TROPiCS-02: A Phase III study investigating sacituzumab govitecan in the treatment of HR+/HER2- metastatic breast cancer.

Patients with HR+/HER2- metastatic breast cancer (MBC) whose cancers have progressed despite conventional therapies represent an unmet clinical need. Trop-2, a transmembrane calcium signal transducer, is highly expressed in MBC and plays a role in tumor growth and progression. Sacituzumab govitecan (SG) is a novel antibody-drug conjugate comprising an Trop-2 antibody coupled to SN-38, the active metabolite of irinotecan, via a unique hydrolyzable linker. SG has demonstrated promising activity in a Phase I/II IMMU-132-01 basket study in heavily pretreated solid tumors, including HR+/HER2- MBC. We describe the registrational Phase III TROPiCS-02 study (NCT03901339), evaluating SG versus treatment of physician's choice in HR+/HER2- MBC. Trial registration number: NCT03901339.

A phase I/II study of epertinib plus trastuzumab with or without chemotherapy in patients with HER2-positive metastatic breast cancer.

BACKGROUND: Epertinib (S-222611) is a potent reversible inhibitor of HER2, EGFR and HER4. This trial evaluated the safety, tolerability, pharmacokinetics and antitumour activity of daily oral epertinib combined with trastuzumab (arm A), with trastuzumab plus vinorelbine (arm B) or with trastuzumab plus capecitabine (arm C), in patients with HER2-positive metastatic breast cancer (MBC). METHODS: Eligible patients, with or without brain metastases, had received prior HER2-directed therapy. A dose-escalation phase determined the tolerability of each combination and established a dose for further study. Further, patients were recruited to expansion cohorts in each of the 3 arms to further explore efficacy and safety. RESULTS: The recommended doses of epertinib were 600 mg, 200 mg and 400 mg in arms A, B and C, respectively. The most frequent grade 3/4 adverse event (AE) was diarrhoea in all arms, which was manageable with medical intervention and dose modification. The objective response rate (complete response [CR] plus partial response [PR]) in heavily pre-treated HER2-positive MBC patients at the recommended doses of epertinib combined with trastuzumab was 67% (N = 9), with trastuzumab plus vinorelbine was 0% (N = 5) and with trastuzumab plus capecitabine was 56% (N = 9). Notably, 4 of 6 patients previously treated with T-DM1 responded in the arm A expansion cohort (epertinib plus trastuzumab). In the arm C expansion cohort (epertinib plus trastuzumab plus capecitabine), 4 of 7 patients responded despite previous exposure to capecitabine. Measurable regression of brain metastases was observed in patients with CNS target lesions treated in both arms A and C. CONCLUSION: We observed safety, tolerability and encouraging antitumour activity of epertinib combined with trastuzumab, or with trastuzumab plus capecitabine. This supports further evaluation of these combinations in patients with pre-treated HER2-positive MBC, with or without brain metastases. TRIAL REGISTRATION: EudraCT Number: 2013-003894-87; registered 09-September-2013.

Pertuzumab in HER2-positive early breast cancer: current use and perspectives.

Although the prognosis of HER2-positive breast cancer patients has dramatically improved with modern chemotherapy and the monoclonal antibody trastuzumab, up to 31% of them will experience a recurrence in the long term. After the unprecedented benefit in overall survival with the addition of the second monoclonal antibody pertuzumab for patients with metastatic disease, the drug was tested with various degrees of success in the preoperative and postoperative settings. In this review, we will focus on the pharmacologic aspects of the drug, including mechanism of action and toxicities, and discuss clinical data regarding its use in advanced and early stage HER2-positive breast cancer, placing in perspective the pros and cons regarding other available drugs and biomarkers.

Neoadjuvant chemotherapy with or without anthracyclines in the presence of dual HER2 blockade for HER2-positive breast cancer (TRAIN-2): a multicentre, open-label, randomised, phase 3 trial.

