S396 I. J. Radiation Oncology d Biology d Physics Volume 78, Number 3, Supplement, 2010

2431 Evaluation of Setup Errors with Daily Image Guidance for Gynecological Cancers

S. Beriwal, H. Kim, N. Kannan

University of Pittsburgh School of Medicine, Pittsburgh, PA

Purpose/Objective(s): The aim of this study was to assess the setup error with daily image guidance for patients with gynecolog-ical cancers treated with external beam radiation (EBRT) and to investigate the difference in setup errors based on body mass index(BMI).

Materials/Methods: 52 patients (1074 fractions) with gynecological cancers treated with EBRT who had daily image guidance(IG) on a Varian 2300IX Linear Accelerator (Varian Medical Systems, Palo Alto, CA) with On Board Imager (OBI 1.4) were an-alyzed. 26 patients had 546 KV x-rays (OBI) while 26 patients had 528 cone beam CT (CBCT) images done for daily IG. Theregistration between daily image and reference image was performed using pelvic bones, and couch corrections were made forany vector displacement of $ 5mm. The daily directional shifts were recorded for each image-guided fraction, and mean displace-ments, population systematic errors (

P) and random errors (s) were calculated. The difference in setup error was calculated based

on BMI ($ 30 vs.\30). Using van Herk’s formula (2.5*P

+ 0.7* s), the clinical target volumes (CTV) to planning target volume(PTV) margins for setup uncertainties were also calculated.

Results: The mean displacements in anterior-posterior (AP), medio-lateral (ML) and superior-inferior (SI) directions for all patientswere -0.03 mm, 0.529mm, and 0.708mm respectively. Population systematic (

P) and random errors (s) were 1.10mm, 2.25mm,

2.34 mm and 3.88mm, 4.95mm, 3.46mm in AP, ML and SI directions respectively. Using van Herk’s formula, the calculated clinicaltarget volume (CTV) to planning target volume (PTV) margins for set up uncertainties were 5.46mm, 9.1mm, 8.26mm in the AP, MLand SI directions respectively. There were 28 patients BMI $ 30 and mean displacements in AP, ML and SI directions for BMI $ 30vs.\30 were -0.02 mm, 0.89 mm and 0.96 mm vs. -0.04 mm, 0.11mm and 0.41 mm respectively (p = .02). CTV to PTV margins forBMI $ 30 vs.\30 were 5.66 mm, 10.3 mm, 9.67 mm vs. 5.3 mm, 7.30 mm, 6.24 mm in AP, ML and SI directions respectively. Thepercentage of fractions with any directional shift $ 5mm was 62.2% vs. 48.2% for patients with BMI $ 30 vs. \ 30.

Conclusions: This study is the first report of assessment of setup error for gynecological cancers using daily IG. The geometricmargin for PTV required for setup error without IG is around 10.3 mm and 7.3 mm for patients with BMI $ 30 vs. \ 30 .IGcan help in reducing both systematic and random setup error, but would likely require daily imaging since . 50% fractionshad at least one directional shift $ 5 mm .The set up error is larger for patients with BMI $ 30 and these patients need largerCTV to PTV margin and would benefit more from daily IG.

Author Disclosure: S. Beriwal, None; H. Kim, None; N. Kannan, None.

2432 Pretreatment Carcinoembryonic Antigen Level is a Risk Factor of Para-aortic Lymph Node Recurrence in

Addition to Squamous Cell Carcinoma Antigen after Definitive Concurrent Chemoradiotherapy ForSquamous Cell Carcinoma Of The Uterine Cervix

E. Huang1, C. Wang1, H. Hsu1, L. Sun2, C. Chanchien1, H. Lin1, H. Chen1, C. Tseng1, Y. Ou1, H. Chang1

1Chang Gung Memorial Hospital-Kaohsiung Medical Center, Kaohsiung 83305, Taiwan, 2Zuoying Armed Forces GeneralHospital, Kaohsiung 813, Taiwan

Purpose/Objective(s): To evaluate the pretreatment carcinoembryonic antigen (CEA) levels as a risk factor of para-aortic lymphnode (PALN) recurrence in addition to squamous cell carcinoma antigen (SCC-Ag) levels following concurrent chemoradiother-apy (CCRT) for cervical cancer.

Materials/Methods: From March 1995 to January 2008, 245 patients with squamous cell carcinoma of the uterine cervix wereanalyzed retrospectively. No patient received PALN irradiation as the initial treatment. PALN recurrence was detected by computertomography (CT) scans. PALN relapse-free status was diagnosed clinically or radiographically. We analyzed the actuarial rates ofPALN recurrence by using Kaplan-Meier curves. Multivariate analyses were carried out with Cox regression models.

Results: The median time of follow-up was 45.5 months (range 1-160). CEA $ 10 ng/mL (p\0.001) was a risk factor of PALNrecurrence in addition to SCC-Ag levels $ 40 ng/mL (p\0.001), SCC-Ag levels of 20-40 ng/mL (p = 0.022), SCC-Ag levels of10-20 ng/mL (p = 0.004) on a multivariate analysis. The 5-year PALN recurrence rates in patients with CEA $ 10 ng/mL, SCC-Aglevels $ 40 ng/mL, SCC-Ag levels of 20-40 ng/mL, SCC-Ag levels of 10-20 ng/mL, and both low levels of tumor markers were39%, 55.5%, 21.9%, 27.2%, and 8%, respectively. The median time of PALN recurrence in patients with CEA levels $ 10 ng/mLwas 6.9 months (range 0-21.5). The corresponding time was 16.3 months (range 3.2-94.3) in patients with both SCC-Ag levels $10 ng/mL and CEA levels\10 ng/mL. The 5-year PALN recurrence rates in patients with high-risk (SCC-Ag levels $ 40 ng/mL),intermediate-risk (either SCC-Ag levels of 10-40 ng/mL or CEA levels $ 10 ng/mL), and low-risk (both SCC-Ag levels\10 ng/mL and CEA levels \10 ng/mL) were 55.5%, 29.5%, and 8%, respectively.

Conclusions: CEA is an additional risk factor of PALN relapse in patients with squamous cell carcinoma of the uterine cervixfollowing definitive CCRT. The onset of PALN relapse is early in patients with high CEA levels. More comprehensive examina-tions before CCRT and intensive follow-up schedules are suggested for early detection and salvage in patients with SCC-Ag orCEA levels $ 10 ng/mL. Further study of prophylactic PALN irradiation may be considered for such patients.

Author Disclosure: E. Huang, None; C. Wang, None; H. Hsu, None; L. Sun, None; C. Chanchien, None; H. Lin, None; H. Chen,None; C. Tseng, None; Y. Ou, None; H. Chang, None.

2433 Long-term Clinical Outcomes and Patterns of Recurrence of 750 Surgically Staged Patients with Stages I-II

Endometrial Carcinoma: A Single Institution Experience

B. Laser, J. Robbins, M. Haley, A. Munkarah, M. Elshaikh

Henry Ford Health System, Detroit, MI

Purpose/Objective(s): To study the different predictors of outcome and pattern of loco-regional recurrences for patients with en-dometrioid carcinoma after surgical staging for stages I-II.