Findings of the phase 2 NeoSphere study, published Online First in The Lancet Oncology shows that by adding monoclonal antibody pertuzumab to standard therapy (trastuzumab [Herceptin] plus the chemotherapy drug docetaxel) for women with an aggressive type of early-stage breast cancer (HER2-positive disease) improved the rate of complete tumor disappearance by over half after just four cycles, i.e. 12 weeks of treatment compared with the standard regimen alone.

The remarkable findings also demonstrated that this combination without adding chemotherapy managed to eradicate tumors in a significant amount of women (17%). Patients suffered no chemotherapy-related toxicities, indicating a potential possibility of treating some tumors without the use of chemotherapy.

Study leader Luca Gianni from the San Raffaele Cancer Center in Milan, Italy explains:

“The tumor response to this new triplet combination is one of the highest reported to date, despite just a short treatment time, and could be a big advance for women with HER-2 positive disease. Moreover, these findings suggest a potential future role for chemotherapy-free HER-2 targeted therapy, although such regimens require further investigation.”

Approximately one in five breast cancer tumors is HER-2 positive. The standard treatment for HER-2 positive women is trastuzumab, a monoclonal antibody that is designed to inhibit the cancer-causing activity of the HER2 protein. Another HER-2 drug to target the disease is pertuzumab, a drug that acts as a complementary therapy to trastuzumab, and which has demonstrated promising anti-tumor activity in an earlier phase 2 trial of women with advanced HER-2 positive breast cancer.

The NeoSphere study was developed in order for researchers to compare different regulated courses of HER-2 targeted therapies with and without chemotherapy. Researchers enrolled 417 previously untreated women with early HER-2 positive disease and assigned them randomly to receive four cycles of treatment prior to surgery. The treatments consisted of trastuzumab plus doctaxel, pertuzumab and trastuzumab plus doctaxel, trastuzumab plus pertuzumab, or pertuzumab plus docetaxel.

In approximately 46% of women receiving the new triple combination the tumor disappeared completely, compared with 29% of women given standard therapy, and 17% given pertuzumab plus trastuzumab without chemotherapy. The researchers observed that the new triple combination was well tolerated by all patients and did not substantially increase side effects or cardiac risk when compared with the other regimens.

Fewer than 2% of women in the chemotherapy-free trastuzumab and pertuzumab group developed grade 3 or higher adverse events compared with 12% to 14% of women in the chemotherapy-containing treatment groups.

In a concluding statement the authors say:

“These findings justify further exploration in adjuvant trials and support the neoadjuvant [before surgery] approach for accelerating assessment in early breast cancer.”

Written by Petra Rattue