BACKGROUND: The optimal chemotherapy backbone for dual HER2 blockade in the neoadjuvant setting for early breast cancer is unknown. We investigated whether the addition of anthracyclines would improve pathological complete response compared with a carboplatin-taxane regimen, when given in combination with the HER2-targeted agents trastuzumab and pertuzumab. METHODS: The TRAIN-2 study is an open-label, randomised, controlled, phase 3 trial being done in 37 hospitals in the Netherlands. We recruited patients aged 18 years or older with previously untreated, histologically confirmed stage II-III HER2-positive breast cancer. Patients were randomly allocated using central randomisation software (1:1 ratio) with minimisation without a random component, stratified by tumour stage, nodal stage, oestrogen receptor status, and age, to receive 5-fluorouracil (500 mg/m2), epirubicin (90 mg/m2), and cyclophosphamide (500 mg/m2) every 3 weeks for three cycles followed by paclitaxel (80 mg/m2 on days 1 and 8) and carboplatin (area under the concentration-time curve [AUC] 6 mg/mL per min on day 1 or optionally, as per hospital preference, AUC 3 mg/mL per min on days 1 and 8) every 3 weeks for six cycles, or to receive nine cycles of paclitaxel and carboplatin at the same dose and schedule as in the anthracycline group. Patients in both study groups received trastuzumab (6 mg/kg, loading dose 8 mg/kg) and pertuzumab (420 mg, loading dose 840 mg) concurrently with all chemotherapy cycles. The primary endpoint was the proportion of patients who achieved a pathological complete response in breast and axilla (ypT0/is ypN0) in the intention-to-treat population. Safety was analysed in patients who received at least one treatment cycle according to actual treatment received. This trial is registered with ClinicalTrials.gov, number NCT01996267, and follow-up for long-term outcome is ongoing. FINDINGS: Between Dec 9, 2013, and Jan 14, 2016, 438 patients were enrolled and randomly assigned to the two treatment groups (219 patients to each group), of whom 418 were evaluable for the primary endpoint (212 in the anthracycline group and 206 in the non-anthracycline group). The median follow-up for all patients was 19 months (IQR 16-23 months). A pathological complete response was recorded in 141 (67%, 95% CI 60-73) of 212 patients in the anthracycline group and in 140 (68%, 61-74) of 206 in the non-anthracycline group (p=0·95). One patient randomly allocated to the non-anthracycline group did receive anthracyclines and was thus included in the anthracycline group for safety analyses; therefore, for the safety analyses there were 220 patients in the anthracycline group and 218 in the non-anthracycline group. Serious adverse events were reported in 61 (28%) of 220 patients in the anthracycline group and in 49 (22%) of 218 in the non-anthracycline group. The most common adverse events of any cause were grade 3 or worse neutropenia (in 131 [60%] of 220 patients in the anthracycline group vs 118 [54%] of 218 in the non-anthracycline group), grade 3 or worse diarrhoea (26 [12%] vs 37 [18%]), and grade 2 or worse peripheral neuropathy (66 [30%] vs 68 [31%]), with no substantial differences between the groups. Grade 3 or worse febrile neutropenia was more common in the anthracycline group than in the non-anthracycline group (23 [10%] vs three [1%], p<0·0001). Symptomatic left ventricular systolic dysfunction was rare in both groups (two [1%] of 220 vs 0 of 218). One patient in the anthracycline group died because of a pulmonary embolism, which was possibly treatment related. INTERPRETATION: In view of the high proportion of pathological complete responses recorded in both groups and the fact that febrile neutropenia was more frequent in the anthracycline group, omitting anthracyclines from neoadjuvant treatment regimens might be a preferred approach in the presence of dual HER2 blockade in patients with early HER2-positive breast cancer. Long-term follow-up is required to confirm these results. FUNDING: Roche Netherlands.

Management of Metastatic HER2-Positive Breast Cancer: Where Are We and Where Do We Go From Here?

Human epidermal growth factor receptor 2 (HER2)/neu-positive breast cancer has changed from being an aggressive disease with a poor prognosis to a disease that is highly treatable, with prolonged survival possible even in patients with metastatic disease. A better understanding of HER2 biology has led to the development of powerful targeted therapies, and four drugs are already approved by the US Food and Drug Administration for treatment in the metastatic setting (trastuzumab, pertuzumab, lapatinib, and trastuzumab emtansine). Optimizing how these drugs are delivered and in what sequence is an important part of modern management of HER2-positive breast cancer. However, while the prognosis has improved, metastatic disease is still not curable; newer, better drugs are needed. This review will summarize the current standard of care; key issues that arise when treating patients with HER2-positive disease; and developments in novel therapeutics, including small-molecule inhibitors, nanoparticles, immunotherapy, and agents targeting resistance pathways.

