Prognostic significance of stromal TILs in metastatic BC has been suggested in various BC subtypes. However, predictive role of stromal TILs for the efficacy of trastuzumab has not been established in patients with HER2-positive BC. This study was performed to evaluate whether the stromal TILs are associated with the efficacy of trastuzumab in patients with metastatic HER2-positve BC.
Between June 2006 and March 2013, a total of 60 women with recurrent or metastatic HER2-positive BC treated with trastuzumab were included. Trastuzumab was administered either as single agent or combination with taxanes. Stromal TILs were assessed using immunohistochemistry in surgical specimen (n = 39, 65%) and biopsy specimen of metastatic lesion (n = 21, 35%). Primary endpoint of this study was progression-free survival (PFS), and secondary endpoints were response rate and overall survival (OS).
Median age was 54 year old (range, 36-76), and all patients had invasive ductal carcinoma. Hormone receptor was positive in 34 patients (57%) and 18 patients (30%) initially presented with metastatic disease. Nine patients (15%) received cytotoxic chemotherapy without trastuzumab before the administration of trastuzumab. Patients were grouped according to the TILs (< 10% [n = 50] and >10% [n = 10]), and there was no significant difference in age (p = 0.68), histologic grade (p = 1.00), metastatic sites (p > 0.05), and number of lines of chemotherapy before the administration of Herceptin (p = 0.33) among patients with low and high stromal TILs. High TILs were more common in hormone receptor-negative tumor compared with –positive tumor (31% vs 6%; p = 0.02). Median PFS in patients with high stromal TILs were longer than that in those with low TILs (22.0 months [95% CI, 9.6-34.4] vs 14.0 months [95% CI, 9.6-18.4]). However, this was marginally significant (p = 0.057). There was no difference in response rates (p = 0.43) and OS (p = 0.94) according to the stromal TILs.
This study suggests that the stromal TILs might be associated with the clinical outcomes of HER2-targeted therapy in patients with metastatic HER2-positive BC. Further validation is necessary.
Clinical trial identification
All authors have declared no conflicts of interest.