Radical Hemithoracic Radiotherapy Versus Palliative Radiotherapy in Non-metastatic Malignant Pleural Mesothelioma: Results from a Phase 3 Randomized Clinical Trial.

PURPOSE: We conducted a phase 3 randomized clinical trial to assess whether radical hemithoracic radiation therapy (RHR) compared with palliative radiation therapy (PR) can achieve overall survival (OS) advantages in patients with malignant pleural mesothelioma (MPM). METHODS AND MATERIALS: From August 2014 to May 2018, patients with histologically diagnosed nonmetastatic MPM, who underwent nonradical lung-sparing surgery and chemotherapy (CHT), were randomly assigned (1:1) to receive RHR or PR. RHR total dose to the involved pleural cavity was 50 Gy in 25 fractions, and the gross residual disease received a simultaneous integrated boost of 60 Gy. The primary endpoint was OS. Secondary endpoints were local control, distant metastasis-free survival, progression-free survival, and acute and late toxicity rates. A sample size of 108 patients considering a type I error (α) of 0.05 and a statistical power of 80% was calculated to prove that RHR could improve the 2-year OS. OS was estimated with the Kaplan-Meier method and the log-rank test (2-sided) tested differences between arms. The univariate and multivariate analyses were performed using Cox proportional hazard model. Possible prognostic factors investigated: age, sex, performance status, lung surgery, gross residual disease, and histology. RESULTS: One hundred eight patients were randomized: 53 to the PR arm and 55 to the RHR arm. Median follow-up was 14.6 months. The 2-year OS rate was 58% in the RHR arm versus 28% in the PR arm (hazard ratio, 0.54; 95% confidence interval, 0.31-0.95; P = .031). In the RHR arm: 11 patients experienced acute toxicity grade ≥3, 17 patients had grade 3 to 4 late toxicity. Nine patients experience a grade ≥2 pneumonitis, including 1 patient with grade 5. CONCLUSIONS: RHR significantly improves survival in patients with MPM treated with nonradical lung-sparing surgery and CHT compared with palliative treatments, although it is associated with a nonnegligible toxicity profile.

Feasibility and Oncological Outcome of Preoperative Chemoradiation With IMRT Dose Intensification for Locally Advanced Esophageal and Gastroesophageal Cancer.

PURPOSE: To explore the feasibility and efficacy of a dose intensification with Intensity Modulated Radiation Therapy and Simultaneous Integrated Boost (IMRT-SIB) in locally advanced esophageal and gastroesophageal cancer (GEJ). METHODS AND MATERIALS: We retrospectively analyzed a series of 69 patients with esophageal or GEJ cancer treated at our Institute, between 2016 and 2019, with preoperative IMRT and SIB up to 52.5-54 Gy in 25 fractions in 5 weeks and concurrent carboplatin (AUC2) and paclitaxel (50 mg/m2), as in the CROSS regimen. RESULTS: All patients completed the planned IMRT-SIB program with a median of four (range 1-5) cycles of concurrent paclitaxel/carboplatin. Compliance to IMRT-SIB was 93%, whereas 54% of patients received four to five cycles and 87% at least three cycles of concurrent carboplatin/paclitaxel. Grade 3 toxicity was reported in 19% of patients. Complete clinical response (cCR) was achieved in 48%, and 13% had disease progression after chemoradiation (CRT). Overall, 49% of patients underwent surgery; reasons for non-operation included cCR in cervical tumor location (10%) or cCR and patient decision (13%). A pathologic complete response (pCR) was achieved in 44% of resected patients. Postoperative complications and mortality rates were 21 and 6%, respectively. At a median follow-up of 12 months (6-25), 2-year overall and progression-free (PFS) survival rates were 81 and 54%, respectively. No difference in PFS by histologic type in operated patients was reported. Non-operated cCR patients had higher PFS, including cervical locations and selected cCR patients who decided for non-operation (75 vs 30%, p < 0.01). CONCLUSION: The study reported favorable results in safety and feasibility of the IMRT-SIB dose intensification in our preoperative CRT program. The toxicity was acceptable, allowing a high compliance to intensified radiation doses with dose reduction of concurrent paclitaxel/carboplatin in some patients. The high rate of cCR and pCR suggested this intensified program is effective in the preoperative CRT and, for selected responsive patients, in the non-operative approach to esophageal and GEJ cancer. The 2-year survival rates were promising. A prospective study is being planned to confirm these observations.

Electron radiotherapy (IOERT) for applications outside of the breast: Dosimetry and influence of tissue inhomogeneities.

