MDACC IMRT MPM Toxicity

Background

Retrospective analysis. N=63 consecutive MPM patients who underwent EPP → hemithoracic IMRT at MD Anderson. Aim: incidence of fatal pulmonary events and dose–volume predictors of fatal pulmonary toxicity. IMRT adopted over earlier 3D-CRT to spare contralateral critical structures.

Interventions and follow up

Treatment: Hemithoracic IMRT post-extrapleural pneumonectomy for MPM
Primary endpoint: Pulmonary toxicity and fatal pneumonitis; dose–volume predictors
mFollow up: Variable per cohort

Results

Deaths within 6 months of IMRT: 23/63 (37%) — 10 cancer recurrence, 6 pulmonary (4 pneumonia, 2 pneumonitis), 7 other non-cancer (2 PE, 1 bronchopleural fistula, 4 unknown)
Pulmonary-related death (PRD): 6 patients (9.5%)
Independent predictor of PRD (multivariate): V20 (% contralateral lung receiving ≥20 Gy): OR 1.50 per 1% increase, P=.017
Independent predictor of non-cancer death: V20: OR 1.21 per 1% increase, P=.033

Adverse events

Fatal pulmonary toxicity: 9.5% (PRD)
Non-cancer deaths within 6 months: 13 patients
Specific events: Fatal pneumonitis 2, pneumonia 4
Critical parameter: Contralateral lung V20; mean V20 of survivors considerably lower than standard thoracic IMRT constraints

Conclusions

Fatal pulmonary toxicity occurred in 9.5% within 6 months of IMRT after EPP, with contralateral lung V20 the sole independent predictor of pulmonary- and non-cancer-related death. IMRT plans after EPP must keep contralateral V20 as low as possible.

Key Limitations

Retrospective, single-institution, small N; early IMRT learning curve; toxicity attribution within heavily pre-treated post-EPP patients; no comparator technique arm.

Clinical Context

Cautionary report on EPP + IMRT mortality that motivated stringent contralateral lung constraints and the shift to lung-sparing P/D + hemithoracic IMRT (IMPRINT).

References