A comprehensive three-dimensional radiation treatment planning system

Biomedical advances and future prospects of high-precision three-dimensional radiotherapy and four-dimensional radiotherapy

Biomedical advances of external-beam radiotherapy (EBRT) with improvements in physical accuracy are reviewed. High-precision (±1 mm) three-dimensional radiotherapy (3DRT) can utilize respective therapeutic open doors in the tumor control probability curve and in the normal tissue complication probability curve instead of the one single therapeutic window in two-dimensional EBRT. High-precision 3DRT achieved higher tumor control and probable survival rates for patients with small peripheral lung and liver cancers. Four-dimensional radiotherapy (4DRT), which can reduce uncertainties in 3DRT due to organ motion by real-time (every 0.1-1 s) tumor-tracking and immediate (0.1-1 s) irradiation, have achieved reduced adverse effects for prostate and pancreatic tumors near the digestive tract and with similar or better tumor control. Particle beam therapy improved tumor control and probable survival for patients with large liver tumors. The clinical outcomes of locally advanced or multiple tumors located near serial-type organs can theoretically be improved further by integrating the 4DRT concept with particle beams.

A Safe and Practical Cycle for Team-Based Development and Implementation of In-House Clinical Software

Purpose

Due to a gap in published guidance, we describe our robust cycle of in-house clinical software development and implementation, which has been used for years to facilitate the safe treatment of all patients in our clinics.

Methods and Materials

Our software development and implementation cycle requires clarity in communication, clearly defined roles, thorough commissioning, and regular feedback. Cycle phases include design requirements and use cases, development, physics evaluation testing, clinical evaluation testing, and full clinical release. Software requirements, release notes, test suites, and a commissioning report are created and independently reviewed before clinical use. Software deemed to be high-risk, such as those that are writable to a database, incorporate the use of a formal, team-based hazard analysis. Incident learning is used to both guide initial development and improvements as well as to monitor the safe use of the software.

Results

Our standard process builds in transparency and establishes high expectations in the development and use of custom software to support patient care. Since moving to a commercial planning system platform in 2013, we have applied our team-based software release process to 16 programs related to scripting in the treatment planning system for the clinic.

Conclusions

The principles and methodology described here can be implemented in a range of practice settings regardless of whether or not dedicated resources are available for software development. In addition to teamwork with defined roles, documentation, and use of incident learning, we strongly recommend having a written policy on the process, using phased testing, and incorporating independent oversight and approval before use for patient care. This rigorous process ensures continuous monitoring for and mitigatation of any high risk hazards.

Deep-learning system to improve the quality and efficiency of volumetric heart segmentation for breast cancer

Although artificial intelligence algorithms are often developed and applied for narrow tasks, their implementation in other medical settings could help to improve patient care. Here we assess whether a deep-learning system for volumetric heart segmentation on computed tomography (CT) scans developed in cardiovascular radiology can optimize treatment planning in radiation oncology. The system was trained using multi-center data (n = 858) with manual heart segmentations provided by cardiovascular radiologists. Validation of the system was performed in an independent real-world dataset of 5677 breast cancer patients treated with radiation therapy at the Dana-Farber/Brigham and Women’s Cancer Center between 2008–2018. In a subset of 20 patients, the performance of the system was compared to eight radiation oncology experts by assessing segmentation time, agreement between experts, and accuracy with and without deep-learning assistance. To compare the performance to segmentations used in the clinic, concordance and failures (defined as Dice < 0.85) of the system were evaluated in the entire dataset. The system was successfully applied without retraining. With deep-learning assistance, segmentation time significantly decreased (4.0 min [IQR 3.1–5.0] vs. 2.0 min [IQR 1.3–3.5]; p < 0.001), and agreement increased (Dice 0.95 [IQR = 0.02]; vs. 0.97 [IQR = 0.02], p < 0.001). Expert accuracy was similar with and without deep-learning assistance (Dice 0.92 [IQR = 0.02] vs. 0.92 [IQR = 0.02]; p = 0.48), and not significantly different from deep-learning-only segmentations (Dice 0.92 [IQR = 0.02]; p ≥ 0.1). In comparison to real-world data, the system showed high concordance (Dice 0.89 [IQR = 0.06]) across 5677 patients and a significantly lower failure rate (p < 0.001). These results suggest that deep-learning algorithms can successfully be applied across medical specialties and improve clinical care beyond the original field of interest.

Incidence and Dosimetric Predictors of Radiation-Induced Gastric Bleeding After Chemoradiation for Esophageal and Gastroesophageal Junction Cancer

Purpose

To determine the incidence and predictors of gastric bleeding after chemoradiation for esophageal or gastroesophageal junction cancer.

Methods and Materials

We reviewed patients receiving chemoradiation to at least 41.4 Gy for localized esophageal cancer whose fields included the stomach and who did not undergo surgical resection. The primary endpoint was grade ≥3 gastric hemorrhage (GB3+). Comprehensive stomach dose-volume parameters were collected, and stomach dose-volume histograms were generated for analysis.

Results

A total of 145 patients met our inclusion criteria. Median prescribed dose was 50.4 Gy (range, 41.4-56 Gy). Median stomach Dmax was 53.0 Gy (1.0-62.7 Gy), and median stomach V40, V45, and V50 Gy were 112 cm³ (0-667 cm³), 84 cm³ (0-632 cm³), and 50 cm³ (0-565 cm³), respectively. Two patients (1.4%) developed radiation-induced GB3+. The only dosimetric factor that was significantly different for these patients was a higher stomach Dmax (58.1 and 58.3 Gy) than the cohort median (53 Gy). One of these patients also had cirrhosis, and the other had a history of nonsteroidal anti-inflammatory drug use. Five other patients had GB3+ events associated with documented tumor progression. A Cox proportional hazards model based on stomach Dmax with respect to the development of GB3+ was found to be statistically significant. Time-to-event curves and dose-volume atlases were generated, demonstrating an increased risk of GB3+ only when stomach Dmax was >58 Gy (P < .05).

Conclusions

We observed a low rate of GB3+ events in patients who received chemoradiation to a median dose of 50.4 Gy to volumes that included a significant portion of the stomach. These results suggest that when prescribing 50.4 Gy for esophageal cancer, there is no need to minimize the irradiated gastric volume or dose for the sake of preventing bleeding complications. Limiting stomach maximum doses to <58 Gy may also avoid bleeding, and particular caution should be taken in patients with other risk factors for bleeding, such as cirrhosis.

Predictive Modeling of Thoracic Radiotherapy Toxicity and the Potential Role of Serum Alpha-2-Macroglobulin

Background: To investigate the impact of alpha-2-macroglobulin (A2M), a suspected intrinsic radioprotectant, on radiation pneumonitis and esophagitis using multifactorial predictive models. Materials and Methods: Baseline A2M levels were obtained for 258 patients prior to thoracic radiotherapy (RT). Dose-volume characteristics were extracted from treatment plans. Spearman's correlation (Rs) test was used to correlate clinical and dosimetric variables with toxicities. Toxicity prediction models were built using least absolute shrinkage and selection operator (LASSO) logistic regression on 1,000 bootstrapped datasets. Results: Grade ≥2 esophagitis and pneumonitis developed in 61 (23.6%) and 36 (14.0%) patients, respectively. The median A2M level was 191 mg/dL (range: 94-511). Never/former/current smoker status was 47 (18.2%)/179 (69.4%)/32 (12.4%). We found a significant negative univariate correlation between baseline A2M levels and esophagitis (Rs = -0.18/p = 0.003) and between A2M and smoking status (Rs = 0.13/p = 0.04). Further significant parameters for grade ≥2 esophagitis included age (Rs = -0.32/p < 0.0001), chemotherapy use (Rs = 0.56/p < 0.0001), dose per fraction (Rs = -0.57/p < 0.0001), total dose (Rs = 0.35/p < 0.0001), and several other dosimetric variables with Rs > 0.5 (p < 0.0001). The only significant non-dosimetric parameter for grade ≥2 pneumonitis was sex (Rs = -0.32/p = 0.037) with higher risk for women. For pneumonitis D15 (lung) (Rs = 0.19/p = 0.006) and D45 (heart) (Rs = 0.16/p = 0.016) had the highest correlation. LASSO models applied on the validation data were statistically significant and resulted in areas under the receiver operating characteristic curve of 0.84 (esophagitis) and 0.78 (pneumonitis). Multivariate predictive models did not require A2M to reach maximum predictive power. Conclusion: This is the first study showing a likely association of higher baseline A2M values with lower risk of radiation esophagitis and with smoking status. However, the baseline A2M level was not a significant risk factor for radiation pneumonitis.

