P3.03-042 Study Comparing Volume and TNM in Predicting Clinical Outcome in Malignant Pleural Mesothelioma: Topic: Mesothelioma Clinical

Abstract

Malignant pleural mesothelioma (MPM) is a rare cancer with relatively poor outcome. Only stage (TNM) and histotype can be considered prognostic factors, but TNM still results inaccurate and difficult to be classified. Several studies investigated the use of tumor volume (TV) for response assessment, but its role as predictor of survival is unclear. A cut-off of 600 cm3 seemed to divide patients (pts) with different prognosis. Our objective is to assess the association between baseline TV, stage/TNM and overall survival (OS). We retrospectively selected 49 MPM pts treated from August 2002 to January 2012. All pts had a digitally available baseline chest computed tomography (CT), performed before any treatment and up to 3 months after histological diagnosis. CT staging was carried out by two thoracic radiologists according to TNM staging system (7th Edition). Pleural disease volume measurements were obtained by a computer system. Major prognostic variables (age, sex, histology, TV, stage/TNM, treatment) were collected. Pts were divided in 2 groups according to baseline TV (large volume >600cm3; small volume <=600cm3). Association of volume groups, stage, T, N, M separately and OS was tested using Cox models adjusted by age, sex, histology and surgery. Thirty-three pts were men, 16 women; median age was 62 years (range 25-78). Forty pts had epithelioid MPM, 7 mixed histology, 2 unknown histology. Four pts were diagnosed in early stage (I-II) and 45 in advanced stage (III-IV). The mean baseline TV was 494.15 cm3 (range 17.91- 2,329.03). Pts with small volume had a slight but not statistically significant tendency to survive longer than pts with large volume (3-year OS=32% vs 21%, respectively). The HR was 1.5 (95% CI=0.6-3.7) for large volume pts, 4.3 (p=0.08;95%CI=0.8-22.1) and 7.5 (p=0.02; 95% CI=1.4-39.9) for stage III and IV, 7.0 (p=0.001; 95% CI=2.3-21) and 5.4 (p=0.005; 95% CI=1.7-17.4) for T3 and T4, respectively. Regarding N and M, not statistically significant results were observed. Coherently with the available literature, we report an association between baseline TV and prognosis; however it seems weak and barely near to statistical significance. On the contrary, stage, in particular T3, showed a stronger association with prognosis. Considering the small sample and the wide 95% CI, our results should be interpreted with caution; nevertheless they open a critical question on the TV prognostic role and suggest a greater relevance of adjacent organs infiltration in predicting prognosis. Further collaborative studies are needed.