When women find themselves diagnosed with breast cancer a second time, their doctors usually choose to repeat the same treatment used on the original cancer. A new study suggests that may not always be the best choice.
Researchers from Princess Margaret Hospital Cancer Program recently completed the world's first study that compared original breast cancer tumours with a biopsy of suspected tumours that recurred elsewhere in the body.
They found that 20 per cent of the women needed a significant change in their treatment, based on the biopsy of the second tumour.
In some cases, this meant a change in drug treatment. In others, the biopsy showed the woman did not actually have an advanced cancer, but a benign condition.
The findings could potentially change current treatment practices, says the study's principal investigator, Dr. Mark Clemons, an oncologist specializing in breast cancer at Princess Margaret.
He says biopsy is not standard practice for metastatic breast cancer. But his findings suggest that cancers can change over time and not respond to treatment that was appropriate for the original cancer.
"These early findings are leading us in a new direction as we understand more about why some women don't respond to treatment," he says.
"This knowledge will help us in our quest to always deliver the right treatment, to the right patient, at the right time."
Clemons' study evaluated 29 biopsies of accessible tumours 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 tumour growth: estrogen, progesterone and Her2 status. The presence or absence of these markers are key for oncologists 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.
The findings are published online today in the Annals of Oncology.
Study participant Danielle Lee says the change in her treatment changed her life. Two years ago, the then 30-year-old mother of two young children was coping with a diagnosis that her breast cancer had spread to her spine. The results of the new biopsy confirmed that there was no cancer in her spine.
"I was so grateful to be part of this study. It was a life-changing event for me during a difficult, dark time when I was trying to accept that I would die from breast cancer and my children would have to grow up without me," says Lee.
Clemons says larger studies are needed to confirm his findings but he says physicians need to begin to think about the fact that tumours can change with time.
