High recurrence risk and use of adjuvant trastuzumab in patients with small, HER2-positive, node-negative breast cancers

Five randomized trials of adjuvant trastuzumab have reported significant improvements in recurrence-free survival (RFS) and overall survival. However, patients with node-negative tumors 1 cm or smaller were excluded from these trials. We assessed the recurrence risk and benefit of adjuvant therapy in such patients with small tumors.

We identified patients with node-negative breast tumors 1 cm or smaller between April 2003 and December 2007. Patients were categorized according to HER2 status and pathological tumor size (pT <5 mm vs. 5-10 mm), hormone receptor (HR) status and adjuvant chemotherapy. The primary endpoint was RFS.

Of 267 patients included in the analysis, 42 had HER2-positive tumors. The median follow-up was 4.3 years. RFS was worse in patients with HER2-positive tumors than HER2-negative tumors (90.5 vs. 97.7% at 5 years; P = 0.031). In the group with HER2-positive tumors, there were no recurrences in patients with pT<5 mm, but 4 recurrences in those with pT 5-10 mm. RFS was worse in patients with pT 5-10 mm than pT <5 mm (79.0 vs. 100%, P = 0.025). Furthermore 3 recurrences occurred in patients without adjuvant trastuzumab, and 1 recurrence occurred as soon as adjuvant trastuzumab was finished. Our results appear to establish the efficacy of adjuvant trastuzumab therapy. HR status and use of adjuvant chemotherapy were not significantly associated with RFS.

Patients with HER2-positive, node-negative breast tumors 1 cm or smaller (especially 0.5-1.0 cm) have a significant recurrence risk and the decision to employ adjuvant trastuzumab therapy should be discussed with patients based on our results and those of other studies.