HER‐2 status discrepancy between primary breast cancer and metastatic sites. Impact on target therapy

In this prospective study, we determined HER-2 status in primary breast invasive carcinomas and in the paired lymph node metastases (synchronous and metachronous), local recurrence and metachronous distant metastases, to verify the percentage of discordant cases. HercepTest and Fluorescence in situ hybridization (FISH) were used to determine HER-2 status on 119 cases of primary infiltrating breast carcinoma and paired metastases (45 cases with synchronous lymph node metastases, 9 cases with metachronous lymph node metastases, 30 cases with local recurrence, and 35 cases with metachronous distant metastases). A therapeutically significant HER-2 status discordance was demonstrated between primary carcinoma and synchronous lymph node metastases (6.7%), local recurrence (13.3%) and metachronous distant metastases (28.6%). In the first comparison, there was a normal HER-2 status in primary tumours and HER-2 amplification in paired metastases, in the second the opposite phenomenon was present, and both types of discordance were evident in the third comparison. Considering the cases of local recurrences and metachronous distant metastases all together, 14 out of 65 cases (21.5%) showed a therapeutically significant discordance of HER-2 status between the primary tumour and the paired metachronous recurrence or metastasis (p < 0.001), the 15.4% of cases showing normal HER-2 status in the primary tumour and HER-2 amplification in the neoplastic relapse. For the treatment of metastatic patients, the evaluation of HER-2 status should be performed in neoplastic tissue from metastatic site, whenever possible. This procedure could be also suggested in the patients that are metastatic at the time of diagnosis.