Prediction of conical collimator collision for stereotactic radiosurgery

The purpose of this study is to predict the collision clearance distance of stereotactic cones with treatment setup devices in cone-based stereotactic radiosurgery (SRS). The BrainLAB radiosurgery system with a Frameless Radiosurgery Positioning Array and dedicated couch top was targeted in this study. The positioning array and couch top were scanned with CT simulators, and their outer contours of were detected. The minimum clearance distance was estimated by calculating the Euclidian distances between the surface of the SRS cones and the nearest surface of the outer contours. The coordinate transformation of the outer contour was performed by incorporating the Beam's Eye View at a planned arc range and couch angle. From the minimum clearance distance, the collision-free gantry ranges for each couch angle were sequentially determined. An in-house software was developed to calculate the clearance distance between the cone surface and the outer contours, and thus determine the occurrence of a collision. The software was extensively tested for various combinations of couch and arc angles at multiple isocenter locations for two combinations of cone-couch systems. A total of 50 arcs were used to validate the calculation accuracies of the software for each system. The calculated minimum distances and collision-free angles from the software were verified by physical measurements. The calculated minimum distances were found to agree with the measurements to within 0.3 ± 0.9 mm. The collision-free arc angles from the software also agreed with the measurements to within 1.1 ± 1.1° with a 5-mm safety margin for 20 arcs. In conclusion, the in-house software was able to calculate the minimum clearance distance with <1.0 mm accuracy and to determine the collision-free arc range for the cone-based BrainLab SRS system.

Trends in Physics Contributions to the 'Red Journal': A 30-year Journey and Comparison to Global Trends

INTRODUCTION

In this study, we catalogued physics contributions in the Red Journal over the past three decades and compared publication trends with global publication trends.

METHODS

We used the website of the Red Journal (International Journal of Radiation Oncology, Biology, and Physics) to access physics contributions published between 1988 and 2017. The contributions were catalogued following taxonomy guidelines endorsed by the American Association of Physicists in Medicine. From each issue, publications classified as "Physics Contributions" or as "Technical Innovations" or listed a physicist as one of the primary authors was indexed. Results are presented using descriptive statistics; chi-square [Formula: see text]² testing were utilized to examine trends in contributions over 10-year time intervals. For global trend comparison of Red Journal physics contributions, we utilized PubMed database to obtain publication counts on the topics of interest.

RESULTS

A total of 2,852 physics contributions were indexed (86 volumes and 436 issues). Overall, 76% of contributions were photon-beam therapy applications, 15% brachytherapy, 7% particle-beam therapy, and 3% electron-beam therapy. [Formula: see text]² analyses revealed significant changes in this distribution over time (p<0.001). Brachytherapy accounted for 23% of publications in the first decade, compared to 7% in the third decade. Particle beam therapy accounted for 4% of publications in the first decade and 12% in the third decade. Among treatment techniques, three-dimensional conformal radiation therapy (3D-CRT) accounted for 64% of contributions in the first decade, compared to 3% in the third decade. Intensity-modulated radiation therapy (IMRT)/volumetric modulated arc therapy (VMAT) accounted for 4% in the first decade, compared to 54% in the third decade. Significant increases in the proportions of studies focused on motion management, functional imaging for treatment planning, and radiation safety/quality assurance during the third decade were observed (p<0.001).

CONCLUSION

Trends of physics publications in the Red Journal and globally, in general, largely mirror technological advances in the field of radiation oncology. These changes reflect a technological transition in the field over three decades from beam's-eye-view designed static treatment ports to functional imaging and knowledge-based treatment planning with biological dose optimization and real-time tumor tracking.

Five years' experience with a customized electronic checklist for radiation therapy planning quality assurance in a multicampus institution

INTRODUCTION

An electronic checklist has been designed with the intention of reducing errors while minimizing user effort in completing the checklist. We analyze the clinical use and evolution of the checklist over the past 5 years and review data in an incident learning system (ILS) to investigate whether it has contributed to an improvement in patient safety.

METHODS AND MATERIALS

The checklist is written as a standalone HTML application using VBScript. User selection of pertinent demographic details limits the display of checklist items only to those necessary for the particular clinical scenario. Ten common clinical scenarios were used to illustrate the difference between the maximum possible number of checklist items available in the code versus the number displayed to the user at any one time. An ILS database of errors and near misses was reviewed to evaluate whether the checklist influenced the occurrence of reported events.

RESULTS

Over 5 years, the number of checklist items available in the code nearly doubled, whereas the number displayed to the user at any one time stayed constant. Events reported in our ILS related to the beam energy used with pacemakers, projection of anatomy on digitally reconstructed radiographs, orthogonality of setup fields, and field extension beyond match lines, did not recur after the items were added to the checklist. Other events related to bolus documentation and breakpoints continued to be reported.

CONCLUSION

Our checklist is adaptable to the introduction of new technologies, transitions between planning systems, and to errors and near misses recorded in the ILS. The electronic format allows us to restrict user display to a small, relevant, subset of possible checklist items, limiting the planner effort needed to review and complete the checklist.

Heart Dosimetry is Correlated With Risk of Radiation Pneumonitis After Lung-Sparing Hemithoracic Pleural Intensity Modulated Radiation Therapy for Malignant Pleural Mesothelioma

PURPOSE

To determine clinically helpful dose-volume and clinical metrics correlating with symptomatic radiation pneumonitis (RP) in malignant pleural mesothelioma (MPM) patients with 2 lungs treated with hemithoracic intensity modulated pleural radiation therapy (IMPRINT).

METHODS AND MATERIALS

Treatment plans and resulting normal organ dose-volume histograms of 103 consecutive MPM patients treated with IMPRINT (February 2005 to January 2015) to the highest dose ≤50.4 Gy satisfying departmental normal tissue constraints were uniformly recalculated. Patient records provided maximum RP grade (Common Terminology Criteria for Toxicity and Adverse Event version 4.0) and clinical and demographic information. Correlations analyzed with the Cox model were grade ≥2 RP (RP2+) and grade ≥3 RP (RP3+) with clinical variables, with volumes of planning target volume (PTV) and PTV-lung overlap and with mean dose, percent volume receiving dose D (V_D), highest dose encompassing % volume V, (D_V), and heart, total, ipsilateral, and contralateral lung volumes.

RESULTS

Twenty-seven patients had RP2+ (14 with RP3+). The median prescription dose was 46.8 Gy (39.6-50.4 Gy, 1.8 Gy/fraction). The median age was 67.6 years (range, 42-83 years). There were 79 men, 40 never-smokers, and 44 with left-sided MPM. There were no significant (P≤.05) correlations with clinical variables, prescription dose, total lung dose-volume metrics, and PTV-lung overlap volume. Dose-volume correlations for heart were RP2+ with V_D (35 ≤ D ≤ 47 Gy, V₄₃ strongest at P=.003), RP3+ with V_D (31 ≤ D ≤ 45 Gy), RP2+ with D_V (5 ≤ V ≤ 30%), RP3+ with D_V (15 ≤ V ≤ 35%), and mean dose. Significant for ipsilateral lung were RP2+ with V_D (38 ≤ D ≤ 44 Gy), RP3+ with V₄₁, RP2+ and RP3+ with minimum dose, and for contralateral lung, RP2+ with maximum dose. Correlation of PTV with RP2+ was strong (P<.001) and also significant with RP3+.

CONCLUSIONS

Heart dose correlated strongly with symptomatic RP in this large cohort of MPM patients with 2 lungs treated with IMPRINT. Planning constraints to reduce future heart doses are suggested.

Geometric dose prediction model for hemithoracic intensity-modulated radiation therapy in mesothelioma patients with two intact lungs

The presence of two intact lungs makes it challenging to reach a tumoricidal dose with hemithoracic pleural intensity-modulated radiation therapy (IMRT) in patients with malignant pleural mesothelioma (MPM) who underwent pleurectomy/decortications or have unresectable disease. We developed an anatomy-based model to predict attainable prescription dose before starting optimization. Fifty-six clinically delivered IMRT plans were analyzed regarding correlation of prescription dose and individual and total lung volumes, planning target volume (PTV), ipsilateral normal lung volume and ratios: contralateral/ipsilateral lung (CIVR); contralateral lung/PTV (CPVR); ipsilateral lung /PTV (IPVR); ipsilateral normal lung /total lung (INTLVR); ipsilateral normal lung/PTV (INLPVR). Spearman's rank correlation and Fisher's exact test were used. Correlation between mean ipsilateral lung dose (MILD) and these volume ratios and between prescription dose and single lung mean doses were studied. The prediction models were validated in 23 subsequent MPM patients. CIVR showed the strongest correlation with dose (R=0.603,p<0.001) and accurately predicted prescription dose in the validation cases. INLPVR and MILD as well as MILD and prescription dose were significantly correlated (R=-0.784,p<0.001 and R=0.554,p<0.001, respectively) in the training and validation cases. Parameters obtainable directly from planning scan anatomy predict achievable prescription doses for hemithoracic IMRT treatment of MPM patients with two intact lungs. PACS number(s): 87.55.de, 87.55.dk.

