Yee C Ung

The impact of 18 FDG-PET on target and critical organs in CT-based treatment planning of patients with poorly defined non-small-cell lung carcinoma: a prospective study ☆

PURPOSEnTo prospectively study the impact of coregistering (18)F-fluoro-deoxy-2-glucose hybrid positron emission tomographic (FDG-PET) images with CT images on the planning target volume (PTV), target coverage, and critical organ dose in radiation therapy planning of non-small-cell lung carcinoma.nnnMETHODS AND MATERIALSnThirty patients with poorly defined tumors on CT, referred for radical radiation therapy, underwent both FDG-PET and CT simulation procedures on the same day, in radiation treatment position. Image sets were coregistered using external fiducial markers. Three radiation oncologists independently defined the gross tumor volumes, using first CT data alone and then coregistered CT and FDG-PET data. Standard margins were applied to each gross tumor volume to generate a PTV, and standardized treatment plans were designed and calculated for each PTV. Dose-volume histograms were used to evaluate the relative effect of FDG information on target coverage and on normal tissue dose.nnnRESULTSnIn 7 of 30 (23%) cases, FDG-PET information changed management strategy from radical to palliative. In 5 of the remaining 23 (22%) cases, new FDG-avid nodes were found within 5 cm of the primary tumor and were included in the PTV. The PTV defined using coregistered CT and FDG-PET would have been poorly covered by the CT-based treatment plan in 17--29% of cases, depending on the physician, implying a geographic miss had only CT information been available. The effect of FDG-PET on target definition varied with the physician, leading to a reduction in PTV in 24-70% of cases and an increase in 30-76% of cases. The relative change in PTV ranged from 0.40 to 1.86. On average, FDG-PET information led to a reduction in spinal cord dose but not in total lung dose, although large differences in dose to the lung were seen for a few individuals.nnnCONCLUSIONnThe coregistration of planning CT and FDG-PET images made significant alterations to patient management and to the PTV. Ultimately, changes to the PTV resulted in changes to the radiation treatment plans for the majority of cases. Where possible, we would recommend that FDG-PET data be integrated into treatment planning of non-small-cell lung carcinoma, particularly for three-dimensional conformal techniques.

Clinical investigation: lungObserver variation in contouring gross tumor volume in patients with poorly defined non-small-cell lung tumors on CT: the impact of 18FDG-hybrid PET fusion☆

PURPOSEnTo quantify interobserver variation in gross tumor volume (GTV) localization using CT images for patients with non-small-cell lung carcinoma and poorly defined tumors on CT and to determine whether variability would be reduced if coregistered 2-[18F]fluoro-2-deoxy-d-glucose (FDG)-hybrid positron emission tomography (PET) with CT images were used.nnnMETHODS AND MATERIALSnProspectively, 30 patients with non-small-cell lung carcinoma had CT and FDG-hybrid PET examinations in radiation treatment position on the same day. Images were coregistered using eight fiducial markers. Guidelines were established for contouring GTVs. Three radiation oncologists performed localization independently. The coefficient of variation was used to assess interobserver variability.nnnRESULTSnThe size of the GTV defined showed great variation among observers. The mean ratios of largest to smallest GTV were 2.31 and 1.56 for CT only and for CT/FDG coregistered data, respectively. The addition of PET reduced this ratio in 23 of 30 cases and increased it in 7. The mean coefficient of variation for GTV based on the combined modalities was significantly smaller (p < 0.01) than that for CT data only.nnnCONCLUSIONSnHigh observer variability in CT-based definition of the GTV can occur. A more consistent definition of the GTV can often be obtained if coregistered FDG-hybrid PET images are used.

Deep inspiration breath hold to reduce irradiated heart volume in breast cancer patients.

Abstract Purpose: To evaluate the use of deep inspiration breath hold (DIBH) during tangential breast radiation therapy as a means of reducing irradiated cardiac volume. Methods and Materials: The Active Breathing Control (ABC) device designed at William Beaumont Hospital, Michigan was used to quantify the potential benefit of radiation delivery during DIBH for five left-sided breast cancer patients. This device initiates a breath hold at a predefined, reproducible lung volume. For each patient, two CT scans were acquired with and without breath hold, and virtual simulation was performed for regular tangent and wide-tangent techniques. The resulting dose–volume histograms were calculated, and the volume of heart irradiated to 25 Gy or more was assessed. Results: The influence of ABC on irradiated heart volumes varied considerably among the five patients. Three patients with substantial cardiac volume in the treatment field during normal respiration showed a significant dose–volume histogram reduction when deep inspiration was applied, with decreases in the heart volume receiving 25 Gy of more than 40 cc observed. For one patient, deep inspiration reduced irradiated cardiac volumes only with the wide-tangent technique, while one patient showed no substantial irradiated volume decrease. Conclusion: A DIBH technique during tangential breast irradiation has the potential to significantly decrease irradiated cardiac volume for suitably selected patients. The magnitude of the impact of the breath hold application depends on patient anatomy, lung capacity, and pulmonary function.

