Effect of radiation on outcome of types II and III PPB: A report from the International Pleuropulmonary Blastoma Registry.

Abstract

9521 Background: Pleuropulmonary blastoma (PPB) is a rare dysembryonic lung neoplasm of early childhood with progression from a purely cystic (Type I) lesion to a solid high-grade sarcoma Type III (T-III), or a mixed solid/cystic stage Type II (T-II). Surgery and chemotherapy are required for T-II and T-III PPB, but the benefit of radiation therapy for T-II and T-III PPB is debated and is being evaluated in this study. Methods: This is a retrospective analysis of central pathology-reviewed Types II and III PPB from the IPPBR. Treatments were chosen by physician, were not randomized, and included surgery and chemotherapy. The outcome of patients treated with upfront radiation (before progression or relapse) was compared to patients who did not receive radiation. Event-free survival (EFS) and overall survival (OS) were determined to last follow-up, using the Kaplan-Meier analysis, with log-rank test. Results: Outcome for 212 patients (117 Type-II and 95 Type III) was significantly better for T-II than T-III: EFS for T-II was 68.1% vs. T-III 45.7% (P=0.002), and OS for T-II was 75.2% vs. T-III 57.9% (p=0.01). Excluding patients with incomplete therapy information, 174 were treated with surgery and chemotherapy. Of these 44 (25%) also received radiation therapy; 130 patients did not. The table below shows comparison of radiated vs. non-radiated. Radiation provided no additional survival benefit, overall or by tumor Type. Multivariate analysis showed that gender and extent of primary tumor resection (biopsy vs. gross total resection) had no effect on outcome, however T-II vs. T-III retained prognostic significance. Conclusions: For this collection of advanced-type PPB, outcome is significantly better for T-II than T-III. For patients treated initially with surgery and chemotherapy, adding radiation therapy offered no improvement in event-free or overall survival. Limitations of this study include its retrospective nature and non-uniform treatment regimens. [Table: see text]