Can pertuzumab improve long-term response rates in HER2-positive breast cancer?

The authors aimed to assess whether adding pertuzumab (Perjeta) to chemotherapy could improve response in women with metastatic (has spread) breast cancer.

This study showed that adding pertuzumab to chemotherapy resulted in higher response rates among women with breast cancer that relied on the human epidermal growth factor 2 (HER2) to grow.

HER2 positive breast cancer has been shown to be a more aggressive disease with a poorer prognosis (outlook). Trastuzumab (Herceptin) is a treatment that blocks (inhibits) HER2. Trastuzumab combined with chemotherapy has been the first line of treatment for this type of cancer.

Pertuzumab is another type of HER2 inhibitor. Previous studies have found that adding pertuzumab to a combination of trastuzumab and docetaxel (Taxotere, a chemotherapy) improved short-term progression-free survival (time from treatment until disease progression) and overall survival (time from treatment until death from any cause). The long-term effectiveness of this combination is not yet known.

This study compared the long-term outcomes of adding pertuzumab to the trastuzumab/docetaxel treatment combination.

This study included 808 women with HER2-positive metastatic breast cancer. 402 patients were assigned to receive pertuzumab, trastuzumab and docetaxel, while the remaining 406 were to receive a placebo (substance with no effect on the body), trastuzumab and docetaxel. Patients were followed for an average of 50 months.

The average overall survival was significantly longer (56.5 months) in the pertuzumab group compared to the placebo group 40.8 months). Progression-free survival was an average of 6.3 months longer in the pertuzumab group. Mortality rates were significantly lower in the pertuzumab group (41.8%) compared to the placebo group (54.4%). Patients in the pertuzumab group responded to treatment for an average of 7.7 months longer than the placebo group.

There was no significant difference in side effects between the two groups. Pertuzumab had less toxic effects on cardiac function. Most of the side effects occurred during docetaxel treatment. Side effects included mild headaches, respiratory tract infections and muscle spasms. 

The authors concluded that the addition of pertuzumab to chemotherapy improved long-term response rates in women with HER2-positive metastatic breast cancer.

The analysis also includes patients who cross-over from the placebo group to the pertuzumab group.

This study was funded by F. Hoffmann–La Roche and Genentech, the manufacturers of pertuzumab.