A review of uncertainties in radiotherapy dose reconstruction and their impacts on dose-response relationships

Proper understanding of the risk of radiation-induced late effects for patients receiving external photon beam radiotherapy requires the determination of reliable dose-response relationships. Although significant efforts have been devoted to improving dose estimates for the study of late effects, the most often questioned explanatory variable is still the dose. In this work, based on a literature review, we provide an in-depth description of the radiotherapy dose reconstruction process for the study of late effects. In particular, we focus on the identification of the main sources of dose uncertainty involved in this process and summarise their impacts on the dose-response relationship for radiotherapy late effects. We provide a number of recommendations for making progress in estimating the uncertainties in current studies of radiotherapy late effects and reducing these uncertainties in future studies.

Peripheral nervous system injury after high-dose single-fraction image-guided stereotactic radiosurgery for spine tumors

OBJECTIVE The object of this study was to determine the percentage of high-dose (1800-2600 cGy) single-fraction stereotactic radiosurgery (SF-SRS) treatments to the spine that result in peripheral nervous system (PNS) injury. METHODS All patients treated with SF-SRS for primary or metastatic spine tumors between January 2004 and May 2013 and referred to the Rehabilitation Medicine Service for evaluation and treatment of neuromuscular, musculoskeletal, or functional impairments or pain were retrospectively identified. RESULTS Five hundred fifty-seven SF-SRS treatments in 447 patients resulted in 14 PNS injuries in 13 patients. All injures resulted from SF-SRS delivered to the cervical or lumbosacral spine at 2400 cGy. The overall percentage of SF-SRS treatments resulting in PNS injury was 2.5%, increasing to 4.5% when the thoracic spine was excluded from analysis. The median time to symptom onset following SF-SRS was 10 months (range 4-32 months). The plexus (cervical, brachial, and/or lumbosacral) was affected clinically and/or electrophysiologically in 12 (86%) of 14 cases, the nerve root in 2 (14%) of 14, and both in 6 (43%) of 14 cases. All patients experienced pain and most (93%) developed weakness. Peripheral nervous system injuries were CTCAE Grade 1 in 14% of cases, 2 in 64%, and 3 in 21%. No dose relationship between SF-SRS dose and PNS injury was detected. CONCLUSIONS Single-fraction SRS to the spine can result in PNS injury with major implications for function and quality of life.

Evaluating inter-campus plan consistency using a knowledge based planning model

BACKGROUND AND PURPOSE

We investigate whether knowledge based planning (KBP) can identify systematic variations in intensity modulated radiotherapy (IMRT) plans between multiple campuses of a single institution.

MATERIAL AND METHODS

A KBP model was constructed from 58 prior main campus (MC) esophagus IMRT radiotherapy plans and then applied to 172 previous patient plans across MC and 4 regional sites (RS). The KBP model predicts DVH bands for each organ at risk which were compared to the previously planned DVHs for that patient.

RESULTS

RS1's plans were the least similar to the model with less heart and stomach sparing, and more variation in liver dose, compared to MC. RS2 produced plans most similar to those expected from the model. RS3 plans displayed more variability from the model prediction but overall, the DVHs were no worse than those of MC. RS4 did not present any statistically significant results due to the small sample size (n=11).

CONCLUSIONS

KBP can retrospectively highlight subtle differences in planning practices, even between campuses of the same institution. This information can be used to identify areas needing increased consistency in planning output and subsequently improve consistency and quality of care.

Impact of Fractionation and Dose in a Multivariate Model for Radiation-Induced Chest Wall Pain

PURPOSE

To determine the role of patient/tumor characteristics, radiation dose, and fractionation using the linear-quadratic (LQ) model to predict stereotactic body radiation therapy-induced grade ≥ 2 chest wall pain (CWP2) in a larger series and develop clinically useful constraints for patients treated with different fraction numbers.

METHODS AND MATERIALS

A total of 316 lung tumors in 295 patients were treated with stereotactic body radiation therapy in 3 to 5 fractions to 39 to 60 Gy. Absolute dose-absolute volume chest wall (CW) histograms were acquired. The raw dose-volume histograms (α/β = ∞ Gy) were converted via the LQ model to equivalent doses in 2-Gy fractions (normalized total dose, NTD) with α/β from 0 to 25 Gy in 0.1-Gy steps. The Cox proportional hazards (CPH) model was used in univariate and multivariate models to identify and assess CWP2 exposed to a given physical and NTD.

RESULTS

The median follow-up was 15.4 months, and the median time to development of CWP2 was 7.4 months. On a univariate CPH model, prescription dose, prescription dose per fraction, number of fractions, D83cc, distance of tumor to CW, and body mass index were all statistically significant for the development of CWP2. Linear-quadratic correction improved the CPH model significance over the physical dose. The best-fit α/β was 2.1 Gy, and the physical dose (α/β = ∞ Gy) was outside the upper 95% confidence limit. With α/β = 2.1 Gy, VNTD99Gy was most significant, with median VNTD99Gy = 31.5 cm(3) (hazard ratio 3.87, P<.001).

CONCLUSION

There were several predictive factors for the development of CWP2. The LQ-adjusted doses using the best-fit α/β = 2.1 Gy is a better predictor of CWP2 than the physical dose. To aid dosimetrists, we have calculated the physical dose equivalent corresponding to VNTD99Gy = 31.5 cm(3) for the 3- to 5-fraction groups.

Local control and toxicity in a large cohort of central lung tumors treated with stereotactic body radiation therapy

PURPOSE

Stereotactic body radiation therapy (SBRT) in central lung tumors has been associated with higher rates of severe toxicity. We sought to evaluate toxicity and local control in a large cohort and to identify predictive dosimetric parameters.

METHODS AND MATERIALS

We identified patients who received SBRT for central tumors according to either of 2 definitions. Local failure (LF) was estimated using a competing risks model, and multivariate analysis (MVA) was used to assess factors associated with LF. We reviewed patient toxicity and applied Cox proportional hazard analysis and log-rank tests to assess whether dose-volume metrics of normal structures correlated with pulmonary toxicity.

RESULTS

One hundred twenty-five patients received SBRT for non-small cell lung cancer (n=103) or metastatic lesions (n=22), using intensity modulated radiation therapy. The most common dose was 45 Gy in 5 fractions. Median follow-up was 17.4 months. Incidence of toxicity ≥ grade 3 was 8.0%, including 5.6% pulmonary toxicity. Sixteen patients (12.8%) experienced esophageal toxicity ≥ grade 2, including 50% of patients in whom PTV overlapped the esophagus. There were 2 treatment-related deaths. Among patients receiving biologically effective dose (BED) ≥80 Gy (n=108), 2-year LF was 21%. On MVA, gross tumor volume (GTV) was significantly associated with LF. None of the studied dose-volume metrics of the lungs, heart, proximal bronchial tree (PBT), or 2 cm expansion of the PBT ("no-fly-zone" [NFZ]) correlated with pulmonary toxicity ≥grade 2. There were no differences in pulmonary toxicity between central tumors located inside the NFZ and those outside the NFZ but with planning target volume (PTV) intersecting the mediastinum.

CONCLUSIONS

Using moderate doses, SBRT for central lung tumors achieves acceptable local control with low rates of severe toxicity. Dosimetric analysis showed no significant correlation between dose to the lungs, heart, or NFZ and severe pulmonary toxicity. Esophageal toxicity may be an underappreciated risk, particularly when PTV overlaps the esophagus.

Bilateral implant reconstruction does not affect the quality of postmastectomy radiation therapy

To determine if the presence of bilateral implants, in addition to other anatomic and treatment-related variables, affects coverage of the target volume and dose to the heart and lung in patients receiving postmastectomy radiation therapy (PMRT). A total of 197 consecutive women with breast cancer underwent mastectomy and immediate tissue expander (TE) placement, with or without exchange for a permanent implant (PI) before radiation therapy at our center. PMRT was delivered with 2 tangential beams + supraclavicular lymph node field (50Gy). Patients were grouped by implant number: 51% unilateral (100) and 49% bilateral (97). The planning target volume (PTV) (defined as implant + chest wall + nodes), heart, and ipsilateral lung were contoured and the following parameters were abstracted from dose-volume histogram (DVH) data: PTV D95% > 98%, Lung V20Gy > 30%, and Heart V25Gy > 5%. Univariate (UVA) and multivariate analyses (MVA) were performed to determine the association of variables with these parameters. The 2 groups were well balanced for implant type and volume, internal mammary node (IMN) treatment, and laterality. In the entire cohort, 90% had PTV D95% > 98%, indicating excellent coverage of the chest wall. Of the patients, 27% had high lung doses (V20Gy > 30%) and 16% had high heart doses (V25Gy > 5%). No significant factors were associated with suboptimal PTV coverage. On MVA, IMN treatment was found to be highly associated with high lung and heart doses (both p < 0.0001), but implant number was not (p = 0.54). In patients with bilateral implants, IMN treatment was the only predictor of dose to the contralateral implant (p = 0.001). In conclusion, bilateral implants do not compromise coverage of the target volume or increase lung and heart dose in patients receiving PMRT. The most important predictor of high lung and heart doses in patients with implant-based reconstruction, whether unilateral or bilateral, is treatment of the IMNs. Refinement of radiation techniques in reconstructed patients who require comprehensive nodal irradiation is warranted.

