Adding Bevacizumab to Chemotherapy Prolongs Survival in Breast Cancer

San Antonio, TX — The addition of bevacizumab (Avastin) to chemotherapy improved progression-free survival (PFS) compared with chemotherapy alone in patients with metastatic breast cancer whose cancer has progressed on first-line therapy. “This is the first Phase III study to show that bevacizumab plus chemotherapy is effective as second-line therapy for metastatic breast cancer. These results are clinically meaningful. We have few options for second-line chemotherapy in metastatic disease,” said Adam Brufsky, MD, University of Pittsburgh, PA. Dr Brufsky discussed this study at an official press conference remotely from his home while recovering from illness.

The study, called Ribbon-2, included 684 women with metastatic breast cancer that progressed on first-line chemotherapy. The women received chemotherapy of the investigators’ choice (taxane [44%], gemcitabine [23%], capecitabine [21%], or vinorelbine [12%]). Women were then randomized 2:1 to receive chemotherapy plus bevacizumab or chemotherapy alone. They were treated until disease progression.

Treatment arms were well balanced for demographic and disease characteristics. Median age was 55 years. A slight imbalance was observed for patients with triple- negative breast cancer (estrogen receptor—negative, progesterone receptor–negative, and HER2-negative): 20% in the chemotherapy arm and 24% in the bevacizumab-containing arm.

For the primary endpoint of progression-free survival (PFS), the addition of bevacizumab achieved a highly statistically significant 22% improvement (P = .0072), from a median of 5.1 months with chemotherapy alone to 7.2 months with the addition of bevacizumab. An exploratory analysis that looked at PFS results according to type of chemotherapy received suggested that the choice of chemotherapy matters.

“As a class, there was a benefit with taxanes and with capecitabine. Patients on gemcitabine or vinorelbine did not appear to benefit from the addition of bevacizumab. But this was a preliminary analysis in very small numbers of patients,” Dr Brufsky told listeners.

Response rates were also much higher with the addition of bevacizumab. Overall response rates were 39.5% with the combination therapy versus 29.6% with chemotherapy alone. No difference in overall survival was seen in this interim analysis. Only 57% of the patients have died, Dr Brufsky said.

“A difference in overall survival may emerge with longer follow-up,” he said.

“We now know that bevacizumab is clearly beneficial as first-line and as second-line therapy. We are interested in a study of continuous bevacizumab in metastatic breast cancer, the so-called Ribbon-3 trial.”

Toxicity with bevacizumab was consistent with previous experience in metastatic breast cancer and other tumor types. No new toxicity signals emerged.

Edith Perez, MD, Mayo Clinic, Jacksonville, FL, who moderated the official press conference where this abstract was discussed, said that a previous study in second-line therapy of metastatic breast cancer showed no benefit for the addition of bevacizumab to capecitabine. “It is an important finding that bevacizumab plus several options of chemotherapy improved PFS in patients who did not get it as first line,” Dr Perez commented.

When asked whether the cost of bevacizumab was worth an extra 2.1 months of PFS, Dr Brufsky acknowledged that cost is an issue. “When we compare trial results, 2.1 months is a mean. There are patients who do much better at one end of the curve. We want to identify characteristics that predict better response,” he commented. SABCS Abstract 42.