Trastuzumab emtansine (T-DM1) in patients with HER2-positive metastatic breast cancer and brain metastases: exploratory final analysis of cohort 1 from KAMILLA, a single-arm phase IIIb clinical trial

Ann Oncol. 2020 Oct;31(10):1350-1358. doi: 10.1016/j.annonc.2020.06.020. Epub 2020 Jul 5.


Background: Patients with brain metastases (BM) from human epidermal growth factor receptor 2 (HER2)-positive breast cancer represent a difficult-to-treat population. Trastuzumab emtansine (T-DM1) has shown potential activity in this subset of patients in small clinical series.

Patients and methods: KAMILLA is an ongoing, phase IIIb study of T-DM1 in patients with HER2-positive locally advanced/metastatic breast cancer with prior HER2-targeted therapy and chemotherapy. Patients received T-DM1 3.6 mg/kg every 3 weeks (intravenously) until unacceptable toxicity, withdrawal of consent, or disease progression. Tumor response and clinical outcomes in patients with baseline BM were evaluated in this post hoc, exploratory analysis. The main outcome measures were best overall response rate (complete response + partial response) and clinical benefit rate (complete response + partial response + stable disease lasting ≥6 months) by RECIST v1.1 criteria, progression-free survival, overall survival, and safety.

Results: Of 2002 treated patients, 398 had baseline BM. In 126 patients with measurable BM, the best overall response rate and clinical benefit rate were 21.4% [95% confidence interval (CI) 14.6-29.6] and 42.9% (95% CI 34.1-52.0), respectively. A reduction in the sum of the major diameters of BM ≥30% occurred in 42.9% (95% CI 34.1-52.0), including 49.3% (95% CI 36.9-61.8) of 67 patients without prior radiotherapy to BM. In the 398 patients with baseline BM, median progression-free survival and overall survival were 5.5 (95% CI 5.3-5.6) months and 18.9 (95% CI 17.1-21.3) months, respectively. The adverse event profile was broadly similar in patients with and without baseline BM, although nervous system adverse events were more common in patients with [208 (52.3%)] versus without [701 (43.7%)] baseline BM.

Conclusion: This exploratory analysis of patients with HER2-positive metastatic breast cancer and BM enrolled in a prospective clinical trial shows that T-DM1 is active and well-tolerated in this population. T-DM1 should be explored further in this setting.

Trial registration: identifier: NCT01702571.

Keywords: HER2-positive breast cancer; KAMILLA; T-DM1; brain metastases; metastatic breast cancer; trastuzumab emtansine.

Publication types

  • Clinical Trial, Phase III
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ado-Trastuzumab Emtansine
  • Antineoplastic Combined Chemotherapy Protocols
  • Brain Neoplasms* / drug therapy
  • Breast Neoplasms* / drug therapy
  • Humans
  • Maytansine* / adverse effects
  • Prospective Studies
  • Receptor, ErbB-2 / genetics
  • Trastuzumab / adverse effects


  • Maytansine
  • Receptor, ErbB-2
  • Trastuzumab
  • Ado-Trastuzumab Emtansine

Associated data