Phase II Study of Weekly Paclitaxel with Trastuzumab and Pertuzumab in Patients with Human Epidermal Growth Receptor 2 Overexpressing Metastatic Breast Cancer: 5-Year Follow-up

BACKGROUND

Favorable progression-free survival (PFS) and overall survival (OS) results were previously reported on a phase II trial of patients with human epidermal growth receptor 2 (HER2)-positive metastatic breast cancer (MBC), treated with weekly paclitaxel in combination with trastuzumab and pertuzumab in the first- and second-line setting, with a median follow-up of 33 months. Here, we report updated PFS and OS results with more than 2 years of additional follow-up.

MATERIALS AND METHODS

In this phase II study, adult patients with HER2-positive MBC who received no or one prior therapy received intravenous paclitaxel (80 mg/m² weekly) with trastuzumab (8 mg/kg loading dose followed by 6 mg/kg every 3 weeks) and pertuzumab (840 mg loading dose followed by 420 mg every 3 weeks), administered in 21-day cycles. Primary endpoint was 6-month PFS, and secondary endpoints included median PFS and OS.

RESULTS

From January 2011 to December 2013, 69 patients were enrolled: 51 (74%) and 18 (26%) were treated in first- and second-line metastatic settings, respectively. As of August 21, 2017, the median follow-up was 59 months (range, 20-75 months; 67 [97%] patients were evaluable for efficacy). The 6-month PFS was 86% (95% confidence interval [CI] 0.76-0.93). The median PFS was 24.2 months (95% CI 17-35) for the overall population; it was 25.7 months (95% CI 17.0 to not reached) and 20.1 months (95% CI 8.5-33.0) for patients with no and one prior treatment, respectively. The median OS was not reached for the overall group; it was not reached and 39.7 months (95% CI 32.9-66.7) for patients with no and one prior treatment, respectively. Treatment was well tolerated with no additional safety concerns.

CONCLUSION

With a longer follow-up of almost 5 years, combination of weekly paclitaxel, trastuzumab, and pertuzumab remains effective with a favorable median PFS and a median OS not reached.

IMPLICATIONS FOR PRACTICE

The combination of weekly paclitaxel, trastuzumab, and pertuzumab has been endorsed by the National Comprehensive Cancer Network as one of the first-line treatment options in patients with human epidermal growth receptor 2 (HER2)-positive metastatic breast cancer (MBC). However, the long-term safety and efficacy are still unknown. Findings from this phase II study provide favorable preliminary data on the safety and efficacy of trastuzumab and pertuzumab in combination with weekly paclitaxel at 5-year follow-up, and it remains an effective first-line treatment option for patients with HER2-positive MBC.

Early and Locally Advanced Metaplastic Breast Cancer: Presentation and Survival by Receptor Status in Surveillance, Epidemiology, and End Results (SEER) 2010-2014

BACKGROUND

Metaplastic breast cancer (MBC) is a rare disease subtype characterized by an aggressive clinical course. MBC is commonly triple negative (TN), although hormone receptor (HR) positive and human epidermal growth receptor 2 (HER2) positive cases do occur. Previous studies have reported similar outcomes for MBC with regard to HR status. Less is known about outcomes for HER2 positive MBC.

MATERIALS AND METHODS

Surveillance, Epidemiology, and End Results Program data were used to identify women diagnosed 2010-2014 with MBC or invasive ductal carcinoma (IDC). Kaplan-Meier curves estimated overall survival (OS) and multivariate Cox models were fitted. For survival analyses, only first cancers were included, and 2014 diagnoses were excluded to allow for sufficient follow-up.

RESULTS

Our MBC sample included 1,516 women. Relative to women with IDC, women with MBC were more likely to be older (63 vs. 61 years), black (16.0% vs. 11.1%), and present with stage III disease (15.6% vs. 10.8%). HER2 positive and HER2 negative/HR positive MBC tumors represented 5.2% and 23.0% of cases. For MBC overall, 3-year OS was greatest for women with HER2 positive MBC (91.8%), relative to women with TN (75.4%) and HER2 negative/HR positive MBC (77.1%). This difference was more pronounced for stage III MBC, for which 3-year OS was 92.9%, 47.1%, and 42.2% for women with HER2 positive, TN, and HER2 negative/HR positive MBC, respectively. A multivariate Cox model of MBC demonstrated that HER2 positive tumors (relative to TN) were associated with improved survival (hazard ratio = 0.32, 95% confidence interval [CI] 0.13-0.79). In a second Cox model of exclusively HER2 positive tumors, OS did not differ between MBC and IDC disease subtypes (hazard ratio = 1.16, 95% CI 0.48-2.81).

