Trastuzumab emtansine plus pertuzumab in patients with HER2-positive breast cancer

This study wanted to find out which treatment was better before surgery for patients with HER2-positive breast cancer, trastuzumab emtansine (Kadcycla) plus pertuzumab (Perjeta), or a standard treatment. The study found that patients treated with trastuzumab emtansine plus pertuzumab (TEP) were more likely to have cancer remaining after 37 months, but had fewer side effects.

HER2-positive breast cancer can be difficult to treat. New or modified medications are being created to try and make treatment more successful. Trastuzumab emtansine is a modified version of a very common drug called trastuzumab (Herceptin). Using this in combination with pertuzumab may result in fewer side effects from treatment. It is not known if using these two medications will result in fewer side effects or a better overall chance of cancer not coming back compared to standard therapies.

This study had 444 patients. 223 of these patients were randomly assigned to have treatment with trastuzumab emtansine plus pertuzumab (TEP). The other 221 patients were treated with docetaxel (Taxotere), carboplatin (Paraplatin), trastuzumab and pertuzumab (standard treatment). The patients were all treated for at least six cycles. All of the patients had surgery to remove tumors from the breast after they finished treatment with these regimens. Once they had recovered from surgery, they began taking the medication again. The patients were all followed up for 37 months.

In the 37 months since treatment began, 13.9% of the patients treated with TEP had the cancer progress after 37 months. 5.9% of the patients on standard treatment had the cancer progress after 37 months. Patients treated with TEP were 2.61 times more likely to have the cancer progress after 37 months than those on standard treatment.

15 patients who were treated with TEP had the cancer continue to grow while getting treated. None of the patients on standard treatment had the cancer continue to grow while getting treated. After surgery and follow up, 13 patients in each group had cancer cells found in the breast.

31.8% of the patients treated with TEP had serious side effects compared to 67.7% of the patients on standard treatment. Common side effects included issues with blood cell counts, and diarrhea.

The study concluded that treatment with trastuzumab emtansine plus pertuzumab resulted in a higher chance of progression before surgery, but the same chance of overall progression and a lower chance of side effects compared to treatment with standard treatment in patients with HER2-positive breast cancer.

This study only looked at the risk of cancer progression or recurrence. It is unclear from this study if treatment with trastuzumab emtansine plus pertuzumab resulted in better overall survival. Further, longer-term studies are needed.