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Identifying Rectal Shift using Cone Beam Computed Tomography during Preoperative Intensity Modulated Radiation Therapy
I. J. Radiation Oncology d Biology d Physics
S274
Volume 72, Number 1, Supplement, 2008
Results: The 5- and 10-year outcomes were: local control 87% and 87%; local-regional control 83% and 83%; freedom from distant metastases 92% and 90%; cause-specific survival 87% and 87%; and overall survival 71% and 54%. No local recurrences occurred for T1 tumors. Successful salvage rates following local recurrence for T2, T3, and T4 tumors were 100%, 75%, and 100% resulting in ultimate local control rates of 97%, 86%, and 100%, respectively. Colostomy-free survival was 74% at 10 years for all patients and 87% and 57% for patients with T1-2 and T3-4 tumors, respectively. Acute toxicity in this series was 39% for Grade 3, 3% for Grade 4, and 1% for Grade 5 toxicities. Late toxicity in this series was 10% for Grade 3, 7% for Grade 4, and 0% for Grade 5 toxicities. Conclusions: Organ preservation with radiotherapy with or without concomitant chemotherapy for anal canal carcinomas results in excellent local control, local-regional control, and disease-specific survival with two-thirds of the patients retaining a functional sphincter. Author Disclosure: A.N. Rabbani, None; R. Zlotecki, None; C.G. Morris, None; W.M. Mendenhall, None.
2233
GTV Spacial Conformity between Different Delineation Methods by 18FDG PET/CT and Surgical Pathology in Esophageal Cancer
W. Yu, X. L. Fu, Y. J. Zhang, J. Q. Xiang, G. L. Jiang Cancer Hospital of Fudan University, Shanghai, China Purposes/Objective(s): The GTV delineations by four different thresholds of 18FDG PET/CT and one by CT were compared with results from surgery to find the optimal way of GTV delineation for primary lesion of esophageal cancer. Materials/Methods: Sixteen patients with esophageal squamous cell carcinoma underwent routine examinations including chest CT, esophagogram, and endoscopy, as well as 18FDG PET/CT before operations. The GTVCT was delineated on CT images blinded to PET results. Four GTVs were determined by PET/CT, using SUVbgd+ 20% (SUVmax-SUVbgd), SUVbgd+ 40% (SUVmax-SUVbgd), 2.5 and 40% SUVmax as thresholds, and called GTV20, GTV40, GTV2.5,and GTV40%, respectively (SUVbgd, average SUV of the background; SUVmax, maximum SUV of every slice of lesions). All patients underwent radical surgery, with titanic clips marked at both ends of tumor beds, and CT scan again 2 weeks later. The GTVsurg was contoured on fusion images of pre and postsurgical CT, according to ranges of markers on postsurgical CT longitudinally and extents of lesions on presurgical CT transversely. The lengths of 6 GTVs were recorded as LCT, L20, L40, L2.5, L40% and Lsurg. The former 5 lengths by means of a conformity index (CI, square of the intersection and corresponding GTVs were compared with Lsurg and GTVsurg 0 of the two lengths or GTVs divided by their product), e.g., CI CT&surg = L2CT&surg/(LCT*Lsurg) and CICT&surg = GTV2CT&surg / (GTVCT*GTVsurg). ± 2.69, 5.55 ± 2.48, 6.80 ± 2.92, 6.65 ± 2.66, 4.88 ± 1.99, and Results: The mean LCT, L20, 0 L40, L2.5, L0 40%, and L0surg were 6.30 0 0 ± 0.16, 0.84 ± 0.17, 0.76 ± 0.14, 5.90 ± 2.38 cm. The mean CI CT&surg,0 CI 20&surg, CI 040&surg, CI 2.5&surg and CI 40%&surg were 0.68 0 0.78 ± 0.15, and 0.80 ± 0.11. The CI 20&surg and CI 40%&surg was significantly superior to CI CT&surg (p \ 0.05) and no difference was observed between each other of the rest. The mean GTVCT, GTV20, GTV40, GTV2.5, GTV40%, and GTVsurg were 29.16 ± 18.56, 18.75 ± 12.37, 12.52 ± 8.08, 22.69 ± 14.84, 9.18 ± 5.96, and 28.16 ± 17.02 cm3. The CIs of GTVs increased significantly from CI40&surg (0.27 ± 0.09) and CI40%&surg (0.28 ± 0.08)\CI20&surg (0.52 ± 0.16), and CI2.5&surg (0.52 ± 0.20)\CICT&surg (0.77 ± 0.17). The median percentage volumes of GTV20, GTV40, GTV2.5, not included in GTVsurg were 8.8%, 18.6%, and 16.3%, respectively and almost 0 for GTV40%. Conclusions: Four GTVs delineated by PET/CT were longitudinally better matched to results from surgery than GTVCT, especially GTV20, but showed great discrepancy transversely. Considered both longitudinally and transversely, GTV20 or GTV2.5 may be most conformed to GTVsurg. Because the gold standard of transverse information of primary lesions was not available, it is recommended that GTV20 or GTV2.5 and the transverse contour of CT should be referred to complementarily when delineating GTV for esophageal cancer. Author Disclosure: W. Yu, None; X.L. Fu, None; Y.J. Zhang, None; J.Q. Xiang, None; G.L. Jiang, None.
