Alyson McIntosh

Computed tomography-based anatomic assessment overestimates local tumor recurrence in patients with mass-like consolidation after stereotactic body radiotherapy for early-stage non-small cell lung cancer.

PURPOSE To investigate pulmonary radiologic changes after lung stereotactic body radiotherapy (SBRT), to distinguish between mass-like fibrosis and tumor recurrence. METHODS AND MATERIALS Eighty consecutive patients treated with 3- to 5-fraction SBRT for early-stage peripheral non-small cell lung cancer with a minimum follow-up of 12 months were reviewed. The mean biologic equivalent dose received was 150 Gy (range, 78-180 Gy). Patients were followed with serial CT imaging every 3 months. The CT appearance of consolidation was defined as diffuse or mass-like. Progressive disease on CT was defined according to Response Evaluation Criteria in Solid Tumors 1.1. Positron emission tomography (PET) CT was used as an adjunct test. Tumor recurrence was defined as a standardized uptake value equal to or greater than the pretreatment value. Biopsy was used to further assess consolidation in select patients. RESULTS Median follow-up was 24 months (range, 12.0-36.0 months). Abnormal mass-like consolidation was identified in 44 patients (55%), whereas diffuse consolidation was identified in 12 patients (15%), at a median time from end of treatment of 10.3 months and 11.5 months, respectively. Tumor recurrence was found in 35 of 44 patients with mass-like consolidation using CT alone. Combined with PET, 10 of the 44 patients had tumor recurrence. Tumor size (hazard ratio 1.12, P=.05) and time to consolidation (hazard ratio 0.622, P=.03) were predictors for tumor recurrence. Three consecutive increases in volume and increasing volume at 12 months after treatment in mass-like consolidation were highly specific for tumor recurrence (100% and 80%, respectively). Patients with diffuse consolidation were more likely to develop grade ≥ 2 pneumonitis (odds ratio 26.5, P=.02) than those with mass-like consolidation (odds ratio 0.42, P=.07). CONCLUSION Incorporating the kinetics of mass-like consolidation and PET to the current criteria for evaluating posttreatment response will increase the likelihood of correctly identifying patients with progressive disease after lung SBRT.

QUANTIFYING THE REPRODUCIBILITY OF HEART POSITION DURING TREATMENT AND CORRESPONDING DELIVERED HEART DOSE IN VOLUNTARY DEEP INHALATION BREATH HOLD FOR LEFT BREAST CANCER PATIENTS TREATED WITH EXTERNAL BEAM RADIOTHERAPY

PURPOSE Voluntary deep inhalation breath hold (VDIBH) reduces heart dose during left breast irradiation. We present results of the first study performed to quantify reproducibility of breath hold using bony anatomy, heart position, and heart dose for VDIBH patients at treatment table. METHODS AND MATERIALS Data from 10 left breast cancer patients undergoing VDIBH whole-breast irradiation were analyzed. Two computed tomography (CT) scans, free breathing (FB) and VDIBH, were acquired to compare dose to critical structures. Pretreatment weekly kV orthogonal images and tangential ports were acquired. The displacement difference from spinal cord to sternum across the isocenter between coregistered planning Digitally Reconstructed Radiographs (DRRs) and kV imaging of bony thorax is a measure of breath hold reproducibility. The difference between bony coregistration and heart coregistration was the measured heart shift if the patient is aligned to bony anatomy. RESULTS Percentage of dose reductions from FB to VDIBH: mean heart dose (48%, SD 19%, p = 0.002), mean LAD dose (43%, SD 19%, p = 0.008), and maximum left anterior descending (LAD) dose (60%, SD 22%, p = 0.008). Average breath hold reproducibility using bony anatomy across the isocenter along the anteroposterior (AP) plane from planning to treatment is 1 (range, 0-3; SD, 1) mm. Average heart shifts with respect to bony anatomy between different breath holds are 2 ± 3 mm inferior, 1 ± 2 mm right, and 1 ± 3 mm posterior. Percentage dose changes from planning to delivery: mean heart dose (7%, SD 6%); mean LAD dose, ((9%, SD 7%)S, and maximum LAD dose, (11%, SD 11%) SD 11%, p = 0.008). CONCLUSION We observed excellent three-dimensional bony registration between planning and pretreatment imaging. Reduced delivered dose to heart and LAD is maintained throughout VDIBH treatment.

Evaluation of coplanar partial left breast irradiation using tomotherapy-based topotherapy.

