For women with recurrent breast cancer, the treatment the doctor chooses is usually based on the properties of their original breast cancer. A group from Toronto has recently completed the world's first study that compared original breast cancer tumors with a biopsy of suspected tumors that recurred elsewhere in the body.
Researchers found that the biopsy resulted in 20% of the women having a significant change in their treatment. In some cases this was a change in drug treatment; in others, the biopsy showed the woman did not actually have an advanced cancer but a benign condition.
"The results show that cancers may change over time and not respond to treatment that was appropriate for the original cancer," says principal investigator Dr. Mark Clemons, a medical oncologist specializing in breast cancer in the Princess Margaret Hospital Cancer Program, University Health Network (UHN).
"These early findings are leading us in a new direction as we understand more about why some women don't respond to treatment. This knowledge will help us in our quest to always deliver the right treatment, to the right patient, at the right time."
The findings were published in the journal Annals of Oncology.
Clemons's study – funded by a $100,000 research grant from the Canadian Breast Cancer Foundation - Ontario Region – evaluated 29 biopsies of accessible, recurrent tumors taken from women whose breast cancer had spread to bone, skin, lymph nodes, lung or liver.
Pathologists compared the results of the original cancer with the results of the new biopsy by analyzing the predictive markers that influence breast cancer tumor growth – estrogen, progesterone and Her2 status. The presence, absence and/or combinations of these markers become the map oncologists use to determine the most effective treatment for each patient.
In 15 cases, the diagnosis was unchanged; in 10 cases the markers in the cancer changed; in three cases, women originally felt to have metastatic breast cancer had benign disease, and in one case, the "recurring" cancer was a different type of cancer, lymphoma which is treated in a very different way to breast cancer.
SOURCES:
Annals of Oncology, online edition, March 18, 2009
Princess Margaret Hospital, University Health Network (http://www.uhn.on.ca)
