IMPRINT

Background

Phase 2 two-center trial (IMPRINT; MSKCC, MD Anderson). N=45 MPM. Lung-sparing surgery (pleurectomy/decortication, P/D) rather than EPP → hemithoracic IMRT to pleural surfaces, preserving the ipsilateral lung and changing the dosimetric challenge vs EPP + IMRT.

Interventions and follow up

Treatment: Pemetrexed + platinum chemotherapy and lung-sparing P/D, followed by hemithoracic IMRT (IMPRINT) to pleural surfaces
Primary endpoint: Grade ≥3 pulmonary toxicity at 6 months
mFollow up: Median 12 months

Results

Started IMPRINT: 27 patients evaluable for primary endpoint
Grade 3 radiation pneumonitis (RP): 2/27 (7.4%); both resolved with corticosteroids
Grade 2 RP: 6 patients
Median PFS: 12.4 months
Median OS: 23.7 months
2-yr OS (resectable tumors): 59%
2-yr OS (unresectable): 25%

Adverse events

Grade ≥3 RP: 7.4% (2/27) — primary endpoint met (acceptable)
Grade 4–5 radiation-related: None
Resolution: Both grade 3 RP events resolved after corticosteroids
Chemotherapy: Pemetrexed + platinum toxicity standard

Conclusions

Hemithoracic IMRT after P/D (IMPRINT) is safe with only 7.4% grade ≥3 RP, avoiding the fatal contralateral lung toxicity seen with EPP + IMRT. Median OS 23.7 months and 2-yr OS 59% (resectable) are encouraging; a feasible lung-sparing alternative to EPP-based trimodality.

Key Limitations

Small single-arm phase 2; only 27 of 45 reached IMRT; no randomized comparator; survival in selected/resectable patients; short follow-up.

Clinical Context

Established lung-sparing P/D + hemithoracic IMRT as a safer alternative to EPP + IMRT; foundation for the subsequent randomized IMPRINT-2 evaluation of pleural IMRT.

References