1. HIGH DOSE RADIOTHERAPY IN THE TREATMENT OF PLEURAL MESOTHELIOMA AFTER PLEURECTOMY/DECORTICATION OR BIOPSY: LONG TERM FOLLW UP, ACUTE AND LATE TOXICITY Parisi E, Romeo A, Ghigi G, Delmonte A, Dipalma B, Micheletti S, Neri E, Sarnelli A, Arienti C, Polico R. IRCCS Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori Meldola (FC) ITALY Digital Poster Discussion 12 Lung 2 - Locally Advanced Disease and Imaging Presentation No. 1143 Abstract 2050 Monitor number: 10 Corresponding author: Antonino Romeo, MD, IRST IRCCS Meldola FC (ITA), t.romeo@libero.itt.romeo@libero.it - a.romeo@irst.emr.ita.romeo@irst.emr.it

2. Purpose In patients with MPM (Malignant Pleural Mesothelioma) the role of radiation therapy in intact lung after pleurectomy/decortication (P/D), or after the biopsy is uncertain. We have implemented a technique that employs the intensity modulated arch therapy (IMAT) and accelerated hypofractionated schedule of radiotherapy to treat them while reducing the lung toxicity (IRST protocol 162.07). Patients 7 female-29 male; median age 70 ys (44-85), median FU 37months (range 7-54); CLINICAL STAGE : I (11 pts); II (4 pts); III (14 pts); IV (7 pts); 19 pts underwent RT after pleurectomy/decortication; 17 pts underwent RT after biopsy ; Key words: Malignant pleural mesothelioma, pleurectomy/decortication, accelerated hypofractionation radiotherapy, Helical Tomotherapy. Objective: To evaluate the feasibility and the efficacy; To evaluate acute and late toxicity; To evaluate overall survival

3. left lung Acute toxicity (n:36) G1G2G3G4 Dyspnea 24 (66%) 4 (11%)-- Cough 13 (36%) 5 (14%)-- Fever 2 (5%) -- Esophagitis 3 (8%) -- Fatigue 5 (14%) -- Pneumonitis 35 (97%) 1 (3%)- Late toxicity (n:36) G1G2G3G4 Dyspnea 8 (22%) 1 (3%) -- Cough -1 (3%) -- Pneumonitis 15 (42%) 1 (3%) - 36 pts studied for acute and late toxicity

4. Overall survival TAKE HOME MESSAGE The hypofractionation protocols are possible thanks to new technologies In our experience was mandatory the maximum sparing of healthy lung (never exceeded the V5/5 ratio) With similar rates of efficacy a shortened treatment time interval would reduce overall treatment costs and improve patient compliance. As high grade (acute and late) toxicity was not observed, there is a margin to enhance the dose to T and N N. patients N. events (%) Median OS (95% CI) NO SURG1713 (76.5)19.4 (12.6-24.1) SURG1912 (63.2)21.6 (13.3-29.5) No Surgery Surgery