Joshua D. Lawson

ACR appropriateness criteria retreatment of recurrent head and neck cancer after prior definitive radiation expert panel on radiation oncology-head and neck cancer.

Recurrent and second primary head-and-neck squamous cell carcinomas arising within or in close proximity to previously irradiated fields are a common clinical challenge. Whereas surgical salvage therapy is recommended for resectable disease, randomized data support the role of postoperative reirradiation in high-risk patients. Definitive reirradiation is an established approach for patients with recurrent disease who are medically or technically inoperable or decline radical surgery. The American College of Radiology Expert Panel on Head and Neck Cancer reviewed the relevant literature addressing re-treatment after prior definitive radiation and developed appropriateness criteria for representative clinical scenarios. Examples of unresectable recurrent disease and microscopic residual disease after salvage surgery were addressed. The panel evaluated the appropriateness of reirradiation, the integration of concurrent chemotherapy, radiation technique, treatment volume, dose, and fractionation. The panel emphasized the importance of patient selection and recommended evaluation and treatment at tertiary-care centers with a head-and-neck oncology team equipped with the resources and experience to manage the complexities and toxicities of re-treatment.

Quantitative evaluation of a cone-beam computed tomography-planning computed tomography deformable image registration method for adaptive radiation therapy

Deformable (non‐rigid) registration is an essential tool in both adaptive radiation therapy and image‐guided radiation therapy to account for soft‐tissue changes during the course of treatment. The evaluation method most commonly used to assess the accuracy of deformable image registration is qualitative human evaluation. Here, we propose a method for systematically measuring the accuracy of an algorithm in recovering artificially introduced deformations in cases of rigid geometry, and we use that method to quantify the ability of a modified basis spline (B‐Spline) registration algorithm to recover artificially introduced deformations. The evaluation method is entirely computer‐driven and eliminates biased interpretation associated with human evaluation; it can be applied to any chosen method of image registration. Our method involves using planning computed tomography (PCT) images acquired with a conventional CT simulator and cone‐beam computed tomography (CBCT) images acquired daily by a linear accelerator–mounted kilovoltage image system in the treatment delivery room. The deformation that occurs between the PCT and daily CBCT images is obtained using a modified version of the B‐Spline deformable model designed to overcome the low soft‐tissue contrast and the artifacts and distortions observed in CBCT images. Clinical CBCT images and contours of phantom and central nervous system cases were deformed (warped) with known random deformations. In registering the deformed with the non‐deformed image sets, we tracked the algorithms ability to recover the original, non‐deformed set. Registration error was measured as the mean and maximum difference between the original and the registered surface contours from outlined structures. Using this approach, two sets of tests can be devised. To measure the residual error related to the optimizers convergence performance, the warped CBCT image is registered to the unwarped version of itself, eliminating unknown factors such as noise and positioning errors. To study additional errors introduced by artifacts and noise in the CBCT image, the warped CBCT image is registered to the original PCT image. Using a B‐Spline deformable image registration algorithm, mean residual error introduced by the algorithms performance on noise‐free images was less than 1 mm, with a maximum of 2 mm. The chosen deformable image registration model was capable of accommodating significant variability in structures over time, because the artificially introduced deformation magnitude did not significantly influence the residual error. On the second type of test, noise and artifacts reduced registration accuracy to a mean of 1.33 mm and a maximum of 4.86 mm. The accuracy of deformable image registration can be easily and consistently measured by evaluating the algorithms ability to recover artificially introduced deformations in rigid cases in which the true solution is known a priori. The method is completely automated, applicable to any chosen registration algorithm, and does not require user interaction of any kind. PACS numbers: 87.57.Gg, 87.57.Ce, 87.62.+n

Markerless lung tumor tracking and trajectory reconstruction using rotational cone-beam projections: a feasibility study

Algorithms for direct tumor tracking in rotational cone-beam projections and for reconstruction of phase-binned 3D tumor trajectories were developed. The feasibility of the algorithm was demonstrated on a digital phantom, a physical phantom and two patients. Tracking results were obtained by comparing reference templates generated from 4DCT to rotational cone-beam projections. The 95th percentile absolute errors (e(95)) in phantom tracking results did not exceed 1.7 mm in either imager dimension, while e(95) in the patients was 3.3 mm or less. Accurate phase-binned trajectories were reconstructed in each case, with 3D maximum errors of no more than 1.0 mm in the phantoms and 2.0 mm in the patients. This work shows the feasibility of a direct tumor tracking technique for rotational images, and demonstrates that an accurate 3D tumor trajectory can be reconstructed from relatively less accurate tracking results. The ability to reconstruct the tumors average trajectory from a 3D cone-beam CT scan on the day of treatment could allow for better patient setup and quality assurance, while direct tumor tracking in rotational projections could be clinically useful for rotational therapy such as volumetric modulated arc therapy (VMAT).

