Patients
The study included patients with metastatic or locally advanced BC not amenable to curative treatment, with tumoral expression of estrogen receptor, progesterone receptor, or both, by immunohistochemistry (IHC). Patients should have progressed after at least one line of ET, including adjuvant ET. Prior treatment with up to one line of chemotherapy for metastatic disease was acceptable.
All patients should have tumor expression of Lewis Y antigen documented by IHC. Tumor expression of the Lewis Y antigen by IHC was performed by central analysis (LIM 14 of the Medical School of the University of São Paulo). The samples were considered positive when any reaction in the membrane of tumor cells was detected.
Other inclusion criteria were ECOG (Eastern Cooperative Oncology Group) performance status of 0 or 1 and preserved organic functions.
Exclusion criteria included the presence of HER2 overexpression (defined as IHC 3 + or positive fluorescence in situ hybridization), life-threatening visceral metastatic disease (defined as extensive hepatic involvement, symptomatic pulmonary lymphangitic carcinomatosis, and cerebral or leptomeningeal metastases) and the need for systemic corticosteroids or immunosuppressive agents.
Outcomes
The primary endpoint was the clinical benefit rate of hu3S193 monoclonal antibody defined as complete response, partial response, or stable disease for at least 24 weeks.
Secondary endpoints were response rate, non-progression rate, overall survival, time to progression, and safety. The response rate was defined as the proportion of patients that presented complete response or partial response. The non-progression rate was defined as the proportion of patients who presented complete response, partial response or stable disease, regardless of the duration of the latter.
Overall survival was the time from the first study drug dose until death from any cause. Patients without this event were censored at the date of last follow-up. Time to progression was the time from first study drug dose until any clinical or radiological progression. Patients without the event were censored at the date of last follow-up or the date of death without progression.
Study Design
HumanaH trial was a phase II, single-arm, trial conducted in 7 Brazilian centers and coordinated by the Instituto do Câncer do Estado de São Paulo (ICESP) (NCT01370239).
Treatment consisted of hu3S193 antibody at intravenous infusions of 20 mg/m2 weekly. Each treatment cycle consisted of 8 weeks. Treatment was continued until clinical or radiological disease progression, unacceptable toxicity, withdrawal of consent, or decision of the investigator. Dose reductions were allowed according to protocol. In case of grades 3 or 4 non-allergic toxicities, treatment was delayed for up to 14 days until improvement to grades 1 or 2 and resumed with a 25% dose reduction. In case of no improvement to grades 1 or 2 within 14 days, treatment was discontinued.
Study Supervision
The Ethics Committee of each participating institution approved the study, which was conducted in accordance with the principles of the Declaration of Helsinki and the International Conference on Harmonisation Good Clinical Practice guidelines. Before any study procedure, the patients read and signed the Informed Consent Form.
Recepta Biopharma (S. Paulo, Brazil) granted the use of hu3S193 antibodies. The study was sponsored by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Grant N0 52/2009 edital CNPq.
The authors were responsible for the design of the study, analysis of results, and writing the manuscript.
Assessments
Radiological response evaluations were performed every 8 weeks. Mandatory radiological images consisted of computed tomography or magnetic resonance imaging of the thorax, abdomen and pelvis. Brain imaging and bone scan were performed if clinically indicated. The radiological responses were evaluated according to Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1.
Adverse events were monitored and their severity was scaled according to the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE), version 4.03.
Human anti-human antibodies (HAHA) tests were performed periodically at baseline, at week 8 of each cycle, at the end of treatment, and if immune-mediated adverse events occurred. Samples were analyzed by ELISA (Enzyme linked Immunosorbent Assay). Treatment with hu3S193 antibody should be interrupted permanently if the tested patient was positive for HAHA.
Statistical analysis
Efficacy analyses were performed according to the intent-to-treat principle. In the safety analysis, all patients receiving at least one dose of the hu3S193 were included.
For sample size calculation, we considered historical clinical benefit rates obtained in three studies that included a similar profile of patients who were treated with endocrine therapy 13,14,30. It was estimated a historical clinical benefit rate of 40% and a clinical benefit rate of hu3S193 of 60%. With a two-sided alpha error of 5%, a power of 85%, and a withdrawal rate of 10%, a total of 60 patients would be required.
Due to the observation that many patients soon discontinued the study because of disease progression, an unplanned interim analysis was done. The interim analysis considered a two-sided alpha error of 5%, a beta error of 20%, and clinical benefit rates of 40% historically and 60% with hu3S193. According to Simon's Two-Stage design, after testing 21 patients at a first stage, the trial should be terminated if 10 or fewer patients responded. If 11 or more patients responded, the trial should go on to the second stage to include a total of 60 patients.
Descriptive statistics were used to summarize patients’ characteristics, radiological response, and adverse events. Continuous variables were presented as median and range, while categorical variables were presented as absolute and relative frequencies. Clinical benefit and non-progression rates were presented as proportion and 95% confidence interval (CI). Survival analyses were performed with the Kaplan-Meier method. Stata software, version 14 (StataCorp, Texas, USA), was used for statistical analyses.