PHILADELPHIAAt the 48th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO), researchers presented two analyses showing that in node-positive breast cancer, the nodal ratiothe number of positive nodes divided by the number of nodes resectedis superior to the absolute nodal count as a clinical predictor of treatment outcomes. Further, using nodal ratios, M.D. Anderson researchers were able to partially reconcile differences in locoregional recurrence rates in trials of postoperative radiation therapy in mastectomy patients. [See also article on page 45 concerning the benefit of radiotherapy after mastectomy.]
Wendy A. Woodward, MD, PhD, of The University of Texas M.D. Anderson Cancer Center (abstract 10), reexamined data from the British Columbia Randomized Radiation Trial, conducted in patients with node-positive breast cancer treated with mastectomy and adjuvant chemotherapy. This study demonstrated improved overall survival in patients with positive nodes who also received postoperative radiation therapy. Similar results were seen when patients were stratified by the number of involved nodes.
Somewhat surprisingly, these results did not lead to universal adoption of radiotherapy, "partially because locoregional recurrence rates in patients with 1 to 3 positive nodes were higher than the rates seen in some North American series," Dr. Woodward said. The apparently higher rate of locoregional failure in women classified as low risk in the British Columbia study may have been an artifact of the relatively small number of nodes resected.
The researchers compared patients from the no-radiation arm of the British Columbia trial (123 women, all premenopausal) with similar patients (505 women 50 years of age or younger) who received mastectomy and chemotherapy but no radiation as part of M.D. Anderson Cancer Center clinical trials.
The median number of nodes dissected was 11 in the British Columbia patients and 17 in the M.D. Anderson patients (P < .0001). Other clinical factors such as T stage, nodal status, estrogen-receptor status, and nodal ratio did not differ between the two datasets.
At 15 years, locoregional recurrence rates were significantly different between the two datasets in risk groups classified by the number of positive nodes: 26% (British Columbia) vs 11% (M.D. Anderson) in women with 1 to 3 positive nodes, and 61% vs 30%, respectively, in women with 4 to 9 positive nodes.
However, when patients were reclassified according to nodal ratio, there were no significant differences between the two datasets in the lowest risk cohorts. Nodal ratios of 0% to 10% were associated with locoregional recurrence rates of 15% (British Columbia) and 9% (M.D. Anderson), and nodal ratios of 10% to 20% with locoregional recurrence rates of 25% and 18%, respectively.