TBCRC 008: early change in 18F-FDG uptake on PET predicts response to preoperative systemic therapy in human epidermal growth factor receptor 2-negative primary operable breast cancer.
UNLABELLED
Epigenetic modifiers, including the histone deacetylase inhibitor vorinostat, may sensitize tumors to chemotherapy and enhance outcomes. We conducted a multicenter randomized phase II neoadjuvant trial of carboplatin and nanoparticle albumin-bound paclitaxel (CP) with vorinostat or placebo in women with stage II/III, human epidermal growth factor receptor 2 (HER2)-negative breast cancer, in which we also examined whether change in maximum standardized uptake values corrected for lean body mass (SUL(max)) on (18)F-FDG PET predicted pathologic complete response (pCR) in breast and axillary lymph nodes.


METHODS
Participants were randomly assigned to 12 wk of preoperative carboplatin (area under the curve of 2, weekly) and nab-paclitaxel (100 mg/m(2) weekly) with vorinostat (400 mg orally daily, days 1-3 of every 7-d period) or placebo. All patients underwent (18)F-FDG PET and research biopsy at baseline and on cycle 1 day 15. The primary endpoint was the pCR rate. Secondary objectives included correlation of change in tumor SUL(max) on (18)F-FDG PET by cycle 1 day 15 with pCR and correlation of baseline and change in Ki-67 with pCR.


RESULTS
In an intent-to-treat analysis (n = 62), overall pCR was 27.4% (vorinostat, 25.8%; placebo, 29.0%). In a pooled analysis (n = 59), we observed a significant difference in median change in SUL(max) 15 d after initiating preoperative therapy between those achieving pCR versus not (percentage reduction, 63.0% vs. 32.9%; P = 0.003). Patients with 50% or greater reduction in SUL(max) were more likely to achieve pCR, which remained statistically significant in multivariable analysis including estrogen receptor status (odds ratio, 5.1; 95% confidence interval, 1.3-22.7; P = 0.023). Differences in baseline and change in Ki-67 were not significantly different between those achieving pCR versus not.


CONCLUSION
Preoperative CP with vorinostat or placebo is associated with similar pCR rates. Early change in SUL(max) on (18)F-FDG PET 15 d after the initiation of preoperative therapy has potential in predicting pCR in patients with HER2-negative breast cancer. Future studies will further test (18)F-FDG PET as a potential treatment-selection biomarker.