Using a novel dose QA tool to quantify the impact of systematic errors otherwise undetected by conventional QA methods: clinical head and neck case studies

Recent studies have demonstrated that per-beam planar intensity-modulated radiation therapy (IMRT) quality assurance (QA) passing rates may not predict clinically relevant patient dose errors. This work is to evaluate the effect of dose variations introduced in dynamic multi-leaf collimator (DMLC) modeling and delivery processes on clinically relevant metrics for IMRT. Ten head and neck (HN) IMRT plans were randomly selected for this study. The conventional per-beam IMRT QA was performed for each plan by 2 different methods: (1) with gantry angle of 0 (gantry pointing downward) for all IMRT fields and (2) with gantry at specific angles as designed in the IMRT plan. For each patient, a batch analysis was done for each scenario and then imported to the 3DVH (Sun Nuclear Corp.) for processing. A "corrected DVH" was generated and compared to the DVH from the treatment plan. Their differences represented errors introduced from the combination of the treatment planning system (TPS) dose calculation algorithm and beam-delivery. The dose metrics from the two scenarios were compared with the corresponding calculated doses, and then their differences were analyzed. Although all per-beam planar IMRT QA had high Gamma passing rates 99.3 ± 1.3% (92.3-100%) for "2%/3 mm" criteria, there were significant errors in some of the calculated clinical dose metrics. Such as, for all the plans studied, there were as much as 3.2%, 5.7%, 5.6%, 2.3%, 4.1%, and 23.8% errors found in max cord dose, max brainstem dose, mean parotid dose, larynx dose, oral cavity dose, and PTV(D95) dose, respectively. The differences in errors for clinical metrics obtained between the two scenarios (zero gantry angle vs. true gantry angles) can also be significant: max cord dose (2.9% vs. 0.2%), max brainstem dose (3.8% vs. 0.4%), mean parotid dose (2.3% vs. 4.5%), mean larynx dose (3.9% vs. 2.0%), mean oral cavity dose (1.6% vs. 3.9%), and PTV(D95) dose (-0.4% vs. -2.6%). However, in the two scenarios, a strong and clear correlation between the dose differences for each of the organ structures was observed. This study confirms that conventional IMRT QA performance metrics are not predictive of dose errors in PTV and organs-at-risk. The clinically-relevant-dose QA has allowed us to predict the patient dose-volume relationships.

Toxicity and outcomes of thoracic re-irradiation using stereotactic body radiation therapy (SBRT)

Background

Patients treated for a thoracic malignancy carry a significant risk of developing other lung lesions. Locoregional control of intrathoracic recurrences is challenging due to the impact of prior therapies on normal tissues. We examined the safety and efficacy of thoracic re-irradiation using high-precision image-guided stereotactic body radiation therapy (SBRT).

Methods

Records of 39 patients with prior intra-thoracic conventionally fractionated radiation therapy (RT) who underwent SBRT for a subsequent primary, recurrent or metastatic lung tumor from 11/2004 to 7/2011 were retrospectively reviewed.

Results

Median dose of prior RT was 61 Gy (range 30–80 Gy). Median biologically effective prescription dose (α/β = 10) (BED₁₀) of SBRT was 70.4 Gy (range 42.6-180 Gy). With a median followup of 12.6 months among survivors, 1- and 2-year actuarial local progression-free survival (LPFS) were 77% and 64%, respectively. Median recurrence-free (RFS) and overall survival (OS) were 13.8 and 22.0 months, respectively. Patients without overlap of high-dose regions of the primary and re-irradiation plans were more likely to receive a BED₁₀ ≥100 Gy, which was associated with higher LPFS (hazard ratio, [HR] = 0.18, p = 0.04), RFS ([HR] = 0.31, p = 0.038) and OS ([HR] = 0.25, p = 0.014). Grade 2 and 3 pulmonary toxicity was observed in 18% and 5% of patients, respectively. Other grade 2–4 toxicities included chest wall pain in 18%, fatigue in 15% and skin toxicity in 5%. No grade 5 events occurred.

Conclusions

SBRT can be safely and successfully administered to patients with prior thoracic RT. Dose reduction for cases with direct overlap of successive radiation fields results in acceptable re-treatment toxicity profile.

Factors Influencing Radiation Therapists' Perceptions of Performing Manual Monitor Unit Calculations in a Computer-Based Work Environment

INTRODUCTION

Despite increased automation in the field of radiation therapy, the need to perform monitor unit calculations manually still exists for a small number of clinical situations. Challenges in maintaining the skill of performing infrequently occurring clinical tasks have been identified among other health professions, but no study has been performed for similar issues in radiation therapy. The aim of this study was to explore radiation therapists' (RT) perceived changes in comfort level to perform manual calculations (MC), an infrequently occurring clinical task, and to evaluate factors that may have influenced the change in comfort level.

METHODS AND MATERIALS

The study sample consisted of RTs working within the radiation therapy department of a cancer hospital. A questionnaire soliticing RTs' comfort level with MC and potential influencing factors was sent to each participant. The difference in responses based on key study variables, including initial mastery of MC, ongoing exposure to MC, recent exposure to MC, and MC continuing education, was analyzed. In addition, a wave analysis was performed to determine whether the responses gathered with the questionnaire were representative of those who did not respond.

RESULTS

Fifty-one responses were obtained. The wave analysis suggested that our study results may reflect the views of those of RTs who were eligible to participate, but did not respond. Ninety percent of the participants reported that their comfort level in performing MC had decreased over the years. A significantly smaller proportion of participants reported being comfortable with orthovoltage MC (14%) compared to other types of MC (75-84%). Participants' years of work experience did not appear to influence their comfort level in performing MC. A higher proportion of participants that had recent or ongoing exposure to MC, including those that performed a MC within the last 12 months, worked in dosimetry, were engaged in on-call activities, or were engaged in continuing education on MC, reported being more comfortable in MC than those participants who did not engage in such activities (91%-92% vs. 47%-71%, P < .001).

DISCUSSION/CONCLUSION

Initial mastery and ongoing exposure were identified in the literature as important factors that influence practitioners' ability in performing clinical tasks. Although initial mastery was found to influence comfort level in performing MC, our study also revealed that ongoing exposure may be relatively more important. Lessons drawn from this study will become more important to the field of radiation therapy as more manually performed clinical tasks become less frequent over time. To address potential reduction in RTs' ability in performing this infrequent clinical task, individual radiotherapy departments have historically put in place effective strategies to assure accuracy. Yet, alternatives to performing MC should be explored in order to maximize safety, efficiency, and quality of patient care.

Reduced-order constrained optimization (ROCO): clinical application to head-and-neck IMRT

PURPOSE

The authors present the application of the reduced order constrained optimization (ROCO) method, previously successfully applied to the prostate and lung sites, to the head-and-neck (H&N) site, demonstrating that it can quickly and automatically generate clinically competitive IMRT plans. We provide guidelines for applying ROCO to larynx, oropharynx, and nasopharynx cases, and report the results of a live experiment that demonstrates how an expert planner can save several hours of trial-and-error interaction using the proposed approach.

METHODS

The ROCO method used for H&N IMRT planning consists of three major steps. First, the intensity space of treatment plans is sampled by solving a series of unconstrained optimization problems with a parameter range based on previously treated patient data. Second, the dominant modes in the intensity space are estimated by dimensionality reduction using principal component analysis (PCA). Third, a constrained optimization problem over this basis is quickly solved to find an IMRT plan that meets organ-at-risk (OAR) and target coverage constraints. The quality of the plan is assessed using evaluation tools within Memorial Sloan-Kettering Cancer Center (MSKCC)'s treatment planning system (TPS).

