Patterns of metastases in malignant pleural mesothelioma in the modern era: Redefining the spread of an old disease.

Abstract

8556 Background: Malignant pleural mesothelioma (MPM) has been historically documented as a locally infiltrative disease in large series from the early 1980s. With the changing landscape of cancer diagnosis and treatment, increased areas of unusual metastases have been published as case reports. With no standard second-line therapies for MPM, referral to early phase trial units is common. We report the metastatic patterns of a large cohort of MPM patients treated at the Royal Marsden Drug Development Unit (DDU). Methods: Clinical data was gathered for MPM patients referred to the DDU from 1992 to 2016. Radiographic details were collected from CT, bone scan and FDG PET imaging. Prior treatment, response, somatic mutations, clinical trial and survival data was obtained from medical records. Results: From the database, 165 evaluable patients with MPM were identified. Median age at diagnosis was 64 years (range 37–90) and 76% were male. Epithelioid MPM comprised 81% and 65% were right sided. Bone metastases were reported in 20%, with the majority lytic in nature ( Table). Peritoneal and omental disease was evident in 24% with ascites in 16%. In 11% of cases lung metastases presented as diffuse miliary-type pattern. Visceral metastases (15%) were predominantly liver (78%), but also occurred in adrenals, spleen and kidneys. Symptomatic brain metastases were recorded in 3%. Median overall survival was 24.2 months (95% CI: 20.8 - 29.2). Conclusions: This large study documents the metastatic patterns of advanced MPM in the 21st century and highlights an increased frequency of traditionally unexpected sites of metastases. Higher than expected incidence of lytic bone metastases (20%) suggests consideration of bone imaging in advanced MPM clinical workflow and trial protocols. [Table: see text]