Proposal for a new local recurrence score in patients with recurrent malignant pleural mesothelioma.

Background: Malignant pleural mesothelioma (MPM) is associated with high rates of local recurrence (LR) up to 75%. Second line treatment should be applied tailored to relapse pattern. We aimed to establish a new score for LR pattern with prognostic impact in this observational study of retrospective nature.

Methods: MPM patients with LR after surgery, verified by serial imaging during follow-up visits or biopsy were included in a retrospective analysis using a new local recurrence score (LRS). We divided the thoracic cavity into six sections and calculated the LRS according to the tumor burden. We assessed the impact on survival after recurrence using cox regression model.

Results: From 2001 until 2017, 128 consecutive MPM patients with LR who underwent macroscopic complete resection (MCR) by extrapleural pneumonectomy (EPP, n=61) or by (extended) pleurectomy/decortication [(E)PD, n=67], were included in the present analysis; 104 patients received second line therapy. Patients with chest wall (CW) recurrence had the shortest survival after recurrence (9 . 16 months, P=0.05) as well as patients with affected lymph nodes (LN) (9 . 17 months, P=0.02). In subgroup analysis, the (E)PD group had a significantly higher LRS (P≤0.001) despite a longer survival time after recurrence of 12.4 months (IQR, 6.45-20.32) compared to 9.3 months (IQR, 2.93-17.40, EPP group) (P=0.04). Patients with LRS ≤4 had a longer survival undergoing radiotherapy or local surgery for second line treatment whereas patients with LRS >4 only if they underwent chemotherapy.

Conclusions: LRS might be a useful prognostic tool in MPM patients with LR after multimodality therapy to guide second line treatment allocation.