The management of the diaphragm during radical surgery for malignant pleural mesothelioma.

OBJECTIVES: Macroscopic complete resection with lung preservation is the objective of radical management of pleural mesothelioma (MPM). Total removal of visceral and parietal pleura (pleurectomy/decortication) almost invariably proceeds to an extended pleurectomy/decortication (EPD) to ensure macroscopic complete resection. We suspected this may not always be necessary.

METHODS: We reviewed 314 patients, 86.0% male, median age 62 years (range 14-81 years) undergoing radical surgery for MPM from 1999 to 2014, by either EPD or extrapleural pneumonectomy. The extent of diaphragmatic muscle involvement was recorded from postoperative pathology. Patients were divided into three groups: no involvement, non-transmural, transmural diaphragmatic invasion.

RESULTS: A total of 213 (68%) patients underwent EPD, 237 (75.5%) had epithelioid disease and 57.6% were node positive. There was no difference between the three groups in terms of age, cell type, laterality, neoadjuvant chemotherapy and operation. There was a higher degree of diaphragm involvement in females (P = 0.01) and in patients with positive lymph nodes (P = 0.01). No evidence of diaphragmatic involvement was found following pathological assessment of the resection specimen in 119 patients (37.9%). The incidence of abdominal disease progression was 23.9%. There was no correlation with degree of diaphragmatic invasion (ρ = 0.01 P = 0.88). Overall survival of those with abdominal progression was similar to those with progression elsewhere: 14.5 vs 13.0 months (P = 0.79), and with those with no progression (16.7 months, P = 0.189). There was no difference in survival when stratified by diaphragmatic involvement (P = 0.44).

CONCLUSIONS: In our cohort, there was no evidence of diaphragmatic invasion in over 30% of patients, and we have also failed to find evidence that peritoneal disease progression affects overall survival following radical management. It may therefore theoretically be unnecessary to resect the diaphragm in all cases, and a pleurectomy-decortication could suffice. However, there is an unknown risk of R2 resection which would prejudice survival, and as such we would advocate resecting the diaphragm in all cases to avoid an R2 resection.