95Abstracts / Brachytherapy 7 (2008) 91e194

the definitive presentation data of more patients will be included in theanalysis).

OR8 Presentation Time: 4:30 PM

Tumor spread and pattern of regression of cervix cancer

on repetitive MRI. Basis for adaptive brachytherapy

Johannes Dimopoulos, M.D., Veronika Bauer, M.S., Primoz Petric, M.D.,

Daniel Berger, M.Sc., Veronika Woehs, M.S., Stefan Lang, D.Sc., Christian

Kirisits, D.Sc., Richard Poetter, M.D. Radiotherapy, Medical University of

Vienna, Vienna, Austria.

Purpose: Accurate target definition for adaptive cervix cancer radiotherapyrequires the understanding of initial tumor spread and of tumor regressionduring EBRT. The aim of this study was to facilitate this understandingfor FIGO stages IIB and IIIB on MRI by: (1) defining different patternsof initial growth and regression and (2) giving the respective distributionsand frequencies.Methods and Materials: 100 cervix cancer patients, treated by EBRT(�chemotherapy) and 3D-MRI guided HDR-brachytherapy (BT),underwent MRI at time of DG and of BT. FIGO stage distribution was:IIB 5 69 and IIIB 5 31. GTV at DG (GTVD) and GTV plus Gray Zonesat time of BT (‘‘GTVBT + GZ’’) were analyzed. Parametrial sides wereevaluated separately (200 parametria (PM)). Different types of PM spreadof GTVD were defined based on the predominant growth pattern(expansive with spiculae, expansive with spiculae and infiltrative parts,infiltrative) and extent of PM invasion (proximal, middle and distal third).With regard to tumor regression, the corresponding remnants within thePM were described by their extent and quality (GTBT or GZ). Therespective frequencies and topographic distributions were given.Results: 5 types of PM spread were defined: (1) expansive with spiculae(13%), (2) expansive with spiculae and infiltrating parts (13%), (3)infiltrative into the inner PM third (34%), (4) infiltrative into the middlePM third (24%) and (5) infiltrative into the distal PM third (12%). Noinvolvement was diagnosed in 4% of the PM. The probability of anyremnants (GTVBT and/or GZ) was overall 92% and it was 23%, 69%,85%, 97% and 100% for type (1), (2), (3), (4) and (5), respectively.Remnants in the middle third were found in 58% and 42% of type (4) and(5), respectively. In the distal third they remained in 33% of type (5). Theratio GTVBT/GZ for the inner, middle and distal third was 0.38, 0.22 and0.25, respectively. Topographic distribution of remnants in the PM withmiddle or distal involvement at BT was: 74% meso-lateral, 22% cranio-lateral and 33% caudo-lateral (coronal orientation); 67% lateral, 74%dorso-lateral and 22% ventro-lateral (axial orientation).Conclusions: The systematic evaluation of tumor spread and regression onMRI enables the recognition of 5 different types of PM spread andregression. Based on this classification and the thorough description ofextent, quality and topography of remnants, it appears practicable todefine the target accurately within the frame of adaptive radiotherapy andimage-guided brachytherapy in particular. Using this adaptive targetapproach these findings are also valuable for the development of novelcombined intracavitary and interstitial BT applicators.

OR9 Presentation Time: 4:40 PM

Spatial relationship of the 3D dose distribution from brachytherapy

and external beam therapy for adding both dose plans in patients

with cervix cancer

Georgina Frohlich, M.Sc.1,2 Stefan Lang, Ph.D.3 Daniel Berger, M.Sc.3

Johannes Dimopoulos, M.D.3 Dietmar Georg, Ph.D.3 Richard Poetter,

M.D.3 Christian Kirisits, Sc.D.3 1School of Ph.D. Studies, Semmelweis

University, Budapest, Hungary; 2Radiotherapy, National Institute of

Oncology, Budapest, Hungary; 3Radiotherapy, Medical University of

Vienna, Vienna, Austria.