The immune system and response to HER2-targeted treatment in breast cancer.

The monoclonal antibody trastuzumab targets the growth factor receptor HER2 and has profoundly improved the course of disease and survival of women with HER2-overexpressing breast cancer. Because trastuzumab targets aberrant expression of HER2 in tumours addicted to HER2 activation, its clinical activity is credited largely to inhibition of intracellular signalling. A growing body of preclinical and clinical evidence shows that the immune system contributes substantially to the therapeutic effects of trastuzumab and other monoclonal antibodies in vivo. Furthermore, findings indicate that immune-related markers can provide useful predictive information and that increased clinical activity might follow activation of the immune system. Development of immunomodulatory drugs with remarkable activity in many solid tumours defines a scenario in which the combination of immune modulation with trastuzumab, or other HER2-directed drugs, will result in augmented response and clinical outcome.

When and how do I use neoadjuvant chemotherapy for breast cancer?

OPINION STATEMENT: Systemic neoadjuvant chemotherapy is utilized along with surgery and radiotherapy for the management of patients with locally advanced breast cancer. The backbone of current chemotherapy regimens include anthracyclines and taxanes given either sequentially or concurrently for up to 8 cycles. Neoadjuvant treatment benefits include in vivo assessment of response to treatment with reduction in the extent of primary and regional metastases. Neoadjuvant chemotherapy for operable breast cancer is used in women who desire breast conservation surgery who are not candidates for such treatment at the time of the diagnosis. The use of neoadjuvant treatment in patients, who present with operable breast cancer, shows equivalent survival outcome compared with adjuvant breast cancer treatment. Several prospective studies have evaluated the role of trastuzumab in combination with neoadjuvant chemotherapy in patients with Her2-positive disease. The addition of trastuzumab to neoadjuvant chemotherapy is associated with improvement of the complete clinical and pathological complete response to therapy and significantly improved event-free survival and overall survival. Dual Her2 blockade is emerging as a new approach to improve pathological complete response rates and therefore survival. To date, in triple-negative breast cancer, there are no predictive markers to identify potential treatment targets. Triple-negative patients who achieve a pathological complete response have more favorable outcome compared with those with residual disease following neoadjuvant treatment. The choice of optimal chemotherapy regimen and the duration of treatment have been studied extensively in the neoadjuvant setting. No consensus has been developed thus far. Following work done with anthracycline and CMF treatments in neoadjuvant chemotherapy, recent studies in locally advanced breast cancer focus on the addition of new and target agents. All of these trials are based on well-established regimes used in the adjuvant setting. Successful use of neoadjuvant chemotherapy requires a coordinated multidisciplinary approach.

Advances and future directions in the targeting of HER2-positive breast cancer: implications for the future.

OPINION STATEMENT: The natural history of HER2-positive breast cancer significantly changed in the past 15 years. Form being the most aggressive type of breast cancer, it became treatable with important cure rates. However, with new and successful drugs, resistance emerges. Progress in research and drug development continues to make available effective anti-HER2 therapies. Our challenge today is to use these tools correctly by looking at the data that support the indications of each compound and to continue clinical trial participation.

Lapatinib with trastuzumab for HER2-positive early breast cancer (NeoALTTO): a randomised, open-label, multicentre, phase 3 trial.

