Compared with physician’s choice of treatment, etirinotecan pegol, a long-acting topoisomerase-I inhibitor, did not significantly improve overall survival in patients with heavily pre-treated advanced breast cancer, a new study published online ahead of print in the journal The Lancet Oncology has shown.1

Because novel options to prolong survival in patients with heavily pre-treated breast cancer are limited, researchers sought to evaluate whether etirinotecan pegol, a chemotherapeutic agent that prolongs exposure to SN38 while also reducing the toxicity of it, is superior to available treatments for patients with previously treated, locally recurrent or metastatic breast cancer.

SN38 is the active metabolite of irinotecan, which is mainly used to treat colon cancer, but is known for causing severe and clinically significant diarrhea and immunosuppression.

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For the multicenter, open-label, phase 3 BEACON study, researchers enrolled 852 patients with locally recurrent or metastatic breast cancer who were previously treated with an anthracycline, a taxane, and capecitabine, as well as 2 to 5 previous regimens for advanced disease.

Participants were randomly assigned 1:1 to receive etirinotecan pegol 145 mg/m2 intravenously over 90 minutes every 3 weeks or single-drug treatment of physician’s choice.

Results showed that median overall survival was 12.4 months (95% CI: 11.0–13.6) with etirinotecan pegol compared with 10.3 months (95% CI: 9.0–11.3) with treatment of physician’s choice (HR = 0.87; 95% CI: 0.75–1.02; P=.084), suggesting no significant difference between the 2 treatment arms.

In regard to safety, significantly fewer patients treated with etirinotecan pegol experienced grade 3 or higher adverse events compared with those in the treatment of physician’s choice group (48% vs 63%; P<.0001).

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The most common adverse events associated with etirinotecan pegol were diarrhea, neutropenia, and peripheral neuropathy. Of note, 3 patients in the etirinotecan pegol group and 2 in the treatment of physician’s choice group died as a result of treatment-related adverse events.

“In view of the frequency of cross-resistance and overlapping toxicities noted with many available drugs and the need for effective drugs in highly refractory disease, etirinotecan pegol may warrant further research in some subgroups of patients,” the authors concluded.


  1. Perez EA, Awada A, O’Shaughnessy J, et al. Etirinotecan pegol (NKTR-102) versus treatment of physician’s choice in women with advanced breast cancer previously treated with an anthracycline, a taxane, and capecitabine (BEACON): a randomised, open-label, multicentre, phase 3 trial [published online ahead of print October 15, 2015]. Lancet Oncol. doi: 10.1016/S1470-2045(15)00332-0.