Anti-HER2 Combo Shrunk Breast Tumors in Under 2 Weeks

A quarter of women with HER2-positive breast cancer treated with a combination of lapatinib plus trastuzumab prior to surgery had significant tumor shrinkage within 11 days. These results, from the EPHOS-B clinical trial in the United Kingdom were presented at the 10^th Annual European Breast Cancer Conference (EBCC-10), held March 9–11, in Amsterdam (abstract LBA6).

“This has groundbreaking potential because it allows us to identify a group of patients who, within 11 days, have had their tumors disappear with anti-HER2 therapy alone and who potentially may not require subsequent chemotherapy,” said researcher Nigel Bundred, MD, professor of surgical oncology at the University of Manchester in the United Kingdom, in a statement. “This offers the opportunity to tailor treatment for each individual woman.”

Following initial news reports of the EPHOS-B trial, the authors earlier today issued a statement urging caution in interpreting the results: “While we do not wish to downplay the significance of the findings,” they wrote, “we wish to emphasize that our research has shown this treatment to be suitable for a group of women with a particular type of breast cancer. We have no evidence that it would be effective for anything other than patients with newly diagnosed, HER2-positive breast tumors.”

The trial was split into two parts and included 257 newly diagnosed, operable, HER2-positive breast cancer patients.

In the first part of the trial, 130 patients were randomized to a control group that received no pre-operative treatment, or to one of three treatment arms that received therapy for 11 days prior to surgery: trastuzumab alone, lapatinib alone, or the combination of trastuzumab and lapatinib. All patients were treated with standard of care after surgery.

In the second part of the trial, 127 patients were randomized to receive trastuzumab alone (n = 32), the combination of trastuzumab and lapatinib (n = 66), or a control group that received no pre-operative treatment (n = 29). Results from this part of the trial showed that in patients who received the combination treatment, 11% had a pathologic complete response (pCR) and 17% had minimal residual disease (MRD). In patients who received trastuzumab alone, none had a pCR and only 3% had MRD. No patient in the control group had either a pCR or MRD. Patients in the combination treatment arm also had a reduction in Ki67, a marker of apoptosis.

Median age of patients in the trial was 52 years, 48% of women had tumors greater than 2 cm, and 51% were grade 3 as assessed by biopsy.

“These results show that we can get an early indication of pathologic response within 11 days, in the absence of chemotherapy, in these patients on combination treatment. Most previous trials have only looked at the pathologic response after several months of treatment,” said Judith Bliss, MD, of the Institute of Cancer Research in London and Vice-Chair of the UK Breast Intergroup, who took part in the clinical trial, at a press conference.

The study researchers emphasized that these results need to be confirmed in larger trials.

“This study proposes a simple way to identify those patients very early on, which could help spare them unnecessary chemotherapy. What is now indispensable is to confirm if these early responses translate into better or equal long-term survival,” said Fatima Cardoso, MD, chair of EBCC-10 and director of the breast unit at the Champalimaud Clinical Centre in Lisbon, in a statement.

The EPHOS-B trial was funded by Cancer Research UK and GlaxoSmithKline.