BACKGROUND: The anti-HER2 monoclonal antibody trastuzumab and the tyrosine kinase inhibitor lapatinib have complementary mechanisms of action and synergistic antitumour activity in models of HER2-overexpressing breast cancer. We argue that the two anti-HER2 agents given together would be better than single-agent therapy. METHODS: In this parallel groups, randomised, open-label, phase 3 study undertaken between Jan 5, 2008, and May 27, 2010, women from 23 countries with HER2-positive primary breast cancer with tumours greater than 2 cm in diameter were randomly assigned to oral lapatinib (1500 mg), intravenous trastuzumab (loading dose 4 mg/kg [DOSAGE ERROR CORRECTED], subsequent doses 2 mg/kg), or lapatinib (1000 mg) plus trastuzumab. Treatment allocation was by stratified, permuted blocks randomisation, with four stratification factors. Anti-HER2 therapy alone was given for the first 6 weeks; weekly paclitaxel (80 mg/m(2)) was then added to the regimen for a further 12 weeks, before definitive surgery was undertaken. After surgery, patients received adjuvant chemotherapy followed by the same targeted therapy as in the neoadjuvant phase to 52 weeks. The primary endpoint was the rate of pathological complete response (pCR), analysed by intention to treat. This trial is registered with ClinicalTrials.gov, NCT00553358. FINDINGS: 154 patients received lapatinib, 149 trastuzumab, and 152 the combination. pCR rate was significantly higher in the group given lapatinib and trastuzumab (78 of 152 patients [51·3%; 95% CI 43·1-59·5]) than in the group given trastuzumab alone (44 of 149 patients [29·5%; 22·4-37·5]; difference 21·1%, 9·1-34·2, p=0·0001). We recorded no significant difference in pCR between the lapatinib (38 of 154 patients [24·7%, 18·1-32·3]) and the trastuzumab (difference -4·8%, -17·6 to 8·2, p=0·34) groups. No major cardiac dysfunctions occurred. Frequency of grade 3 diarrhoea was higher with lapatinib (36 patients [23·4%]) and lapatinib plus trastuzumab (32 [21·1%]) than with trastuzumab (three [2·0%]). Similarly, grade 3 liver-enzyme alterations were more frequent with lapatinib (27 [17·5%]) and lapatinib plus trastuzumab (15 [9·9%]) than with trastuzumab (11 [7·4%]). INTERPRETATION: Dual inhibition of HER2 might be a valid approach to treatment of HER2-positive breast cancer in the neoadjuvant setting. FUNDING: GlaxoSmithKline.

How do I treat inflammatory breast cancer?

Inflammatory breast cancer (IBC) is an uncommon and aggressive presentation of locally advanced breast cancer that is potentially curable when localized but may be associated with distant metastasis in up to one-third of patients at presentation. The diagnosis of IBC is made based on clinical features, including the presence of skin edema and erythema involving at least one-third of the breast, with or without a mass, and usually associated with dermal lymphatic invasion (DLI) on skin biopsy. Management requires combined modality therapy, including neoadjuvant chemotherapy with an anthracycline and taxane-based regimen, followed by surgery and radiotherapy, plus concurrent anti-HER2 therapy for HER2-positive disease, and endocrine therapy for at least 5 years after surgery for estrogen-receptor-positive disease (Fig. 1). There have been few large clinical trials focused on IBC; therefore, most data regarding treatment are derived from retrospective analyses, small studies, and extrapolation of results from trials of noninflammatory locally advanced breast cancer. Patients with IBC should be encouraged to enroll in clinical trials whenever possible. In addition, further research into the biology of IBC may help to elucidate the mechanisms underlying its aggressive clinical behavior and to assist in the development of therapies targeted for this specific population.

Efficacy and safety of neoadjuvant pertuzumab and trastuzumab in women with locally advanced, inflammatory, or early HER2-positive breast cancer (NeoSphere): a randomised multicentre, open-label, phase 2 trial.

