PTV margin definition in hypofractionated IGRT of localized prostate cancer using cone beam CT and orthogonal image pairs with fiducial markers.

PURPOSE: To evaluate PTV margins for hypofractionated IGRT of prostate comparing kV/kV imaging or CBCT. PATIENTS AND METHODS: Between 2009 and 2012, 20 patients with low- (LR), intermediate- (IR) and high-risk (HR) prostate cancer were treated with VMAT in supine position with fiducial markers (FM), endorectal balloon (ERB) and full bladder. CBCT's and kV/kV imaging were performed before and additional CBCT's after treatment assessing intra-fraction motion. CTVP for 5 patients with LR and CTVPSV for 5 patients with IR/HR prostate cancer were contoured independently by 3 radiation oncologists using MRI. The van Hark formula (PTV margin =2.5Σ +0.7σ) was applied to calculate PTV margins of prostate/seminal vesicles (P/PSV) using CBCT or FM. RESULTS: 172 and 52 CBCTs before and after RT and 507 kV/kV images before RT were analysed. Differences between FM in CBCT or in planar kV image pairs were below 1 mm. Accounting for both random and systematic uncertainties anisotropic PTV margins were 5-8 mm for P (LR) and 6-11 mm for PSV (IR/HR). Random uncertainties like intra-fraction and inter-fraction (setup) uncertainties were of similar magnitude (0.9-1.4 mm). Largest uncertainty was introduced by CTV delineation (LR: 1-2 mm, IR/HR: 1.6-3.5 mm). Patient positioning using bone matching or ERB-matching resulted in larger PTV margins. CONCLUSIONS: For IGRT CBCT or kV/kV-image pairs with FM are interchangeable in respect of accuracy. Especially for hypofractionated RT, PTV margins can be kept in the range of 5 mm or below if stringent daily IGRT, ideally including prostate tracking, is applied. MR-based CTV delineation optimization is recommended.

Clinical outcome of postoperative highly conformal versus 3D conformal radiotherapy in patients with malignant pleural mesothelioma.

BACKGROUND: Radiotherapy (RT) is currently under investigation as part of a trimodality treatment of malignant pleural mesothelioma (MPM). The introduction of highly conformal radiotherapy (HCRT) technique improved dose delivery and target coverage in comparison to 3-dimensional conformal radiotherapy (3DCRT). The following study was undertaken to investigate the clinical outcome of both radiation techniques. METHODS: Thirty-nine MPM patients were treated with neoadjuvant chemotherapy, extrapleural pneumonectomy (EPP) and adjuvant RT. Twenty-five patients were treated with 3DCRT, and 14 with HCRT (Intensity modulated radiotherapy or volumetric modulated arc therapy). Overall survival, disease free survival, locoregional recurrence and pattern of recurrence were assessed. A matched pair analysis was performed including 11 patients of each group. RESULTS: After matching for gender, age, histology, tumor stage and resection status, HCRT seemed superior to 3DCRT with a local relapse rate of 27.3% compared to 72.7% after 3DCRT (p = 0.06). The median time to local relapse was increased by 49% with HCRT in comparison to 3DCRT from 10.9 ± 5.4 months to 16.2 ± 3.1 months (p = 0.06). The median overall survival was 22.3 ± 15.3 months for HCRT and 21.2 ± 9.2 months for 3DCRT (p = 0.57). Recurrence analysis showed that in-field local relapses occurred in previously underdosed regions of the tumor bed in 16% of patients treated with 3DCRT and in 0% of HCRT patients. CONCLUSIONS: The use of HCRT increases the probability of local control as compared to 3DCRT by improving target volume coverage. HCRT did not improve overall survival in this patient series due to the high rate of distant recurrences.

Intensity-modulated radiotherapy and volumetric-modulated arc therapy for malignant pleural mesothelioma after extrapleural pleuropneumonectomy.

Radiotherapy reduces the local relapse rate after pleuropneumonectomy of malignant pleural mesothelioma (MPM). The optimal treatment technique with photons remains undefined. Comparative planning for intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) was performed. Six MPM patients with significant postoperative intrathoracic air cavities were planned with IMRT and VMAT. A dose comparison for the targets and organ at risks (OAR) was performed. Robustness was assessed in respect to the variation of target dose with change in volume of air cavities. VMAT reduced the dose to the contralateral lung by reducing the volume covered by 13 Gy and 20 Gy by a factor 1.8 and 2.8, in respect to IMRT (p = 0.02). Dose distribution with VMAT was the most stable technique in regard to postsurgical air cavity variation. For IMRT, V90, V95, and the minimal target dose decreased by 40%, 64%, and 12% compared to 29%, 47%, and 7% with VMAT when air cavity decreased. Two arcs compared to one arc decreased the dose to all the organs at risk (OAR) while leaving PTV dose coverage unchanged. Increasing the number of arcs from two to three did not reduce the dose to the OAR further, but increased the beam-on time by 50%. Using partial arcs decreased the beam-on time by 43%. VMAT allows a lower lung dose and is less affected by the air cavity variation than IMRT. The best VMAT plans were obtained with two partial arcs. VMAT seems currently the most suitable technique for the treatment of MPM patients when air cavities are remaining and no adaptive radiotherapy is performed.

Remission rates in breast cancer treated with preoperative chemotherapy and radiotherapy.

PURPOSE: Evaluation of remission rates after neoadjuvant chemotherapy alone or followed by preoperative radiotherapy. PATIENTS AND METHODS: 194 women with 198 biopsy-proven breast tumors were evaluated in this retrospective study. Of the 198 cases evaluated, 64 received neoadjuvant chemotherapy followed by surgery and adjuvant irradiation (CT group). In 134 cases, sequential preoperative chemo-/radiotherapy (CT-RT group) was given. In both groups, endocrine treatment was initiated in case of positive hormone receptor status after chemotherapy. The whole breast was homogeneously irradiated using 2-Gy fractions up to a total dose of 50 Gy, followed by a boost of 6-11 Gy to the tumor. RESULTS: A histologically proven complete remission (pCR) was achieved in 3% (2/64) in the CT and in 42% (56/134) in the CTRT group. The logistic regression analysis, including clinical tumor category (cT), lymph node (cN) and metastasis status (cM), grading (G), hormone receptor status (HRS), number of preoperative chemotherapy cycles, preoperative tumor volume, and preoperative radiotherapy, revealed that HRS (p = 0.0232) and radiotherapy (p < 0.0001) were significant factors for achieving pCR. CONCLUSION: Combination of neoadjuvant chemo-/radiotherapy results in significantly higher rates of complete remission than neoadjuvant chemotherapy alone. The significance for tumor-free and overall survival has to be evaluated.