Abstract P2-12-01: Real-world use and outcomes of trastuzumab for HER2+ metastatic breast cancer in Australia: Analysis of the herceptin program, 2001-2015
Authors: Daniels B , Kiely BE , Lord SJ , Houssami N , Pearson S-A 
Published: February 2018

Aims

Between December 2001 and July 2015 Australian women with HER2-positive metastatic breast cancer (MBC) accessed trastuzumab in combination with taxane chemotherapy or as monotherapy via the government funded Herceptin Program (HP); we characterise their treatment patterns and survival outcomes.

Methods

This retrospective, whole-of-population cohort study used linked dispensing, medical services, and death records. We stratified patients into three year-of-trastuzumab-initiation groups: 1. 2001-2002 (may include patients accessing trastuzumab in later lines); 2. 2003 - October 2006 (likely first-line treated but prior to trastuzumab availability for early breast cancer (EBC)); and 3: October 2006–June 30 2015 (most representative of contemporary practice). Patients were observed until death or censored at June 30 2016.

We estimated duration of trastuzumab therapy from the initial dispensing date for MBC until 30 days after the last dispensing. We considered a gap of ≥90 days between trastuzumab dispensings a separate course of treatment. We estimated overall survival (OS) as the time from first trastuzumab dispensing until death from any cause. We used Kaplan-Meier methods to estimate the total duration of trastuzumab therapy and OS. We used dispensing dates of cancer medicines to determine concomitant treatments and used claims for echocardiography and MUGA scans to determine the timing of cardiac monitoring.

Results

5,895 patients accessed trastuzumab for MBC. Median age at trastuzumab initiation was 57 years (IQR: 48 – 66). 800 patients (22%) from Group 3 also received trastuzumab for EBC. Treatment details and OS are tabulated:

 Overall (n = 5,895)Group 1 (n = 495)Group 2 (n = 1,709)Group 3 (n = 3,691)Median time on trastuzumab for MBC, first course, months (IQR)13.2 (5.7 – 26.6)9.2 (3.8 – 22.5)12.3 (5.4 – 23.3)14.0 (6.1 – 29.8)Median OS from first trastuzumab dispensing for MBC, months (IQR)30.3 (13.4 – 68.7)19.8 (8.9 – 38.8)27.5 (12.5 – 58.9)34.6 (15.1 – 82.8)Patients initiating trastuzumab, n (%):    monotherapy1,571 (27)226 (46)625 (37)720 (20)+ taxane3,150 (53)157 (32)800 (47)2,193 (59)+ hormonal therapy763 (13)47 (9)169 (10)561 (15)+ non-taxane chemotherapy376 (6)65 (13)115 (7)217 (6)Cardiac assessment:    at baseline (60 days prior to 30 days following trastuzumab initiation)3,721 (63%)189 (38%)831 (49%)2,701 (73%)during treatment3,324 (56%)150 (30%)778 (46%)2,396 (65%)

Conclusions

Our real-world estimates of OS for each patient group are both similar to and shorter than those from clinical trials published during similar time periods. Group 3 median OS is 6 months shorter than the control arm of the CLEOPATRA study (34.6 v 40.8 months) while median duration of first trastuzumab course was 4 months longer (14.0 v 10.4 months), suggesting patients continue trastuzumab beyond progression. In Group 3, 25% of patients died within 15 months of starting trastuzumab, 50% survived beyond 3 years and 25% survived beyond 7 years. These estimates will be useful for clinicians discussing expected survival time with patients in routine practice. Although the cardiotoxicity of trastuzumab is well recognised, baseline cardiac assessment was not universal, even in the most recent cohort.

Citation Format: Daniels B, Kiely BE, Lord SJ, Houssami N, Pearson S-A. Real-world use and outcomes of trastuzumab for HER2+ metastatic breast cancer in Australia: Analysis of the herceptin program, 2001-2015 [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-12-01.