BACKGROUND: Studies with pertuzumab, a novel anti-HER2 antibody, show improved efficacy when combined with the established HER2-directed antibody trastuzumab in breast cancer therapy. We investigated the combination of pertuzumab or trastuzumab, or both, with docetaxel and the combination of pertuzumab and trastuzumab without chemotherapy in the neoadjuvant setting. METHODS: In this multicentre, open-label, phase 2 study, treatment-naive women with HER2-positive breast cancer were randomly assigned (1:1:1:1) centrally and stratified by operable, locally advanced, and inflammatory breast cancer, and by hormone receptor expression to receive four neoadjuvant cycles of: trastuzumab (8 mg/kg loading dose, followed by 6 mg/kg every 3 weeks) plus docetaxel (75 mg/m(2), escalating, if tolerated, to 100 mg/m(2) every 3 weeks; group A) or pertuzumab (loading dose 840 mg, followed by 420 mg every 3 weeks) and trastuzumab plus docetaxel (group B) or pertuzumab and trastuzumab (group C) or pertuzumab plus docetaxel (group D). The primary endpoint, examined in the intention-to-treat population, was pathological complete response in the breast. Neither patients nor investigators were masked to treatment. This study is registered with ClinicalTrials.gov, number NCT00545688. FINDINGS: Of 417 eligible patients, 107 were randomly assigned to group A, 107 to group B, 107 to group C, and 96 to group D. Patients given pertuzumab and trastuzumab plus docetaxel (group B) had a significantly improved pathological complete response rate (49 of 107 patients; 45·8% [95% CI 36·1-55·7]) compared with those given trastuzumab plus docetaxel (group A; 31 of 107; 29·0% [20·6-38·5]; p=0·0141). 23 of 96 (24·0% [15·8-33·7]) women given pertuzumab plus docetaxel (group D) had a pathological complete response, as did 18 of 107 (16·8% [10·3-25·3]) given pertuzumab and trastuzumab (group C). The most common adverse events of grade 3 or higher were neutropenia (61 of 107 women in group A, 48 of 107 in group B, one of 108 in group C, and 52 of 94 in group D), febrile neutropenia (eight, nine, none, and seven, respectively), and leucopenia (13, five, none, and seven, respectively). The number of serious adverse events was similar in groups A, B, and D (15-20 serious adverse events per group in 10-17% of patients) but lower in group C (four serious adverse events in 4% of patients). INTERPRETATION: Patients given pertuzumab and trastuzumab plus docetaxel (group B) had a significantly improved pathological complete response rate compared with those given trastuzumab plus docetaxel, without substantial differences in tolerability. Pertuzumab and trastuzumab without chemotherapy eradicated tumours in a proportion of women and showed a favourable safety profile. These findings justify further exploration in adjuvant trials and support the neoadjuvant approach for accelerating drug assessment in early breast cancer. FUNDING: F Hoffmann-La Roche.

Lapatinib, trastuzumab or the combination added to preoperative chemotherapy for breast cancer: a meta-analysis of randomized evidence.

We compared the efficacy and safety of the addition of lapatinib versus trastuzumab or their combination to neoadjuvant chemotherapy in HER2-positive breast cancer. Potentially eligible trials were located through PubMed and Cochrane Library searches and abstracts of major international conferences. The endpoints that we assessed were pathologic complete response (pCR) rate, and toxicity. Pooled risk ratios (RR) were estimated for each endpoint with fixed or random effects models, depending on between studies heterogeneity. Six trials were identified with 1,494 eligible patients. The probability to achieve pCR was higher for the trastuzumab plus chemotherapy arm versus lapatinib plus chemotherapy (RR 1.25, 95 % confidence interval [CI] 1.08-1.43; p = 0.003) (6 trials; 1,494 patients). Probability to pCR was significantly higher in the group receiving lapatinib and trastuzumab than in the group with trastuzumab alone (RR 1.39, 95 % CI 1.20-1.63; p < 0.001) (4 trials; 779 patients). Grade III-IV diarrhea and dermatologic toxicities were statistically more frequent in patients receiving lapatinib. No differences were observed regarding cardiac adverse events among patients receiving trastuzumab, lapatinib, or their combination. These data supports the superiority of a dual-HER2 inhibition for the treatment of HER2-positive breast cancer in the neoadjuvant setting. The direct comparison of trastuzumab and lapatinib showed that lapatinib is inferior in terms of pCR and associated with a higher risk for toxicity.

A phase II study of afatinib (BIBW 2992), an irreversible ErbB family blocker, in patients with HER2-positive metastatic breast cancer progressing after trastuzumab.