PURPOSE To investigate the use of topotherapy for accelerated partial breast irradiation through field-design optimization and dosimetric comparison to linear accelerator-based three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiation therapy (IMRT). METHODS AND MATERIALS Hypothetical 3-cm lumpectomy sites were contoured in each quadrant of a left breast by using dosimetric guidelines from the National Surgical Adjuvant Breast and Bowel Project B-39/Radiation Therapy Oncology Group 0413 protocol. Coplanar intensity-modulated topotherapy treatment plans were optimized by using two-, three-, four-, five-, and seven-field arrangements for delivery by the tomotherapy unit with fixed gantry angles. Optimized noncoplanar five-field 3D-CRT and IMRT were compared with corresponding topotherapy plans. RESULTS On average, 99.5% +/- 0.5% of the target received 100% of the prescribed dose for all topotherapy plans. Average equivalent uniform doses ranged from 1.20-2.06, 0.79-1.76, and 0.10-0.29 Gy for heart, ipsilateral lung, and contralateral lung, respectively. Average volume of normal breast exceeding 90% of the prescription and average area of skin exceeding 35 Gy were lowest for five-field plans. Average uniformity indexes for five-field plans using 3D-CRT, IMRT, and topotherapy were 1.047, 1.050, and 1.040, respectively. Dose-volume histograms and calculated equivalent uniform doses of all three techniques illustrate clinically equivalent doses to ipsilateral breast, lung, and heart. CONCLUSIONS This dosimetric evaluation for a single patient shows that coplanar partial breast topotherapy provides good target coverage with exceptionally low dose to organs at risk. Use of more than five fields provided no additional dosimetric advantage. A comparison of five-field topotherapy to 3D-CRT and IMRT for accelerated partial breast irradiation illustrates equivalent target conformality and uniformity.

Use of megavoltage computed tomography with image registration for high-dose rate treatment planning of an oral tongue cancer using a custom oral mold applicator with embedded lead shielding.

PURPOSE A patient with a lateral oral tongue cancer was treated with high-dose rate brachytherapy using an oral applicator with embedded lead shielding making conventional simulation, using either kilovoltage computed tomography or radiographs, impossible because of scatter artifact. METHODS AND MATERIALS Treatment simulation was accomplished using megavoltage computed tomography (MVCT) simulation on a helical tomotherapy unit. Because of difficulty in visualization of the catheters on the patient MVCT images, Velocity AI image registration software (Velocity Medical Solutions, Atlanta, GA) was used to register an MVCT of the applicator itself with the patient MVCT simulation. The treatment plan was manually optimized to prescribe 4Gy/fraction to the gross tumor volume. RESULTS The patient tolerated the treatment well, with no evidence of disease 6 months after treatment. Thermoluminescent dosimeter measurements showed that the shielding reduced the dose by up to 90%, depending on the location of the thermoluminescent dosimeter. While the patient was treated using dose distributions calculated in a homogeneous medium (Task Group-43), an approximation of the true dose distributions was retrospectively calculated using Acuros (Varian Medical Systems Inc., Palo Alto, CA), which accounts for heterogeneities in the patient. DISCUSSION Use of the MVCT with image registration allowed treatment planning in the presence of lead shielding. Dose-volume histograms showed that recalculation of the dose using heterogeneity correction did not affect the dose to the gross tumor volume, but that the dose to normal structures (maxilla and mandible) was reduced by the lead shielding. CONCLUSION The use of MVCT and image registration allows for optimized planning in the presence of shielding, which would not be possible with conventional kilovoltage computed tomography.

Helical Tomotherapy-Based STAT RT: Dosimetric Evaluation for Clinical Implementation of a Rapid Radiation Palliation Program

