Research presented Sept. 26 at the 2011 European Multidisciplinary Cancer Congress indicates that breast cancer tumors change their hormonal status throughout the course of disease, prompting researchers to recommend regular biopsies to ensure correct treatment in patients who relapse.

Oncologists typically base the decision about the most effective treatment for the patient on one biopsy of the primary tumor. However, because approximately one-third of tumors alter hormone receptor status during disease progression, biopsy verifications of any relapse will be important because it may completely change clinical management of some patients, Linda Lindström, MD, from the Karolinska Institutet department of oncology-pathology, in Stockholm, said in a statement.

The study examined changes in tumors in multiple relapses in breast cancer patients who relapsed from Jan. 1, 1997, to Dec. 31, 2007.

"Our study demonstrates tumor instability in clinically used markers throughout tumor progression. We saw, for example, that one in three breast cancer patients alter estrogen (ER) or progesterone (PR) hormone receptor status, and 15 percent of patients change human epidermal growth factor receptor 2, or HER2, status during the course of disease," Lindstrom said.

Information on ER status in several relapses from the same individual was assessed in 119 patients: 34 percent of patients had changes in tumor status between the different sites of relapse (local, loco-regional and metastases) whereas 36 percent of the patients were stable ER positive, and 30 percent were stable ER negative, according to the study abstract. Sixteen percent of patients changed from ER positive to negative during the course of their disease, 13 percent changed from negative to positive, and 5 percent altered back and forth throughout tumor progression.

In the PR group, 30 percent of patients altered hormone receptor status, with the majority changing from positive to negative. "Until now we thought that these predictive markers remained stable during the course of the cancer. But it is now apparent that these breast tumor markers, which are used to decide the best treatment for the patient, change as the tumor progresses and this significantly affects the way patients respond to particular therapies. This has important implications for the future management of the disease," Lindström said.

The researchers plan to carry out a prospective study in which they will follow a group of breast cancer patients and examine the standard clinical markers throughout their tumor progression. "With cancer treatments becoming more and more efficacious and targeted to specific groups, it is particularly important that the correct treatment is given throughout the disease," Lindström said, adding, "An additional advantage of carrying out regular biopsies would be that they could detect other primary cancers, or benign lesions, which could spare patients inappropriate or unnecessary therapies."

"This finding is of clinical importance because it shows that many cancer patients who relapse do not receive optimal treatment for their disease. While the price of regular biopsies may seem high for both patients and healthcare systems, in the long run they may avoid inappropriate and costly treatments and, even more importantly, may be the basis for selecting more effective treatments for individual patients," professor Michael Baumann, European CanCer Organisation president, said in a statement.