The IASLC Mesothelioma Staging Project: Proposals for Revisions of the T descriptors in the forthcoming Eighth edition of the TNM classification for pleural mesothelioma

Journal of Thoracic Oncology 2016 September 23 [Epub ahead of print] [Link]

Nowak AK, Chansky K, Rice DC, Pass HI, Kindler HL, Shemanski L, Billé A, Rintoul R, Batirel HF, Thomas CF, Friedberg J, Cedres S, de Perrot M, Rusch VW; Staging and Prognostic Factors Committee, Advisory Boards and Participating Institutions


Current T component for malignant pleural mesothelioma (MPM) has been predominantly informed by surgical datasets and consensus. The International Association for the Study of Lung Cancer undertook revision of the 7th Edition staging system for MPM with the goal of developing recommendations for the 8th edition.
Data elements including detailed T descriptors were developed by consensus. Tumor thickness at three pleural levels was also recorded. An electronic data capture system was established to facilitate data submission.
3,519 cases were submitted to the database. Of those eligible for T component analysis, 509 cases had only clinical staging; 836 cases had only surgical staging; and 642 cases had both available. Survival was examined for T categories according to the current 7th edition staging system. There was clear separation between all clinically staged categories except T1a vs. T1b (HR 0.99, p=0.95) and T3 vs. T4 (HR 1.22, P=0.09), although numbers of T4 cases were small. Pathological staging failed to demonstrate a survival difference between adjacent categories with the exception of T3 vs. T4. Performance improved with collapse of T1a and T1b into a single T1 category; no current descriptors were shifted or eliminated. Tumour thickness and nodular or rind-like morphology were significantly associated with survival.
A recommendation to collapse both clinical and pathological T1a and T1b into a T1 classification will be made for the 8th edition staging system. Simple measurement of pleural thickness has prognostic significance and should be examined further with a view to incorporation into future staging.