CONCLUSION

In this contemporary, population-based study of women with MBC, HER2 but not HR status was associated with improved survival. Survival was similar between HER2 positive MBC and HER2 positive IDC. This suggests HER2 positive MBC is responsive to HER2-directed therapy, a finding that may offer insights for additional therapeutic approaches to MBC.

IMPLICATIONS FOR PRACTICE

This population-based study reports recent outcomes, by receptor status, for women with metaplastic breast cancer. Survival in metaplastic breast cancer is not impacted by hormone receptor status. To the authors' knowledge, this is the first report indicating that women with human epidermal growth receptor 2 (HER2) positive metaplastic breast cancer have survival superior to women with HER2 negative metaplastic breast cancer and survival similar to women with HER2 positive invasive ductal carcinoma. This information can be used for counseling patients diagnosed with metaplastic breast cancer. Further understanding of HER2 positive metaplastic breast cancer could offer insights for the development of therapeutic approaches to metaplastic breast cancer more broadly.

First-Line Palliative HER2-Targeted Therapy in HER2-Positive Metastatic Breast Cancer Is Less Effective After Previous Adjuvant Trastuzumab-Based Therapy

BACKGROUND

Survival of patients with human epidermal growth receptor 2 (HER2)-positive metastatic breast cancer (MBC) has improved dramatically since trastuzumab has become available, although the disease eventually progresses in most patients. This study investigates the outcome (overall survival [OS] and time to next treatment [TNT]) in MBC patients pretreated with trastuzumab in the adjuvant setting (TP-group) compared with trastuzumab-naïve patients (TN-group) in order to investigate the possibility of trastuzumab resistance.

PATIENTS AND METHODS

Patients treated with first-line HER2-targeted-containing chemotherapy were eligible for the study. A power analysis was performed to estimate the minimum size of the TP-group. OS and TNT were estimated using Kaplan-Meier curves and multivariable Cox proportional hazards models.

RESULTS

Between January 1, 2000, and June 1, 2014, 469 patients were included, of whom 82 were in the TP-group and 387 were in the TN-group. Median OS and TNT were significantly worse in the TP-group compared with the TN-group (17 vs. 30 months, adjusted hazard ratio [HR] 1.84 [1.15-2.96], p = .01 and 7 vs. 13 months, adjusted HR 1.65 [1.06-2.58], p = .03) after adjustment for age, year of diagnosis, disease-free interval, hormone receptor status, metastatic site, and cytotoxic regimens.

CONCLUSION

First-line trastuzumab-containing treatment regimens are less effective in patients with failure of adjuvant trastuzumab compared with trastuzumab-naïve patients and might be due to trastuzumab resistance. The impact of trastuzumab resistance on the response on dual HER2 blockade with trastuzumab and pertuzumab and how resistance mechanisms can be used in the optimization of HER2-targeted treatment lines need further investigation.

IMPLICATIONS FOR PRACTICE

Evidence on the efficacy of palliative trastuzumab-based therapy after failure of trastuzumab in the adjuvant setting is limited because of a minority of patients treated with adjuvant trastuzumab in clinical trials. In this study, less clinical benefit of palliative trastuzumab-based therapy was observed in patients relapsing after adjuvant trastuzumab compared with no adjuvant trastuzumab treatment. Subgroup analyses and multivariable analyses revealed that this was independent of possible confounding factors, including adjuvant taxane-treatment. This might suggest a clinically meaningful impaired efficacy of trastuzumab after previous, in this case adjuvant, trastuzumab therapy. These results could have implications for treatment decision-making after short progression-free intervals on trastuzumab-containing regimens in the palliative setting.