Neurocognitive assessment following whole brain radiation therapy and radiosurgery for patients with cerebral metastases

The treatment of metastatic brain lesions remains a central challenge in oncology. Because most chemotherapeutic agents do not effectively cross the blood–brain barrier, it is widely accepted that radiation remains the primary modality of treatment. The mode by which radiation should be delivered has, however, become a source of intense controversy in recent years. The controversy involves whether patients with a limited number of brain metastases should undergo whole brain radiation therapy (WBRT) or stereotactic radiosurgery (SRS) delivered only to the radiographically visible tumours. Survival is comparable for patients treated with either modality. Instead, the controversy involves the neurocognitive function (NCF) of radiating cerebrum that appeared radiographically normal relative to effects of the growth from micro-metastatic foci. A fundamental question in this debate involves quantifying the effect of WBRT in patients with cerebral metastasis. To disentangle the effects of WBRT on neurocognition from the effects inherent to the underlying disease, we analysed the results from randomised controlled studies of prophylactic cranial irradiation in oncology patients as well as studies where patients with limited cerebral metastasis were randomised to SRS versus SRS+WBRT. In aggregate, these results suggest deleterious effects of WBRT in select neurocognitive domains. However, there are insufficient data to resolve the controversy of upfront WBRT versus SRS in the management of patients with limited cerebral metastases.

A survey of image‐guided radiation therapy use in the United States

Image‐guided radiation therapy (IGRT) is a novel array of in‐room imaging modalities that are used for tumor localization and patient setup in radiation oncology. The prevalence of IGRT use among US radiation oncologists is unknown.

Frame-less and mask-less cranial stereotactic radiosurgery: a feasibility study

Currently, high-precision delivery in stereotactic radiosurgery (SRS) is achieved via high-precision target localization and rigid patient immobilization. Rigid patient immobilization can result in, however, patient discomfort, which is exacerbated by the long duration of SRS treatments and may induce patient movement. To address this issue, we developed a new SRS technique that is aimed to minimize patient discomfort while maintaining high-precision treatment, based on a less-rigid patient immobilization combined with continuous patient motion monitoring. In this paper, we examine the feasibility of this new technique. An anthropomorphic head phantom is used to check the accuracy of a 3D surface imaging system that provides the monitoring. Volunteers are used to study patient motion inside a new type of head mold that is used for minimal immobilization. Results show that for different couch angles, the difference between the phantom positions recorded by the surface imaging system and by an infrared optical tracking system was within 1 mm in displacements and 1 degrees in rotation. The motion detected by both systems during couch shifts is within 1 mm agreement. The average maximum volunteer head motion in the head mold during the 20 min interval in any direction was 0.7 mm (range: 0.4-1.1 mm). Patient motion due to couch motion was always less than 0.2 mm. We conclude that motion inside the minimally immobilizing head mold is small and can be accurately detected by real-time surface imaging.

Prospective Study of Functional Bone Marrow-Sparing Intensity Modulated Radiation Therapy With Concurrent Chemotherapy for Pelvic Malignancies

PURPOSE To test the hypothesis that intensity modulated radiation therapy (IMRT) can reduce radiation dose to functional bone marrow (BM) in patients with pelvic malignancies (phase IA) and estimate the clinical feasibility and acute toxicity associated with this technique (phase IB). METHODS AND MATERIALS We enrolled 31 subjects (19 with gynecologic cancer and 12 with anal cancer) in an institutional review board-approved prospective trial (6 in the pilot study, 10 in phase IA, and 15 in phase IB). The mean age was 52 years; 8 of 31 patients (26%) were men. Twenty-one subjects completed (18)F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) simulation and magnetic resonance imaging by use of quantitative IDEAL (IDEAL IQ; GE Healthcare, Waukesha, WI). The PET/CT and IDEAL IQ were registered, and BM subvolumes were segmented above the mean standardized uptake value and below the mean fat fraction within the pelvis and lumbar spine; their intersection was designated as functional BM for IMRT planning. Functional BM-sparing vs total BM-sparing IMRT plans were compared in 12 subjects; 10 were treated with functional BM-sparing pelvic IMRT per protocol. RESULTS In gynecologic cancer patients, the mean functional BM V(10) (volume receiving ≥10 Gy) and V(20) (volume receiving ≥20 Gy) were 85% vs 94% (P<.0001) and 70% vs 82% (P<.0001), respectively, for functional BM-sparing IMRT vs total BM-sparing IMRT. In anal cancer patients, the corresponding values were 75% vs 77% (P=.06) and 62% vs 67% (P=.002), respectively. Of 10 subjects treated with functional BM-sparing pelvic IMRT, 3 (30%) had acute grade 3 hematologic toxicity or greater. CONCLUSIONS IMRT can reduce dose to BM subregions identified by (18)F-fluorodeoxyglucose-PET/CT and IDEAL IQ. The efficacy of BM-sparing IMRT is being tested in a phase II trial.

