Poor Prognostic Factors in Patients with Malignant Pleural Mesothelioma Classified as Pathological Stage IB According to the Eighth Edition TNM Classification.

INTRODUCTION

The change in TNM classification of malignant pleural mesothelioma (MPM) between the seventh and eighth edition classifications has resulted in the downstaging of many advanced-stage patients into pathological stage IB. Many mesotheliomas without lymph node metastasis have been classified as stage IB in the eighth edition classification. Stage IB mesotheliomas comprised a heterogeneous group with different prognosis. It is necessary to clarify the prognostic factors in this group.

METHODS

Between September 2009 and August 2016, a total of 89 patients with MPM underwent curative intent surgery [pleurectomy decortication n = 57 (64.1%), extrapleural pneumonectomy n = 32 (35.9%)] at our institution. Of these, 40 were reclassified as stage IB according to the eighth edition TNM classification. Independent unfavorable prognostic factors were identified by univariate analyses using the log-rank test and Cox proportional hazards regression models.

RESULTS

Three independent significant factors were identified that indicated an unfavorable prognosis: a nonepithelioid subtype, lymphovascular invasion, and preoperative forced expiratory volume in 1 s (FEV1) < 2000 ml. Patients with no, one, and two of these risk factors showed 3-year overall survival probabilities of 94.7, 62.5, and 0%, respectively. The 3-year survival of patients with one factor did not differ significantly from that of patients with stage III MPM, whereas that of patients with two factors was significantly shorter (p = 0.015).

CONCLUSIONS

Independent poor prognostic factors for patients with stage IB MPM patients, allowing subgroups with poorer and more favorable prognoses to be identified. This should help personalize decisions on adjuvant chemotherapy.