RESULTS

The authors generated ten H&N IMRT plans for previously treated patients using the ROCO method and processed them for deliverability by a dynamic multileaf collimator (DMLC). The authors quantitatively compared the ROCO plans to the previously achieved clinical plans using the TPS tools used at MSKCC, including DVH and isodose contour analysis, and concluded that the ROCO plans would be clinically acceptable. In our current implementation, ROCO H&N plans can be generated using about 1.6 h of offline computation followed by 5-15 min of semiautomatic planning time. Additionally, the authors conducted a live session for a plan designated by MSKCC performed together with an expert H&N planner. A technical assistant set up the first two steps, which were performed without further human interaction, and then collaborated in a virtual meeting with the expert planner to perform the third (constrained optimization) step. The expert planner performed in-depth analysis of the resulting ROCO plan and deemed it to be clinically acceptable and in some aspects superior to the clinical plan. This entire process took 135 min including two constrained optimization runs, in comparison to the estimated 4 h that would have been required using traditional clinical planning tools.

CONCLUSIONS

The H&N site is very challenging for IMRT planning, due to several levels of prescription and a large, variable number (6-20) of OARs that depend on the location of the tumor. ROCO for H&N shows promise in generating clinically acceptable plans both more quickly and with substantially less human interaction.

Photons or protons for non-central nervous system solid malignancies in children: a historical perspective and important highlights

Over the years, major advances have occurred in radiotherapy techniques, delivery, and treatment planning. Although radiotherapy is an integral treatment component of pediatric solid tumors, it is associated with potential acute and long-term untoward effects and risk of secondary malignancy particularly in growing children. Two major advances in external beam radiotherapy are intensity-modulated radiotherapy (IMRT) and proton beam radiotherapy. Their use in the treatment of children with cancer has been steadily increasing. IMRT uses multiple modulated radiation fields that enhance the conformality of the dose distribution to the target volume and avoid high doses to normal tissues. However, IMRT may be associated with increased volume of normal tissue that receives low doses and potential risk of secondary malignancy. Contrary to IMRT, proton beam radiotherapy uses a few beams and a fast dose fall-off distal to the target volume. Although both modalities require substantial personnel time and effort, the very high cost and limited availability of proton radiotherapy have constrained its widespread use. It is anticipated that both modalities may markedly improve tumor control and quality of life for long-term cancer survivors. Clinical trials with long-term follow-up are needed to confirm the premise that proton beam therapy will decrease late effects and secondary malignancies without compromising local control in pediatric patients with cancer.

Confirmation of Skin Doses Resulting from Bolus Effect of Intervening Alpha-cradle and Carbon Fiber Couch in Radiotherapy

In this study, we verified the treatment planning calculations of skin doses with the incorporation of the bolus effect due to the intervening alpha-cradle (AC) and carbon fiber couch (CFC) using radiochromic EBT2 films. A polystyrene phantom (25 × 25 × 15 cm3) with six EBT2 films separated by polystyrene slabs, at depths of 0, 0.1, 0.2, 0.5, 1, 1.4 cm, was positioned above an AC, which was ~1 cm thick. The phantom and AC assembly were CT scanned and the CT-images were transferred to the treatment planning system (TPS) for calculations in three scenarios: (A) ignoring AC and CFC, (B) accounting for AC only, (C) accounting for both AC and CFC. A single posterior 10 × 10 cm2 field, a pair of posterior-oblique 10 × 10 cm2 fields, and a posterior IMRT field (6 MV photons from a Varian Trilogy linac) were planned. For each radiation field configuration, the same MU were used in all three scenarios in the TPS. Each plan for scenario C was delivered to expose a stack of EBT2 films in the phantom through AC and CFC. In addition, in vivo EBT2 film measurement on a lung cancer patient immobilized with AC undergoing IMRT was also included in this study. Point doses and planar distributions generated from the TPS for the three scenarios were compared with the data from the EBT2 film measurements. For all the field arrangements, the EBT2 film data including the in vivo measurement agreed with the doses calculated for scenario (C), within the uncertainty of the EBT2 measurements (~4%). For the single posterior field (a pair of posterior-oblique fields), the TPS generated doses were lower than the EBT2 doses by 34%, 33%, 31%, 13% (34%, 31%, 31%, 11%) for scenario A and by 27%, 25%, 22%, 8% (25%, 21%, 21%, 6%) for scenario B at the depths of 0, 0.1, 0.2, 0.5 cm, respectively. For the IMRT field, the 2D dose distributions at each depth calculated in scenario C agree with those measured data. When comparing the central axis doses for the IMRT field, we found the TPS generated doses for scenario A (B) were lower than the EBT2 data by 35%, 34%, 31%, 16% (29%, 26%, 23%, 10%) at the depths of 0, 0.1, 0.2, 0.5 cm, respectively. There were no significant differences for the depths of 1.0 and 1.4 cm for all the radiation fields studied. TPS calculation of doses in the skin layers accounting for AC and CFC was verified by EBT2 film data. Ignoring the presence of AC and/or CFC in TPS calculation would significantly underestimate the doses in the skin layers. For the clinicians, as more hypofractionated regimens and stereotactic regimens are being used, this information will be useful to avoid potential serious skin toxicities, and also assist in clinical decisions and report these doses accurately to relevant clinical trials/cooperative groups, such as RTOG.

Pleural intensity-modulated radiotherapy for malignant pleural mesothelioma

PURPOSE

In patients with malignant pleural mesothelioma who are unable to undergo pneumonectomy, it is difficult to deliver tumoricidal radiation doses to the pleura without significant toxicity. We have implemented a technique of using intensity-modulated radiotherapy (IMRT) to treat these patients, and we report the feasibility and toxicity of this approach.

METHODS AND MATERIALS

Between 2005 and 2010, 36 patients with malignant pleural mesothelioma and two intact lungs (i.e., no previous pneumonectomy) were treated with pleural IMRT to the hemithorax (median dose, 46.8 Gy; range, 41.4-50.4) at Memorial Sloan-Kettering Cancer Center.

RESULTS

Of the 36 patients, 56% had right-sided tumors. The histologic type was epithelial in 78%, sarcomatoid in 6%, and mixed in 17%, and 6% had Stage I, 28% had Stage II, 33% had Stage III, and 33% had Stage IV. Thirty-two patients (89%) received induction chemotherapy (mostly cisplatin and pemetrexed); 56% underwent pleurectomy/decortication before IMRT and 44% did not undergo resection. Of the 36 patients evaluable for acute toxicity, 7 (20%) had Grade 3 or worse pneumonitis (including 1 death) and 2 had Grade 3 fatigue. In 30 patients assessable for late toxicity, 5 had continuing Grade 3 pneumonitis. For patients treated with surgery, the 1- and 2-year survival rate was 75% and 53%, and the median survival was 26 months. For patients who did not undergo surgical resection, the 1- and 2-year survival rate was 69% and 28%, and the median survival was 17 months.

CONCLUSIONS

Treating the intact lung with pleural IMRT in patients with malignant pleural mesothelioma is a safe and feasible treatment option with an acceptable rate of pneumonitis. Additionally, the survival rates were encouraging in our retrospective series, particularly for the patients who underwent pleurectomy/decortication. We have initiated a Phase II trial of induction chemotherapy with pemetrexed and cisplatin with or without pleurectomy/decortication, followed by pleural IMRT to prospectively evaluate the toxicity and survival.

Esophageal toxicity from high-dose, single-fraction paraspinal stereotactic radiosurgery

PURPOSE

To report the esophageal toxicity from single-fraction paraspinal stereotactic radiosurgery (SRS) and identify dosimetric and clinical risk factors for toxicity.

METHODS AND MATERIALS

A total of 204 spinal metastases abutting the esophagus (182 patients) were treated with high-dose single-fraction SRS during 2003-2010. Toxicity was scored using the National Cancer Institute Common Toxicity Criteria for Adverse Events, version 4.0. Dose-volume histograms were combined to generate a comprehensive atlas of complication incidence that identifies risk factors for toxicity. Correlation of dose-volume factors with esophageal toxicity was assessed using Fisher's exact test and logistic regression. Clinical factors were correlated with toxicity.

RESULTS

The median dose to the planning treatment volume was 24 Gy. Median follow-up was 12 months (range, 3-81). There were 31 (15%) acute and 24 (12%) late esophageal toxicities. The rate of grade ≥3 acute or late toxicity was 6.8% (14 patients). Fisher's exact test resulted in significant median splits for grade ≥3 toxicity at V12 = 3.78 cm(3) (relative risk [RR] 3.7, P=.05), V15 = 1.87 cm(3) (RR 13, P=.0013), V20 = 0.11 cm(3) (RR 6, P=0.01), and V22 = 0.0 cm(3) (RR 13, P=.0013). The median split for D2.5 cm(3) (14.02 Gy) was also a significant predictor of toxicity (RR 6; P=.01). A highly significant logistic regression model was generated on the basis of D2.5 cm(3). One hundred percent (n = 7) of grade ≥4 toxicities were associated with radiation recall reactions after doxorubicin or gemcitabine chemotherapy or iatrogenic manipulation of the irradiated esophagus.