Purpose: To sum up doses from brachytherapy (BT) and external beamtherapy (EBT) it is generally assumed that the most exposed parts ofOAR from BT receive the prescribed dose (PD) of EBT. This study was

performed to test this assumption for IMRT and 3D conformal EBT witha 4-field box (4F).Methods and Materials: 11 patients treated with IMRT (PD 5 45e50.4 Gyin 1.8 Gy fractions) and 4 fractions of MRI based HDR BT (PD 5 4� 7 Gy)using either tandem-ring applicators, vaginal cylinders and/or needles wereinvestigated. For the BT plans the dose to the most exposed 2, 1 and 0.1 cm3

(D2cc, D1cc, D0.1cc) of OAR was calculated for each fraction by DVH-analysis, and the spatial anatomical location of these BT volumes wasrecorded. IMRT plans were evaluated for D10cc, D5cc, D2cc, D1cc andD0.1cc in percentage of the PD, and the spatial location recorded. 4Ftreatment plans were created, and the same evaluation was performed asfor IMRT. To investigate the spatial and dosimetric relationship of EBTversus BT, the D2cc-volumes from BT were manually superimposed tothe EBT plans, and the dose from EBT in the corresponding anatomicalareas was estimated.Results: D10cc e D0.1cc were significantly higher for IMRT compared to4F plans (p!0.05) except for D10cc and D5cc of rectum. Compared to thePD, the D10cc, D2cc and D0.1cc of IMRT were (mean� 1SD) for bladder 8� 2%, 10 � 2%, 11 � 2%, for rectum 5 � 3%, 8 � 3%, 10 � 3% and forsigmoid 6 � 3%, 10 � 1%, 11 � 1% higher than the PD. The D10cc,D2cc and D0.1cc of 4F for bladder were 3 � 3%, 4 � 3%, 4 � 3%, forrectum 4 � 3%, 4 � 3%, 5 � 3% and for sigmoid-1 � 3%, 0 � 2%, 1 �2% higher than the PD. The D2cc-volume of IMRT was frequentlydiscontinuously spread over the organ, and generally not equal or close tothe D2cc-volume of 4F and BT. When superimposing the D2cc-volume ofBT to the IMRT, the dose in these areas was for bladder-2 � 3%, forrectum 3 � 2% and for sigmoid 5 � 0% higher than the PD. The doses tothe D2cc-volumes of BT from the 4F plans were for bladder 1 � 2%, forrectum 3 � 3% and for sigmoid 0 � 0% higher than the PD.Conclusions: 4F and even more pronounced IMRT result in higher D10cc eD0.1cc to OAR than the PD. However, the D2cc-volumes of 4F and IMRT(spread out over the organ) are located at different anatomical areascompared to BT (close to the applicator). The clinically relevant, mostexposed anatomical areas given by the D2cc-volumes of BT receive thePD within � 5% (1SD) for both IMRT and 4F.

OR10 Presentation Time: 4:50 PM

Impact of the rectosigmoid junction location on dose assessment for

rectum and sigmoid in MRI-based cervix cancer brachytherapy

Stefan Lang, Ph.D., Petra Trnkova, M.Sc., Christian Kirisits, D.Sc.,

Johannes Dimopoulos, M.D., Dietmar Georg, Ph.D., Richard Poetter,

M.D. Radiotherapy, Medical University of Vienna, Vienna, Austria.

Purpose: If the most exposed part of the rectum and sigmoid is located inthe region of the rectosigmoid junction, evaluating the DVH of rectumand sigmoid separately splits the D2cc-volume (dose to the most exposed2cm3) into 2 organs. Consequently an underestimation of the relevantD2cc is expected.Methods and Materials: At our department optimization for MRI-basedHDR cervix cancer brachytherapy is based on DVH-constraints for high-risk CTV and OAR. D2cc of the rectum and sigmoid is limited to 70e75Gy equivalent dose in 2 Gy fractions (EQD2 with a/b 5 3 Gy; EBRT 45Gy+4 fractions BT). The rectum is delineated from the anus to therectosigmoid junction, which is defined by an enlargement of thecircumference and change of organ shape and position. The sigmoid isdelineated from the rectosigmoid junction up to the fundus of the uterus.However, the position of the rectosigmoid junction can vary due tointerobserver variations and slice orientation. For this study the rectumand sigmoid of 12 patients (26 MRI sets) were investigated. If the D2cc-volume was located in the region of the rectosigmoid junction, thecontoured length of rectum and sigmoid was enlarged / reduced in cranio-caudal direction on MRI slices by �1.5 cm. For a worst case assumptiona combined reference structure of rectum and sigmoid was created(‘‘rectosigmoid’’). The respective D2cc were evaluated.Results: In 2/12 patients (4/26 MRI sets) the D2cc-volume was located in theregion of the rectosigmoid junction. In patient 1 the maximum erroroccurred with the rectosigmoid junction at the most cranial position(+1.5cm). The D2cc-volume was split in 2 parts with 67 Gy (rectum) and72 Gy (sigmoid). With the most caudal position the D2cc was 64 Gy