PURPOSE: The purpose of study is to investigate the dosimetry of electron intraoperative radiotherapy (IOERT) of the Intraop Mobetron 2000 mobile LINAC in treatments outside of the breast. After commissioning and external validation of dosimetry, we report in vivo results of measurements for treatments outside the breast in a large patient cohort, and investigate if the presence of inhomogeneities can affect in vivo measurements. METHODS AND MATERIALS: Applicator factors and profile curves were measured with a stereotactic diode. The applicators factors of the 6 cm flat and beveled applicators were also confirmed with radiochromic films, parallel-plate ion chamber and by an external audit performed with ThermoLuminescent Dosimeters (TLDs). The influence of bone on dose was investigated by using radiochromic films attached to an insert equivalent to cortical bone, immersed in the water phantom. In vivo dosimetry was performed on 126 patients treated with IOERT using metal oxide-silicon semiconductor field effect transistors (MOSFETs) placed on the tumor bed. RESULTS: Relatively small differences were found among different detectors for measurements of applicator factors. In the external audit, the agreement with the TLD was mostly within ±0.2%. The largest increase of dose due to the presence of cortical bone insert was +6.0% with energy 12 MeV and 3 cm applicator. On average, in vivo dose was significantly (+3.1%) larger than prescribed dose. CONCLUSION: IOERT in applications outside the breast results in low discrepancies between in vivo and prescribed doses, which can be also explained with the presence of tissue inhomogeneity.

Prediction of skin dose in low-kV intraoperative radiotherapy using machine learning models trained on results of in vivo dosimetry.

PURPOSE: The purpose of this study was to implement a machine learning model to predict skin dose from targeted intraoperative (TARGIT) treatment resulting in timely adoption of strategies to limit excessive skin dose. METHODS: A total of 283 patients affected by invasive breast carcinoma underwent TARGIT with a prescribed dose of 6 Gy at 1 cm, after lumpectomy. Radiochromic films were used to measure the dose to the skin for each patient. Univariate statistical analysis was performed to identify correlation of physical and patient variables with measured dose. After feature selection of predictors of in vivo skin dose, machine learning models stepwise linear regression (SLR), support vector regression (SVR), ensemble with bagging or boosting, and feed forward neural networks were trained on results of in vivo dosimetry to derive models to predict skin dose. Models were evaluated by tenfold cross validation and ranked according to root mean square error (RMSE) and adjusted correlation coefficient of true vs predicted values (adj-R2 ). RESULTS: The predictors correlated with in vivo dosimetry were the distance of skin from source, depth-dose in water at depth of the applicator in the breast, use of a replacement source, and irradiation time. The best performing model was SVR, which scored RMSE and adj-R2 , equal to 0.746 [95% confidence intervals (CI), 95% CI 0.737,0.756] and 0.481 (95% CI 0.468,0.494), respectively, on the tenfold cross validation. CONCLUSION: The model trained on results of in vivo dosimetry can be used to predict skin dose during setup of patient for TARGIT and this allows for timely adoption of strategies to prevent of excessive skin dose.

Radical Radiation Therapy After Lung-Sparing Surgery for Malignant Pleural Mesothelioma: Survival, Pattern of Failure, and Prognostic Factors.

PURPOSE: To prospectively assess the survival, patterns of failure, and prognostic factors in a large cohort of patients with malignant pleural mesothelioma who had undergone a novel trimodal therapeutic approach, including lung-sparing surgery, chemotherapy, and subsequent treatment with high doses of intensity modulated radiation therapy (IMRT) to the whole hemithorax. METHODS AND MATERIALS: The analysis was conducted on the data from 69 patients. Of the 69 patients, 35 underwent extended pleurectomy/decortication (P/D), with resection of the entire pleura, along with portions of the pericardium and diaphragm and 34, partial pleurectomy, defined as partial removal of parietal or visceral pleura for diagnostic purposes, leaving gross tumor behind in all cases. All patients received cisplatin/pemetrexed chemotherapy. Postoperative IMRT was delivered to the entire hemithorax, excluding the intact lung. The IMRT dose was 50 Gy in 25 fractions. Any fluorodeoxyglucose-avid areas or regions of particular concern for residual disease were given a simultaneous boost to 60 Gy. RESULTS: The median follow-up duration was 19 months. No difference was seen in overall survival and locoregional control between the extended P/D group and the partial pleurectomy group. The 2-year overall survival was 65% and 58% in the extended P/D and partial pleurectomy groups, respectively (P=.94). Locoregional control at 2 years was 65% and 64% in the extended P/D and partial pleurectomy groups, respectively (P=.75). The predominant pattern of failure was distant: 19 patients (27.5%) developed distant metastases as the first site of relapse. Gross residual disease after surgery was significantly associated with overall survival (hazard ratio 3.45). One fatal pneumonitis was reported; 14 cases (20%) of grade 2 to 3 pneumonitis were documented. CONCLUSIONS: Radical IMRT after lung-sparing surgery and chemotherapy for malignant pleural mesothelioma leads to promising survival results and acceptable toxicity rates. The similarity of survival between patients treated with extended P/D or partial pleurectomy observed in our study is intriguing.