CONCLUSIONS

High-dose, single-fraction paraspinal SRS has a low rate of grade ≥3 esophageal toxicity. Severe esophageal toxicity is minimized with careful attention to esophageal doses during treatment planning. Iatrogenic manipulation of the irradiated esophagus and systemic agents classically associated with radiation recall reactions are associated with development of grade ≥4 toxicity.

Using generalized equivalent uniform dose atlases to combine and analyze prospective dosimetric and radiation pneumonitis data from 2 non-small cell lung cancer dose escalation protocols

PURPOSE

To demonstrate the use of generalized equivalent uniform dose (gEUD) atlas for data pooling in radiation pneumonitis (RP) modeling, to determine the dependence of RP on gEUD, to study the consistency between data sets, and to verify the increased statistical power of the combination.

METHODS AND MATERIALS

Patients enrolled in prospective phase I/II dose escalation studies of radiation therapy of non-small cell lung cancer at Memorial Sloan-Kettering Cancer Center (MSKCC) (78 pts) and the Netherlands Cancer Institute (NKI) (86 pts) were included; 10 (13%) and 14 (17%) experienced RP requiring steroids (RPS) within 6 months after treatment. gEUD was calculated from dose-volume histograms. Atlases for each data set were created using 1-Gy steps from exact gEUDs and RPS data. The Lyman-Kutcher-Burman model was fit to the atlas and exact gEUD data. Heterogeneity and inconsistency statistics for the fitted parameters were computed. gEUD maps of the probability of RPS rate≥20% were plotted.

RESULTS

The 2 data sets were homogeneous and consistent. The best fit values of the volume effect parameter a were small, with upper 95% confidence limit around 1.0 in the joint data. The likelihood profiles around the best fit a values were flat in all cases, making determination of the best fit a weak. All confidence intervals (CIs) were narrower in the joint than in the individual data sets. The minimum P value for correlations of gEUD with RPS in the joint data was .002, compared with P=.01 and .05 for MSKCC and NKI data sets, respectively. gEUD maps showed that at small a, RPS risk increases with gEUD.

CONCLUSIONS

The atlas can be used to combine gEUD and RPS information from different institutions and model gEUD dependence of RPS. RPS has a large volume effect with the mean dose model barely included in the 95% CI. Data pooling increased statistical power.

Comparison of heart and coronary artery doses associated with intensity-modulated radiotherapy versus three-dimensional conformal radiotherapy for distal esophageal cancer

PURPOSE

To compare heart and coronary artery radiation exposure using intensity-modulated radiotherapy (IMRT) vs. four-field three-dimensional conformal radiotherapy (3D-CRT) treatment plans for patients with distal esophageal cancer undergoing chemoradiation.

METHODS AND MATERIALS

Nineteen patients with distal esophageal cancers treated with IMRT from March 2007 to May 2008 were identified. All patients were treated to 50.4 Gy with five-field IMRT plans. Theoretical 3D-CRT plans with four-field beam arrangements were generated. Dose-volume histograms of the planning target volume, heart, right coronary artery, left coronary artery, and other critical normal tissues were compared between the IMRT and 3D-CRT plans, and selected parameters were statistically evaluated using the Wilcoxon rank-sum test.

RESULTS

Intensity-modulated radiotherapy treatment planning showed significant reduction (p < 0.05) in heart dose over 3D-CRT as assessed by average mean dose (22.9 vs. 28.2 Gy) and V30 (24.8% vs. 61.0%). There was also significant sparing of the right coronary artery (average mean dose, 23.8 Gy vs. 35.5 Gy), whereas the left coronary artery showed no significant improvement (mean dose, 11.2 Gy vs. 9.2 Gy), p = 0.11. There was no significant difference in percentage of total lung volume receiving at least 10, 15, or 20 Gy or in the mean lung dose between the planning methods. There were also no significant differences observed for the kidneys, liver, stomach, or spinal cord. Intensity-modulated radiotherapy achieved a significant improvement in target conformity as measured by the conformality index (ratio of total volume receiving 95% of prescription dose to planning target volume receiving 95% of prescription dose), with the mean conformality index reduced from 1.56 to 1.30 using IMRT.

CONCLUSIONS

Treatment of patients with distal esophageal cancer using IMRT significantly decreases the exposure of the heart and right coronary artery when compared with 3D-CRT. Long-term studies are necessary to determine how this will impact on development of coronary artery disease and other cardiac complications.

Reduced order constrained optimization (ROCO): clinical application to lung IMRT

PURPOSE

The authors use reduced-order constrained optimization (ROCO) to create clinically acceptable IMRT plans quickly and automatically for advanced lung cancer patients. Their new ROCO implementation works with the treatment planning system and full dose calculation used at Memorial Sloan-Kettering Cancer Center (MSKCC). The authors have implemented mean dose hard constraints, along with the point-dose and dose-volume constraints that the authors used for our previous work on the prostate.

METHODS

ROCO consists of three major steps. First, the space of treatment plans is sampled by solving a series of optimization problems using penalty-based quadratic objective functions. Next, an efficient basis for this space is found via principal component analysis (PCA); this reduces the dimensionality of the problem. Finally, a constrained optimization problem is solved over this basis to find a clinically acceptable IMRT plan. Dimensionality reduction makes constrained optimization computationally efficient.

RESULTS

The authors apply ROCO to 12 stage III non-small-cell lung cancer (NSCLC) cases, generating IMRT plans that meet all clinical constraints and are clinically acceptable, and demonstrate that they are competitive with the clinical treatment plans. The authors also test how many samples and PCA modes are necessary to achieve an adequate lung plan, demonstrate the importance of long-range dose calculation for ROCO, and evaluate the performance of nonspecific normal tissue ("rind") constraints in ROCO treatment planning for the lung. Finally, authors show that ROCO can save time for planners, and they estimate that in the clinic, planning using their approach would save a median of 105 min for the patients in the study.

CONCLUSIONS

New challenges arise when applying ROCO to the lung site, which include the lack of a class solution, a larger treatment site, an increased number of parameters and beamlets, a variable number of beams and beam arrangement, and the customary use of rinds in clinical plans to avoid high-dose areas outside the PTV. In the authors previous work, use of an approximate dose calculation in the hard constraint optimization sometimes meant that clinical constraints were not met when evaluated with the full dose calculation. This difficulty has been removed in the current work by using the full dose calculation in the hard constraint optimization. The authors have demonstrated that ROCO offers a fast and automatic way to create IMRT plans for advanced NSCLC, which extends their previous application of ROCO to prostate cancer IMRT planning.

Dose-volume parameters predict for the development of chest wall pain after stereotactic body radiation for lung cancer

PURPOSE

Chest wall (CW) pain has recently been recognized as an important adverse effect of stereotactic body radiation therapy (SBRT) for non-small-cell lung cancer (NSCLC). We developed a dose-volume model to predict the development of this toxicity.

METHODS AND MATERIALS

A total of 126 patients with primary, clinically node-negative NSCLC received three to five fractions of SBRT to doses of 40-60 Gy and were prospectively followed. The dose-absolute volume histograms of two different definitions of the CW as an organ at risk (CW3cm and CW2cm) were examined for all 126 patients.

RESULTS

With a median follow-up of 16 months, the 2-year estimated actuarial incidence of Grade ≥ 2 CW pain was 39%. The median time to onset of Grade ≥ 2 CW pain (National Cancer Institute Common Terminology Criteria for Adverse Events, Version 3.0) was 9 months. There was no predictive advantage for biologically corrected dose over physical dose. Neither fraction number (p = 0.07) nor prescription dose (p = 0.07) were significantly correlated with the development of Grade ≥ 2 CW pain. Cox Proportional Hazards analysis identified significant correlation with a broad range of dose-volume combinations, with the CW volume receiving 30 Gy (V30) as one of the strongest predictors (p < 0.001). CW2cm consistently enabled better prediction of CW toxicity. When a physical dose of 30 Gy was received by more than 70 cm(3) of CW2cm, there was a significant correlation with Grade ≥ 2 CW pain (p = 0.004).

CONCLUSIONS

CW toxicity after SBRT is common and long-term follow-up is needed to identify affected patients. A volume of CW ≥ 70 cm(3) receiving 30 Gy is significantly correlated with Grade ≥ 2 CW pain. We are currently applying this constraint at our institution for patients receiving thoracic SBRT. An actuarial atlas of our data is provided as an electronic supplement to facilitate data-sharing and meta-analysis relating to CW pain.

