New monoclonal antibody therapies offer significant survival advantage for non-hormone responsive breast cancer patients

Results from the first and only interim analysis of an important trial assessing the potential of Herceptin (trastuzumab) to improve disease-free survival (DFS) in HER-2 positive breast cancer patients after adjuvant chemotherapy, have shown that Herceptin affords a significant survival advantage. These new findings were released at the 13th European Cancer Conference (ECCO) on the recommendation of the Independent Data Monitoring Committee.

The study in question, an international, multicentre, randomised, 3-arm trial is being conducted by the Breast International Group (BIG) in collaboration with the pharmaceutical company Roche AG, manufacturers of Herceptin. In total, 5,090 early breast cancer patients have been enrolled into this trial by the 478 participating institutions from Europe, Canada, South Africa, Israel, the Asia Pacific Region, Japan and Latin America. All women accrued had HER-2 positive breast cancer (either node negative or positive) and had completed at least four cycles of an acceptable (neo) adjuvant chemotherapy regimen. For women with hormone receptor positive disease, adjuvant endocrine therapy (most commonly tamoxifen) followed chemotherapy. The average age of study participants is 49 years.

The aim of this trial is to compare the effect of 1 year of Herceptin infusions, given every 3 weeks, with one year of simple observation, on survival – primarily DFS but also overall survival (OS), relapse-free survival (RFS) and distant disease free survival (DDFS), as well as comparable assessment of overall and cardiac safety. The study also consists of a 2-year arm – where 2 years of 3-weekly Herceptin is being compared with observation.

Results from the 1-year arm of the study, showcased at ECCO 13, show that Herceptin is associated with a significant improvement in DFS in this group of patients. The difference in Herceptin treated women was 85.8% compared to 77.4% of women on observation alone.

Patients receiving Herceptin therapy for 1 year also showed significant improvements in other survival measures – including RFS and DDFS. OS was also better in the Herceptin group versus observation, although the difference was not significant. In terms of safety, Herceptin-treated women experienced a higher incidence of cardiac side effects, which occurred in 0.5% of patients. In contrast, no observational patient experienced an adverse cardiac event.

These positive results are further supported by preliminary survival data from the 2-year Herceptin arm which also demonstrate a highly significant improvement in DFS compared with observation (p<0.0001). This important trial is continuing, gathering further data to assess and compare 2 years versus 1 year of Herceptin treatment, as well as carefully monitoring potential late-stage effects. Professor Michael Untch, the study’s Principle Investigator, from the Frauenklinik der LMU München Klinikum Grosshadern, Germany remarked: “These notable early findings show that Herceptin can provide significant improvements in survival for women with early HER-2 positive breast cancer who have completed initial chemotherapy cycles. By reducing the incidence of recurrences and metastasis by 50 % it means that patients have a significant gain in their chance to survive and a tremendous increase of their life quality. “ Another new monoclonal antibody, bevacizumab has recently completed Phase III clinical trials for the treatment of locally advanced or metastatic breast cancer. Bevacizumab is a monoclonal antibody to vascular endothelial growth factor (VEGF) and acts to inhibit tumour angiogenesis (process of diverting nutrients to the tumour). The randomised Phase III trial was coordinated by the Eastern Cooperative Oncology Group to compare the efficacy and safety of paclitaxel with or without bevacizumab as first line therapy in patients with locally advanced or metastatic breast cancer. 722 patients were recruited between December 2001 and May 2004 and were divided into two groups receiving either paclitaxel alone or the combination of paclitaxel and bevacizumab. The primary endpoint was progression-free survival (PFS). The results were positive and indicated that the combination of paclitaxel and bevacizumab improved overall survival of patients than receiving paclitaxel alone (no final data available yet). Importantly the progression-free survival was improved with combination therapy, 10.97 months vs 6.11 months for paclitaxel alone. In addition, the investigators noted that combination therapy did not cause significant toxicity effects. Speaking at ECCO 13, Dr Kathy Miller from the Indiana University Cancer Centre, USA, commented, “This is the first study to confirm the benefit of anti-angiogenic therapy in patients with breast cancer. Importantly, the improvements in response rate and progression-free survival were obtained with minimal increase in side effects. Given the benefit of bevacizumab in patients with metastatic disease, we look forward to initiating trials in the adjuvant setting.”