Defining the role of adjuvant radiotherapy for malignant pleural mesothelioma: a propensity-matched landmark analysis of the National Cancer Database.

backgroundMultimodality therapy may prolong survival among resectable malignant pleural mesothelioma (MPM). However, the role of adjuvant radiation remains controversial. We explored a large nationwide database to determine whether adjuvant radiation is associated with improved survival.

methodsThe National Cancer Database (NCDB) was queried to identify patients with MPM who received cancer-directed surgery between 2004-2013. Adjuvant radiation included intensity modulated radiation therapy or conformal 3D radiation. Propensity matching was performed with a 150-day landmark to address survivorship bias. Cox regression was used with an interaction term between pathologic stage and radiation.

resultsA total of 2,846 patients were identified as having undergone cancer-directed surgery for MPM; among whom 213 (7%) received adjuvant radiation. Adjuvant radiation was associated with improved survival among those who were stage I-II (P=0.024), but not stage III or IV (P=0.890 and P=0.183, respectively). After propensity matching, adjuvant radiation was associated with improved survival for those who were stage I-II [hazard ratio (HR) 0.52, P=0.035], whereas no similar effect was observed for those who were stage III or IV (P=0.190 and P=0.562, respectively). Multivariable regression revealed that sarcomatoid histology (HR 1.80, P=0.018) and stage IV disease (HR 1.65, P=0.033) were also associated with worse survival.

conclusionsAdjuvant radiation was associated with improved survival among those with pathologic stage I-II MPM. No survival advantage was observed for those with pathologic stage III or stage IV MPM, however. Our results justify the need for further prospective trials to investigate the utility of adjuvant radiotherapy among those with MPM.