96 Abstracts / Brachytherapy 7 (2008) 91e194

(rectum) and 74 Gy (sigmoid). D2cc of rectosigmoid was 74 Gy. With themost cranial position, the clinically relevant D2cc of sigmoid (74 Gy) wastherefore underestimated by 2 Gy. In patient 2 the maximum erroroccurred with the rectosigmoid junction at the most caudal position (-1.5cm). D2cc was 70 Gy (rectum) and 70 Gy (sigmoid) in this case. Withthe most cranial position the D2cc was 74 Gy (rectum) and 56 Gy(sigmoid). D2cc of rectosigmoid was 74 Gy. With the most caudalposition, the clinically relevant D2cc of rectum (74 Gy) was thereforeunderestimated by 4 Gy.Conclusions: When delineating the rectum and sigmoid, the rectosigmoidjunction should be located distant from the most exposed part of rectumand sigmoid, or a combined rectosigmoid reference structure should beevaluated. The D2cc of rectum or sigmoid may be underestimated by thiseffect up to about 4 Gy, resulting in overdosage by plan optimization. It iscrucial to inspect the 3D dose distribution visually in addition toevaluating DVH parameters.

OR11 Presentation Time: 5:00 PM

Preliminary results of a prospective multicentric French study

of PDR 3D brachytherapy for cervix carcinoma

Christine Brunaud, Christine Haie-Meder, M.D.2 Didier Peiffert, M.D.,

Ph.D.1 STIC PDR Group 1Radiation Oncology, Alexis Vautrin Center,

Vandoeuvre-les-Nancy, France; 2Radiation Oncology, Gustave Roussy

Institute, Villejuif, France.

Purpose: In 2005 a French multicentric prospective study (‘‘STIC PDR’’)was initiated for patients treated for cervix carcinoma comparingbrachytherapy method: based on orthogonal X rays (2D group), or basedon 3D-imaging and performed with PDR brachytherapy (3D group). Thestudy has ended after 2.5 years accrual and the enrollment of 801patients. We describe the first 650 patients.Methods and Materials: 287 patients were included in the 2D group, and363 in the 3D group. Three subgroups of patients were defined: (1)brachytherapy-surgery; (2) external beam radiotherapy (EBRT)-brachytherapy-surgery; (3) EBRT-brachytherapy. Clinical data werecomparable between 2D and 3D groups in each subgroup (histology,FIGO stage, EBRT dose, chemotherapy.In both groups, ICRU bladder and rectal points were drawned; in the 3Dgroup, CTV volumes were delineated according to GEC ESTROrecommendations (high-risk CTV and intermediate-risk CTV), as werethe external wall of the organs at risk (OAR) (bladder, rectum andsigmoid); cumulative DVH were performed on CTV and OAR. Themedian dose to 100% (D100) and 90% (D90) of CTV and the volume ofCTV receiving 60 Gy (V60) were analyzed.Results: Brachytherapy (461 patients): for each subgroup, results arecomparable between 2D and 3D (isodose 60 Gy volume, dose to ICRUbladder and rectal points, TRAK). In the 3D group, CTV coverage anddoses to 2 cc of OARs were a little higher in subgroup 3.Surgical data (308 patients): the same proportion of patients were incomplete cervical pathologic remission between 2D and 3D groups (52and 55%). There was no difference in coverage of CTVs betweencomplete and partial remission in the 3D group.Conclusions: The first results of the ‘‘STIC PDR’’ study show greatsimilarity in dosimetric data between 2D and 3D groups. This preliminaryexperience may correspond to a learning curve during which physiciansdidn’t modify to a large extent their mode of prescription while evolvingtowards 3D brachytherapy. The followup of the patients will lead toprecious data in the 3D group about the relationship between DVHs, latecomplications and local control.

OR12 Presentation Time: 5:10 PM

Correlation of Point B and lymph node dose in 3D-planned

high-dose-rate cervical cancer brachytherapy

Larissa Lee, M.D.1 Cheryl Sadow, M.D.2 Anthony Russell, M.D.3 Akila

Viswanathan, M.D., M.P.H.4 1Harvard Radiation Oncology Program,

Boston, MA; 2Radiology, Brigham and Women’s Hospital, Boston, MA;3Radiation Oncology, Massachusetts General Hospital, Boston, MA;

4Radiation Oncology, Brigham and Women’s Hospital/Dana-Farber

Cancer Institute, Boston, MA.

