Real-World Data on Treatment Patterns Before and After Reporting of the KATHERINE Trial

At SABCS 2018 and simultaneous publication in the New England Journal of Medicine, results of the phase 3 KATHERINE clinical trial comparing trastuzumab emtansine (T-DM1) versus trastuzumab as adjuvant therapy in patients with HER2+ early-stage breast cancer with residual invasive disease after receiving neoadjuvant chemotherapy and trastuzumab, showed that T-DM1 reduced the risk of invasive recurrence or death by 50%.1,2

At SABCS 2019, the authors sought to determine the effect of the release of these data on clinical practice of general medical oncologists in the United States by comparing the requests for treatment authorization for T-DM1 in the quarters preceding and following SABCS 2018.3 Data from a preauthorization platform used by multiple commercial insurance companies in the United States (Eviti) were analyzed. Analysis for request for use of T-DM1 was limited to second- and third-line therapy in patients with a diagnosis of HER2+ breast cancer in stage <IV patients. A total of 29,525 breast cancer treatment plans were identified, of which 7969 were identified as HER2-NEU+ (27%), either IHC3+ or FISH+. T-DM1 was prescribed at any line of therapy in 886 patients (11%).

Before the adjuvant T-DM1 regimen was published, users who entered would have to choose one of the other 2 T-DM1 regimens (first line or ≥second line). T-DM1 authorizations indicated an immediate increase in first-line T-DM1 use in the quarter following SABCS 2018 (from 19 authorizations in 4Q2018 to 59 authorizations in 1Q2019), and based on the 2Q2019 data, showed a 42% adjuvant-use rate; the authors model that 99 cases would have received adjuvant T-DM1 in the 1Q2019 after 0 cases in the 4Q2018. The authors conclude that clinical uptake of practice-changing data presented at SABCS 2018 regarding T-DM1 was relatively rapid, suggesting that presentation of these data at SABCS and rapid simultaneous publication serve as an important and effective mechanism to communicate practice-changing clinical data to practicing oncologists in the United States.


  1. Geyer CE, et al. SABCS 2018. Abstract GS1-10.
  2. von Minckwitz G, et al. N Engl J Med. 2019;380:617-662.
  3. Margolis N, et al. SABCS 2019. Abstract P1-15-08.

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