S478 I. J. Radiation Oncology d Biology d Physics Volume 72, Number 1, Supplement, 2008

Following final tangential beam planning, the ipsilateral total lung area and the lung area included within the treatment port arecontoured for each CT slice. It is multiplied by slice thickness, and then integrated in all CT slices to give respective volumes.Similarly, for left sided tumors, volume of entire heart and the portion of heart included in the tangential fields were calculated.Parameters related to lung (n = 121) studied from the DRRs included: Central lung distance (CLD), Maximum perpendicular dis-tance (MPD), Length of the lung (L). Parameters related to heart (n = 61)included: Maximum heart distance - (MHD), Maximumheart length (MHL). Linear regression analysis is applied to test relationship between the percentage of ipsilateral lung volumeinvolved and the CLD / MPD / L and similarly between MHD / MHL and the cardiac volume in irradiation.

Results: Equation Predicting percentage irradiated volume (PIV) for: Right Lung = 4.0118+6.6474 (CLD) OR -5.965 + 6.827(MLD). Left Lung = 6.6395 (CLD) OR 5.431(MLD). Heart = 7.325(MHD) OR 6.742(CLD)

Conclusions: The conclusion of the present study, to the best of our knowledge, is the largest series reported so far in literature.CLD and MLD deduced from the DRR, are the direct measures of the lung volumes irradiated in tang. breast RT (r2 = 0.91 and0.79). While MHD and CLD appear to be direct measure of the irradiated heart volume (r2 = 0.98 and 0.91). CT Based simulationhelps in minimizing the normal structures irradiated volume and thus complications resulting from such treatments.

Author Disclosure: C. Haritha, None; V. Shankar, None; J. Prajapathi, None; G. Senthil, None; P.R. Shah, None; R. Bhatt, None;M. Patel, None; A. Shanubhogue, None.

2692 Hypofractionated Radiotherapy as Definitive Treatment of Stage I Non-small Cell Lung Cancer in Older

Patients

E. Ahmad1, A. P. Sandhu1, M. Fuster2, K. Messer3, M. Pu3, P. Nobiensky1, L. Bazhenova4, S. Seagren1

1Department of Radiation Oncology, Moores Cancer Center, University of California San Diego School of Medicine, La Jolla,CA, 2Division of Pulmonary & Critical Care, University of California, San Diego & VA San Diego Healthcare System, La Jolla,CA, 3Division of Biostatistics, Moores Cancer Center, University of California San Diego School of Medicine, La Jolla, CA,4Division of Hematology and Medical Oncology, Moores Cancer Center, University of California San Diego School of Medicine,La Jolla, CA

Purpose/Objective(s): With the increase in life expectancy and advancing age, there is growing demand to consider definitiveradiotherapy as a treatment option for older patients with lung cancer. There is a paucity of published literature on the use of hy-pofractionated radiotherapy schedules for treating elderly patients. We report our experience utilizing hypofractionated radiother-apy regimens in older patients.

Materials/Methods: This analysis includes patients 60 years of age and older at our institution with inoperable Stage T1/T2 N0non-small cell lung cancer who completed a curative course of radiotherapy alone using a hypofractionated schedule. Between1991 and 2006, 75 such patients were identified with median age of 74 years (range, 60-86). The majority of the patients (50;67.7%) were aged 70 years or more. Patient characteristics were as follows: male, 65/75 (86.7%); stage T1, 47/75 (62.7%); stageT2, 28/75 (37.3%). Thirteen patients (17.3%) were treated without tissue diagnosis. Patients received a median total dose of 6,500cGy using median daily dose fractions of 250 cGy. The following outcomes were analyzed: local failure free survival (LFFS; timeto local failure or death from any cause), time to distal failure as first event and overall survival (OS). Local failure was defined as anincrease in size on imaging studies. Toxicities were evaluated using CTCAE v 3.0.

Results: The median follow-up was 19.8 months (range, 4.0 - 128.8 months). Median LFFS was 19.6 months (95% CI: 14.4-28.8 months); and median OS was 21.2 months (95% CI: 14.9-29.3 months). Analysis of competing risks showed that at 5years, the probability of local failure as the first detected event was 22.1% (95% CI: 12.8-32.9%); the probability of distal failureas the first detected event was 14.5% (95% CI: 7.3-24.0%); and the probability of death without recording a failure was 48.6%(95% CI: 36.1-60.1%). Radiation related toxicity of grade 3 or greater was seen in 4 patients and there were no treatment relateddeaths.