Locoregional and distant failure following image-guided stereotactic body radiation for early-stage primary lung cancer

PURPOSE To report our institutional experience using image-guided stereotactic body radiation therapy (SBRT) for early stage lung cancer, including an analysis into factors associated with nodal and distant failures (NF, DF). METHODS Forty-eight patients with early-stage primary lung cancer were treated with image-guided SBRT between 2007 and 2009. Median prescription dose was 48 Gy in 4 fractions. Toxicity was graded according to the NCI CTCAE v3.0 scale. RESULTS Local failure was detected in two lesions and actuarial 24-month local control was 95%. At 24 months, the cumulative incidence of NF was 6%, and DF was 29%. Larger lesions (>3 cm) and younger age (<70 years) were the only factors found to be significantly correlated with increased DF (p=0.005 and p=0.015, respectively). A single grade ≥ 3 toxicity was observed. After adjusting for age and lesion size, distant failure was significantly associated with a poorer OS (Cox regression, p=0.0059). CONCLUSION Image-guided SBRT can produce excellent LC rates with minimal toxicity. Distant failure was a major determinant of OS and the most common pattern of failure, indicating a potential role for systemic therapy in younger patients with large lesions.

Single-Isocenter Frameless Intensity-Modulated Stereotactic Radiosurgery for Simultaneous Treatment of Multiple Brain Metastases: Clinical Experience

PURPOSE To describe our clinical experience using a unique single-isocenter technique for frameless intensity-modulated stereotactic radiosurgery (IM-SRS) to treat multiple brain metastases. METHODS AND MATERIALS Twenty-six patients with a median of 5 metastases (range, 2-13) underwent optically guided frameless IM-SRS using a single, centrally located isocenter. Median prescription dose was 18 Gy (range, 14-25). Follow-up magnetic resonance imaging (MRI) and clinical examination occurred every 2-4 months. RESULTS Median follow-up for all patients was 3.3 months (range, 0.2-21.3), with 20 of 26 patients (77%) followed up until their death. For the remaining 6 patients alive at the time of analysis, median follow-up was 14.6 months (range, 9.3-18.0). Total treatment time ranged from 9.0 to 38.9 minutes (median, 21.0). Actuarial 6- and 12-month overall survivals were 50% (95% confidence interval [C.I.], 31-70%) and 38% (95% C.I., 19-56%), respectively. Actuarial 6- and 12-month local control (LC) rates were 97% (95% C.I., 93-100%) and 83% (95% C.I., 71-96%), respectively. Tumors <or=1.5 cm had a better 6-month LC than those >1.5 cm (98% vs. 90%, p = 0.008). New intracranial metastatic disease occurring outside of the treatment volume was observed in 7 patients. Grade >or=3 toxicity occurred in 2 patients (8%). CONCLUSION Frameless IM-SRS using a single-isocenter approach for treating multiple intracranial metastases can produce clinical outcomes that compare favorably with those of conventional SRS in a much shorter treatment time (<40 minutes). Given its faster treatment time, this technique is appealing to both patients and personnel in busy clinics.

Concurrent platinum‐based chemotherapy and simultaneous modulated accelerated radiation therapy for locally advanced squamous cell carcinoma of the tongue base

Randomized data support use of chemotherapy concurrently with radiation in treatment of advanced squamous cell carcinoma (SCC) of the oropharynx. Intensity modulated radiation therapy (IMRT) is increasingly being used to deliver such radiotherapy; no published reports specifically describe results of chemotherapy with IMRT for SCC of the base of tongue (BOT). We present outcomes data using simultaneous modulated accelerated radiation therapy (SMART) combined with platinum‐based chemotherapy in treatment of locally advanced SCC of the BOT