Purpose: To compare the dose per fraction to point B with dose to the pelviclymph nodes using CT-based dosimetry for HDR brachytherapy.Methods and Materials: 35 tandem-based HDR applications wereperformed using CT-based treatment planning for cervical cancerbrachytherapy. Each patient received 5 HDR fractions of 5e5.5 Gyprescribed to point A. Pelvic lymph node contours (obturator, externaland internal iliac) were based on RTOG definitions and modified witha radiologist. Using the cumulative average from right and left sides,point B dose was compared to dose volume parameters (D100, D90, D50,D2cc, D1cc, D0.1cc) for each nodal group using the Pearson correlationcoefficient (cor) and a paired t-test.Results: The mean tumor size by MRI was 4.4 cm. The mean point B dosewas 1.42 � 0.16 Gy, which was 25% of the mean point A dose. For theobturator group, mean D2cc was 1.45 � 0.27 Gy, cor to point B 5 0.61, p! 0.0001. The mean D0.1cc was 1.86 � 0.36 Gy, cor 5 0.53, p 5 0.001.D2cc was not significantly different from point B (t test p 5 0.5),whereas D100, D90, D50, D1cc and D0.1cc were all statistically differentfrom point B (all p ! 0.001). For the external iliac chain, mean D2cc was1.10 � 0.24 Gy, cor 5 0.63, p ! 0.0001. The mean D0.1cc was 1.41 �0.28 Gy, cor 5 0.58, p 5 0.0002. D0.1cc was not significantly differentfrom point B (t test p 5 0.79), in contrast to the other volumetricparameters (all p ! 0.0001). For the internal iliac nodes, mean D2cc was1.56 � 0.29 Gy, cor 5 0.30, p 5 0.08. The mean D0.1cc was 1.94 � 0.40Gy, cor 5 0.23, p 5 0.11. Point B dose differed significantly from allvolumetric parameters (all p ! 0.008).Conclusions: Point B receives approximately 25% of the HDR prescriptiondose per fraction. This results in an additional 1.4 Gy per fraction to thepelvic lymph nodes for a total dose of 7 Gy over 5 HDR fractions. PointB correlates significantly with and most closely represents the D2cc doseto the obturator nodes and the D0.1cc dose to the external iliac lymphnodes. Given the large fraction size utilized in HDR brachytherapy, pointB dose should be recorded in all cervical cancer brachytherapy cases todescribe accurately the cumulative dose administered to the pelvic lymphnodes.

OR13 Presentation Time: 5:20 PM

Computed tomography-based dose-volume parameters of the rectum

and late rectal complications in patients with cervical carcinoma

treated by high-dose-rate intracavitary brachytherapy

Shingo Kato, M.D.1 Hiroki Kiyohara, M.D.1 Tomoaki Tamaki, M.D.1

Tatsuya Ohno, M.D.2 Hirohiko Tsujii, M.D.1 1Research Center Hospital

for Charged Particle Therapy, National Institute of Radiological Sciences,

Chiba, Chiba, Japan; 2Heavy Ion Medical Center, Gunma University

Graduate School of Medicine, Maebashi, Gunma, Japan.

Purpose: To evaluate the efficacy of CT-based dose-volume parameters of therectum as predictive factors for late rectal complications (LRC) in patientswith cervical carcinoma treated with a combination of external beamradiotherapy and high-dose-rate intracavitary brachytherapy (HDR-ICBT).Methods and Materials: Between January 2000 and December 2004, 92patients who were treated with definitive radiotherapy alone were enrolledinto the study. All patients received three or four sessions of HDR-ICBTusing the standard technique. Patients also underwent CT scans of thepelvis in the same position on the same treatment couch to generatethree-dimensional dose distributions. The external contours of the rectumwere delineated on the CT images, and the minimum doses delivered to1cc, 2cc, and 5cc of the rectal volumes receiving the highest dose (D1cc,D2cc, and D5cc) were determined from the DVHs. The ICRU rectalreference point dose (DICRU) was derived from the conventional method.These doses were transformed to the biologically effective doses (BEDs)by summing the BEDs of both external beam radiotherapy andbrachytherapy using a/b ratio of 3 Gy. The correlation between the BEDof each parameter and the actuarial rate of LRC was analyzed.Results: The median followup duration for all patients was 47 months(range, 12e79 months). Twenty-six patients developed LRC (Grade 1: 18,