Afatinib is an oral, ErbB family blocker, which covalently binds and irreversibly blocks all kinase-competent ErbB family members. This phase II, open-label, single-arm study explored afatinib activity in human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients progressing after trastuzumab treatment. Patients had stage IIIB/IV HER2-positive metastatic breast cancer, with progression following trastuzumab or trastuzumab intolerance and an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. Patients received 50 mg afatinib once-daily until disease progression. Primary endpoint was objective response rate (Response Evaluation Criteria in Solid Tumors 1.0), with tumor assessments every 8 weeks. Forty-one patients were treated. Patients had received a median of three prior chemotherapy lines (range, 0-15) and 68.3% had received trastuzumab for >1 year. Four patients (10% of 41 treated; 11% of evaluable patients) had partial response. Fifteen patients (37% of 41) had stable disease as best response and 19 (46% of 41) achieved clinical benefit. Median progression-free survival was 15.1 weeks (95% confidence interval [CI]: 8.1-16.7); median overall survival was 61.0 weeks (95% CI: 56.7-not evaluable). Most frequent common terminology criteria for adverse events grade 3 treatment-related adverse events were diarrhea (24.4%) and rash (9.8%). Afatinib monotherapy was associated with promising clinical activity in extensively pretreated HER2-positive breast cancer patients who had progressed following trastuzumab treatment.

A phase I/II prospective, single arm trial of gefitinib, trastuzumab, and docetaxel in patients with stage IV HER-2 positive metastatic breast cancer.

Inhibition of the HER-2 pathway via the monoclonal antibody trastuzumab has had a major impact in treatment of HER-2 positive breast cancer, but de novo or acquired resistance may reduce its effectiveness. The known interplay between the epidermal growth factor receptor (EGFR) and HER-2 receptors and pathways creates a rationale for combined anti-EGFR and anti-HER-2 therapy in HER-2 positive metastatic breast cancer (MBC), and toxicities associated with the use of multiple chemotherapeutic agents together with biological therapies may also be reduced. We conducted a prospective, single arm, phase I/II trial to determine the efficacy and toxicity of the combination of trastuzumab with the EGFR inhibitor gefitinib and docetaxel, in patients with HER-2 positive MBC. The maximum tolerated dose (MTD) was determined in the phase I portion. The primary end point of the phase II portion was progression-free survival (PFS). Immunohistochemical analysis of biomarker expression of the PKA-related proteins cAMP response element-binding protein (CREB), phospho-CREB and DARPP-32 (dopamine and cAMP-regulated phosphoprotein of 32 kDa) plus t-DARPP (the truncated isoform of DARPP-32); PTEN; p-p70 S6K; and EGFR was conducted on tissue from metastatic sites. Nine patients were treated in the phase I portion of the study and 22 in the phase II portion. The MTD was gefitinib 250 mg on days 2-14, trastuzumab 6 mg/kg, and docetaxel 60 mg/m(2) every 21 days. For the 29 patients treated at the MTD, median PFS was 12.7 months, with complete and partial response rates of 18 and 46%, and a stable disease rate of 29%. No statistically significant correlation was found between response and expression of any biomarkers. We conclude that the combination of gefitinib, trastuzumab, and docetaxel is feasible and effective. Expression of the biomarkers examined did not predict outcome in this sample of HER-2 overexpressing metastatic breast cancer.

Continued use of trastuzumab beyond disease progression in the national comprehensive cancer network: should we practice ahead of the evidence?

BACKGROUND: The role of continued trastuzumab after progression in women with human epidermal growth factor receptor (HER)-2+ metastatic breast cancer is controversial. Controlled clinical trials that establish a benefit from continued trastuzumab have been difficult to complete. METHODS: In the National Comprehensive Cancer Center Network (NCCN) Breast Cancer Outcomes Database, we identified women treated with trastuzumab for metastatic or relapsed HER-2+ breast cancer at eight NCCN centers who subsequently progressed. Patients were eligible for this analysis if they initiated treatment at an NCCN institution between July 1997 and December 2004, received trastuzumab-containing treatment, and progressed while on therapy. We calculated the proportion of patients who received trastuzumab after progression, and in a multivariate analysis assessed the association of patient and provider characteristics with continued trastuzumab therapy. RESULTS: Our final cohort consisted of 218 women who experienced disease progression while on trastuzumab-containing therapy. Of these, 168 (77%) continued trastuzumab. Of these, 36 patients (17%) received therapy as part of a clinical trial. The only factors significantly associated with continuation of trastuzumab beyond progression were the presence of bone metastases and more recent year of development of progressive disease. CONCLUSIONS: Prior to the availability of any high-quality evidence supporting this practice, over three quarters of patients treated with trastuzumab for HER-2+ metastatic breast cancer at eight NCCN centers continued therapy beyond progression. Further work is needed to understand how physicians adopt new treatments when there is ambiguity surrounding their benefit.

