Phase III trial of nonpegylated liposomal doxorubicin in combination with trastuzumab and paclitaxel in HER2-positive metastatic breast cancer

One of our major findings is that nonpegylated liposomal doxorubicin (NPLD; Myocet((TM))), an anthracycline with an optimized cardiac safety profile, can be safely combined with trastuzumab: the frequency of cardiac events was extremely low and similar in both arms, with no cardiac deaths registered in the trial. Our study opens a potential new avenue for clinical research.Nonpegylated liposomal doxorubicin liposomal doxorubicin, (Myocet (TM); Sopherion Therapeutics, Inc Canada, and Cephalon, Europe) (NPLD; Myocet((R))) in combination with trastuzumabHerceptin((R)) (Hoffmann-La Roche) has shown promising activity and cardiac safety. We conducted a randomized phase III trial of first-line NPLD plus trastuzumab and paclitaxel (Pharmachemie B.V.) (MTP) versus trastuzumab plus paclitaxel (TP) in patients with human epidermal growth factor 2 receptor (HER2)-positive metastatic breast cancer. Patients were randomly assigned to NPLD (M, 50 mg/m(2) every 3 weeks for six cycles), trastuzumab (T, 4 mg/kg loading dose followed by 2 mg/kg weekly), and paclitaxel (P, 80 mg/m(2) weekly) or T + P at the same doses until progression or toxicity. The primary efficacy outcome was progression-free survival (PFS). One hundred and eighty-one patients were allocated to receive MTP, and 183 to TP. Median PFS was 16.1 and 14.5 months with MTP and TP, respectively [hazard ratio (HR) 0.84; two-sided P = 0.174]. In patients with estrogen receptor (ER)- and progesterone receptor (PR)-negative tumors, PFS was 20.7 and 14.0 months, respectively [HR 0.68; 95% confidence interval (CI) 0.47-0.99]. Median overall survival (OS) was 33.6 and 28.9 months with MTP and TP, respectively (HR 0.79; two-sided P = 0.083). In ER- and PR-negative tumors, OS was 38.2 and 27.9 months, respectively (HR 0.63; 95% CI 0.42-0.93). The frequency of adverse events was higher with MTP, but there was no significant difference in cardiac toxicity between treatment arms. The trial failed to demonstrate a significant clinical improvement with the addition of M to TP regimen. The clinical benefit observed in an exploratory analysis in the ER- and PR-negative population deserves consideration for further clinical trials.