POS0701 LUNG TRANSPLANTATION OUTCOMES IN PATIENTS WITH INTERSTITIAL PNEUMONIA WITH AUTOIMMUNE FEATURES

Background: Interstitial pneumonia with autoimmune features (IPAF) is a designation proposed in 2015 by the European Respiratory Society/American Thoracic Society (ERS/ATS) to describe patients who have interstitial lung disease (ILD) and combinations of clinical, serologic, and/or pulmonary morphologic features of an underlying systemic autoimmune condition, but do not meet rheumatologic criteria for a characterized connective tissue disease (CTD) [1]. Previous studies have suggested that patients with IPAF have worse clinical outcomes and survival compared to those with CTD-associated ILD, but better than those with idiopathic pulmonary fibrosis (IPF) [2]. Survival after lung transplantation is similar between CTD-associated ILD and IPF [3]. Limited data are available regarding post-lung transplant outcomes in patients with IPAF. Objectives: The objective of our study is to compare post-transplant survival, lung function, and other complications in IPAF with IPF. Methods: We reviewed the data of all patients who underwent lung transplantation in British Columbia, Canada between January 1, 2014, and April 30, 2024. Diagnoses of IPAF were made through a multidisciplinary approach in conjunction with ILD respirologists, chest radiologists, rheumatologists, and pulmonary pathologists. All IPAF cases met the 2015 ERS/ATS criteria and had compatible explant pathology. Continuous variables were assessed with the Mann-Whitney U test and categorical variables with Fisher's Exact test. Results: We identified 20 patients with IPAF and compared them to 64 patients with IPF who underwent double lung transplantation during the same period (Table 1). IPAF patients more likely to be female (50% vs 17%, p=0.006). Before transplant, patients with IPAF were more likely to be on immunosuppression (60% vs 6%, p<0.001), and less likely to be on antifibrotics (20% vs 64%, p<0.001). Age, smoking status, sex, Charleson comorbidity index, and pre-transplant forced vital capacity (FVC), diffusing capacity for carbon monoxide (DLCO), and pulmonary artery systolic pressure (PASP) were similar between the two groups. The median duration of post-lung transplant follow-up was 3.6 years in the IPAF group and 3.8 years in the IPF group. No significant difference was seen in survival at 1 year or cumulative survival at the last follow-up. At 1-year follow-up, no difference was seen in FVC and DLCO, rates of acute rejection, or hospitalization for infection. At last follow-up, no difference was seen in the rates of chronic lung allograft dysfunction (CLAD) or post-transplant malignancy. Conclusion: We found no significant difference in post-transplant survival, lung function, infectious or rejection complications in patients who underwent lung transplantation for IPAF compared with IPF at our centre. This study is the first of its kind to report both short-term and long-term outcomes of lung transplantation in patients with IPAF. REFERENCES: [1] Fischer A, Antoniou KM, Brown KK, Cadranel J, Corte TJ, du Bois RM, et al. An official european respiratory society/american thoracic society research statement: Interstitial pneumonia with autoimmune features. Eur Respir J 2015;46:976-87. [2] Dai J, Wang L, Yan X, Li H, Zhou K, He J, et al. Clinical features, risk factors, and outcomes of patients with interstitial pneumonia with autoimmune features: A population-based study. Clin Rheumatol 2018;37:2125-32. [3] Zhang N, Liu S, Zhang Z, Liu Y, Mi L, Xu K. Lung transplantation: A viable option for connective tissue disease? Arthritis Care Res (Hoboken) 2023;75:2389-98. Table 1Summary of Pre- and Post-transplant Data.VariablesIPF (n=64)IPAF (n=20)p-valueDemographicsAge at ILD Diagnosis, median [IQR]60.5 [58 – 64]58 [53 - 62]0.08Age at Transplant, mean [IQR]65 [62 – 68]63 [59 - 67]0.31Sex (women), n (%)11 (17)10 (50)0.006Race (White), n (%)51 (80)16 (80)1.0Smoker, n (%)47 (73)13 (65)0.57BMI, median [IQR]27.6 [24 – 29.2]28.6 [22 – 30]0.65Charleson Comorbidity index, median [IQR]3 [2 - 4]3 [2 – 3]0.88Variables at TransplantFVC (%), median [IQR]51 [39 – 64]49 [37 – 55]0.23DLCO (%), median [IQR]31 [24 – 38]27 [23 – 30]0.06PASP (mmHg), median [IQR]35 [31 – 42]35 [28 – 39]0.90Diagnosis to Transplant (years), median [IQR]3.9 [2.3 – 5.8]5.2 [2.8 – 5.9]0.31Immunosuppression*, n (%)4 (6)12 (60)< 0.001Antifibrotic, n (%)41 (64)4 (20)< 0.001ICU admission prior to transplant, n (%)9 (14)5 (25)0.31CMV mismatch Donor (+)/ Recipient (-), n (%)9 (14)6 (30)0.18Dominant Explant PathologyUIP, n (%)62 (97)7 (35)< 0.001NSIP, n (%)0 (0)8 (40)< 0.001Other, n (%)0 (0)1 (5)0.24Unclassifiable, n (%)2 (3)4 (20)0.031 Year OutcomesAlive, n (%)59 (92)18 (90)0.67Post-transplant ICU days, median [IQR]4 [3 – 9]3.5 [2 – 6.5]0.16Post-transplant hospitalization days, median [IQR]22 [17 – 31]22 [16 – 26]0.42FVC (%), median [IQR]84 [67 – 99]80 [68 – 99]0.69DLCO (%), median [IQR]61 [45 – 75]64 [56 – 72]0.59Acute Rejection, n (%)31 (48)9 (45)0.80Pneumonia requiring hospitalization, n (%)20 (31)5 (25)0.78Non-pulmonary infection requiring hospitalization, n (%)14 (22)6 (30)0.54Fungal infection requiring therapy, n (%)22 (34)5 (25)0.59CMV viremia requiring therapy, n (%)15 (23)6 (30)0.56Long-term OutcomesLength of follow-up (years), median [IQR]3.6 [2.1 – 6.2]3.8 [1.5 – 7.3]0.98Alive at last follow-up**, n (%)42 (66)17 (85)0.16CLAD**, n (%)18 (28)6 (30)0.98Post-transplant malignancy**, n (%)16 (25)4 (20)0.97All continuous variables analyzed with the Mann-Whitney U testAll categorical variables analyzed with the Fisher's Exact test*Does not include prednisone/ methylprednisone** Analyzed with Kaplan Meier survival or incidence analysis Acknowledgements: The authors express their gratitude to BC Transplant and all of the members of the Vancouver General Hospital Lung Transplant team. 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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