Comparing log file to measurement-based patient-specific quality assurance.

Recent technological advances have allowed the possibility of performing patient-specific quality assurance (QA) without time-intensive measurements. The objectives of this study are to: (1) compare how well the log file-based Mobius QA system agrees with measurement-based QA methods (ArcCHECK and portal dosimetry, PD) in passing and failing plans, and; (2) evaluate their error sensitivities. To these ends, ten phantom plans and 100 patient plans were measured with ArcCHECK and PD on VitalBeam, while log files were sent to Mobius for dose recalculation. Gamma evaluation was performed using criteria 3%/2 mm, per TG218 recommendations, and non-inferiority of the Mobius recalculation was determined with statistical testing. Ten random plans were edited to include systematic errors, then subjected to QA. Receiver operating characteristic curves were constructed to compare error sensitivities across the QA systems, and clinical significance of the errors was determined by recalculating dose to patients. We found no significant difference between Mobius, ArcCHECK, and PD in passing plans at the TG218 action limit. Mobius showed good sensitivity to collimator and gantry errors but not MLC bank shift errors, but could flag discrepancies in treatment delivery. Systematic errors were clinically significant only at large magnitudes; such unacceptable plans did not pass QA checks at the TG218 tolerance limit. Our results show that Mobius is not inferior to existing measurement-based QA systems, and can supplement existing QA practice by detecting real-time delivery discrepancies. However, it is still important to maintain rigorous routine machine QA to ensure reliability of machine log files.

Are heart doses associated with survival in patients with non-small cell lung cancer who received post-operative thoracic radiotherapy?: A national population-based study.

The aim of this retrospective national cohort study is to assess the association between various radiation heart dosimetric parameters (RHDPs), acute myocardial infarct (AMI) and overall survival (OS) outcomes in non-small cell lung cancer (NSCLC) patients treated with post-operative thoracic radiotherapy (PORT) using contemporary radiation techniques.We identified patients with stage I to III NSCLC treated with PORT at the 2 national cancer institutions from 2007 to 2014. We linked their electronic medical records to the national AMI and death registries. Univariable Cox regression was performed to assess the association between various RHDPs, AMI, and OS.We included 43 eligible patients with median follow-up of 36.6 months. Median age was 64 years. Majority of the patients had pathological stage III disease (72%). Median prescription dose was 60Gy. Median mean heart dose (MHD) was 9.4Gy. There were no AMI events. The 5-year OS was 34%. Univariable Cox regression showed that age was significantly associated with OS (hazard ratio, 1.06; 95% confidence interval, 1.01 to 1.10; P = .008). Radiation heart doses, including MHD, volume of heart receiving at least 5, 25, 30, 40, 50Gy and dose to 30% of heart volume, were not significantly associated with OS.There is insufficient evidence to conclude that RHDPs are associated with OS for patients with NSCLC treated with PORT in this study. Studies with larger sample size and longer term follow-up are needed to assess AMI outcome.

Comparing a volume based template approach and ultrasound guided freehand approach in multicatheter interstitial accelerated partial breast irradiation.

PURPOSE: Currently, there are two described methods of catheter insertion for women undergoing multicatheter interstitial accelerated partial breast irradiation (APBI). These are a volume based template approach (template) and a non-template ultrasound guidance freehand approach (non-template). We aim to compare dosimetric endpoints between the template and non-template approach. MATERIAL AND METHODS: Twenty patients, who received adjuvant multicatheter interstitial APBI between August 2008 to March 2010 formed the study cohort. Dosimetric planning was based on the RTOG 04-13 protocol. For standardization, the planning target volume evaluation (PTV-Eval) and organs at risk were contoured with the assistance of the attending surgeon. Dosimetric endpoints include D90 of the PTV-Eval, Dose Homogeneity Index (DHI), V200, maximum skin dose (MSD), and maximum chest wall dose (MCD). A median of 18 catheters was used per patient. The dose prescribed was 34 Gy in 10 fractions BID over 5 days. RESULTS: The average breast volume was 846 cm(3) (526-1384) for the entire cohort and there was no difference between the two groups (p = 0.6). Insertion time was significantly longer for the non-template approach (mean 150 minutes) compared to the template approach (mean: 90 minutes) (p = 0.02). The planning time was also significantly longer for the non-template approach (mean: 240 minutes) compared to the template approach (mean: 150 minutes) (p < 0.01). The template approach yielded a higher D90 (mean: 95%) compared to the non-template approach (mean: 92%) (p < 0.01). There were no differences in DHI (p = 0.14), V200 (p = 0.21), MSD (p = 0.7), and MCD (p = 0.8). CONCLUSIONS: Compared to the non-template approach, the template approach offered significant shorter insertion and planning times with significantly improved dosimetric PTV-Eval coverage without significantly compromising organs at risk dosimetrically.