Table 6. Standard Adjuvant Chemotherapy Regimens for Stage I, II, IIIA, and Operable IIICHER2/neuNon-Overexpressing Breast Cancer continued...
Lapatinib is a small molecule tyrosine kinase inhibitor that is capable of dual-receptor inhibition of both EGFR and HER2. In the Adjuvant Lapatinib and/or Trastuzumab Treatment Optimization trial (ALTTO [NCT00553358]), the role of lapatinib (in combination with, in sequence to, in comparison to, or as an alternative to trastuzumab) in the adjuvant setting is being investigated. In phase I/II studies as a single agent, lapatinib has resulted in objective responses between 4.3% and 7.8% in ER2-positive patients who had progressed on multiple trastuzumab-containing regimens with a substantial number having stable disease at 4 months (34%–41%) and 6 months (18%–21%). In a phase III trial (GSK-EGF100151), lapatinib plus capecitabine was superior to capecitabine alone in women with HER2-positive advanced breast cancer that has progressed after treatment with regimens that included an anthracycline, a taxane, and trastuzumab. The hazard ratio for time to progression was 0.49 (95% CI, 0.34–0.71; P < .001), with 49 events in the combination-therapy group and 72 events in the monotherapy group. The median time to progression was 8.4 months in the combination-therapy group as compared with 4.4 months in the monotherapy group.
The combination of lapatinib and trastuzumab in the ALTTO trial is further supported by a demonstration that lapatinib combined with trastuzumab confers a significantly improved progression-free survival in patients with metastatic breast cancer who experience progression on prior trastuzumab-containing treatment when compared to lapatinib alone.
In September 2011, the ALTTO trial was amended to discontinue the lapatinib alone arm of the trial. The Independent Data Monitoring Committee of the trial determined that the patients assigned to the lapatinib alone arm were not likely to do as well as the patients assigned to the trastuzumab alone control arm. Final results of this trial are pending.
Cardiac toxic effects with adjuvant trastuzumab
In the HERA (BIG-01-01) trial, severe congestive heart failure (CHF NYHA class III–IV) occurred in 0.6% of patients treated with trastuzumab. Symptomatic CHF occurred in 1.7% and 0.06% of patients in the trastuzumab and observation arms, respectively. Fifty-one patients experienced a confirmed left ventricular ejection fraction (LVEF) decrease (defined as an EF decrease of >10 points from baseline to an LVEF <50%) with trastuzumab, which recovered or stabilized within 3 to 6 weeks of initial treatment in 86% of cases. In the NSABP B-31 (NCT00004067) trial, 31 of 850 patients in the trastuzumab arm had confirmed symptomatic cardiac events, compared with 5 of 814 patients in the control arm. The 3-year cumulative incidence of cardiac events for trastuzumab-treated patients was 4.1%, compared with 0.8% of patients in the control arm (95% CI, 1.7%–4.9%). Asymptomatic decline in LVEF (defined by >10% decline or to 55%) occurred in 17% of patients in the trastuzumab arm (95% CI, 15%–20%) and 34% of patients in the control arm (95%CI, 31%–38%), with a HR, 2.1 (95%CI, 1.7–2.6; P < .001). In the NCCTG-N9831 trial, 39 cardiac events were reported in the three arms over a 3-year period. The 3-year cumulative incidence of cardiac events in arm A was 0.35% (no trastuzumab), arm B, 3.5% (trastuzumab following paclitaxel) and arm C, 2.5% (trastuzumab concomitant with paclitaxel).