millimeter level, such “human” variations (at the centimeter level) may overshadow the gain from technical advancement andimpact treatment planning. Strategies of standardization and training in tumor delineation should be developed.

This work is in part supported by NIH RO1CA71906-05.

2247 IMRT of Whole Pelvis and Inguinal Nodes: Evaluation of Dose Distributions Produced by an InverseTreatment Planning System

M. Ahmad,1,2 H. Song,1 M. Moran,1,2 M. Lund,1,2 Z. Chen,1 J. Deng,1 B. Haffty,1,2 R. Nath1,2

1Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT, 2Radiation Therapy Center,William W. Backus Hospital, Norwich, CT

Purpose/Objective: Concomitant irradiation of inguinal lymphatics in patients diagnosed with primary pelvic malignanciespresents dosimetric challenges involving abutting fields at the groin. We have previously described and compared a novel“modified segmental boost technique” (MSBT), to other commonly used photon and electron techniques for concurrenttreatment of the pelvis and inguinal nodes. To date, no data exist on intensity-modulated radiotherapy of the whole pelvis(IM-WPRT) including the inguinal/femoral nodes. This is the first inverse planning effort aimed at investigating the efficacyof IM-WPRT and comparing it with the MSBT to irradiate the inguinal lymph nodes included with the pelvis.

Materials/Methods: First, the mushroom-shaped planning target volume (PTV), encompassing the whole pelvis including thebilateral inguinal nodes to a depth of 5 cm, and femurs were delineated on computerized tomography (CT) slices of ahomogeneous phantom. Two prototype plans using the MSBT (1) and a 3-field IM-WPRT technique were designed. TheIM-WPRT plan was based on the dose prescription for the PTV and dose constraints placed on bilateral structuresincluding the femurs. This optimized technique was utilized in the inverse planning of a number of sample patients. Inaddition, film dosimetry was performed to validate dose distributions resulting from the inverse and forward planningtechniques.

Results: The dose volume histograms (DVHs) of PTV and femurs were analyzed to evaluate the MSBT and IM-WPRT plans.The dose inhomogeneity (D05), defined by the dose received by 5% of PTV, was reduced slightly from 116% for the MSBTto 110% with the IM-WPRT. For comparison, Table 1 lists values of the target conformity index (TCI), a figure of merit,representing how closely the planned isodose distribution reproduces the shape of the PTV. Following the definition proposedby Baltas et al. (2): TCI � C1* C2; with C1 � fraction of PTV covered by � 95% of the prescribed dose, and C2 � ratio ofthe volume of PTV covered by � 95% of prescribed dose to the total body volume covered by � 95% of the prescribed dose.Calculated values of TCI for the MSBT and IM-WPRT plans were 0.60 and 0.73, respectively. Summary of DVH analysis ispresented in Table 1.

Conclusions: We demonstrated the feasibility of inversely optimized IMRT for treating pelvic malignancies includinginguinal/femoral nodes. Compared to our MSBT, it produces a more uniform and conformal dose distribution in the entire targetvolume while protecting the femurs from the risk of radiation-induced fracture. A clinically significant advantage of the IMRTapproach is that it eliminates dose modulations across abutting/overlap regions often encountered in traditional treatmenttechniques.

References:1. Moran M, Lund M, Ahmad M, et al. Improved treatment of pelvis and inguinal nodes using modified segmental boost

technique: Dosimetric evaluation. Int J Radiat Oncol Biol Phys 2004;59. (in press)2. Baltas D, Kolotas C, Geramani K, et al. A conformal index to evaluate implant quality and dose specification in

brachytherapy. Int J Radiat Oncol Biol Phys 1998;40:515–524.

