Baseline characteristics
Most of the 885 patients enrolled with TCZ (64.1%) had one or more bDMARD failures (Table 1): 318 (35.9%) were biologic-naïve (first-line TCZ), 286 (32.3%) had one bDMARD failure (second-line TCZ), 186 (21.0%) two (third-line TCZ), and 95 (10.7%) ≥ 3 prior bDMARD failures (fourth-line TCZ). Patients with prior bDMARD failures were significantly different from biologic-naïve patients: they were younger, had longer disease duration, more csDMARD failures, more erosive changes and more severe fatigue. The functional status was significantly lower in patients with one or at least three bDMARD failures and more patients had three or more comorbidities compared to biologic-naïve patients. In the group with ≥ 3 prior bDMARD failures, nearly 50% of the patients had three or more comorbidities, in particular significantly more osteoporosis, diabetes and heart failure than biologic-naïve patients. No difference was found for fibromyalgia, psoriasis and depression.
Table 1 Baseline characteristics of patients enrolled with tocilizumab
Patient follow-up
Overall, 379 patients (first-line: 118, second-line: 119, third-line: 83, fourth-line: 59) terminated TCZ but were still under observation in the register with other DMARD treatments. In contrast, only 60 out of 885 patients (6.8%) were lost to follow-up over 3 years of observation (first-line: 19, second-line: 17, third-line: 21, 4th-line: 3). Apart from discontinuation and dropout, a total of 288 patients (1st-line: 120, 2nd-line: 87, 3rd-line: 63, fourth-line: 18) were enrolled later than 3 years prior to October 31 2015 and could therefore not complete 3 years of follow-up.
Therapy adherence
Retention rates
After the first year, 65–70% of the patients with ≤ 2 prior bDMARD failures were still on TCZ therapy compared to only 43% in the group with ≥ 3 bDMARD failures (Fig. 1). The Kaplan–Meier estimates after 3 years of follow-up were also similar in the first three strata: 52.2% (bDMARD naïve), 50.8% (1 bDMARD failure) and 46.5% (2 bDMARD failures) compared to 31.3% in the group with ≥ 3 bDMARD failures. In the group with three or more bDMARD failures, 41% of patients stopped TCZ therapy already during the first 6 months.
Characteristics of patients discontinuing TCZ
The unadjusted hazard ratios show that the probability for stopping TCZ therapy was 2.2 times higher in patients with at least three prior bDMARD failures compared to biologic-naïve patients and 1.8 times higher compared to patients with two prior bDMARD failures.
Patients who discontinued TCZ had higher doses of TCZ at baseline (> 6 mg/kg) than those who maintained their treatment. They also had higher DAS28 at baseline and more often three or more comorbidities, especially diabetes. Besides biologic-naive patients, those who discontinued had a lower functional status.
Reasons for terminations
The most frequent reasons for discontinuation were adverse events and ineffectiveness (multiple reasons could be named). In biologic-naïve patients who discontinued TCZ treatment, 32% stopped because of ineffectiveness and 47% due to adverse events (AEs). After one failure (2 failures, ≥ 3 failures), 38% (46, 42%) stopped due to ineffectiveness and 57% (47, 53%) due to AEs. During the first 6 months the percentage of patients who stopped TCZ due to AEs was 15% (17, 35%) higher for patients with no (1; ≥ 3) prior failures than during the following 2.5 years. Overall, the most frequent serious adverse event was “hospitalized surgery”. In patients with ≥ 3 bDMARD failures, this event occurred 14.9 times per 100 patient-years, whereas the incidence rates in the other three groups were 3–7 per 100 patient-years. More than 75% of the surgeries were bone and joint surgeries in all strata. In patients who stopped TCZ therapy, the rates for serious infections were 36.5 (first-line), 33.4 (second), 48.5 (third), and 49.2 (fourth) per 1000 py, and rates for neoplasms were 14.6 (first-line), 20.0 (second), 19.4 (third), and 0 (fourth). This was higher than in patients who continued therapy (serious infections: IR: 7.8–27.3; neoplasms: IR: 4.8 in third-line and no event in all other patients). There was no difference regarding the occurrence of major cardiovascular events. Four patients died under TCZ therapy.
Effectiveness
In both approaches, all patients had significant DAS28 improvements, irrespective of the number of prior bDMARD failures. In the first approach, only 335 patients who remained on TCZ were included (completers). Of them, 130 (39%) were biologic-naïve, 111 (33%) had one bDMARD failure, 70 (21%) had two and 24 (7%) had three or more prior failures. The percentage of completers after 3 years of follow-up was 41% in biologic-naive patients, 39% in second line, 38% in third line and 25% in fourth line users. The average improvement after 3 years of follow-up varied between 2.4 and 3.0 DAS28 units. On average, the patients reached LDA (Table 2).
Table 2 Adjusted baseline DAS28 and least-square means of the course of the DAS28 over 3 years of follow-up separated by the number of prior bDMARD-failures
In approach 2 (ITT analysis), the DAS28 was reduced by 2.0–2.7 points on average after 3 years. Consequently, the estimated means of the DAS28 were higher than in the first model. After 36 months, patients with less than three bDMARD failures on average reached LDA, whereas patients with ≥ 3 bDMARD failures remained on average in moderate disease activity. The difference in the DAS28 scores after 3 years between biologic-naïve patients and those with three or more prior bDMARD failures is larger than in the completer analysis but still not significant (Table 2). Additional adjustment for the dose had no influence on the results. However, the overall mean of the DAS28 averaged over 3 years was significantly higher in patients with ≥ 3 prior bDMARD failures compared to biologic-naïve patients or patients with 1 bDMARD failure [first-line: 2.79 (2.67;2.91), second-line: 2.96 (2.84;3.09), third-line: 3.00 (2.84;3.15), fourth-line: 3.34 (3.10;3.59)]. This result is supported by the predicted probability for achieving LDA over 3 years. It was decreasing from 66 to 48% with the number of prior bDMARD failures. A similar result was also obtained for swollen joint counts (SJC): the mean probability over 3 years for ≤ 2 SJC decreased from 74 to 62% (Table 3). The probability for remaining in high disease activity was 10% in patients with ≥ 3 bDMARD failures.
Table 3 Mean baseline SJC and adjusted least-square means of the percentage of patients with SJC ≤ 2 for all strata of prior bDMARD failures
Concomitant therapy
Conventional synthetic DMARDs
Overall, 430 patients (first-line: 148, second-line: 145, third-line: 89, fourth-line: 48) started TCZ as monotherapy. Of them, 73 (17%, first-line: 12%, second-line: 20%, third-line: 16%, fourth-line: 25%) added a csDMARD during observation. There was no difference in effectiveness between TCZ monotherapy or TCZ in combination with MTX or another csDMARD or more than one csDMARD. Compared to concomitant MTX only use, TCZ monotherapy resulted on average in an insignificantly higher DAS28 of 0.03 [− 0.1; 0.2] points and the effect of other combinations was 0.04 [− 0.1; 0.2]. Moreover, the time to stop TCZ therapy was similar for the three groups (data not shown).
Glucocorticoids
Overall, 9.6% [95%-KI:(7.7; 11.7%)] of patients were enrolled with a high GC dose (> 10 mg/d) and 38.3% did not receive GCs at baseline. However, the mean GC doses during follow-up barely differed between the strata: 3.1 (first-line), 3.4 (second-line), 4.1 (third-line), and 4.1 mg/d (fourth-line).
During follow-up, the percentage of patients with high GC doses decreased and the percentage of patients without GCs increased (Fig. 2). The changes were larger for the patients who were enrolled later.