A combination of two drugs was able to shrink breast cancer tumors in just 11 days, the results from a clinical trial found.
According to the researchers, roughly 25 percent of women with newly diagnosed HER2 (human epidermal growth factor receptor 2) positive breast cancer, who received lapatinib (Tyverb) and trastuzumab (Herceptin) prior to chemotherapy and surgery, either had their tumors shrink completely or significantly.
"This has ground-breaking 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," Nigel Bundred said. "This offers the opportunity to tailor treatment for each individual woman."
The two-part clinical trial recruited 257 women with HER2 positive breast cancer between November 2010 and September 2015. All of the cancers were considered to be operable.
In the first part of the trial, 130 patients were randomized into three groups: no treatment before an operation, lapatinib only and trastuzumab only. The second-half of the trial involved 127 women, who were divided into a control group that did not receive preoperative treatment, a trastuzumab only group and a combination drug group. The researchers decided to add the combination drug group after other trials found evidence that trastuzumab and lapatinib can effectively fight HER2 positive breast cancer together.
The researchers analyzed tumor tissue samples that were taken before and after surgery to monitor levels of the Ki67 protein, which can indicate cell proliferation, a process that leads to a higher number of cells. Tumors tend to have an increased rate of cell proliferation.
The researchers had also examined the women's pathology reports that were conducted on tumor tissue taken during surgery. Women were grouped into three groups: pathological complete response (pCR), which meant that they had no active cancer cells, minimal residual disease (MRD), which indicated that their tumor had a diameter that was less than 5mm, or other.
Women in the combination drug group had noticeable drops in their Ki67 protein levels. 11 percent of the women in this group had pCR and 17 percent had MRD. The pCR and MRD rates were the highest out of all three groups from the second part of the clinical trial.
"These results show that we can get an early indication of pathological response within 11 days, in the absence of chemotherapy, in these patients on combination treatment. Most previous trials have only looked at the pathological response after several months of treatment," co-leader of the trial, Judith Bliss, from The Institute of Cancer Research, London, said. "Clearly these results need further confirmation, but I suspect the excitement from seeing the speed of disappearance of the tumors will mean that several trials will attempt to confirm these results."
The findings were presented at the 10th European Breast Cancer Conference.