S484 I. J. Radiation Oncology ● Biology ● Physics Volume 60, Number 1, Supplement, 2004

2248 Phase I/II Study of Alternating Chemoradiotherapy Using 5FU and Nedaplatin for Patients with High-Risk Group of Cervical Carcinoma; A Comparison to the Historical Control Group Using Pre-TreatmentMRI Evaluation

T. Kodaira,1 N. Fuwa,1 K. Kuzuya,2 K. Furutani,1 H. Tachibana,1 Y. Ichimiya,1 N. Tomita1

1Radiation Oncology, Aichi Cancer Center, Nagoya, Aichi, Japan, 2Gynecology, Aichi Cancer Center, Nagoya, Aichi,Japan

Purpose/Objective: In previous manuscripts, we reported pre-treatment MRI had a great advantage for prediction of clinicaloutcome of patients with cervical carcinoma. With aid of MRI, patients with stage II disease could be divided into the favorablegroup (tumor size �50mm and negative pelvic node; expected disease-free survival (DFS) 93.2%) and the unfavorablegroup (tumor size � 50mm or positive pelvic node; expected DFS 25–53.3%). To improve the clinical outcome of patientswith high risk factor including stage III disease, we performed alternating chemoradiotherapy (ALCRT) using 5FU andnedaplatin (NDP).

Materials/Methods: Previously untreated patients with histologically diagnosed as squamous cell carcinoma of uterine cervixwere entered into this study. Eligible patient was defined as with high risk factor (stage I-II; tumor size � 50mm or positivepelvic node, OR all stage III-IV disease); good PS, adequate organ function; aged 20–75; and informed consent. Before the startof treatment, patients underwent MRI to evaluate the tumor size/volume and the status of lymph node. Three courses ofsystemic chemotherapy with 5FU (700mg/m2 d1–5) and NDP (100 –150 mg/m2 d6) combined with definitive radiotherapywere planned in alternating setting. A dose of NDP was escalated as follows: 100,120,140 and 150 mg/m2. Radiationtherapy consisted of both 45.6 –51.3Gy of external beam radiotherapy (EBRT) using two axial dynamic conformaltechnique and intracavitary brachytherapy (ICBT). Para-aortic irradiation of 36 Gy using dynamic conformal techniquewas added in case of positive pelvic node or stage III-IV disease. Clinical outcome was compared to the data of historicalcontrol group (N � 43) treated with radiation alone which was thought to be eligible for this criteria with pre-treatmentevaluation by MRI.

Results: From 1998 to 2002, 32 patients were entered into this analysis, of which 2, 11,16 and 3 patients were diagnosed asstage I, II, III and IV disease, respectively. The median age was 55.5 years (range 39–78). The follow-up period for the 27survivors ranged from 9.3 to 69.9 months (median 33.8months). The maximum tumor diameter was 35 mm to 100 mm (median62mm). Twenty-two patients were diagnosed as positive pelvic lymph node. In the phase I portion, the maximum tolerated dose(MTD) of NDP among 18 patients was 150 mg/m2. The recommended dose of the phase II study was 140mg/m2. In the phaseII portion, common toxicities were leucopenia, anemia, thrombocytopenia, and diarrhea with frequencies of grade 3 � of 76.9,46.2, 69.2 and 23%, respectively. Planned treatment was completed in 81.3% of 32 patients. The 3-year overall survival (OAS)and progression-free survival (PFS) rates of phase I/II proportion were 83% (95%CI � 69.3–96.7%) and 66.3% (95%CI �47.3–85.3 %), respectively. Twenty-three patients lived without disease, while 9 patients developed treatment failures in thisseries. Six patients had failures at pelvic, 7 at distant, and 4 at both pelvic and distant sites. Four patients lived with disease and5 patients died of cancer progression. In the historical group, the 3-year OAS and PFS rates were 67.4% (95%CI �53.5–81.3%) and 48.8% (95%CI � 33.9–63.7 %), respectively. ALCRT showed a tendency for factor of better OAS (P �0.083) and PFS (P � 0.055) by univariate analyses, however, it proved to be a significant prognostic factor of better PFS (P �0.039) in multivariate analysis.

Conclusions: ALCRT is efficacious and manageable in patients with high-risk group of cervical carcinoma. The MTD of NDPin ALCRT was 150 mg/m2. Improved PFS of this study in comparison with the historical control group was thought to bepromising, considering the fact of large proportion of stage III disease in this cohort.

S485Proceedings of the 46th Annual ASTRO Meeting