Integration of radiobiological modeling and indices in comparative plan evaluation: A study comparing VMAT and 3D-CRT in patients with NSCLC.

PURPOSE: The purpose of this article was to generate an algorithm to calculate radiobiological endpoints and composite indices and use them to compare volumetric modulated arc therapy (VMAT) and 3-dimensional conformal radiation therapy (3D-CRT) techniques in patients with locally advanced non-small cell lung cancer. METHODS AND MATERIALS: The study included 25 patients with locally advanced non-small cell lung cancer treated with 3D-CRT at our center between January 1, 2010, and December 31, 2014. The planner generated VMAT plans using clones of the original computed tomography scans and regions of interest volumes, which did not include the original 3D plans. Both 3D-CRT and VMAT plans were generated using the same dose-volume constraint worksheet. The dose-volume histogram parameters for planning target volume and relevant organs at risk (OAR) were reviewed. The calculation engine was written in the R programming language; the user interface was developed with the "shiny" R Web library. Dose-volume histogram data were imported into the calculation engine and tumor control probability (TCP), normal tissue complication probability (NTCP), composite cardiopulmonary toxicity index (CPTI), morbidity index: MI = ∑j = 1#ofrelevantOARs(wj ∗ NTCPj), uncomplicated TCP (UTCP=TCP∗∏k=1#ofOARs1-NTCPK100, and therapeutic gain (TG): ie, TG = TCP ∗ (100 - MI) were calculated. RESULTS: TCP was better with 3D-CRT (12.62% vs 11.71%, P < .001), whereas VMAT demonstrated superior NTCP esophagus (4.45% vs 7.39%, P = .02). NTCP spinal cord (0.001% vs 0.009%, P = .001), and NTCP heart/perfusion defect (44.57% vs 56.42%, P = .016). There was no difference in NTCP lung (6.27% vs 7.62%, P = .221) and NTCP heart/pericarditis (0.001% vs 0.15%, P = .129) between 2 techniques. VMAT showed substantial improvement in morbidity index (11.06% vs. 14.31%, P = 0.01), CPTI (47.59% vs 59.41%, P = .03), TG (P = .035), and trend toward superiority in UTCP (5.89 vs 4.75, P=.057). CONCLUSION: The study highlights the utility of the radiobiological algorithm and summary indices in comparative plan evaluation and demonstrates benefits of VMAT over 3D-CRT.

Randomized prospective study comparing high-dose-rate intraluminal brachytherapy (HDRILBT) alone with HDRILBT and external beam radiotherapy in the palliation of advanced esophageal cancer.

PURPOSE: HDRILBT is one of the best methods of palliation for advanced esophageal cancer (AEC) by improving dysphagia-free survival (DFS) and overall survival (OS). This study examines if the addition of EBRT would further improve the outcome by improving DFS in AEC. METHODS AND MATERIALS: Patients with inoperable AEC were entered into a randomized prospective study. HDRILBT of 16 Gy/2 fractions/3 days was given initially to all patients. Following treatment, patients were randomized to receive no further treatment (Group A) or additional EBRT of 30 Gy/10 fractions/2 weeks (Group B) and were followed for 1 year. Statistical analysis of the data was done using the SAS statistical software package (SAS Institute, Cary, NC). Prognostic variables were analyzed using the chi(2) and log-rank tests and survival curves were drawn using the Kaplan-Meier method. Multivariate survival analysis was done using the Cox proportional hazards model. RESULTS: Sixty patients were entered into the study. Patient and tumor characteristics were comparable among the groups. Of 30 patients in Group B, 2 refused additional EBRT (no dysphagia). At 6 months, >50% had DFS in both groups and this was comparable. There was no difference statistically (p >0.05) in the DFS and OS between the two groups at the end of 12 months. Median survival for Group A was 7.23 months and 7.5 months for Group B. Additional EBRT did not improve DFS or OS. Eleven patients developed strictures related to radiotherapy and were dilated successfully (Group A, 7; Group B, 4; p >0.05). Four patients had progressive luminal disease which progressed to fistula (Group A, 3; Group B, 1; p >0.05). There was no effect of any patient or treatment parameter on DFS. Presenting weight and ECOG score had an impact on OS. CONCLUSIONS: From the preliminary analysis, additional EBRT to HDRILBT does not improve DFS or outcomes in inoperable AEC.