Three-dimensional radiobiological dosimetry (3D-RD) with 124I PET for 131I therapy of thyroid cancer

Radioiodine therapy of thyroid cancer was the first and remains among the most successful radiopharmaceutical (RPT) treatments of cancer although its clinical use is based on imprecise dosimetry. The positron emitting radioiodine, (124)I, in combination with positron emission tomography (PET)/CT has made it possible to measure the spatial distribution of radioiodine in tumors and normal organs at high resolution and sensitivity. The CT component of PET/CT has made it simpler to match the activity distribution to the corresponding anatomy. These developments have facilitated patient-specific dosimetry (PSD), utilizing software packages such as three-dimensional radiobiological dosimetry (3D-RD), which can account for individual patient differences in pharmacokinetics and anatomy. We highlight specific examples of such calculations and discuss the potential impact of (124)I PET/CT on thyroid cancer therapy.

Development and evaluation of a comprehensive clinical decision support taxonomy: comparison of front-end tools in commercial and internally developed electronic health record systems

BACKGROUND

Clinical decision support (CDS) is a valuable tool for improving healthcare quality and lowering costs. However, there is no comprehensive taxonomy of types of CDS and there has been limited research on the availability of various CDS tools across current electronic health record (EHR) systems.

OBJECTIVE

To develop and validate a taxonomy of front-end CDS tools and to assess support for these tools in major commercial and internally developed EHRs.

STUDY DESIGN AND METHODS

We used a modified Delphi approach with a panel of 11 decision support experts to develop a taxonomy of 53 front-end CDS tools. Based on this taxonomy, a survey on CDS tools was sent to a purposive sample of commercial EHR vendors (n=9) and leading healthcare institutions with internally developed state-of-the-art EHRs (n=4).

RESULTS

Responses were received from all healthcare institutions and 7 of 9 EHR vendors (response rate: 85%). All 53 types of CDS tools identified in the taxonomy were found in at least one surveyed EHR system, but only 8 functions were present in all EHRs. Medication dosing support and order facilitators were the most commonly available classes of decision support, while expert systems (eg, diagnostic decision support, ventilator management suggestions) were the least common.

CONCLUSION

We developed and validated a comprehensive taxonomy of front-end CDS tools. A subsequent survey of commercial EHR vendors and leading healthcare institutions revealed a small core set of common CDS tools, but identified significant variability in the remainder of clinical decision support content.

Evaluation of tumor motion effects on dose distribution for hypofractionated intensity-modulated radiotherapy of non-small-cell lung cancer

Respiration‐induced tumor motion during intensity‐modulated radiotherapy (IMRT) of non‐small‐cell lung cancer (NSCLC) could cause substantial differences between planned and delivered doses. While it has been shown that, for conventionally fractionated IMRT, motion effects average out over the course of many treatments, this might not be true for hypofractionated IMRT (IMHFRT). Numerical simulations were performed for nine NSCLC patients (11 tumors) to evaluate this problem. Dose distributions to the Clinical Target Volume (CTV) and Internal Target Volume (ITV) were retrospectively calculated using the previously‐calculated leaf motion files but with the addition of typical periodic motion (i.e. amplitude 0.36–1.26 cm, 3–8 sec period). A typical IMHFRT prescription of 20 Gy × 3 fractions was assumed. For the largest amplitude (1.26 cm), the average ± standard deviation of the ratio of simulated to planned mean dose, minimum dose, D95 and V95 were 0.98±0.01, 0.88±0.09, 0.94±0.05 and 0.94±0.07 for the CTV, and 0.99±0.01, 0.99±0.03, 0.98±0.02 and 1.00±0.01 for the ITV, respectively. There was minimal dependence on period or initial phase. For typical tumor geometries and respiratory amplitudes, changes in target coverage are minimal but can be significant for larger amplitudes, faster beam delivery, more highly‐modulated fields, and smaller field margins.

PACS number: 87.55.dk

Acute skin toxicity following stereotactic body radiation therapy for stage I non-small-cell lung cancer: who's at risk?

PURPOSE

We examined the rate of acute skin toxicity within a prospectively managed database of patients treated for early-stage non-small-cell lung cancer (NSCLC) and investigated factors that might predict skin toxicity.

METHODS

From May 2006 through January 2008, 50 patients with Stage I NSCLC were treated at Memorial Sloan-Kettering Cancer Center with 60 Gy in three fractions or 44-48 Gy in four fractions. Patients were treated with multiple coplanar beams (3-7, median 4) with a 6 MV linac using intensity-modulated radiotherapy (IMRT) and dynamic multileaf collimation. Toxicity grading was performed and based on the National Cancer Institute Common Terminology Criteria for Adverse Effects. Factors associated with Grade 2 or higher acute skin reactions were calculated by Fisher's exact test.

RESULTS

After a minimum 3 months of follow-up, 19 patients (38%) developed Grade 1, 4 patients (8%) Grade 2, 2 patients (4%) Grade 3, and 1 patient Grade 4 acute skin toxicity. Factors associated with Grade 2 or higher acute skin toxicity included using only 3 beams (p = 0.0007), distance from the tumor to the posterior chest wall skin of less than 5 cm (p = 0.006), and a maximum skin dose of 50% or higher of the prescribed dose (p = 0.02).

CONCLUSIONS

SBRT can be associated with significant skin toxicity. One must consider the skin dose when evaluating the treatment plan and consider the bolus effect of immobilization devices.

The Translational Research Working Group developmental pathway for interventive devices

The interventive device pathway refers to one of six pathways developed by the Translational Research Working Group (TRWG) that, together, describe the core domains of early translational cancer research. This pathway focuses on the development of devices (as classified by the Food and Drug Administration), designed for local ablation of cancer or precancerous lesions (e.g., radiation therapy, microwave, radiofrequency ablation, and high-intensity focused ultrasound systems). This article describes the distinctive features of the pathway and issues that are encountered in the real-world development of interventive devices for the treatment of cancer. The interventive device pathway is envisioned to be a general guideline of the steps required for effective development, optimization, testing, and validation of developing devices, to be dynamic and adaptable, and to form a framework for discussions focused on improving the efficiency and effectiveness of new device development.

Three-dimensional imaging-based radiobiological dosimetry

Targeted radionuclide therapy holds promise as a new treatment for cancer. Advances in imaging are making it possible for researchers to evaluate the spatial distribution of radioactivity in tumors and normal organs over time. Matched anatomical imaging, such as combined single-photon emission computed tomography/computed tomography and positron emission tomography/computed tomography, has also made it possible to obtain tissue density information in conjunction with the radioactivity distribution. Coupled with sophisticated iterative reconstruction algorithms, these advances have made it possible to perform highly patient-specific dosimetry that also incorporates radiobiological modeling. Such sophisticated dosimetry techniques are still in the research investigation phase. Given the attendant logistical and financial costs, a demonstrated improvement in patient care will be a prerequisite for the adoption of such highly-patient specific internal dosimetry methods.

Innovations in chemotherapy and radiation therapy: Implications and opportunities for the Asia-Pacific Rim

New cases of invasive cancer in the United States occur among nearly 1.5 million people annually. In 2007, more than 1,500 people died per day with this diagnosis. Cancer is responsible for nearly one in every four deaths reported in the country. Enormous amounts of money and research have been, and are being spent, in an attempt to improve these numbers. While prevention and early detection remain the key to long-term success, treatment in the neo-adjuvant, adjuvant and metastatic settings still centre around two main treatment modalities – radiation therapy and chemotherapy. This article will review the advances that have been made in both areas that are making these treatments more precise and convenient, as well as less toxic, for the patient. In the field of radiation therapy this involves the development of new therapy planning and delivery systems, such as intensity-modulated radiation therapy (IMRT), and positron emission and computed tomography, PET-CT. Chemotherapy has also evolved with the development of targeted chemotherapy for the treatment of specific malignancies as well as improved supportive care agents which allow for the administration of dose-dense chemotherapy when appropriate.

(18)F-fluorodeoxyglucose positron emission tomography-based assessment of local failure patterns in non-small-cell lung cancer treated with definitive radiotherapy

PURPOSE

To assess the pattern of local failure using (18)F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) scans after radiotherapy (RT) in non-small-cell lung cancer (NSCLC) patients treated with definitive RT whose gross tumor volumes (GTVs) were defined with the aid of pre-RT PET data.

METHOD AND MATERIALS

The data from 26 patients treated with involved-field RT who had local failure and a post-RT PET scan were analyzed. The patterns of failure were visually scored and defined as follows: (1) within the GTV/planning target volume (PTV); (2) within the GTV, PTV, and outward; (3) within the PTV and outward; and (4) outside the PTV. Local failure was also evaluated as originating from nodal areas vs. the primary tumor.

