The Dosimetric Characteristics and Potential Limitation in Clinical Application of a Low Energy Photon Intra-Operative Radiotherapy System

Purpose: To investigate the dosimetric characteristics of a low energy photon intra-operative radiotherapy (IORT) system and explore its potential limitation in clinical application. Methods: A special water phantom, a parallel-plate ionization chamber and an electrometer were used to measure the depth dose rate, isotropy of dose distribution in X/Y plane, dosimetry reproducibility of bare probe and spherical applicators of different size which were used in comparison with the system data. Results: The difference in depth dose rate between the measurement and system data for bare probe is -2.16% ± 1.36%, the range of the relative deviation for isotropy in the X/Y plane is between -1.9% and 2.1%. The difference in depth dose rate, transfer coefficient, isotropy in X/Y plane between the measurement and system data for the whole set of spherical applicators is -10.0% - 2.3%, -8.9% - 4.2% and -1.6% - 2.6%, respectively. Higher surface dose rate and steeper gradient depth dose are observed in smaller spherical applicators. The depth dose rate and isotropy for bare probe and spherical applicators have been shown good reproducibility. The uncertainty of measurement is associated with the positioning accuracy, energy response, noise current and correction function f’(R). Conclusions: Thorough commissioning of the low energy photon IORT system helps us better understand the dosimetry characteristics, verify the system data, obtain adequate data for clinical application and routine quality assurance. The steep gradient depth dose and limited treatment range may restrain its potential in clinical application.

Dosimetric Comparison of Volumetric Modulated Arc Therapy (VMAT), 5F Intensity Modulated Radiotherapy (IMRT) and 3D Conformal Radiotherapy (3DCRT) in Rectal Carcinoma Receiving Neoadjuvant Chemoradiotherapy

Objective: To investigate better dosimetric distribution of volumetric modulated arc therapy (VMAT) vs. 5F intensity modulated radiotherapy (IMRT) and 3D conformal radiotherapy (3DCRT) in patients with locally advanced rectal cancer (LARC) when treated with neoadjuvant chemoradiotherapy. Methods: 3D-CRT, 5F-IMRT and VMAT plans for preoperative radiotherapy were 66011designed in 12 patients with locally advanced rectal cancer. The conformity index (CI) and homogeneity index (HI) in target volume, and the dose and volume of the organs at risk (OAR) irradiated including small bowel, bladder and bilatera1 femoral heads were compared among the three plans. Results: The CI for planning target volume (PTV) 2 and HI for PTV1 of VMRT and 5F-IMRT were superior to 3D-CRT. The CI of VMAT, 5F-IMRT and 3D-CRT plans were 0.71, 0.69 and 0.62 (p = 0.011 and p = 0.019, respectively). The HI of the VMAT and 5F-IMRT plans were both 1.04 and 3D-CRT planning was 1.06 (p = 0.022 and p = 0.006, respectively). The V35 - V45 of small bowel in VMAT were significantly less than in 5F-IMRT and 3D-CRT. V35 was 47.0, 56.4, and 72.8 cm3 for VMAT, 5F-IMRT, and 3D-CRT (p = 0.021 and p = 0.034, respectively), while V40 was 30.5, 35.5, 45.1 cm3 (p = 0.024 and p = 0.032, respectively) and V45 was 15.1, 18.1, 30.0 cm3 (p = 0.033 and p = 0.032, respectively). The D5, V30 and V50 of bladder in 3D-CRT were less than in VMAT and 5F-IMRT planning (p = 0.034, 0.004, 0.002 and p = 0.027, 0.003, 0.002, respectively). The Dmean of left femoral head in VMAT and 5F-IMRT were less than in 3D-CRT planning (p = 0.028 and p = 0.022, respectively) and the Dmean, V30 of right femoral head in VMAT and 5F-IMRT were better than in 3D-CRT planning (p = 0.044, 0.036 and p = 0.023, 0.028, respectively). Conclusions: Dosimetric analyses demonstrated that IMRT is superior to 3D-CRT in the conformity and homogeneity of dose distribution to the target volume, and provide a better protection to OARs sparing in patients with locally advanced rectal cancer for preoperative radiotherapy. With similar target coverage, VMRT is superior to 5F-IMRT in normal tissue sparing.

Impact of Olaparib for Maintenance Monotherapy on Survival in Breast and Ovarian Cancer: A Systematic Review and Pooled Analysis of Published Trials

Purpose: To assess the efficacy and safety of Olaparib, a PARP inhibitor on progression-free survival (PFS), objective response rate (ORR) and overall survival (OS) in patients with breast and ovarian cancer. Methods: Research data from clinical trials through PubMed, Science Citation Index, Elsevier Science Direct and Cochrane Library of all published studies exploring the PFS, ORR or OS of Olaparib for maintenance monotherapy on survival in breast and ovarian cancer were analysed. Pooled estimates of the ORR, weighted medians of PFS and OS from all Olaparib were calculated. Assessment of quality and level of evidence was assigned by Cochrane guidelines and guidelines of Oxford Centre for Evidence-Based Medicine. Results: Data of 893 patients (731 olaparib;162 control) from 6 trials, 2 randomised controlled trials and 4 non-randomised trials, were included. The overall median weighted PFS and OS in patients treated with Olaparib were 5.9 and 19.1 months, respectively. The pooled ORR was 25%. Olaparib showed a greater effect on PFS in patients with both wild-type BRCA and BRCA mutant gene. The most common toxicity were nausea and vomiting. Conclusions: Olaparib as maintenance monotherapy for breast and ovarian cancer is associated with promising outcomes including increased response rate and improved PFS. Its potential in clinical application is needed for further investigation in phase III trials.

