Comparing Combination Treatments in HER2-Positive Early Breast Cancer

Sara A. Hurvitz, MD

In patients with HER2-positive early breast cancer, data from a phase III trial has shown a significantly higher pathological complete response (pCR) rate with neoadjuvant docetaxel plus carboplatin plus trastuzumab plus pertuzumab (TCH+P) versus trastuzumab emtansine plus pertuzumab (T-DM1+P).

According to the results of the KRISTINE trial, the TCH+P regimen was also associated with a higher rate of breast conserving surgery. However, researchers reported that T-DM1+P had a notably better safety profile and that health-related quality of life and physical functioning were maintained longer.

“Neoadjuvant TCH+P achieved a superior pCR rate compared with T-DM1+P and was associated with a higher breast-conserving-surgery rate,” said Sara A. Hurvitz, MD, General Internal Medicine, Hematology & Oncology, UCLA Medical Center in Santa Monica, CA. “However, neoadjuvant T-DM1+P had a more favorable safety profile, with lower incidence of grade 3 or greater adverse events, serious adverse events, and adverse events leading to treatment discontinuation.”

As Dr. Hurvitz reported at the 2016 ASCO Annual Meeting, trastuzumab, emtansine, and pertuzumab bind different HER2 domains and have marked antitumor activity in HER2-positive breast cancer. KRISTINE presents the first phase III data for a neoadjuvant regimen that omits standard chemotherapy for HER2-positive breast cancer.

KRISTINE Study Design

From June 2014 to June 2015, researchers at 68 centers in 10 countries enrolled 444 patients with centrally confirmed HER2-positive breast cancer greater than 2cm in size. Patients were randomly assigned to receive T-DM1+P or the TCH+P regimen. Both regimens were given every 3 weeks for 6 cycles. At the end of the first cycle, patients underwent a core needle biopsy of the tumor for biomarker endpoints.

After 6 cycles, patients received standard of care surgery, and after surgery, they went on to receive 12 more doses of HER2-directed therapy according to the arm they were in.

Patients in the T-DM1+P arm who had significant residual disease at the time of the surgery were encouraged to receive standard chemotherapy before receiving a maintenance therapy regimen.

Baseline characteristics were well distributed to 2 treatment arms by age, world region, estrogen receptor (ER)/progesterone receptor (PR) status, and stage.

Results

As Dr. Hurvitz reported, the pCR rate in the breast and lymph nodes was 56% in the TCH+P arm and 44% in the T-DM1+P arm. This 11% difference was statistically significant, said Dr. Hurvitz, favoring the TCH+P arm.

In patients with ER- and PR-negative breast cancer, TCH+P yielded a pCR of 73% in breast and lymph nodes, compared to 54% in the T-DM1+P arm.

In hormone receptor (HR)—positive breast cancer, the pCR was 44% in the TCH+P arm and 35% in the T-DM1+P arm, also favoring TCH+P. Over 60% of patients had HR-positive breast cancer, Dr. Hurvitz noted.

A preplanned, subgroup analysis showed that TCH+P tended to favor all subgroups (age, world region, clinical stage at diagnosis and HR status). In addition, more women in the TCH+P underwent breast conserving surgery (52.6% vs 41.7%,P= 0.0228).

In contrast, neoadjuvant T-DM1+P was associated with longer maintenance of patient-reported health-related quality of life and physical functioning, said Dr. Hurvitz. Neoadjuvant T-DM1+P also had a more favorable safety profile with a lower rate of grade 3/4 adverse events (AEs) (13% vs. 64%), serious AEs (5% vs. 29%), and AEs leading to treatment discontinuation (3% vs. 9%).

Biomarker data and longer-term follow-up will be reported at a later date, said Dr. Hurvitz. In addition, there are several studies evaluating the use of T-DM1 in the early stage setting, including the KATHERINE and KAITLIN trials.

Cardiac event rates were unusual and were similar in the 2 treatment arms. Grade 3/4 AEs occurring in at least 3% of patients in either treatment arm included febrile neutropenia, neutropenia, diarrhea, and cytopenias, all of which were more common in the traditional chemotherapy arm compared to the T-DM1+P regimen.

Hurvitz SA, Martin M, Symmans WF, et al. Pathologic complete response (pCR) rates after neoadjuvant trastuzumab emtansine (T-DM1 [K]) + pertuzumab (P) vs docetaxel + carboplatin + trastuzumab + P (TCHP) treatment in patients with HER2-positive (HER2+) early breast cancer (EBC) (KRISTINE).J Clin Oncol34, 2016 (suppl; abstr 500).