2234
Identifying Rectal Shift using Cone Beam Computed Tomography during Preoperative Intensity Modulated Radiation Therapy
A. S. DeNittis, A. Thompson, G. Marks, E. Valsdottir, E. Zeger, J. Marks Lankenau Hospital, Wynnewood, PA Purpose/Objective(s): To assess our single institution experience using cone beam computed tomography as a tool to identify daily rectal shift throughout a course of preoperative radiation. Materials/Methods: From April 2007 to January of 2008, data was collected for 264 intensity-modulated radiation treatments from 9 patients. Patients were set up to skin marks, then pretreatment verification using daily cone beam image guidance (CBIG) was used to assess for discrepancy of the planned rectal position to subsequent daily rectal position in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) dimensions. Results: Of 264 treatments, 98.5% required a non-zero shift to align the patient to the planned treatment volume. Shifts were made in the LR, SI, and AP dimensions in 90.5%, 91.3%, and 89.8% of treatments, respectively. In the LR dimension, 39.0% were in the left direction for a mean distance of 3.6 mm, and 51.5% were in the right direction for a mean distance of 4.4 mm. In the SI dimension, 48.1% were in the superior direction for a mean distance of 4.9 mm, and 43.2% were in the inferior direction for a mean distance of 4.5 mm. In the AP dimension, 38.6% were in the anterior direction for a mean distance of 6.0 mm, and 51.1% were in the posterior direction for a mean distance of 3.9 mm. Conclusions: The CBIG demonstrates that interfraction rectal motion is significant during preoperative IMRT. Quantification of interfraction motion will lead to more accurate planning tumor volumes. Author Disclosure: A.S. DeNittis, None; A. Thompson, None; G. Marks, None; E. Valsdottir, None; E. Zeger, None; J. Marks, None.
S274
Volume 72, Number 1, Supplement, 2008
Results: The 5- and 10-year outcomes were: local control 87% and 87%; local-regional control 83% and 83%; freedom from distant metastases 92% and 90%; cause-specific survival 87% and 87%; and overall survival 71% and 54%. No local recurrences occurred for T1 tumors. Successful salvage rates following local recurrence for T2, T3, and T4 tumors were 100%, 75%, and 100% resulting in ultimate local control rates of 97%, 86%, and 100%, respectively. Colostomy-free survival was 74% at 10 years for all patients and 87% and 57% for patients with T1-2 and T3-4 tumors, respectively. Acute toxicity in this series was 39% for Grade 3, 3% for Grade 4, and 1% for Grade 5 toxicities. Late toxicity in this series was 10% for Grade 3, 7% for Grade 4, and 0% for Grade 5 toxicities. Conclusions: Organ preservation with radiotherapy with or without concomitant chemotherapy for anal canal carcinomas results in excellent local control, local-regional control, and disease-specific survival with two-thirds of the patients retaining a functional sphincter. Author Disclosure: A.N. Rabbani, None; R. Zlotecki, None; C.G. Morris, None; W.M. Mendenhall, None.
