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Incidence of malignancy and survival in patients with idiopathic pleuritis.

Background
The long-term outcome after non-diagnostic thoracoscopy (idiopathic pleuritis) has not been investigated in nationwide studies, and the survival has never been estimated. Therefore, we decided to investigate the three-year incidence of malignancy and survival of patients with idiopathic pleuritis.


Methods
Retrospective, register-based, nationwide study of patients undergoing diagnostic video-assisted thoracoscopic surgery (VATS) thoracoscopy ≤30 days after thoracentesis, using The National Patient Registry and The Danish Cancer Registry. Idiopathic pleuritis was defined as; no diagnosis of malignancy within 31 days after VATS. Patients were followed for 36 months after VATS.


Results
In total, idiopathic pleuritis were identified in 547 out of 658 patients undergoing VATS (83%), and 29 (5%) were diagnosed with malignancy during the 3 years follow-up period after VATS. Of these, 93% were diagnosed with malignancy within the first year. Numbers-needed-to-follow-up for detecting one case of malignancy was 18 during the first year after VATS and 250 in the two subsequent years. Survival was independent on type of malignancy (MPM vs. other malignancies; P=0.13) and of time from VATS to diagnosis (≤31 days vs. 1-36 months; P=0.15). Median survival in the non-malignant group was 1,095 days.


Conclusions
Our study confirms a low incidence of malignancy in idiopathic pleuritis after VATS. Nearly all incident cases of malignancy were diagnosed within 12 months from VATS. No survival disadvantage was observed in patients with incident malignancy. Our data suggest that follow-up of idiopathic pleuritis could safely be limited to 1 year. The optimal follow-up strategy remains to be investigated.