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

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 (SULmax) on ¹⁸F-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/m2 weekly) with vorinostat (400 mg orally daily, days 1-3 of every 7-d period) or placebo. All patients underwent ¹⁸F-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 SULmax on ¹⁸F-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 5 62), overall pCR was 27.4% (vorinostat, 25.8%; placebo, 29.0%). In a pooled analysis (n 5 59), we observed a significant difference in median change in SULmax 15 d after initiating preoperative therapy between those achieving pCR versus not (percentage reduction, 63.0% vs. 32.9%; P 5 0.003). Patients with 50% or greater reduction in SULmax 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 5 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 SULmax on ¹⁸FFDG 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 ¹⁸F-FDG PET as a potential treatmentselection biomarker.