The Application of Image Guided Radiotherapy on the Precision of Intensity Modulated Radiotherapy in Patients with Locally Advanced Rectal Cancer

Objective: To investigate the effect of onboard image (OBI) system-based image guided radiotherapy (IGRT) on the precision of fractionated intensity modulated radiotherapy (IMRT) for patients with locally advanced rectal cancer. Methods: The IGRT validation images of the 12 patients with rectal cancer were obtained after initial setup by the OBI system of Varian Novalis TX linear accelerator, and registered to the planning CT image system. Subsequently, the setup deviations on three translational directions [ventral-dorsal direction (VD), cranial-caudal direction (CD) and lateral direction (LD)] for the three-validation phase including Pre-treatment (Pre-RT1), repositioning (Pre-RT2) and Post-treatment (Post-RT) were obtained and comparatively analyzed. Results: The frequency of setup deviation of ≤2.0 mm in the lateral, cephalocaudal and ventral direction was 83.01%, 65.71%, and 68.91%, respectively for Pre-RT1;100%, 98.72% and 100%, respectively for Pre-RT2;100%, 97.76%, and 99.68%, respectively for Post-RT. Compared with the Pre-RT1 phase, the ranges of setup deviation on Pre-RT2 and Post-RT phases possessed a significant contraction trend. The absolute values of setup deviations on the three translation directions between the Pre-RT1 and Pre-RT2 or Post-RT were statistically significant (p < 0.05). Through positioning adjustment based on IGRT based on the OBI system, the setup deviations on the three translational directions decreased significantly. Conclusion: Application of OBI-based daily IGRT may help improve the precise delivery of fractionated IMRT by decreasing the inter- and intra-fractionated setup deviation in the ventral-dorsal direction, cranial-caudal direction and lateral direction for patients with locally advanced rectal cancer.

Clinicopathological and Prognostic Significance of Circulating Tumor Cells in Patients with Head and Neck Cancer: A Meta-Analysis

Purpose: The aim of the study was to evaluate the association between clinicopathological and prognostic significance and circulating tumor cells (CTCs) in patients with head and neck cancer. Methods: We searched PubMed, MEDLINE, BioMed, and EMbase databases for studies that assessed the association between clinicopathological and prognostic significance and CTCs in patients with head and neck cancer. Studies obtained from search strategy were screened using pre-specified criteria, and necessary data were retrieved for meta-analysis. Results: Seventeen studies with 816 patients were eligible for combined analysis. Presence of CTCs in peripheral blood was significantly associated with N stage (OR 0.50, 95%CI [0.30, 0.81], n = 10, P = 0.005). Patients in the high-CTC group were significantly associated with poorer disease-free survival (DFS;HR = 1.73, 95%CI [1.01 - 2.96], P = 0.050) and poorer overall survival (OS;HR = 2.53, 95%CI [1.37 - 4.69] P = 0.003). Further analyses indicated strong prognostic powers of CTCs in non-RT-PCR group and pre-treatment group. Conclusion: Our meta-analysis indicates that presence of CTCs is associated with higher N stage and poorer prognosis in patients with head and neck cancer. The potential for further clinical application may be needed for further investigation.Purpose: The aim of the study was to evaluate the association between clinicopathological and prognostic significance and circulating tumor cells (CTCs) in patients with head and neck cancer. Methods: We searched PubMed, MEDLINE, BioMed, and EMbase databases for studies that assessed the association between clinicopathological and prognostic significance and CTCs in patients with head and neck cancer. Studies obtained from search strategy were screened using pre-specified criteria, and necessary data were retrieved for meta-analysis. Results: Seventeen studies with 816 patients were eligible for combined analysis. Presence of CTCs in peripheral blood was significantly associated with N stage (OR 0.50, 95%CI [0.30, 0.81], n = 10, P = 0.005). Patients in the high-CTC group were significantly associated with poorer disease-free survival (DFS;HR = 1.73, 95%CI [1.01 - 2.96], P = 0.050) and poorer overall survival (OS;HR = 2.53, 95%CI [1.37 - 4.69] P = 0.003). Further analyses indicated strong prognostic powers of CTCs in non-RT-PCR group and pre-treatment group. Conclusion: Our meta-analysis indicates that presence of CTCs is associated with higher N stage and poorer prognosis in patients with head and neck cancer. The potential for further clinical application may be needed for further investigation.