Helical tomotherapy-based STAT radiation therapy (RT) uses an efficient software algorithm for rapid intensity-modulated treatment planning, enabling conformal radiation treatment plans to be generated on megavoltage computed tomography (MVCT) scans for CT simulation, treatment planning, and treatment delivery in one session. We compared helical tomotherapy-based STAT RT dosimetry with standard linac-based 3D conformal plans and standard helical tomotherapy-based intensity-modulated radiation therapy (IMRT) dosimetry for palliative treatments of whole brain, a central obstructive lung mass, multilevel spine disease, and a hip metastasis. Specifically, we compared the conformality, homogeneity, and dose with regional organs at risk (OARs) for each plan as an initial step in the clinical implementation of a STAT RT rapid radiation palliation program. Hypothetical planning target volumes (PTVs) were contoured on an anthropomorphic phantom in the lung, spine, brain, and hip. Treatment plans were created using three planning techniques: 3D conformal on Pinnacle³, helical tomotherapy, and helical tomotherapy-based STAT RT. Plan homogeneity, conformality, and dose to OARs were analyzed and compared. STAT RT and tomotherapy improved conformality indices for spine and lung plans (CI spine = 1.21, 1.17; CI lung = 1.20, 1.07, respectively) in comparison with standard palliative anteroposterior/posteroanterior (AP/PA) treatment plans (CI spine = 7.01, CI lung = 7.30), with better sparing of heart, esophagus, and spinal cord. For palliative whole-brain radiotherapy, STAT RT and tomotherapy reduced maximum and mean doses to the orbits and lens (maximum/mean lens dose: STAT RT = 2.94/2.65 Gy, tomotherapy = 3.13/2.80 Gy, Lateral opposed fields = 7.02/3.65 Gy), with an increased dose to the scalp (mean scalp dose: STAT RT = 16.19 Gy, tomotherapy = 15.61 Gy, lateral opposed fields = 14.01 Gy). For bony metastatic hip lesions, conformality with both tomotherapy techniques (CI = 1.01 each) is superior to AP/PA treatments (CI = 1.21), as expected. Helical tomotherapy-based STAT RT treatment planning provides clinically acceptable dosimetry, with conformality and homogeneity that is superior to standard linac-based 3D conformal planning and is only slightly inferior to standard helical tomotherapy IMRT dosimetry. STAT RT facilitates rapid treatment planning and delivery for palliative radiation of patients with metastatic disease, with relative sparing of adjacent OARs compared with standard 3D conformal plans.

Helical tomotherapy simultaneous integrated boost provides a dosimetric advantage in the treatment of primary intracranial tumors

Abstract Objective: The research quantitatively evaluates the dosimetric advantage of a helical tomotherapy (HT) intensity-modulated radiation therapy simultaneous integrated boost (SIB) compared to a conventional HT sequential (SEQ) boost for primary intracranial tumors. Methods: Hypothetical lesions (planning target volumes or PTVs) were contoured within computed tomography scans from normal controls. A dose of 50 Gy was prescribed to the larger PTV1, while the boost PTV2 received a total of 60 Gy. HT SEQ and HT SIB plans were generated and compared. We evaluated the mean brain dose, the volume of normal brain receiving 45 Gy (V45), the volume of normal brain receiving 5 Gy (V5), and the integral dose. In addition, patients who were treated with the HT SEQ technique were replanned with the HT SIB technique and compared. Results: The average reduction in mean brain dose with the HT SIB plan compared to the composite HT SEQ plan was 11·0% [standard error (SE): 0·5]. The reductions in brains V45 and V5 were 43·7% (SE: 2·3) and 3·9% (SE: 0·6), respectively. The reduction in the integral dose was 11·0% (SE: 0·5). When comparing the SIB plan to the first 50 Gy only of the SEQ plan, there was only a 2·5% increase in the mean brain dose and a 2·9% increase in brain V45. This increase was dependent on the relative volumes of PTV2 and PTV1. These results were confirmed for the patient plans compared. Conclusions: Treating primary brain tumors with the HT SIB technique provides significant sparing of normal brain parenchyma compared to a conventional HT SEQ boost.

SU‐GG‐T‐45: Use of MVCT with Image Registration for Planning HDR Treatments Using a Custom Oral Applicator with Lead Shielding

Purpose:Treatment planning for HDR brachytherapy can be difficult in cases in which it is necessary to create custom applicators that incorporate shielding for the protection of normal structures. This can be overcome by the use of MVCT, which reduces artifacts in the image set. Method and Materials: A custom oral applicator was created by a dentist for the treatment of a superficial recurrence of an oral tongue cancer. The applicator contained two interstitial catheters placed one cm. apart, along with approximately 2.1 mm of lead sheeting to shield the maxilla, mandible, and supporting structures. At time of simulation, the applicator was placed in the patients mouth, with dummy strands inside the catheters, and an MVCT was performed on the Tomotherapy® system. Another MVCT was performed of just the applicator with dummy strands. The MVCT images were transferred to the Velocity ®system for image registration. The catheters were visualized on the scan of the applicator, and then the contours were transferred to the full MVCT set. The MVCT and contour DICOM sets were transferred to BrachyVision for HDR planning. Dwell times were manually optimized to cover the target volume, with a prescription of 32 Gy in 8 BID fractions. Results: Due to the lead shielding, 3DCT treatment planning would have been difficult without the use of MVCT. TLDs placed inside the applicators tooth cavities for a test run showed that the lead shield reduced the dose by 65–75%, depending on the location of the TLD.Conclusion: The use of MVCT along with image registration software allows visualization of HDR applicators in the presence of shielding or other high‐Z materials. This work can be extended to the use of MVCT for planning treatments with standard applicators, such as T&O, which may not be kVCT compatible.

