Romeo Tirona

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 ☆

PURPOSE To 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. METHODS AND MATERIALS Thirty 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. RESULTS In 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. CONCLUSION The 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.

Digital fluoroscopy to quantify lung tumor motion: potential for patient-specific planning target volumes ☆

PURPOSE To apply digital fluoroscopy integrated with CT simulation to measure lung tumor motion and aid in the quantification of individualized planning target volumes. METHODS AND MATERIALS A flat panel digital fluoroscopy unit was modified and integrated with a CT simulator. The stored fluoroscopy images were overlaid with digitally reconstructed radiographs, allowing measurement of the observed lung tumor motion in relation to the corresponding contours on the static digitally reconstructed radiographs. CT simulation and digital fluoroscopy was performed on 10 patients with non-small-cell lung cancer. Actual tumor motion was measured in three dimensions using the overlaid images. RESULTS Combining the dynamic data with digitally reconstructed radiographs allowed the tumor shadow from the fluoroscopy to be tracked in relation to the CT lung tumor contour. For all patients, the extent of tumor motion in three dimensions was unique. The motion was greatest in the superoinferior direction and minimal in the AP and lateral directions. CONCLUSION We have developed a tool that allows CT simulation to be combined with digital fluoroscopy. Quantitative evaluation of the tumor motion in relation to the CT plan allows for customization of the planning target volume. The variability observed clearly demonstrates the need to generate patient-specific internal motion margins.

Autocontouring and Manual Contouring: Which Is the Better Method for Target Delineation Using 18F-FDG PET/CT in Non–Small Cell Lung Cancer?

Previously, we showed that a CT window and level setting of 1,600 and –300 Hounsfield units, respectively, and autocontouring using an 18F-FDG PET 50% intensity level correlated best with pathologic results. The aim of this study was to compare this autocontouring with manual contouring, to determine which method is better. Methods: Seventeen patients with non–small cell lung cancer underwent 18F-FDG PET/CT before surgery. The maximum diameter on pathologic examination was determined. Seven sets of gross tumor volumes (GTVs) were defined. The first set (GTVCT) was contoured manually using only CT information. The second set (GTVAuto) was autocontoured using a 50% intensity level for 18F-FDG PET images. The third set (GTVManual) was manually contoured using a visual method on PET images. The other 4 sets combined CT and 18F-FDG PET images fused to one another to become composite volumes: GTVCT+Auto, GTVCT+Manual, GTVCT−Auto, and GTVCT–Manual. To quantitate the degree to which CT and 18F-FDG PET defined the same region of interest, a matching index was calculated for each case. The maximum diameter of GTV was compared with the maximum diameter on pathologic examination. Results: The median GTVCT, GTVAuto, GTVManual, GTVCT+Auto, GTVCT+Manual, GTVCT–Auto, and GTVCT–Manual were 6.96, 2.42, 4.37, 7.46, 10.17, 2.21, and 3.38 cm3, respectively. The median matching indexes of GTVCT versus GTVCT+Auto, GTVAuto versus GTVCT+Auto, GTVCT versus GTVCT+Manual, and GTVManual versus GTVCT+Manual were 0.86, 0.65, 0.88, and 0.81, respectively. Compared with the maximum diameter on pathologic examination, the correlations of GTVCT, GTVAuto, GTVManual, GTVCT+Auto, and GTVCT+Manual were 0.87, 0.83, 0.93, 0.86, and 0.94, respectively. Conclusion: The matching index was higher for manual contouring than for autocontouring using a 50% intensity level on 18F-FDG PET images. When using a 50% intensity level to contour the target of non–small cell lung cancer, one should also consider using manual contouring of 18F-FDG PET to check for any missed disease.

Biochemical, pathologic, toxicity, and quality-of-life outcomes in a five-fraction hypofractionated accelerated radiotherapy treatment using standard linear accelerators and gold seed fiducials

186 Background: Biological dose escalation through hypofractionated image-guided radiotherapy (H-IGRT) holds the promise of improved patient outcomes, system capacity but decreased cost. In 2006 we initiated a prospective trial of H-IGRT of patients with low risk localized prostate cancer. In this report, we report the toxicities, quality of life (QOL), biochemical and pathologic outcomes of this cohort with more mature follow-up. METHODS A phase I/II study in which patients with T1-2b, Gleason≤6, and PSA≤10 ng/ml prostate cancer received 35 Gy in 5 fractions, once a week over 29 days. No patients received hormone therapy. Treatment was delivered with intensity modulated radiotherapy (IMRT) on standard linear accelerators, with daily image guidance using gold seed fiducials, and a 4 mm CTV-PTV margin. CTCAE v3.0 and RTOG late morbidity scores were used to assess acute and late toxicities, respectively. QOL was assessed by the Expanded Prostate Cancer Index Composite (EPIC). Biochemical control (BC) was defined by the Phoenix definition, adjusted for benign bounce. RESULTS As of September 2011, 83 patients have completed treatment with a median follow-up of 42 months (range 12-60 months). Median age was 67y (42 - 82y). 78 patients (92%) were T1a-c; all had Gleason 6 cancers; median PSA was 5.3 (0.8 - 9.9 ng/ml). 82 (99%) had BC; the remaining patient had a negative biopsy and a history of chronic prostatitis. The median PSA on last visit was 0.69 ng/ml (.02 - 2.6 ng/ml). Of 59 patients who have had a biopsy to date, 2 (3%) were positive but both are under BC. The following toxicities were observed: acute grade 3+: 0% GI, 1% GU, 0% fatigue; late grade 3+: 1% GI, 1% GU. Median transformed QOL scores at baseline (0.5 SD) and 36mo follow-up are: urinary - 95% (4.1), 93%; bowel - 96% (4.8), 96%; sexual - 65% (13.7), 51%; and hormonal - 95% (5.3), 95%. CONCLUSIONS This novel technique employing standard linear accelerators to deliver an extreme hypofractionated schedule of radiotherapy is feasible, well tolerated and shows excellent pathologic and biochemical control. A randomized study versus standard fractionation should be performed.