A phase II study published in the Journal of Clinical Oncology found that a pertuzumab combination significantly extended progression free survival in women with human epidermal growth factor receptor 2 positive (HER2+) and hormone receptor positive (HR+) metastatic or locally advanced breast cancer.
The continuing two-arm, open-label, international PERTAIN trial randomized women with HER2+, HR+ advanced breast cancer to receive either intravenous pertuzumab plus trastuzumab and oral anastrozole or letrozole or to receive trastuzumab and an aromatase inhibitor. Participating investigators could add induction intravenous docetaxel or paclitaxel for 18 to 24 weeks.
Pertuzumab vials. Source
Researchers led by Mothffar Rimawi, MD, of the Baylor College of Medicine in Houston, Texas, analyzed results from 129 women assigned to each arm between February 2012 and October 2014. Of those 75 in one group and 71 in the other received induction therapy.
Women who received the three-drug pertuzumab combination had a median progression free survival of 18.89 months, while women who received the two-drug combination had a progression free survival that was three months shorter, 15.80 months. The difference represented a 35% improvement in the progression free survival associated with pertuzumab. The researchers found a benefit from the addition of pertuzumab for all predefined subgroups.
Patients who did not receive induction chemotherapy saw a 45% improvement in progression free survival with the addition of pertuzumab. Among women who did not receive induction therapy, the median progression free survival for women who received the pertuzumab combination reached 21.72 months compared to 12.45 months for those who received the two-drug combination.
Patients who received induction therapy were typically younger, had more metastatic disease and were more likely to have three or more involved organs. Among those who had induction therapy, the median progression free survival in the pertuzumab arm was 16.89 months compared to 16.85 months in the group that did not receive pertuzumab.
Median duration of response was also significantly longer for patients in the pertuzumab combination arm, 27.10 months, compared to those in the trastuzumab/AI arm, 15.11 months.
No deaths occurred as a result of adverse effects. Grade 3 or higher adverse effects arose in half of the patients who received the pertuzumab combination and in 38.7% of women who did not.