The past two decades have seen a dramatic increase in the number of women diagnosed with T1a and T1b breast cancer. This rise in early-stage breast cancer is largely attributed to the increase in screening mammography that can detect cancer in its early stages, in some cases when the tumors are under 1cm and before the tumor has spread to the lymph nodes. In T1a breast cancer, the tumor size is less than or equal to 5 millimeters (mm); in T1b, the tumor size is greater than 5 mm, but less than or equal to 10 mm.
T1a and T1b breast cancers without lymph node spread have excellent long-term outcomes, with more than 95% of women alive at 10 years. However, important clinical questions remain: Are there subsets of patients—characterized by certain combinations of tumor size and hormone receptor subtype (HR+/-, HER2+/-)— who could enjoy the same strong survival rates while skipping chemotherapy altogether? And are there others—with different combinations of tumor size and subtype—for whom chemotherapy would significantly increase survival?
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These questions are at the heart of a new study in the Journal of Clinical Oncology (JCO), “Outcomes by Tumor Subtype and Treatment Pattern in Women with Small, Node-Negative Breast Cancer: a Multi-Institutional Study,” published online ahead of print, June 2. The study found that specific breast cancer characteristics—tumor size, grade, and hormone subtype—may help to predict which patients stand to gain additional benefits from chemotherapy and which patients would stand to do well with endocrine therapy alone or without adjuvant systemic therapy.According to study co-author Nancy Lin, MD, the study “can help doctors identify patients who do not need chemo as well as those who could probably benefit from treatment.”
The prospective study used the National Comprehensive Cancer Network Database to look at 4,113 patients who had been treated for breast cancer between 2000 and 2009. Patients were divided by tumor size, tumor subtype, and whether they had received chemotherapy or not. Previous studies have also tried to look at the prognosis of patients with small node negative tumors. However, the current JCO study is the largest to simultaneously stratify patients by hormone receptor and HER2 status, tumor size and treatment.
Upon analyzing the data, patients with breast cancer tumors less than 1cm were found to have a strong prognosis without chemotherapy— Indeed, the five-year survival rate was a robust 90% among all women who did not receive chemotherapy, regardless of tumor subtype.
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Additionally, the researchers found that among women with T1a or T1b cancer who have low grade, HR+ and HER2- tumors, there was an overall risk of distant recurrence lower than 5% whether patients received chemotherapy or not.
However, among women who were HR-, HER2 and not treated with chemotherapy the risk of five-year recurrence was higher—at 7% for those with T1a tumors and at 10% for patients with T1b tumors. Among women with HER2+ HR- tumors, the risk of recurrence in a distant site was also higher than 5%.
According to first author, Ines Vaz-Luis, MD, this research might give doctors greater confidence in advising patients with early-stage breast cancer about the risks and benefits of chemotherapy.
“This current study shows that for women with larger tumors, or who have HR- tumors , we can probably appropriately discuss the use of chemo among those patients. On the other hand, for patients with low-grade, hormone receptor positive tumors [HR+] and HER2- receptors, we can be very confident that the majority of these patients can do well without chemotherapy.”
The need for different chemotherapy
Dr. Vaz-Luis stated that even among the women whose subtypes indicated they might benefit from treatment, traditional forms of chemotherapy may not be necessary.
“This study highlights the need for clinical trials that can identify chemotherapy regimens that give extra benefit to some of these patients, but are less toxic and without the traditional short- and long-term side effects,” said Dr. Vaz-Luis.
A choice for informed patients
According to the study’s co-author, Dr. Lin, the current study—and others like it—will ultimately enable patients to weigh the costs and benefits of chemotherapy and make personal decisions regarding their treatment.
“For one patient, a 2 or 3% absolute benefit in terms of recurrence rate may be important enough that she would choose to take chemotherapy with all of its various side effects,” said Dr. Lin. “And for another patient, that same exact amount of benefit is not enough to warrant taking chemotherapy. We want to make sure our patients have an understanding of how much risk they’re taking on and for what potential benefit.”
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