Conclusions: Hypo fractionated radiotherapy is an effective and safe treatment for older patients with Stage I non-small cell lungcancer. The results are limited as this is a single-institution observational study. Nevertheless, a large majority of patients remainedfree of local recurrence and without significant clinical toxicity.

Author Disclosure: E. Ahmad, None; A.P. Sandhu, None; M. Fuster, None; K. Messer, None; M. Pu, None; P. Nobiensky, None; L.Bazhenova, Astra Zeneca, B. Research Grant; Genentech, D. Speakers Bureau/Honoraria; Sanofi Aventis, D. Speakers Bureau/Honoraria; S. Seagren, None.

2693 Subclinical Impairment of Renal Function Following Abdominal Radiotherapy: An Analysis using Specific

Scintigraphic and Biochemical Endpoints

G. Y. Yang1, L. Flaherty1, T. D. Wagner2, J. C. Yap1, R. Chandrasekhar1, G. Wilding1, N. I. Khushalani1, R. V. Iyer1,D. Lamonica1, C. R. Thomas3

1Roswell Park Cancer Institute, Buffalo, NY, 2Brooke Army Medical Center, Fort Sam Houston, TX, 3Oregon Health and ScienceUniversity, Portland, OR

Purpose/Objective(s): Specific aims were to evaluate pre- and post-radiotherapy (RT) relative renal function changes in patientsbased on renal scintigraphy (RS), hemoglobin and creatinine. Our hypothesis was that renal function is altered from abdominalradiation and can be quantified.

Materials/Methods: Between 2004 and 2006, RS was performed before and at regular intervals after RT in 17 patients. The RSwas evaluated in the posterior projection following the intravenous administration of 6 mCi of 99mTc MAG-3. Sequential renalimages were examined out to 30 minutes enabling quantitative analysis of the RS. The kidney with greater volume receiving morethan 20 Gy was defined as the primary radiated kidney. RS of the primary radiated kidney was used as an index of the relativekidney function. The relationship between renal function and kidney dose-volume parameters was established. Area under curve(AUC) with reduced activity in RS of primary radiated kidney with time after the onset of RT was also analyzed.

Proceedings of the 50th Annual ASTRO Meeting S479

Results: Median age was 59 years (range, 39-78) and 12 patients (12/17, 70.6%) were female. Primary sites were: pancreas 11(65%), stomach 3, duodenum 2, and ampulla 1. Mean radiation dose was 48.5 Gy (range, 41.4-50.4) given in daily 1.8 Gy fractionsusing a 3D conformal technique. Median follow-up was 23 months. Mean RS in the primary radiated kidney was reduced from48.7% (range, 39-55, SD 5.3) pre-RT to 46.6% (range, 36-55, SD 6.4) 6-12 months after RT (p = 0.07). Mean creatinine was reducedfrom 0.92 mg/dl (range, 0.6-1.3) pre-RT to 1.02 mg/dl (range, 0.6-1.5) after RT (p = 0.18). Mean hemoglobin was reduced from 12.1g/dl pre-RT to 11.4 g/dl after RT (p = 0.16). Mean V10 (percentage of the volume of the primary radiated kidney that received morethan 10 Gy), V15, V20, V25, V30, V35, and V40 were 63.2%, 59.6%, 55.3%, 50.2%, 30%, 24.8%, and 22.3%, respectively. MeanAUC was 992.4. V25, V30, V35, V40 and AUC were associated with $5% decrease of RS in the primary radiated kidney (p\0.04,Wilcoxon rank-sum test). On multivariate analysis, decrease in primary radiated kidney function did not correlate significantly withtime, gender, hypertension, AUC or age, however smoking status (p = 0.01) was a significant predictor of decreased renal function.

Conclusions: We confirmed our hypothesis, since renal scintigraphy allows for the identification of radiation effects in partial kid-ney volumes. The extent of scintigraphic change correlates with dose-volume parameters for the primary radiated kidney. Our ob-servations may suggest that renal dose from image guidance warrant further scrutiny.

Author Disclosure: G.Y. Yang, None; L. Flaherty, None; T.D. Wagner, None; J.C. Yap, None; R. Chandrasekhar, None; G. Wild-ing, None; N.I. Khushalani, None; R.V. Iyer, None; D. Lamonica, None; C.R. Thomas, None.