Human epidermal growth factor receptor-2-positive breast cancer: Current management of early, advanced, and recurrent disease.

PURPOSE OF REVIEW: This review describes the current treatment of human epidermal growth factor receptor-2 (HER2)-positive breast cancer with a focus on recently reported clinical trials.Treatment of resistant disease and central nervous system metastases will be reviewed as will new agents that are being developed to target HER2-amplified breast cancers. RECENT FINDINGS: Recent studies evaluating trastuzumab-resistant breast cancer have shown a benefit of continuing trastuzumab with chemotherapy or with another HER2-targeted agent.Targeting the vascular endothelial growth factor, mammalian target of rapamycin, and PI3 kinase pathways in addition to HER2 may enhance efficacy compared with individual agents. Several novel anti-HER2 compounds are being evaluated with promising early data. SUMMARY: HER2-positive breast cancer has traditionally been associated with poor prognosis.However, treatment with HER2-targeted therapies has changed the natural history of this disease. Greater success depends on elucidating mechanisms of resistance and exploring new methods of blocking signal transduction via HER2 and related pathways.

Impact of Dose Delays and Alternative Dosing Regimens on Pertuzumab Pharmacokinetics.

PERJETA (pertuzumab), administered with Herceptin (trastuzumab), is used in the treatment of human epidermal growth factor receptor 2-positive breast cancer. Pertuzumab is currently approved with an initial loading dose of 840 mg, followed by a 420-mg maintenance dose intravenously every 3 weeks. A reloading dose is required if there is a ≥6-week delay in treatment. In response to the potential treatment disruption due to COVID-19, the impact of dose delays and alternative dosing regimens on intravenous pertuzumab for human epidermal growth factor receptor 2-positive breast cancer treatment is presented. Simulations were conducted by using the validated population pharmacokinetic model for pertuzumab, and included (1) 4-, 6-, and 9-week dose delays of the 840 mg/420 mg every 3 weeks dosing regimen and (2) 840 mg/420 mg every 4 weeks and 840 mg every 6 weeks alternative dosing regimens. Simulations were compared with the currently approved pertuzumab dosing regimen. The simulations in 1000 virtual patients showed that a dose reload (840 mg) is required following a dose delay of ≥6 weeks to maintain comparable Ctrough (lowest concentration before the next dose is given) levels to clinical trials. The 840 mg/420 mg every 4 weeks and 840 mg every 6 weeks alternative dosing regimens decrease median steady-state Ctrough by ≈40% compared with the approved regimen, and <90% of patients will be above the target Ctrough . Thus, the alternative 840 mg/420 mg every 4 weeks and 840 mg every 6 weeks pertuzumab dosing regimens are not recommended. Flexibility for intravenous PERJETA-based regimens is available with an alternative route of pertuzumab administration (subcutaneous vs intravenous).

Resistance mechanisms to anti-HER2 therapies in HER2-positive breast cancer: Current knowledge, new research directions and therapeutic perspectives.

HER2-positive breast cancer (HER2 + BC) represents 15-20% of all BCs. In the last two decades, the introduction of monoclonal antibodies (MoAbs), tyrosine kinase inhibitors (TKIs) and antibody-drug conjugates (ADCs) directed against HER2 impressively improved patient prognosis in all disease stages. Yet, not all patients with limited-stage disease are cured, and HER2+ metastatic BC (mBC) remains an almost invariably deadly disease. Primary or acquired resistance to anti-HER2 therapies is responsible for most treatment failures. In recent years, several resistance mechanisms have been identified, such as impaired drug binding to HER2, constitutive activation of signaling pathways parallel or downstream of HER2, metabolic reprogramming or reduced immune system activation. However, only a few of them have been validated in clinical series; moreover, in the era of standard-of-care dual HER2 blockade, these mechanisms should be re-assessed and, in case, confirmed with anti-HER2 combinations. Defining the best strategies to delay or revert resistance to anti-HER2 treatments will be crucial to improve their clinical efficacy.