POS1239 PAGET'S DISEASE OF BONE: CLINICAL AND EPIDEMIOLOGICAL PROFILING OF A PORTUGUESE COHORT AT A TERTIARY CENTER

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Background: Paget's disease of bone (PDB), the second most prevalent metabolic bone disorder, is influenced by genetic and environmental factors which remain unclear. Objectives: To characterize the clinical and demographic profile of a Portuguese PDB cohort. This is the first phase of a two-step project aimed at identifying environmental and genetic etiological factors in PDB. Methods: We performed a retrospective observational study including patients with PDB. Demographic and clinical data were collected. Professional occupations were classified according to the International Standard Classification of Occupations-2008. Parametric and non-parametric tests were applied as appropriate. Multivariable analysis was performed with binomial logistic regression to find independent associations with polyostotic involvement. Drug survival of first treatment was analysed using Kaplan Meier analysis and non-retreatment rate was compared between patients treated with zoledronate as first line and patients not treated with zoledronate as first line, using log-rank test and crude and adjusted hazard ratios (HR) calculated with Cox regression analysis. Results: Eighty patients with a diagnosis of PDB between 1974 and 2021 were included (Table 1). Forty-seven (58.8%) were female and the mean age at diagnosis was 63.0±12.2 years. Fifty-eight (72.5%) patients were born in rural areas. Their parent's birthplaces showed a concentration in the region of Alentejo (35.0% of mothers and 38.9% of fathers) and 86.3% of mothers and 81.3% of fathers were born in rural areas. Family history of PDB was reported in 11 (13.9%) patients. The five most common places of PDB affection were the pelvis (75.0%), sacrum (25.0%), femur (25.0%), vertebra (21.3%) and skull (13.8%), with 41 (51.2%) patients having polyostotic involvement. Forty-one (51.2%) patients had polyostotic involvement, with a median percentage of bone tissue affected of 5.2% (IQR 5.3) according to Howarth's table. Polyostotic patients had higher exposure to goats (39.0% vs 12.8%, p=0.008), more years working in elementary occupations (16.5±21.7 vs 7.9±15.0, p=0.027) and fewer in professional occupations (2.0±8.9 vs 7.1±14.5, p=0.049). Polyostotic disease was associated with higher baseline levels of alkaline phosphatase (ALP, U/L) (200.0 [167.0] vs 149.0 [123.5], p=0.035), P1NP (ng/mL) (196.2 [188.1] vs 115.3 [75.8], p=0.015) and CTx (ng/mL) (0.7±0.3 vs 0.6 [0.3], p=0.031). Polyostotic patients had a higher frequency of involvement of the following bones: skull (22.0% vs 2.5%, p=0.029), pelvis (87.8% vs 61.5%, p=0.007), vertebrae (36.6% vs 5.1%, p<0.001), femur (39.0% vs 10.3%, p=0.003), and sacrum (36.6% vs 12.8%, p=0.014). In multivariate analysis, affection of vertebrae (OR 279.4 [10.2-7670.6], p<0.001), femur (OR 150.6 [7.2-3131.8], p=0.001), pelvis (OR 101.2 [7.1-1431.6.], p<0.001), sacrum (OR 61.6 [5.1-737.6], p=0.001) and skull (OR 47.5 [1.1-2052.5], p=0.044) were associated with polyostotic disease. First line treatment was with zoledronate in 60 (75.0%) patients, pamidronate in 8 (10.0%) patients, alendronate in 4 (5.0%) patients, calcitonin in 3 (3.8%) patients, risedronate in 1 (1.3%) patient and denosumab in 1 (1.3%) patient. Three (3.8%) patients did not undergo any treatment. Thirteen (16.3%) patients were treated with two or more different drugs. Overall, zoledronate was the most commonly used drug (88.8%). Of note, zoledronate was first used in this cohort in 2006. We observed a statistically significant difference in the number of patients with elevated ALP at baseline and 6-12 months after the last treatment (p=0.002) and in the absolute value of ALP, P1NP and CTx at these timepoints (p<0.001) (Table 1). Sixteen (20.8%) patients had to undergo retreatment. The mean drug survival of the first treatment in the group treated with zoledronate as first line therapy was 16.0 years (95% CI 14.3-17.6) while in the group treated with another drug as first line therapy was 11.7 years (95% CI 4.9-18.4), presented in Figure 1. Drug survival was significantly lower in the latter group, with a higher rate of retreatment (crude HR 9.49 (95% CI 3.28-27.44); log-rank p<0.001). When adjusted for age at diagnosis, smoking, ALP and calcium levels at baseline, treatment with a drug other than zoledronate as first line remained independently associated with lower drug survival (adjusted HR 10.10 (95% CI 2.12-48.0); p=0.004). Conclusion: To the best of our knowledge, this study describes the largest Portuguese cohort of PDB patients. A high prevalence of this disease in rural areas and a high biochemical remission rate after treatment were noted. Patients treated with a non-zoledronate drug as first line therapy had a higher rate of retreatment than patients treated with zoledronate as first line therapy (HR 10.10). A genetic characterization of this cohort is currently under work. REFERENCES: NIL . Acknowledgements: NIL . Disclosure of Interests: None declared . © The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.

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