The following article is part of conference coverage from the 17th St. Gallen International Breast Cancer Symposium, which is being held virtually from March 7-21, 2021. The team at Cancer Therapy Advisor will be reporting on the latest research conducted by leading experts in breast cancer. Check back for more from the 17th St. Gallen International Breast Cancer Symposium.

Treatment with pertuzumab-based dual HER2 blockade was found to be beneficial among patients with metastatic breast cancer previously treated with anti-HER2 therapy, according to the results of a meta-analysis presented at the St. Gallen International Breast Cancer Conference.

These results indicate that dual blockade with a pertuzumab-based regimen “should be recommended as a standard first-line treatment for HER2-positive metastatic breast cancer patients who relapse post-adjuvant/neoadjuvant anti-HER2 treatment,” according to Shanshan Chen, MD, of the National Clinical Research Center for Cancer/Cancer Hospital, China, and colleagues.

According to the poster presentation, dual HER2 blockade is recommended as standard first-line therapy in patients with HER2-positive metastatic breast cancer, but its use in the treatment of patients with previous anti-HER2 therapy is controversial.  Chen and colleagues therefore conducted a systematic review of randomized controlled trials and cohort studies assessing dual HER2 blockade with pertuzumab and trastuzumab plus chemotherapy. The following clinical trials were included: CLEOPATRA ( Identifier:  NCT00567190), PERTAIN ( Identifier:  NCT01491737), PHEREXA ( Identifier: NCT01026142), MARIANNE ( Identifier:  NCT01120184), and PRECIOUS ( Identifier: NCT02514681).

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The hazard ratio for progression-free survival comparing dual vs single HER2 blockade-containing regimens in pretreated patients was 0.79 (95% CI, 0.69-0.92) overall. Looking at each trial, the HRs were 0.62, 0.83, 0.68, 0.89, 0.75, and 0.79, for CLEOPATRA, PHEREXA, PERTAIN, MARIANNE, and PRECIOUS, respectively.

For overall survival, the HR was 0.76 (95% CI, 0.63-0.93). HR for overall survival was only calculated in CLEOPATRA (0.86), PHEREXA (0.76), and PRECIOUS (0.71).

Based on these results, “a pertuzumab-based dual HER2 blockade regimen could be a reasonable option for patients that experience disease progression during or after trastuzumab-based therapy,” the researchers concluded.

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Chen S, Sun X, Liu B, Ma F. The efficacy and safety of dual HER2 blockade with a pertuzumab-based regimen for metastatic breast cancer patients previously exposed to an anti-HER2 agent: a systematic review and meta-analysis. Poster presentation at St. Gallen International Breast Cancer Conference; March 17-21, 2021.  Abstract P059.