, tolerability, and pharmacokinetics of motesanib when combined with docetaxel or paclitaxel in patients with metastatic breast cancer. In this open-label, dose-finding, phase 1b study, patients received motesanib 50 or 125-mg orally once daily (QD), beginning day 3 of cycle 1 of chemotherapy, continuously in combination with either paclitaxel 90 mg/m² on days 1, 8, and 15 every 28-day cycle (Arm A) or docetaxel 100 mg/m² on day 1 every 21-day cycle (Arm B). Dose escalation to motesanib 125 mg QD occurred if the incidence of dose-limiting toxicities (DLTs, primary endpoint) was ≤33 %. If the maximum tolerated dose (MTD) of motesanib was established in Arm B, additional patients could receive motesanib at the MTD plus docetaxel 75 mg/m². Forty-six patients were enrolled and 45 received ≥1 dose of motesanib. The incidence of DLTs was <33 % in all cohorts; thus, motesanib 125 mg QD was established as the MTD. Seven patients (16 %) had grade 3 motesanib-related adverse events including cholecystitis (2 patients) and hypertension (2 patients). Pharmacokinetic parameters of motesanib were similar to those reported in previous studies. The objective response rate was 56 % among patients with measurable disease at baseline who received motesanib in combination with taxane-based chemotherapy. The addition of motesanib to either paclitaxel or docetaxel was generally tolerable up to the 125-mg QD dose of motesanib. The objective response rate of 56 % suggests a potential benefit of motesanib in combination with taxane-based chemotherapy.