WE‐C‐303A‐04: Quantifying the Reproducibility of Heart Position with Respect to Bony Anatomy in Daily Set Up and the Corresponding Delivered Heart Dose in Voluntary Deep Inhalation Breath Hold for Left Breast Cancer Patients Via External Beam Radiotherapy

Purpose: Voluntary deep inhalation breath hold (DIBH) technique help reduce the heart toxicity during radiation treatment of the left breast. We present the results of the first study performed to quantify the reproducibility of heart position and the heartdose in daily setup for voluntary DIBH patients. Method and Materials: Ten left breast patients undergoing treatment with voluntary DIBH were studied. Each patient had two CT scans, one with free breathing and one with voluntary DIBH, to evaluate the dose under these two conditions to the Heart, anterior most point of left anterior descending (LAD) coronary artery, and left Lung. At the treatment machine, daily and weekly KV orthogonal images were acquired using onboard imaging for each patient. Mosaiq™ software was used to register the full bony anatomy of thorax (including the spine, ribs, anterior chest wall and heart) with KV images to the planning DRRs. Once the patient is aligned on the treatment machine using bony anatomy registration, the difference between the bony anatomy registration and the heart registration is the daily heart position. These differences were transferred into treatment planning system to obtain the delivered dose.Results: The dosimetric evaluation shows clinically significant reduced dose to heart,lung, and LAD in the DIBH case compared to the free breathing case, as previous studies have shown. The weekly heart position shifts are in the order of few mm. Dosimetric evaluations for these shifts indicate that dose to the heart in the daily treatment with DIBH remains low. Conclusion: The setup and breath hold accuracy and the daily delivered dose to the heart was evaluated for voluntary DIBH breast patients. Results indicate a clear reduction of dose delivered to the heart throughout the treatment when voluntary DIBH technique is employed.

Utilization of tomotherapy-based topotherapy for emerging breast radiation techniques: boost integration and accelerated partial breast irradiation.

Abstract #5148 Background: Helical Tomotherapy-based intensity modulated radiation therapy (IMRT) can be delivered using fixed gantry angles, known as Topotherapy, with daily image guidance. With the advent of accelerated or hypofractionated treatment schemes to shorten courses of radiation, conformality and accuracy is imperative for breast radiotherapy techniques since high doses of targeted radiation are used. The purpose of this study was to characterize the dosimetry of Topotherapy for delivery of Accelerated Partial Breast Irradiation (APBI) and hypofractionated Simultaneous Integrated Boost (SIB) breast irradiation in comparison with conventional techniques.
 Materials and Methods: Ten patients with early stage left sided breast cancer were evaluated for this study using Topotherapy planning. The planning target volume (PTV) was contoured as the lumpectomy cavity with a 1.5cm margin, and the breast was defined by the tissue encompassed by tangent fields minus the PTV and 5mm of skin. To evaluate SIB, nine patients were comparatively planned using a standard sequential treatment of 50Gy tangents to the whole breast with a 10Gy electron boost in 30 fractions versus Topotherapy integrated boost with the same cumulative dose in 25 fractions versus hypofractionated Topotherapy with 42.4Gy to the breast and 51.2Gy to the PTV in 16 fractions. For evaluation of APBI, 3cm hypothetical lumpectomy cavities were contoured in the four breast quadrants of a single patient, with a similar 1.5cm expansion and breast volume. Plans to deliver 38.5Gy in 10 fractions were generated for each lesion using Topotherapy and compared to 3-dimensional conformal radiation therapy (3DCRT) and IMRT using the dosimetric guidelines from the National Surgical Adjuvant Breast and Bowel Project B-39/Radiation Therapy Oncology Group 0413 protocol.
 Results: Target coverage and dose to heart and lung were clinically equivalent when comparing Topotherapy APBI and SIB to conventional techniques. For ABPI, the Topotherapy conformality index was superior to 3DCRT for all breast quadrants, but inferior to IMRT for lesions located in the medial quadrants of the breast. For SIB, Topotherapy provided an improvement in conformality over conventional sequential techniques, however there was no intensity modulated comparison. Equivalent target uniformity was observed in all APBI techniques however for SIB, Topotherapy provided a superior uniformity index for the whole breast target.
 Discussion: Topotherapy is capable of delivering clinically acceptable dosimetry for accelerated or hypofractionated breast radiation without compromising dose to structures at risk. This treatment modality will be utilized in the near future pending FDA approval. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5148.