Are there high-risk subgroups for isolated locoregional failure in patients who had T1/2 breast cancer with one to three positive lymph nodes and received mastectomy without radiotherapy?

To define the factors associated with increased risk of isolated locoregional failure that may justify postmastectomy radiotherapy in patients with T1/2 breast cancer and 1–3 positive lymph nodes. Between 1990 and 2002, 248 patients who had pT1–2 breast cancer and 1–3 positive lymph nodes were treated with mastectomy without radiotherapy (age 32–84, median 54). Median follow-up time was 82 months (range 2–189 months). For all patients, the 8-year isolated locoregional failure-free rate was 95 %. In univariate analysis, hormone receptor status and administration of hormone therapy were statistically significant factors, and vascular invasion was the borderline significant factor for isolated locoregional failure-free rates (P = 0.0377, 0.0181, and 0.0555, respectively). The 8-year isolated locoregional failure-free rates were 98 % for patients with positive hormone receptor status and 90 % for patients with negative hormone receptor status, 97 % for patients who received hormone therapy and 89 % for patients who did not receive hormone therapy, 92 % for patients with vascular invasion and 97 % for patients without vascular invasion. In multivariate analysis for hormone receptor status and vascular invasion, the former was statistically significant (P = 0.0491) and the latter was borderline significant (P = 0.0664). When patients had both negative hormone receptor and positive vascular invasion status, the 8-year isolated locoregional failure-free rates decreased to 83 %. With regard to patients who had pT1/2 breast cancer and 1–3 positive lymph nodes, isolated locoregional failure was not common in general; however, patients who had both negative hormone receptor status and vascular invasion were comparatively high-risk patients for isolated locoregional failure.