Abstract P1-14-07: Neoadjuvant chemotherapy and pathologic complete response in relation to the clinical response, results from a phase III study (INTENS) of the Dutch breast cancer trialists' group (BOOG)

Background Taxanes have an established role as (neo-)adjuvant treatment of breast cancer. In the present study, we compared 4 AC–4 T with 6 cycles of TAC in the neoadjuvant setting (A = adriamycine, C = cyclophosphamide, T = docetaxel). Previously, we reported that AC-T resulted in a trend for improved outcome (odds ratio of the pathologic complete response (pCR) of the breast 1.60; 95% CI 0.90–3.21). This present analysis focuses on the results of treatment and pCR in the breast in relation to clinical response.

Methods Women with breast cancer, eligible for neoadjuvant chemotherapy, were randomized to AC (60/600 mg/m2 q3wk × 4 cycles) followed by T (100 mg/m2 q3wk × 4 cycles), or to TAC (75/50/500 mg/m2 q3wk × 6 cycles). If indicated, trastuzumab and/or endocrine therapy were given as adjuvant treatment. Physical examination, ultrasound of breast and axillary lymph nodes and breast MRI were performed before start of chemotherapy, halfway and after completion of chemotherapy. These results together determined the clinical response (c) halfway and after chemotherapy. The clinical response was classified as cCR (complete response), cPR (partial response), cSD (stable disease) or cPD (progressive disease). pCR was defined as no invasive tumor in the breast at surgery.

Results In total, 201 patients (n = 100 AC-T, n=101 TAC) were enrolled between February 2006 and April 2009. Baseline characteristics (AC-T/TAC) were well balanced. The clinical overall response rate (cCR and cPR) to 4 AC was comparable to that seen with 3 cycles TAC (48% versus 54%). Also, the clinical overall response rate to 8 AC-T was comparable to that seen with 6 TAC (81% versus 72%). In the AC-T arm, a third of the patients with cSD halfway reached a cCR or cPR after 8 cycles, whereas in the TAC arm only 18% of patients with cSD halfway reached a cCR or cPR after chemotherapy. In the sequential AC-T arm, 16% of the patients with cSD halfway reached a pCR after switching to docetaxel monotherapy. In contrast, in the TAC arm cSD halfway rarely resulted in pCR after 6 cycles. Patients with a cCR after chemotherapy had a pCR in 58% and 49% of cases, respectively. For patients with cPR these rates were 29% and 18%, respectively, and for patients with cSD 6% and 0%, respectively.

Conclusion: Clinical response rates are related to pCR rates. The meaning of cSD halfway should be differently interpreted for sequential versus concurrent chemotherapy. In concurrent chemotherapy schedules, a switch to a non-cross resistant drug may be worthwhile. Early clinical response may be used as a decision aid during neoadjuvant chemotherapy to recognize non-responders.

Support: Unrestricted grants from sanofi-aventis NL BV and Amgen BV. Dutch breast cancer trialists' group (BOOG).

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-14-07.