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MO14 - Mesothelioma II - Surgery and Multimodality (ID 121)
- Event: WCLC 2013
- Type: Mini Oral Abstract Session
- Track: Mesothelioma
- Presentations: 1
MO14.11 - Safety of hemithoracic pleural intensity-modulated radiation therapy (IMRT) for malignant pleural mesothelioma (MPM) in the multimodality setting: interim analysis of a phase II study. (ID 2802)
10:30 - 12:00 | Author(s): A. Rimner
Pleurectomy/decortication (P/D) is increasingly used for the surgical management of MPM. The presence of the remaining ipsilateral lung poses a challenge when delivering adjuvant radiation therapy, as the risk for radiation pneumonitis (RP) is high. We developed an IMRT technique targeting the entire pleura of the involved hemithorax, with promising early results. Here, we present the interim results of a prospective phase II study to determine the safety and toxicity profile of pleural IMRT following induction chemotherapy and P/D.
Twenty-nine patients with locally advanced MPM have been enrolled to date. All patients received up to four cycles of pemetrexed/platinum chemotherapy. P/D was performed for all resectable patients. Sequential hemithoracic pleural IMRT was then administered with the intent of achieving a total planned dose of 50.4Gy in 28 fractions, as previously described (Rosenzweig et al., IJROBP 2012). All patients were simulated with a 4D-CT scan. A PET scan for image fusion and radiation planning was available for all patients. A Simon two-stage design was applied. A safety analysis after the first 9 patients led to the identification of only one case with ≥grade 3 RP in the first 3 months. The cohort was therefore expanded to 28 evaluable patients, defined as having initiated RT. The primary endpoint is the incidence of ≥grade 3 RP defined per Common Terminology Criteria for Adverse Events, v4.0. Steroids are typically initiated for ≥grade 2 RP.
To date, 21 out of 29 patients total are evaluable. The median follow-up is 10 months. The median age at diagnosis is 66 years (range 38-79). Median KPS was 90% (range 70-90%). Three patients had sarcomatoid, 3 had biphasic and 23 had epithelioid MPM. All patients received chemotherapy. Eight patients (28%) had a partial response, nine patients (38%) progressed, and all others had stable disease. Twenty-four patients (83%) underwent surgical exploration. Five patients underwent an extended P/D or P/D, 11 had a partial P/D, and 8 were found to be unresectable. Eight patients were removed from the study prior to receiving IMRT (7 due to disease progression and 1 due to grade 4 pulmonary embolism after one cycle of chemotherapy). To date, nineteen patients have completed IMRT [median dose 4680cGy (range 4500 to 5040cGy)]; one patient had distant disease progression after 16 fractions; one patient is currently on treatment. Five patients experienced grade 2 RP that was successfully controlled with steroids. One patient experienced grade 3 RP requiring supplemental oxygen, but quickly improved after steroid initiation. Other commonly observed ≥grade 2 radiation-related toxicities included fatigue (37%), dyspnea (47%), nausea (42%), esophagitis (26%), and cough (11%). No grade 4 or 5 radiation-related toxicities were observed.
Hemithoracic pleural IMRT appears to have an acceptable toxicity profile in this ongoing phase II study. Early intervention with steroids is effective in controlling RP. This novel radiation technique has great promise as a component of lung-sparing multi-modality therapy in locally advanced MPM.
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