6 versus 12 months of adjuvant trastuzumab in HER2+ early breast cancer: A systematic review and meta-analysis

BACKGROUND

Adjuvant trastuzumab improves survival outcomes of human epidermal receptor 2 positive early breast cancer patients. Currently, administration of 12 months adjuvant trastuzumab is the standard therapy. However, whether 6 months treatment is non-inferior to the standard 12 months treatment remains controversial.

METHODS

Relevant records were searched in PubMed, Cochrane Library, Web of Science, and EMBASE through Jan 14, 2020. Pooled hazard ratios (HRs) and 95% confidence intervals (CIs) for disease-free survival (DFS) and overall survival (OS) were meta-analyzed. The primary endpoint was DFS with a non-inferiority hazard margin of 1.2 and the second was OS with 1.43.

RESULTS

Three randomized clinical studies met the inclusion criteria, including 3974 patients in 6 months group and 3976 in 12 months group. HR for DFS was 1.18 (95% CI 0.97-1.44, P = .09), with the non-inferiority margin comprised in the 95% CI. HR for OS was 1.14 (95% CI 0.98-1.32, P= .08), whereas the upper limit of 95% CI did not exceed the non-inferiority hazard margin.

CONCLUSION

Our analysis failed to show that 6 months treatment was non-inferior to 12 months treatment in improving the DFS. Although the non-inferiority of the 6-month adjuvant trastuzumab treatment was found for OS, considering that breast cancer patients should receive additional systematic therapies when disease progression or relapse happens, we suggest that 12 months adjuvant trastuzumab treatment should remain the standard therapeutic strategy for patients with early human epidermal receptor 2 positive breast cancer.

Nine weeks versus 1 year adjuvant trastuzumab in patients with early breast cancer: an observational study by the Turkish Oncology Group (TOG)

BACKGROUND

Optimal duration of adjuvant trastuzumab in early breast cancer is an unresolved issue. In this observational study, we compared the outcome of 9 weeks and 1 year adjuvant trastuzumab in early breast cancer patients in Turkey.

METHODS

Records of 680 patients with HER2-positive early breast cancer who received adjuvant trastuzumab plus chemotherapy were obtained and patients were followed up to compare the disease-free survival (DFS) outcome of 9 weeks versus 1 year trastuzumab.

RESULTS

Nine weeks and 1 year trastuzumab was given to 202 (29.7 %) and 478 (70.3 %) patients, respectively. There was a significantly lower rate of patients with negative lymph nodes in the 9-week trastuzumab group. At median 3 years of follow-up from the date of starting trastuzumab, the DFS rates were 88.6 and 85.6 %, respectively (p = 0.670). When adjusted for all the prognostic factors that were significant on univariate analysis, again there was no significant difference in DFS between the groups (HR 0.675; 95 % CI 0.370-1.231; p = 0.200). Cardiac toxicity defined as a ≥15 % decrease in LVEF was significantly higher in the 1-year trastuzumab group (1.88 % versus none for 1-year and 9-week trastuzumab groups, respectively; p = 0.050).

CONCLUSION

The results of this observational study suggest that DFS outcome of 9 weeks of adjuvant trastuzumab may be comparable to 1 year adjuvant trastuzumab: this needs confirmation by randomized trials.