2233
GTV Spacial Conformity between Different Delineation Methods by 18FDG PET/CT and Surgical Pathology in Esophageal Cancer
W. Yu, X. L. Fu, Y. J. Zhang, J. Q. Xiang, G. L. Jiang Cancer Hospital of Fudan University, Shanghai, China Purposes/Objective(s): The GTV delineations by four different thresholds of 18FDG PET/CT and one by CT were compared with results from surgery to find the optimal way of GTV delineation for primary lesion of esophageal cancer. Materials/Methods: Sixteen patients with esophageal squamous cell carcinoma underwent routine examinations including chest CT, esophagogram, and endoscopy, as well as 18FDG PET/CT before operations. The GTVCT was delineated on CT images blinded to PET results. Four GTVs were determined by PET/CT, using SUVbgd+ 20% (SUVmax-SUVbgd), SUVbgd+ 40% (SUVmax-SUVbgd), 2.5 and 40% SUVmax as thresholds, and called GTV20, GTV40, GTV2.5,and GTV40%, respectively (SUVbgd, average SUV of the background; SUVmax, maximum SUV of every slice of lesions). All patients underwent radical surgery, with titanic clips marked at both ends of tumor beds, and CT scan again 2 weeks later. The GTVsurg was contoured on fusion images of pre and postsurgical CT, according to ranges of markers on postsurgical CT longitudinally and extents of lesions on presurgical CT transversely. The lengths of 6 GTVs were recorded as LCT, L20, L40, L2.5, L40% and Lsurg. The former 5 lengths by means of a conformity index (CI, square of the intersection and corresponding GTVs were compared with Lsurg and GTVsurg 0 of the two lengths or GTVs divided by their product), e.g., CI CT&surg = L2CT&surg/(LCT*Lsurg) and CICT&surg = GTV2CT&surg / (GTVCT*GTVsurg). ± 2.69, 5.55 ± 2.48, 6.80 ± 2.92, 6.65 ± 2.66, 4.88 ± 1.99, and Results: The mean LCT, L20, 0 L40, L2.5, L0 40%, and L0surg were 6.30 0 0 ± 0.16, 0.84 ± 0.17, 0.76 ± 0.14, 5.90 ± 2.38 cm. The mean CI CT&surg,0 CI 20&surg, CI 040&surg, CI 2.5&surg and CI 40%&surg were 0.68 0 0.78 ± 0.15, and 0.80 ± 0.11. The CI 20&surg and CI 40%&surg was significantly superior to CI CT&surg (p \ 0.05) and no difference was observed between each other of the rest. The mean GTVCT, GTV20, GTV40, GTV2.5, GTV40%, and GTVsurg were 29.16 ± 18.56, 18.75 ± 12.37, 12.52 ± 8.08, 22.69 ± 14.84, 9.18 ± 5.96, and 28.16 ± 17.02 cm3. The CIs of GTVs increased significantly from CI40&surg (0.27 ± 0.09) and CI40%&surg (0.28 ± 0.08)\CI20&surg (0.52 ± 0.16), and CI2.5&surg (0.52 ± 0.20)\CICT&surg (0.77 ± 0.17). The median percentage volumes of GTV20, GTV40, GTV2.5, not included in GTVsurg were 8.8%, 18.6%, and 16.3%, respectively and almost 0 for GTV40%. Conclusions: Four GTVs delineated by PET/CT were longitudinally better matched to results from surgery than GTVCT, especially GTV20, but showed great discrepancy transversely. Considered both longitudinally and transversely, GTV20 or GTV2.5 may be most conformed to GTVsurg. Because the gold standard of transverse information of primary lesions was not available, it is recommended that GTV20 or GTV2.5 and the transverse contour of CT should be referred to complementarily when delineating GTV for esophageal cancer. Author Disclosure: W. Yu, None; X.L. Fu, None; Y.J. Zhang, None; J.Q. Xiang, None; G.L. Jiang, None.
2234
Identifying Rectal Shift using Cone Beam Computed Tomography during Preoperative Intensity Modulated Radiation Therapy
A. S. DeNittis, A. Thompson, G. Marks, E. Valsdottir, E. Zeger, J. Marks Lankenau Hospital, Wynnewood, PA Purpose/Objective(s): To assess our single institution experience using cone beam computed tomography as a tool to identify daily rectal shift throughout a course of preoperative radiation. Materials/Methods: From April 2007 to January of 2008, data was collected for 264 intensity-modulated radiation treatments from 9 patients. Patients were set up to skin marks, then pretreatment verification using daily cone beam image guidance (CBIG) was used to assess for discrepancy of the planned rectal position to subsequent daily rectal position in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) dimensions. Results: Of 264 treatments, 98.5% required a non-zero shift to align the patient to the planned treatment volume. Shifts were made in the LR, SI, and AP dimensions in 90.5%, 91.3%, and 89.8% of treatments, respectively. In the LR dimension, 39.0% were in the left direction for a mean distance of 3.6 mm, and 51.5% were in the right direction for a mean distance of 4.4 mm. In the SI dimension, 48.1% were in the superior direction for a mean distance of 4.9 mm, and 43.2% were in the inferior direction for a mean distance of 4.5 mm. In the AP dimension, 38.6% were in the anterior direction for a mean distance of 6.0 mm, and 51.1% were in the posterior direction for a mean distance of 3.9 mm. Conclusions: The CBIG demonstrates that interfraction rectal motion is significant during preoperative IMRT. Quantification of interfraction motion will lead to more accurate planning tumor volumes. Author Disclosure: A.S. DeNittis, None; A. Thompson, None; G. Marks, None; E. Valsdottir, None; E. Zeger, None; J. Marks, None.