Background: Discordance rates of hormone receptor (HR) and human epidermal growth factor-2 (HER2) status between primary and recurrent breast cancer were reported to be in the wide range of 10-40 %, although its prognostic relevance remains to be elucidated.
Methods: Fifty-five breast cancer patients had biopsies or resections of recurrent lesions. Pathological assessments of the HR and HER2 status of primary and recurrent lesions were performed in a single laboratory at Keio University Hospital. Tumors were classified as luminal (HR+ and HER2-), luminal/HER2 (HR+ and HER2+), HER2 (HR- and HER2+), or triple negative (HR- and HER2-).
Results: Discordance rates in estrogen receptor (ER), progesterone receptor (PgR) and HER2 status between primary tumors and recurrent lesions were 16.4, 30.9 and 10.2 %, respectively. Overall, 14 patients (25.5 %) changed subtypes at recurrent lesions. Patients with a gain in ER and PgR status had a significantly longer disease-free interval compared with the corresponding concordant-negative patients (ER: 99.0 vs. 18.5 months, p = 0.037, PgR: 141.0 vs. 24.4 months, p = 0.011). Patients with a loss of HER2 status experienced a trend toward shorter time to progression, compared with patients who maintained HER2 positivity (4.0 vs. 18.4 months, p = 0.051).
Conclusions: Discordance in receptor status between primary and recurrent breast cancers were seen in 10-30 %. A gain in HR status was significantly associated with better prognosis.