2694 An Analysis of Consent Form Modification of RTOG Healthcare Institutions Consent Forms: A

Readability Impact Study

L. J. Chin1, J. P. Allegrante1, W. M. Sage2, R. Marks1, J. L. James3, W. Curran4

1Columbia University Teachers College, New York, NY, 2University of Texas at Austin, Law School, Austin, TX, 3RadiationTherapy Oncology, Philadelphia, PA, 4Emory University, Atlanta, GA

Purpose/Objective(s): Ethically valid informed consent requires participants of clinical trials to comprehend consent form infor-mation. A factor impeding comprehension is the readability of the consent form. This study examined the extent healthcare insti-tutions participating in Radiation Therapy Oncology Group (RTOG) clinical trials modify the clinical trials’ model consent formsto create the institutional consent form and determine if the modification of the model consent form information affects consentform information readability.

Materials/Methods: Four RTOG clinical trials, RTOG 0324, RTOG 0232, RTOG 0411, and RTOG 0412 were chosen for thisanalysis. These trials used the NCI consent form template to develop the trial’s sample/model consent form. Healthcare institutionsthat enrolled patients onto aforementioned trials by a cut-off date were contacted for study participation. Participating institutionsprovided a copy of institutional consent form. Institutional consent forms were compared to RTOG model consent form for sixsections (purpose, procedure, risks, alternatives, benefits, and voluntary participation) to ascertain information variances (consentform modifications). FOG and SMOG readability formulas were used to determine the readability of consent form information.Characteristics of RTOG healthcare institutions were collected from secondary data sources. Descriptive statistics were performedon consent form modification data. Regression analysis was used to determine if institutional characteristics impacted consent formmodification. Correlation analysis was used to determine the association between consent form modification and its readability.

Results: Forty-four consent forms were analyzed (n = 18, RTOG 0324; n = 14, RTOG 0232; n = 10, RTOG 0411; n = 2, RTOG0412). Average total number of consent form modifications was 21.1 (range, 0-62), 23.9 (range, 0-61), 27.5 (range, 1-51), and 32.5(range, 29-36) for RTOG 0324, 0232, 0411, and 0412, respectively. Regression analysis did not show any institutional character-istics impacting consent form modifications. Correlation analysis demonstrated that consent form modification was associated withthe readability of consent form information; some modifications were associated with improved readability of consent form infor-mation while other modifications were associated with reduced the readability of consent form information.

Conclusions: Healthcare institutions participating in RTOG clinical trials will modify the RTOG model consent forms to createtheir institutional consent forms. These modifications can impact the readability of the consent form information. Issues regardingreadability of consent form information may affect the ethical requirement of informed consent.

Author Disclosure: L.J. Chin, None; J.P. Allegrante, None; W.M. Sage, None; R. Marks, None; J.L. James, None; W.Curran, None.

2695 Outcomes Comparison of IMRT vs. 3D Conformal Therapy of the Breast

M. L. Haley, J. Greenberger, D. E. Heron, H. Jones, C. J. Lin

University of Pittsburgh School of Medicine, Pittsburgh, PA

Purpose/Objective(s): The local control rate with radiation after breast-conserving surgery is comparable to that of mastectomy.This has shifted the goals of breast radiotherapy from cure to those that affect quality of life, such as cosmesis. IMRT (intensity-modulated radiation therapy) has become a popular method to achieve dose homogeneity which in some studies has resulted insuperior outcomes. Most of these studies have compared 2D (two-dimensional) to IMRT treatment. The purpose of this studywas to compare outcomes in patients treated with 3D (three-dimensional) radiation therapy to those treated with IMRT.

Materials/Methods: 30 patients with right-sided breast malignancies treated at a single institution were selected for review (15 3Dand 15 IMRT). The patients were matched based on parameters known to affect cosmetic outcomes: age, race, volume of breastirradiated, stage, and chemotherapy use. All patients received 50 Gy in 25 fractions to the whole breast followed by a boost usingelectrons or mini-tangents. Patients with chest wall reconstructions, previous breast surgery, or whole breast doses .50 Gy wereexcluded from analysis. 3D patients had forward planning and IMRT patients had inverse planning. Both groups used fixed gantryangles for treatment. Wilcoxon and McNemar tests were used to compare differences between the two treatment groups.

Results: Twenty-two (73.3%) of the patients were under 60 years, 28 (93.3%) were white, 26 (86.7%) had at least 600 cc breastvolume irradiated, and 14 (46.7%) had sequential systemic chemotherapy. The mean age was 51 years for the 3D group and 57years for the IMRT group. Cost (based on Medicare fee schedule) was $8,088.44 for each 3D patient and $18,040.05 for eachIMRT patient. The majority of the cost differences were due to the technical components of treatment. Median follow-up was