Automated Closed- and Open-Loop Validation of Knowledge-Based Planning Routines Across Multiple Disease Sites.

PURPOSE: Knowledge-based planning (KBP) clinical implementation necessitates significant upfront effort, even within a single disease site. The purpose of this study was to demonstrate an efficient method for clinicians to assess the noninferiority of KBP across multiple disease sites and estimate any systematic dosimetric differences after implementation. We sought to establish these endpoints in a plurality of previously treated patients (validation set) with both closed-loop (training set overlapping validation set) and open-loop (independent training set) KBP routines. METHODS AND MATERIALS: We identified 53 prostate, 24 prostatic fossa, 54 hypofractionated lung, and 52 head and neck patients treated with volumetric modulated arc therapy in the year directly preceding our clinic's broad adoption of RapidPlan (Varian Medical Systems, Palo Alto, CA). Using the Varian Eclipse Scripting API, our program takes as input a list of patients, then performs semiautomated structure matching, fully automated RapidPlan-driven optimization, and plan comparison. All plans were normalized to the planning target volume (PTV) D95% = 100%. Dose metric differences (ΔDx = Dx,clinical - Dx,KBP) were computed for standard PTV and organ-at-risk (OAR) dose-volume histogram parameters across disease sites. A 2-tailed paired t test quantified statistical significance (P < .001). RESULTS: Statistically significant organ dose-volume histogram improvements were observed in the KBP cohort: the rectum, bladder, and penile bulb in prostate/prostatic fossa; and the larynx, esophagus, cricopharyngeus, parotid glands, and cochlea in head and neck. No OAR dose metric was statistically worse in any KBP sample. PTV ΔD1% increases in prostatic fossa were deemed acceptable given organ-sparing gains. PTV ΔD1% and internal target volume ΔD99% increase for the lung was by design owing to the prescription normalization variance in the pre-KBP lung sample. CONCLUSIONS: Our automated method showed multiple disease sites' KBP routines to be noninferior to manual planning, with statistically significant superiority in some aspects of OAR sparing. This method is applicable to any institution implementing either closed-loop or open-loop KBP autoplanning routines.

Geometric and dosimetric evaluation of atlas based auto-segmentation of cardiac structures in breast cancer patients.

BACKGROUND AND PURPOSE: Auto-segmentation represents an efficient tool to segment organs on CT imaging. Primarily used in clinical setting, auto-segmentation plays an increasing role in research, particularly when analyzing thousands of images in the "big data" era. In this study we evaluate the accuracy of cardiac dosimetric endpoints derived from atlas based auto-segmentation compared to gold standard manual segmentation. MATERIAL AND METHODS: Heart and cardiac substructures were manually delineated on 54 breast cancer patients. Twenty-seven patients were used to build the auto-segmentation atlas, the other 27 to validate performance. We evaluated accuracy of the auto-segmented contours with standard geometric indices and assessed dosimetric endpoints. RESULTS: Auto-segmented contours overlapped geometrically with manual contours of the heart and chambers with Dice-similarity coefficients of 0.93 ±â€¯0.02 (mean ±â€¯standard deviation) and 0.79 ±â€¯0.07 respectively. Similarly, there was a strong link between dosimetric parameters derived from auto-segmented and manual contours (R2 = 0.955-1.000). On the other hand, the left anterior descending artery had little geometric overlap (Dice-similarity coefficient 0.09 ±â€¯0.07), though acceptable representation of dosimetric parameters (R2 = 0.646-0.992). CONCLUSIONS: The atlas based auto-segmentation approach delineates heart structures with sufficient accuracy for research purposes. Our results indicate that quality of auto-segmented contours cannot be determined by geometric values only.

Stereotactic Body Radiation Therapy Versus Surgery for Early Lung Cancer Among US Veterans.

BACKGROUND: Stereotactic body radiation therapy (SBRT) has been proposed as a potential alternative to surgery for early lung cancer, although we lack well-powered prospective randomized data comparing these treatments, and existing studies suffer from incomplete information on confounders that can bias results. Here, we evaluated the comparative effectiveness of surgery and SBRT in lung cancer treatment using a large extensively detailed database from the Veteran's Affairs system. METHODS: We identified veterans with biopsy-proven clinical stage I non-small cell lung cancer diagnosed between 2006 and 2015 from within the Veteran's Affairs Informatics and Computing Infrastructure. We compared cancer-specific survival among patients receiving lobectomy, sublobar resection, or SBRT using univariable and multivariable competing risk analyses. Multivariable analyses adjusted for confounders including preoperative pulmonary function, smoking status, comorbidity, and staging workup procedures. RESULTS: In all, 4,069 patients were included (449 SBRT, 2,986 lobectomy, 634 sublobar resection). Unadjusted analysis found higher immediate postprocedural mortality in the surgery groups compared with the SBRT group. The multivariable analysis considering long-term survival found higher cancer-specific mortality for SBRT compared with lobectomy (subdistribution hazard ratio 1.45, 95% confidence interval: 1.09 to 1.94, p = 0.01), although no survival difference between SBRT and sublobar resection (subdistribution hazard ratio 1.25, 95% confidence interval: 0.93 to 1.68, p = 0.15). CONCLUSIONS: Among a large cohort of early stage lung cancer patients, we found that lobectomy had improved survival compared with SBRT, although we found no survival difference between sublobar resection and SBRT. Despite these findings, the potential for unmeasured confounding remains and prospective randomized trials are needed to better compare these treatment modalities.