Specimen weight and volume: important predictors of survival in malignant pleural mesothelioma

The tumour/node/metastasis (TNM) staging system for malignant pleural mesothelioma (MPM) is a worldwide standard, but has many limitations. Tumour volume has been suggested as a predictor of survival. Due to the complex anatomy, estimation of tumour volume via CT scan can be challenging. Surgical volume may be more accurate. Therefore, we prospectively determined resected specimen volumes and weights in consecutive patients undergoing extended pleurectomy and decortication (EPD) and correlated this with overall survival and T and N stage.

We evaluated 116 patients undergoing EPD for MPM in a single university centre over a 6-year period. All resected specimens were weighed, and the volume was measured by a fluid displacement method. A Cox regression model was used to identify significant predictors of survival; hazard ratios were calculated. A Kaplan-Meier method was used to summarize overall and subgroup survival. Logistic regression models were used to identify predictors of T and N stage.

There were 95 males and 21 females with a median age of 68 range 43-88 years. Forty-one patients had an ECOG performance status (PS) 0, 70 had 1 and 4 had 2. The median time between initial diagnosis and surgery was 134 days. Histology was epithelioid in 59, biphasic in 55 and sarcomatoid in 2. The mean volume was 641 ml with an SD of 393.34 ml. The median volume was 567.5 ml. The mean weight was 620.8 g with an SD of 361.92 g. The median weight was 552.0 g. Two-year survival from initial diagnosis and from EPD was 44 and 28%, respectively. PS (P = 0.002), epithelioid histology (P < 0.001), specimen weight (P < 0.001), volume (P < 0.001), platelet count (P = 0.015), T1 stage (P = 0.04) and adjuvant therapy (P = 01) were predictive of survival. Tumour volume was a predictor of T stage (P = 0.048) and survival (P = 0.03). There was no relationship between N stage and tumour volume, weight or histology.

PS, specimen weight, volume, epithelioid histology platelet count and adjuvant chemotherapy are significant predictors of survival in patients undergoing EPD for MPM. There is a correlation between specimen volume and T stage. These data suggest that tumour weight and volume may be valuable components for staging MPM.