ACCELERATED HYPOFRACTIONATION FOR EARLY-STAGE NON-SMALL- CELL LUNG CANCER

PURPOSEnTo describe the outcome of treating early-stage non-small-cell lung cancer (NSCLC) with an accelerated hypofractionated course of radiotherapy.nnnMETHODS AND MATERIALSnA policy of treating early-stage NSCLC with a dose of 48 Gy in 12 once-daily fractions without elective irradiation of radiologically uninvolved regional nodes was adopted in 1996. We describe the outcome in 33 patients with NSCLC treated with this dose-fractionation schedule.nnnRESULTSnThe median patient age was 72.0 years. Most patients (75.8%) were not surgical candidates because of medical comorbidities or old age. For staging, 97.0% underwent CT of the thorax, and mediastinoscopy was performed in 6.1%. All patients had Stage T1-T2N0, except for 4 patients with positive nodes based on pathologically involved or clinically enlarged lymph nodes adjacent to the primary tumor. The overall survival rate was 80.1% at 1 year and 46.0% at 2 years. The median survival was 22.6 months. The cause-specific survival rate was 89.8% at 1 year and 54.1% at 2 years. The recurrence-free survival rate was 66.4% at 1 year and 40.0% at 2 years. Lateral radiotherapy field margins of <2 cm predicted for inferior overall survival, cause-specific survival, and recurrence-free survival on univariate and multivariate analyses (p <0.05). The most commonly reported toxicities were acute dermatitis (30.3%) and late cutaneous/subcutaneous fibrosis (24.2%).nnnCONCLUSIONnAccelerated hypofractionation for early-stage NSCLC appears to be safe and produces promising early results. Very small radiotherapy field margins may lead to an inferior outcome. Prospective studies are needed to determine the optimal dose-fractionation schedule.

The influence of patient geometry on the selection of chest wall irradiation techniques in post-mastectomy breast cancer patients

BACKGROUND AND PURPOSEnTo evaluate three chest wall (CW) irradiation techniques: wide tangential photon beams, direct appositional electron field and electron arc therapy with regards to target coverage and normal tissue tolerance.nnnMATERIALS AND METHODSnThirty-two post-mastectomy breast cancer patients were planned using three CW irradiation techniques. Computed tomography (CT) simulation was done on all patients and clinical target, heart and lung volumes were contoured. For each technique, dose distributions and dose-volume histograms (DVH) were calculated. Pass/fail criteria were applied based on volumetric target and critical structure dose coverage. Passing criteria for target was 95% of target receiving 95% of dose using a standard dose of 50 Gy/25 fractions, for heart </=10% volume receiving 50% dose (i.e. 25 Gy) and for lung </=25% volume ipsilateral lung receiving 50% dose (i.e. 25 Gy).nnnRESULTSnThe number of patients optimally treated by each technique were as follows: wide tangential photon beams 23/32 (72%), direct appositional electron field 1/32 (3%), electron arc 4/32 (12.5%) and in 4/32 (12.5%) no technique was optimal. Geometric predictors for technique suitability include CW thickness, medial to lateral CW curvature, uniformity of superior to inferior CW curvature and length of mastectomy scar.nnnCONCLUSIONSnThis study confirms the utility of CT planning and DVH analysis for treatment planning of breast cancer. Patient factors that predict for treatment technique suitability and aid in technique selection can be identified. In a small subset of patients, none of the currently studied techniques were optimal and more novel methods of chest wall irradiation are required.

Deep inspiration breath hold to reduce irradiated heart volume in breast cancer patients

Adjuvant radiation therapy can significantly increase both disease-free and overall survival for breast cancer patients. However, long-term complications resulting from cardiac toxicity are a serious concern, especially for young patients with left-sided tumours. This issue becomes critical when patients are treated with wide tangents in order to include internal mammary nodes in the radiation field, thus increasing the amount of heart irradiated. The authors postulate is that deep inspiration breath hold will maximize the distance between chest wall and heart during tangential breast irradiation and will therefore minimize the irradiated cardiac volume. In this study, the Active Breath Control device (ABC) designed at William Beaumont Hospital, Michigan was used to quantify the potential effect of treating during breath hold for 5 left-sided breast cancer patients. This device forces breath hold at a predefined, reproducible lung volume. For each patient, two CT scans were acquired respectively with and without breath hold, and virtual simulation was performed for regular tangent and wide tangent techniques. The resulting dose volume histograms were calculated, and the volume of heart irradiated to 25 Gy or more was assessed. The authors results show that the use of the ABC can decrease the portion of irradiated heart from 6% to 1% if treating with regular tangents and from 16% to 4% with wide tangents in the most significant case. The methodology used and detailed results for the five patients will be presented in this feasibility study.

FDG-PET/CT integration: impact on tumour localization and dose volume histograms in radiation therapy

Conventional radiotherapy for non-small cell lung cancer (NSCLC) is often unable to achieve local control. For this reason, 3DCRT with dose escalation is being investigated as a means of improving outcome. It is essential to accurately define the gross tumour volume (GTV) for 3DCRT to succeed. Unfortunately, anatomic imaging techniques such as CT or MRI are often unable to distinguish tumour from normal tissue. Functional imaging with /sup 18/F-FDG PET has the potential to define the GTV more accurately. A prospective study of the use of FDG-hybrid-PET images fused to CT simulation images in radiotherapy treatment planning for NSCLC is described. In a significant fraction of cases, the addition of functional information produces dramatic changes both in the GTV and in dose volume histograms for normal tissues.