Adjuvant trastuzumab duration trials in HER2 positive breast cancer - what results would be practice-changing? Persephone investigator questionnaire prior to primary endpoint results

Optimum duration of adjuvant trastuzumab in treatment of human epidermal growth factor receptor-2 positive early breast cancer: protocol for a network meta-analysis of randomised controlled trials

INTRODUCTION

Controversy regarding optimum duration of trastuzumab treatment remains in patients with human epidermal growth factor receptor-2 (HER2) positive early breast cancer. The objective of applying network meta-analysis (NMA) is to integrate existing evidence based on direct and indirect comparisons of efficacy and safety, and then to determine the duration of trastuzumab treatments with the greatest impact on therapeutic outcomes in HER2-positive early breast cancers.

METHODS AND ANALYSIS

Electronic searching of trastuzumab treatments for early breast cancer by titles and abstracts will be conducted for the period from inception to 16 June 2019 in PubMed, Cochrane Library, Embase and ClinicalTrils.gov, as well as the annual meetings of San Antonio Breast Cancer Symposium (SABCS), European Society of Medical Oncology (ESMO) and American Society of Clinical Oncology (ASCO) online archives. The outcomes of interest are overall survival, disease-free survival, acceptability, cardiotoxicities and grade 3 to 4 non-haematological toxicities. Two independent reviewers will screen and extract eligible data based on the inclusion and exclusion criteria, and then assess the risk of bias and evidence quality of individual studies using Cochrane Collaboration's tool and Grades of Recommendation, Assessment, Development and Evaluation (GRADE). The heterogeneity, transitivity and inconsistency of NMA will be evaluated. In addition, we will perform subgroup and sensitivity analyses to assess the robustness and reliability of findings in our NMA.

ETHICS AND DISSEMINATION

Ethics approval is not required for our NMA. Findings from our NMA will be submitted as peer-reviewed journal manuscripts and international conference reports.

TRIAL REGISTRATION NUMBER

CRD42019139109.

Randomised clinical endpoint studies for trastuzumab biosimilars: a systematic review

PURPOSE

Uptake of biosimilars depends on clinicians and patients having confidence in the evidential basis of marketing approval. The aim of this systematic review was to assess the evidential role of randomised clinical endpoint studies in the marketing approval of trastuzumab biosimilars.

METHODS

We searched PubMed for any published reports of randomised studies associated with the five trastuzumab biosimilars approved by the EMA, as on 31 January 2019. We also searched ClinicalTrials.gov for any ongoing studies for other trastuzumab biosimilars.

RESULTS

We identified eight published papers or abstracts for seven randomised clinical endpoint studies for five trastuzumab biosimilars approved by the EMA: four studies in the neoadjuvant setting and three in the first-line metastatic setting. Another six unpublished or ongoing studies for other trastuzumab biosimilars were identified via ClinicalTrials.gov. According to GRADE, and considered in isolation, the randomised studies would be categorised as low-quality evidence because of the use of surrogate endpoints and the small sample size. However, according to GRADE, the totality-of-evidence for each of the five approved trastuzumab biosimilars would be categorised as high quality in that further data would be unlikely to change the conclusion that each biosimilar was not different from Herceptin in any clinically important way.

CONCLUSION

The pivotal data for each marketing approval was not the randomised clinical endpoint study, but the in vitro analytic characterisation. Regulatory confidence in in vitro analytic characterisation stems from years of experience with manufacturing changes for originator biological medicines. This emphasis on in vitro data, as the most sensitive way to detect clinically important differences, will be a new way of thinking for many oncologists.

Short-duration versus 1-year adjuvant trastuzumab in early HER2 positive breast cancer: A meta-analysis of randomized controlled trials

BACKGROUND

One year of adjuvant trastuzumab treatment is the standard of care for early stage human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients; however, controversy remains regarding the optimal schedule of trastuzumab because the selection of the 1-year schedule was arbitrary. After the remarkable results of the PERSEPHONE trial as well as the updated final results of the PHARE trial, we performed an updated meta-analysis to reassess the efficacy and safety of shorter durations of trastuzumab.

