Hemithoracic Helical Tomotherapy (Ht) For Malignant Pleural Mesothelioma (Mpm): Early Results Of A Dose Escalation Experience

MPM has an aggressive course and high mortality rate. We report our experience using moderate hypofractionated HT. Initially 12 patients, 8 men and 4 women, with a median age of 65 at diagnosis, were treated for MPM with HT at San Raffaele Hospital, Milan, Italy, between 05/2006 – 11/2007. Following PET/CT simulation, HT was prescribed to a dose of 56 Gy in 2,24 Gy daily fractions. Ten patients had epithelioid mesothelioma, 2 nonepithelioid histology. Six patients were right sided, 6 left sided. Five patients had I Stage, 4 II Stage and 3 III Stage. One patient had extrapleural pneumectomy, 4 had pleurectomy and the others talc pleurodhesis. Ten of them received permetrexed-based chemotherapy. All patients were in progression. Median interval between diagnosis and HT was 11 months (6– 20). The lowest contra lateral lung V5, V10 and V20 possible were obtained. Median values were, right sided vs. left sided: 69% vs. 57,5%; 13,5% vs. 16% and 0 vs. 4%, respectively. Then 11 patients, 10 men and 1 women, with a median age of 66,5 years at diagnosis were treated with HT and simultaneous integrated boost (SIB) between 03/2008–03/2009. We prescribed 56 Gy to the PTV and 62,5 Gy to the BTV (2,5 Gy/fr). Two patients had biphasic and 9 epithelioid mesothelioma. Six were right sided and 5 left sided. Three patients had initially Stage I, 4 Stage II, 3 Stage III and 1 Stage IV. Six patients had pleurectomy and 3 patients had talc pleurodhesis. Nine patients received permetrexed based chemotherapy. Median interval between diagnosis and HT was 11,5 months (5–24 months). Median values of contra lateral lung V5, V10 and V20 were, right sided vs. left sided: 65,71 vs. 66%, 15,55 vs. 12,19%, 0,1 vs. 0,97% V20, respectively. After a median follow-up of 5 months (0–32) the first group of patients developed an acceptable acute and late toxicity (under G2 RTOG). At PET/CT or contrast enhanced CT evaluation we registered: 1 complete response and 4 partial response. The others had progressive disease. Two patients died in the first month (but not for HT toxicity). The CR patient had a recurrence 6 months later but is alive at 32 months. In the second group acute toxicity was higher, with 3 patients presenting G3 pulmonary toxicity. Six patients were evaluated with PET/CT and 2 with contrast enhanced CT: 4 PR (1 with contra lateral progression), 3 stable disease and 1 not evaluable response were recorded. The median survival in the second group was 7 months (1–12 months). The HT succeeds in an excellent target coverage and homogeneity of the dose distribution within PTV together with acceptable sparing of organs at risk. With SIB on BTV dose escalation, higher, but acceptable toxicity was registered. The second group follow-up is too short to evaluate the results.