[1603] Thymoma Type According to World Health Organization Classification Does Not Provide Significant Prognostic Value by Stage: An International Study of Thymomas

R Gupta, M Okumura, O Rena, C Casadio, DJ Kim, NA Jambhekar, AM Marchevsky. Cedars Sinai Medical Center, LA, CA; Osaka University Graduate School of Medicine, Osaka, Japan; University of Eastern Piedmont, Maggiore della Carit General Hospital, Novara, Italy; Yonsei University College of Medicine, Seoul, Korea; Tata Memorial Hospital, Mumbai, India

Background: The World Health Organization (WHO) has proposed to categorize thymomas into A, B1, B2, B3 and AB types. Recent studies with metaanalysis have suggested that only 3 classes, A-B1-AB, B2 and B3 appear to be associated with significant prognostic differences. However, there is limited information regarding the prognostic value of thymoma WHO type, by Masaoka stage.
Design: 811 cases of thymoma classified by Stage and WHO type were collected from 6 medical centers in India, Italy, Japan, Korea, Germany and U.S. They included 317, 267, 144 and 73 patients in stages I-IV respectively and 73, 233, 141, 265 and 99 by WHO types A-B3 respectively. A minimum of 5-year follow up information was obtained as participating centers did not have 10-year follow-up information for the majority of their patients. Survival proportions were analyzed with Comprehensive Metaanalysis software version 2 ((Biostat, Inc, Englewood, NJ) to determine the prognostic value of WHO type by Stage.
Results: Metaanalysis of survival proportions using multiple comparisons of WHO types by Stage showed that in none of the 4 Stages, WHO class provided significant prognostic information.

Evaluation with Meta analysis of the Prognostic Value of WHO Classification of Thymomas: P values obtained by multiple paired comparisons of thymomas by WHO type and Stage

Stage	A vs. B	AB vs. B1	B1vs. B2	B2 vs. B3
I	0.84	0.56	0.59	0.12
II	0.28	0.46	0.64	0.4
III	0.51	0.95	0.7	0.86
IV	Not possible*	0.56	0.7	0.55

*None of the institutions encountered type A thymoma in stage IV.


Conclusions: Quantitative metaanalysis is difficult to perform when the data is split into 20 categories, including 4 stages and 5 WHO types and is limited by probable interobserver variability problems. A 5-year follow-up period is not optimal for tumors that are known to have an indolent clinical course. There is no current evidence to support the hypothesis that WHO classification provides significant prognostic 5-year survival information by Masaoka stage.
Category: Pulmonary

Monday, March 9, 2009 1:00 PM

Poster Session II # 214, Monday Afternoon