RESULTS

We analyzed 34 lesions. All 26 patients had recurrence originating from their primary tumor. Of the 34 lesions, 8 (24%) were in nodal areas, 5 of which (63%) were marginal or geographic misses compared with only 1 (4%) of the 26 primary recurrences (p = 0.001). Of the eight primary tumors that had received a dose of <60 Gy, six (75%) had failure within the GTV and two (25%) at the GTV margin. At doses of > or = 60 Gy, 6 (33%) of 18 had failure within the GTV and 11 (61%) at the GTV margin, and 1 (6%) was a marginal miss (p < 0.05).

CONCLUSION

At lower doses, the pattern of recurrences was mostly within the GTV, suggesting that the dose might have been a factor for tumor control. At greater doses, the treatment failures were mostly at the margin of the GTV. This suggests that visual incorporation of PET data for GTV delineation might be inadequate, and more sophisticated approaches of PET registration should be evaluated.

Intensity-modulated radiation therapy (IMRT) for inoperable non-small cell lung cancer: the Memorial Sloan-Kettering Cancer Center (MSKCC) experience

INTRODUCTION

Intensity-modulated radiation therapy (IMRT) is an advanced treatment delivery technique that can improve the therapeutic dose ratio. Its use in the treatment of inoperable non-small cell lung cancer (NSCLC) has not been well studied. This report reviews our experience with IMRT for patients with inoperable NSCLC.

METHODS AND MATERIALS

We performed a retrospective review of 55 patients with stage I-IIIB inoperable NSCLC treated with IMRT at our institution between 2001 and 2005. The study endpoints were toxicity, local control, and overall survival.

RESULTS

With a median follow-up of 26 months, the 2-year local control and overall survival rates for stage I/II patients were 50% and 55%, respectively. For the stage III patients, 2-year local control and overall survival rates were 58% and 58%, respectively, with a median survival time of 25 months. Six patients (11%) experienced grade 3 acute pulmonary toxicity. There were no acute treatment-related deaths. Two patients (4%) had grade 3 or worse late treatment-related pulmonary toxicity.

CONCLUSIONS

IMRT treatment resulted in promising outcomes for inoperable NSCLC patients.

Radiation therapy of large intact breasts using a beam spoiler or photons with mixed energies

Radiation treatment of large intact breasts with separations of more than 24 cm is typically performed using x-rays with energies of 10 MV and higher, to eliminate high-dose regions in tissue. The disadvantage of the higher energy beams is the reduced dose to superficial tissue in the buildup region. We evaluated 2 methods of avoiding this underdosage: (1) a beam spoiler: 1.7-cm-thick Lucite plate positioned in the blocking tray 35 cm from the isocenter, with 15-MV x-rays; and (2) combining 6- and 15-MV x-rays through the same portal. For the beam with the spoiler, we measured the dose distribution for normal and oblique incidence using a film and ion chamber in polystyrene, as well as a scanning diode in a water tank. In the mixed-energy approach, we calculated the dose distributions in the buildup region for different proportions of 6- and 15-MV beams. The dose enhancement due to the beam spoiler exhibited significant dependence upon the source-to-skin distance (SSD), field size, and the angle of incidence. In the center of a 20 x 20-cm(2) field at 90-cm SSD, the beam spoiler raises the dose at 5-mm depth from 77% to 87% of the prescription, while maintaining the skin dose below 57%. Comparison of calculated dose with measurements suggested a practical way of treatment planning with the spoiler--usage of 2-mm "beam" bolus--a special option offered by in-house treatment planning system. A second method of increasing buildup doses is to mix 6- and 15-MV beams. For example, in the case of a parallel-opposed irradiation of a 27-cm-thick phantom, dose to D(max) for each energy, with respect to midplane, is 114% for pure 6-, 107% for 15-MV beam with the spoiler, and 108% for a 3:1 mixture of 15- and 6-MV beams. Both methods are practical for radiation therapy of large intact breasts.

Involved-field radiation therapy for inoperable non small-cell lung cancer

PURPOSE

Dose escalation has been shown to improve local control in non-small-cell lung cancer (NSCLC) treated with definitive radiation therapy, but with increased complications. We implemented the use of involved-field radiotherapy (IFRT) in an effort to reduce toxicity while treating the gross tumor to higher doses. This analysis reports failure rates in uninvolved nodal regions with the use of IFRT.

PATIENTS AND METHODS

A total of 524 patients with NSCLC treated with three-dimensional conformal radiotherapy at Memorial Sloan-Kettering Cancer Center between 1991 and 2005 were reviewed. Only lymph node regions initially involved with tumor by either biopsy or radiographic criteria were included in the clinical target volume. Elective nodal failure (ENF) was defined as a recurrence in an initially uninvolved lymph node in the absence of local failure.

RESULTS

Only 32 patients (6.1%) with ENF were identified. The 2-year actuarial rates of elective nodal control and primary tumor control were 92.4% and 51%, respectively, with a median follow-up of 41 months in survivors. In patients who achieved local disease control, the 2-year elective nodal control rate was 91%. The median time to ENF was 6 months (range, 0 to 56 months). Many patients experienced treatment failure in multiple lymph node regions simultaneously.

CONCLUSION

The use of IFRT did not cause a significant amount of failure in lymph node regions not included in the tumor volume. Therefore, IFRT remains an acceptable method of treatment that allows for dose escalation while minimizing toxicity.

Is a 3-mm intrafractional margin sufficient for daily image-guided intensity-modulated radiation therapy of prostate cancer?

PURPOSE

To determine whether a 3-mm isotropic target margin adequately covers the prostate and seminal vesicles (SVs) during administration of an intensity-modulated radiation therapy (IMRT) treatment fraction, assuming that daily image-guided setup is performed just before each fraction.

MATERIALS AND METHODS

In-room computed tomographic (CT) scans were acquired immediately before and after a daily treatment fraction in 46 patients with prostate cancer. An eight-field IMRT plan was designed using the pre-fraction CT with a 3-mm margin and subsequently recalculated on the post-fraction CT. For convenience of comparison, dose plans were scaled to full course of treatment (75.6 Gy). Dose coverage was assessed on the post-treatment CT image set.

RESULTS

During one treatment fraction (21.4+/-5.5 min), there were reductions in the volumes of the prostate and SVs receiving the prescribed dose (median reduction 0.1% and 1.0%, respectively, p<0.001) and in the minimum dose to 0.1 cm(3) of their volumes (median reduction 0.5 and 1.5 Gy, p<0.001). Of the 46 patients, three patients' prostates and eight patients' SVs did not maintain dose coverage above 70 Gy. Rectal filling correlated with decreased percentage-volume of SV receiving 75.6, 70, and 60 Gy (p<0.02).

CONCLUSIONS

The 3-mm intrafractional margin was adequate for prostate dose coverage. However, a significant subset of patients lost SV dose coverage. The rectal volume change significantly affected SV dose coverage. For advanced-stage prostate cancers, we recommend to use larger margins or improve organ immobilization (such as with a rectal balloon) to ensure SV coverage.

High-Dose Radiotherapy for the Treatment of Inoperable Non–Small Cell Lung Cancer

PURPOSE

Local failure continues to be a major cause of mortality in patients with inoperable non-small cell lung cancer (NSCLC) treated with radiation therapy. Dose escalation is one method of improving local control. We investigated whether high-dose radiotherapy enhances outcomes in patients with inoperable NSCLC.

MATERIALS AND METHODS

Eighty-two patients with inoperable NSCLC stage I-IIIB were treated with three-dimensional conformal radiotherapy to doses of > or =80 Gy. Patients were divided into 2 groups based on stage: those with stage I/II disease (55 patients) and those with stage III (IIIA or IIIB) disease (27 patients).

RESULTS

The 5-year local control and overall survival rates for the patients with stage I/II disease were 67% and 36%, respectively, with a median survival time of 41 months. For the patients with stage III disease, 5-year local control and overall survival rates were observed to be 39% and 31%, respectively, with a median survival time of 32 months.

CONCLUSIONS

Our data show a favorable 5-year overall survival rate (36%) with an acceptable toxicity profile in patients with early-stage NSCLC treated to doses of > or =80 Gy using three-dimensional conformal radiotherapy. Sequential chemotherapy combined with high-dose radiation gave survival rates equivalent to those seen with concurrent chemoradiation therapy in locally advanced disease. The overall survival and local control rates observed among patients with all stages of disease are consistent with and comparable to results from other dose-escalation studies reported in the literature.

Modern radiation treatment planning and delivery--from Röntgen to real time

The field of radiation oncology has advanced exponentially since the discovery of X-rays just over 100 years ago. With the advent of three-dimensional treatment planning, the therapeutic index was increased by dose escalation and more accurate shielding of normal tissues. Now, even greater advances are under way with IMRT, image-guided radiation therapy, delineation and control of organ motion, and real-time imaging. Similarly, the use of particle therapies such as protons has the potential to effect even more accurate dose distributions. Clinical studies investigating these modalities will likely further increase the efficacy of radiation in years to come.