Stray Breast Cancer Cells Yield to Post-Op Chemo
WEDNESDAY, Aug. 12 -- Breast cancer patients with isolated tumor cells or tiny "micrometastases" in the lymph nodes benefit from adjuvant treatment, such as post-surgical chemotherapy or hormonal therapy, a new study finds.
Until now, many doctors doubted that the presence of micrometastases or isolated tumor cells affected long-term recovery, said Dr. Vivianne Tjan-Heijnen, head of the division of medical oncology at Maastricht University Medical Center in the Netherlands, the lead author of the study.
So these patients often are not offered adjuvant therapy after they undergo breast cancer surgery. But the results of her team's study, published in the Aug. 13 issue of the New England Journal of Medicine, suggest they should be.
Micrometastases, which are too small to be seen on standard screening or diagnostic tests, range from 0.2 to 2.0 millimeters in size. Isolated tumor cells or tumor cell groups are even tinier, less than 0.2 millimeters, said Tjan-Heijnen.
To assess the value of additional treatments of chemo or other adjuvant methods, Tjan-Heijnen and her colleagues followed 2,707 women treated surgically for early-stage breast cancer. They were divided into three groups. The first group included 856 women diagnosed with breast cancer whose sentinel node -- the first node the breast tissue drains into -- was negative and cancer-cell free, who didn't get additional treatment. The second group included 856 women diagnosed with breast cancer with cancer cells found in the nodes, but who didn't get additional treatment. The third group included 995 patients with cancer cells found in the nodes who did get additional treatment.
The additional treatment included chemotherapy (such as taxanes), endocrine therapy (such as tamoxifen or aromatase inhibitors), or systemic therapy (both chemo and endocrine).
The researchers followed the women for a median of 5.1 years (half followed longer, and half for less time) to see if the extra therapy reduced cancer recurrence and increased disease-free survival. They associated the tiny metastases and isolated tumor cells with an absolute decline in five-year disease-free survival of 10 percent. In other words, those with the tiny cancer cells present who are treated with additional therapy had a nearly 10 percent improvement in disease-free survival at five years, they found.
"So, five years after the diagnosis of every 100 patients with micrometastases or isolated tumor cells, 10 more will have a disease event compared with 100 patients with comparable primary tumor characteristics who did not have metastases in the axillary nodes," Tjan-Heijnen said.
The study proves that the micrometastases and the isolated tumor cells are important considerations when evaluating the prognosis, she said.
Cancer specialists have debated how to treat a patient with these small metastases and isolated tumor cells, said Dr. Minetta Liu, director of translational breast cancer research at the Georgetown University Lombardi Comprehensive Cancer Center in Washington, D.C.
The study results suggest that "looking for these cells may be another tool to determine how likely a recurrence is," she said. But more study is needed to validate the findings, she added.
Dr. Hannah Linden, a medical oncologist and associate professor of medicine at the University of Washington School of Medicine in Seattle, said the study results could change current practice. "If these findings are true, they will influence decision making significantly, and help us know which patients really 'need' chemo to give them an advantage in reducing the risk that the tumor recurs," she said.
To learn more about adjuvant therapy for breast cancer, visit the U.S. National Cancer Institute.
Posted: August 2009