March 19, 2014
GLASGOW, Scotland — For women with early breast cancer who undergo mastectomy and axillary dissection, radiotherapy is recommended for those who are found to have 4 or more positive lymph nodes, but is not usually given to women who are found to be node-negative.
However, for the women who fall into the gray area in between, who are found to have 1 to 3 positive axillary nodes, there has been insufficient evidence to make a recommendation one way or another.
Now there are data to show that radiation is also beneficial in this group.
The results were presented March 19 here at the 9th European Breast Cancer Conference, and published onlinesimultaneously in the Lancet.
The finding comes from a meta-analysis of individual data for a total of 8135 women participating in clinical trials who were followed for an average of 11 years; 1314 of these women were found to have 1 to 3 positive nodes.
The results for this subgroup of women showed that postmastectomy radiotherapy significantly reduced both recurrence and breast cancer mortality, even when systemic therapy was given.
The meta-analysis was conducted by the Early Breast Cancer Trialists' Collaborative Group (EBCTCG), and presented at the meeting by Paul McGale, PhD, senior statistician at the University of Oxford, United Kingdom.
In women who had 1 to 3 positive nodes, postmastectomy radiotherapy reduced the recurrence rate by 32% and reduced the breast cancer mortality rate by 20%. The benefit was similar whether women had only 1 positive node or whether they had 2 or 3 positive nodes.
"Giving radiotherapy to these women led to nearly 12 fewer recurrences per 100 women after 10 years and 8 fewer deaths per 100 women after 20 years," Dr. McGale said in a statement.
The results from the meta-analysis also confirmed previous findings of benefit from radiotherapy for women with 4 or more positive nodes, and the lack of benefit for women with node-negative disease.
For women with 4 or more positive nodes (n = 1772), the meta-analysis showed that radiotherapy reduced overall recurrence by 21% and breast cancer mortality by 13%. In other words, radiotherapy for these women led to 9 fewer recurrences per 100 women after 10 years, and 9 fewer breast cancer deaths per 100 women after 20 years.
These results are statistically similar to those found for the subgroup of women with 1 to 3 positive nodes, commented coauthor Carolyn Taylor, FRCR, a clinical oncologist at Oxford University Hospitals and a clinical research fellow at the University of Oxford. She noted that the women with more positive nodes would be at a higher risk for recurrence, but the proportional reduction in risk was similar to that seen in women with fewer positive nodes.
In this meta-analysis, a total of 5821 women had node-positive disease; of these, 3131 (54%) had axillary dissection (defined as removal of axillary lymph nodes in at least levels I and II) and 2541 (44%) had axillary sampling (less extensive axillary surgery), while for 149 (2%), the extent of axillary surgery was unknown.
The meta-analysis also confirmed that there was no significant benefit from radiotherapy for women who were found to be node-negative (n = 700). "There was no evidence that radiotherapy provided any benefit" in this group, the researchers write.
Benefit Seen Regardless of Chemotherapy
"Another result from our study is that the proportional benefits of radiotherapy were similar in women regardless of whether or not they had also received chemotherapy or hormonal therapy," Dr. McGale said. The most common chemotherapy used in the trials was cyclophosphamide, methotrexate, and fluorouracil, and the most common hormonal therapy used was tamoxifen
"This is important because most women today receive these therapies. Our results suggest that women being treated today are likely also to benefit from radiotherapy if they have any positive lymph nodes," he added.
The meta-analysis included trials that were conducted between 1964 and 1986.
"Since the time when the women in these trials were randomized, there have been advances in radiotherapy and also in breast screening, surgery, lymph node staging, and systemic therapy," Dr. McGale commented. "So the absolute benefits from postmastectomy radiotherapy today may be smaller than those we have reported here. But the proportional benefits from radiotherapy are likely to be at least as big."