P232 In the absence of idiopathic inflammatory myopathy, is the presence of anti-transcriptional intermediary factor-1 gamma clinically relevant for malignancy?

Abstract

Background/Aims The idiopathic inflammatory myopathies (IIMs) are associated with a number of antibodies which are linked to certain clinical phenotypes. The presence of anti-transcriptional intermediary factor-1 gamma (TIF-1y) is strongly associated with malignancy. However, it is uncertain whether the presence of this antibody, in the absence of IIM, should prompt further investigations to exclude an underlying malignancy. Methods Patients were identified who had undergone myositis immunoblot testing at Liverpool University Foundation Trust laboratories as part of their clinical care between January 2015 and January 2020. Adult patients were included if they tested TIF-1y antibody positive but had no evidence of IIM. Data was collected on patient demographics, whether this was a weak or strong antibody finding and whether there was the presence of other antibodies on the immunoblot panel. The clinical notes were then used to assess whether the patient was known to have a malignancy or went on to develop a malignancy during the follow up period. Results The presence of TIF-1y antibody occurred in 66 patients. Four patients were excluded from analysis, three due to a diagnosis of IIM and one due to a lack of clinical information. The average age was 69 years (range 35 - 88 years) and 59% were female. A strongly positive TIF-1y antibody was found in 19 patients, of which eight were associated with another positive antibody available on the immunoblot panel. There were five malignancies identified, two were historic diagnoses, one patient was found to have a lung malignancy at the time the panel was sent and two patients subsequently developed pancreatic malignancy. A weakly positive TIF-1y antibody was found in 43 patients, of which 16 results were associated with another positive antibody on immunoblot analysis, excluding three patients with a positive anti-Ro antibody. Of 11 patients with malignancy, five had a historic diagnosis and six patients developed malignancy over the follow up period. Conclusion The myositis immunoblot is a useful tool in patients with IIM. However, when used outside of this context can produce a number of positive results, the significance of which are unclear. In the case of TIF-1y and its known association with malignancy, this can lead to unnecessary investigations and increase patient anxiety. This data has obvious limitations as there may have been incomplete information if patients were managed elsewhere and the presence of TIF-1y did not lead to investigation for underlying malignancy in the majority of patients, meaning some cancers may have been present but remained undetected. The results do not suggest the presence of this antibody increases the likelihood of malignancy in patients without IIM but further studies are recommended. Disclosure C.V. Cotton: None. C. Keymer: None. Z. McLaren: None.