METHODS

A literature search of databases was conducted to identify randomized controlled trials reporting the efficacy and cardiotoxicity of shorter-duration and standard 1-year trastuzumab treatment. The hazard ratios (HRs) of disease-free survival (DFS) and overall survival (OS), and the odds ratios (ORs) of cardiac events were also estimated and pooled.

RESULTS

Six studies were eligible, including a total of 11,496 patients. Both DFS (HR = 1.13; 95% confidence interval [CI] = 1.03-1.25; p = 0.01) and OS (HR = 1.16; 95% CI = 1.01-1.32; p = 0.03) were significantly improved with conventional 1-year trastuzumab treatment compared with shorter treatments. The more pronounced survival benefits observed in patients with negative estrogen receptor (ER) tumor and nodal involvement should be interpreted cautiously because of the lack of interaction between the survival benefit and ER, as well as the nodal status (interaction test, ER status: p = 0.26; nodal status: p = 0.60). One year of trastuzumab treatment resulted in a substantial DFS benefit compared with shorter schedules when administered concurrently with chemotherapy (HR = 1.22; 95% CI = 1.09-1.38; p = 0.0008; p = 0.02 for the interaction test). Patients in the shorter duration group experienced significantly fewer cardiac events (OR = 0.52; 95% CI = 0.43-0.62; p < 0.00001).

CONCLUSIONS

Though correlated with an increasing risk of cardiotoxicity, 1 year of adjuvant trastuzumab treatment conferred substantial survival benefits and should remain as the preferred treatment for early stage HER2-positive breast cancer. Shorter durations of trastuzumab may serve as an alternative choice for patients with cardiac disease and those at lower risk of recurrence.

Adjuvant trastuzumab duration trials in HER2 positive breast cancer - what results would be practice-changing? Persephone investigator questionnaire prior to primary endpoint results

BACKGROUND

Twelve months treatment is the current standard of care for adjuvant trastuzumab in patients with HER2 positive early breast cancer however the optimal duration is not known. Persephone is a non-inferiority randomised controlled trial comparing 6- to 12-months of trastuzumab. In this trial there will be a trade-off between a possible small decrease in disease-free survival (DFS) with 6-months and reduced cardiotoxicity and cost.

METHODS

A structured questionnaire asked clinicians who had recruited patients into the Persephone trial about their prior beliefs with regards to the clinical effectiveness of trastuzumab and cardiotoxicity profile, in the comparison of 6- and 12-month durations.

RESULTS

Fifty-one clinicians from 40 of the 152 Persephone sites completed the questionnaire. 30/50 responders (60%) believed that 6-months trastuzumab would give the same 4-year DFS rate as 12-months trastuzumab, with 21/50 (42%) holding this belief across all breast cancer subsets. In addition, 46/49 responders (94%) reported expecting to change their clinical practice to 6-months, with their prior beliefs (most commonly 85% 4-year DFS rate with 6-months) being greater than their lowest acceptable rate (most commonly 83% 4-year DFS rate with 6-months). Low levels of cardiotoxicity were expected with both 6 and 12-months trastuzumab, with the majority expecting lower levels with 6-months. With increasing hypothesised differences of cardiotoxicity rates between the two durations, significantly lower levels of 4-year DFS with 6-months trastuzumab were deemed acceptable (p < 0.0001).

CONCLUSION

Most responders believe that 6-months trastuzumab is adequate, both overall and within each subset of breast cancer, and plan to change their clinical practice if the Persephone results support their prior belief. An individual patient meta-analysis of the duration trials would give greater precision to estimates of the differences in efficacy and toxicity, and adequate statistical power to establish a 2% level of non-inferiority for 6-months adjuvant trastuzumab.