Background/Purpose: Patients with giant-cell arteritis (GCA) and polymyalgia rheumatica (PMR) are treated with high cumulative glucocorticoid (GC) dose during their disease course. We sought to determine the accrual of comorbidity as well as survival in patients with GCA and PMR.

Methods: We conducted a retrospective follow-up study of an inception cohort of patients diagnosed with GCA and PMR according to ACR criteria and persistently followed at our rheumatology clinic from January 1990 until March 2018. Disease manifestations, time duration of GC dose tapering and discontinuation as well as calculated cumulative GC dose were determined. Baseline and last encounter age-adjusted Charlson Comorbidity Index (CCI) and Rheumatic Disease Comorbidity Index (RDCI) as well as the increment (Δ) of CCI and RDCI at the last study encounter were scored. Mortality rate and cause were recorded.

Results: The cohort consisted of 69 patients (24 GCA and 45 PMR, 68.1% female). Mean age at diagnosis was 71.38±5.58 years and 74.53±9.67 for GCA and PMR, respectively. The mean daily initial prednisone dose for GCA was 61.25±11.91mg and for PMR 18.11±7.85mg (p<0.001), and prednisone cumulative dose was 13,382.19±6189.21 mg and 6,610.36±4,755.55 mg for GCA and PMR, respectively (p<0.001). Systemic symptoms such as fever and weight loss as well as ESR at diagnosis were comparable in GCA and PMR. Time duration until achieving 50% and 25% of the initial prednisone dose was longer for patients with PMR vs. GCA (3.87±2.22 months vs. 3.02±1.15 months, p=0.049 and p=0.03, respectively), however, the disease duration until achieving daily prednisone dose of 7.5mg and 5 mg was longer in the GCA group (9.88±3.08 months vs. 4.4±2.4 months, p<0.001, and 12.85±6.35 months vs. 7.28±7.48 months, p=0.005, respectively). Nevertheless, the time duration to discontinuation of prednisone and prednisone-free survival did not differ among GCA and PMR patients, as well as the time duration to the first disease flare. Disease remission rate for the entire cohort was 28.9% for a follow-up period of 7.5±3.9 years (range: 2.4 – 16.9 years). The CCI and RDCI scores for GCA at diagnosis and at the last study encounter did not differ between GCA and PMR groups. Interestingly, initial prednisone dose, time to achieving 50% and 25% of initial prednisone dose, time to daily prednisone dose of 7.5mg and 5mg as well as time to prednisone discontinuation and prednisone-free survival did not differ when comparing ΔCCI ≥1 and RDCI ≥1 with ΔCCI=0 and RDCI =0, respectively. Mortality rate did not differ between GCA and PMR groups: 5-, 10-, and 15-years survival were 62.5% and 71.1%, 25% and 24.4%, and 8.33% and 4.44%, respectively. Comorbidity was associated with higher mortality rate: CCI and RDCI at diagnosis (HR 1.9, CI95% 1.3-2.6, p=0.0002 and HR 1.7, CI95% 1.2-2.2, p=0.004, respectively) and at last study encounter (HR 1.4, CI95% 1.3-2.6, p=0.0002 and HR 1.5, CI95% 1.04-2.1, p=0.03, respectively).

Conclusion: Despite significant higher cumulative dose of prednisone for patients with GCA compared to patients with PMR, comorbidity scores and mortality rate are comparable. Our results emphasize the unmet need for novel steroid-sparing drugs in PMR as well as in GCA.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/comorbidity-accrual-and-mortality-in-an-inception-cohort-of-patients-with-giant-cell-arteritis-and-polymyalgia-rheumatica-a-single-center-observational-long-term-study/