Between 2005 and 2016, 7,156 incident HER2-positive breast cancer patients were identified in the Danish National Pathology Register. Among those, 4,153 (58%) were treated with trastuzumab within the first year after diagnosis (see flow chart, Figure 1) and thus were included in the study population. Of these, 1,109 (27%) women were identified as patients with recurrence of cancer and 3,044 (73%) women were identified as patients without recurrence.
Basic characteristics of the study population are presented in Table 1. Age and highest obtained education at diagnosis did not vary in correlation to the population with recurrence of breast cancer and the population without recurrence. However, there was some variation in region of residence.
Average healthcare costs
Table 2 presents the annual average healthcare costs per person among patients with HER2-positive breast cancer treated with trastuzumab compared to matched controls free of breast cancer among the total study population, the population with recurrence of breast cancer and the population without recurrence of breast cancer.
In the year before diagnosis (year -1), we found no statistically significant difference between recurrence cases’ and controls’ average individual healthcare costs. The differences in total costs between cases in the total study population and controls, and between cases without recurrence and controls, were statistically significant (p=0.0209); however, the costs were only slightly higher among cases compared to the costs among controls (1.2 times).
In the year of diagnosis, the average healthcare costs were 25.9 (p<0.001) times higher among cases in the total study population compared to controls, 27.3 (p<0.001) times higher among cases with recurrence compared to controls and 25.3 (p<0.001) times higher among cases without recurrence compared to controls, corresponding to differences in actual costs of EUR 58,217, EUR 67,099 and EUR 54,910, respectively.
In subsequent years, the average healthcare costs remained statistically significantly higher among cases alive compared to controls alive in all study populations. In the 10th year after diagnosis, the average healthcare costs remained significantly higher among the total study population and among patients with recurrence. Among all cases, the costs were 2.3 (p=0.003) times higher compared to controls in year 10, whereas the costs were 10.0 (p=0.002) times higher among cases with recurrence and 1.2 (p=0.402) times higher among cases without recurrence compared to controls.
Labour productivity
Figure 2 presents the average individual labour productivity among HER2-positive breast cancer patients compared to controls who were free of breast cancer from year -1 to year 10. In the year prior to index date, cases and controls in all study populations did not differ significantly regarding labour productivity: p=0.180 among the total study population, p=0.99 among cases with recurrence and p=0.103 among cases without recurrence. For all three study populations, labour productivity was slightly higher among cases compared to controls.
Among the total study population, labour productivity decreased significantly in the year of diagnosis and remained statistically significantly lower during the entire follow-up period. Among the population of cases with recurrence, labour productivity was significantly lower throughout the study period; in year 10, labour productivity was 2.8 (p <0.001) times lower among cases compared to controls, whereas cases without recurrence showed labour productivity comparable to controls from year 9 and onwards (p=0.114).
Healthcare costs of recurrence
Among patients experiencing recurrence, 201 patients (5.5% of cases) were identified with metastatic breast cancer at the time of diagnosis (i.e. de novo breast cancer), while the rest experienced a recurrence after a mean time of 1.5 years. Table 3 presents average individual healthcare costs three years after recurrence. In the first year after recurrence, the average individual cost increased to EUR 38,383 among cases, compared to EUR 2,129 among their matched controls. Thus, a second spike in healthcare costs was related to recurrence among breast cancer patients.
Prescription medicine
The average individual costs of prescription medicines are presented in Table 4. In the year prior to index date, the costs of prescription medicines did not vary significantly between cases and controls. In year 1 and year 3, cases had slightly higher costs of prescription medicines compared with controls. In the remaining years, however, we found no differences in costs of prescription medicines between cases and controls. During the entire study period, the average yearly cost of prescription medicine was EUR 343 for cases and EUR 330 for controls.