Effect of HER2 status on risk of recurrence in women with small, node-negative breast tumours

Background: Adjuvant trastuzumab for small, node-negative, human epidermal growth factor receptor 2 (HER2)-positive breast cancer remains controversial. The purpose of this study was to investigate the risk of recurrence in women with pathological tumour node (pTN) T1 N0 tumours. Methods: Patients with pT1 N0 breast cancer diagnosed at the National Kyushu Cancer Centre between 2001 and 2007 were reviewed. Patients were categorized according to HER2 status. Results: Four hundred and fifty-four patients who had pT1 N0 tumours, and had not received adjuvant trastuzumab, were identified. The HER2-negative and -positive groups comprised 376 and 78 patients (17.2 per cent) respectively. At a median follow-up of 46.3 months, there were 18 recurrences. The 5-year relapse-free survival (RFS) rates were 97.2 and 88 per cent in the HER2-negative and -positive groups respectively (P < 0.001). Multivariable analysis identified HER2-positive tumour as an independent predictor of RFS in patients with pT1 N0 tumours (hazard ratio 6.65, 95 per cent confidence interval 2.53 to 17.49; P < 0.001). Conclusion: Women with pT1 N0 HER2-positive breast cancer have a high risk of recurrence.