161Abstracts / Brachytherapy 7 (2008) 91e194

Conclusions: Endoscopic retrograde HDR-192Ir ILBT combined with metalstents is a feasible and safe method. Another abstract shows our clinicalresults.

PO67

Usefulness of endoscopically-placed radio-opaque clips in the

localization of esophageal cancer for endoluminal brachytherapy

and external beam radiation therapy

George Wakil, M.D.1 Te Vuong, M.D.1 Marc David, M.D.1 David Roberge,

M.D.1 Peter Szego, M.D.2 Slobodan Devic, Ph.D.3 1Radiation Oncology,

McGill University Health Center, Montreal, QC, Canada;2Gastroenterology, McGill University Health Center, Montreal, QC,

Canada; 3Medical Physics, McGill University Health Center, Montreal,

QC, Canada.

Purpose: Local failure with external beam radiation therapy and concurrentchemotherapy ranges from 40e50%. In our institution, high-dose-rateendoluminal brachytherapy is routinely used as a boost in order toimprove local control. The localization of the tumor bed (GTV) by CTscan or by distance from incisors as assessed by gastroscopy remainssuboptimal. In our routine, prior to HDRBT, radio-opaque clips areplaced endoscopically to improve the accuracy of our treatment. Thisstudy is aiming to evaluate the impact of these clips on the treatmentvolume during HDRBT.Methods and Materials: Patients treated with radical intent for esophagealcancer where planned initially at the CT simulator using 0.5 mm cut slicesinitially prior to the HDRBT. The same day, endoscopy was done and underdirect visualization, four radio-opaque clips are placed above and below thetumor bed as references markers for the subsequent HDRBT treatment (20Gy in 5 fractions). A second CT scan is done immediately after the clipplacement. Two radiation oncologists were involved in delineating thegross tumor volume (GTV) on the CT scan images obtained without thelocalization clips. In a second time, these volumes were compared to theGTV delineated on the CT images with the radio-opaque clips. The GTVvolume (cm3), GTV length (cm) and the longitudinal miss (cm) wereobtained. The GTV volume ratio was defined as the tumor volumewithout clips divided by the tumor volume with clips. The relativelongitudinal miss was defined as the longitudinal miss (cm) divided bythe length of the tumor as assessed by the clips (cm).Results: Tumor volumes were delineated on 20 patients. The average tumorvolume outlined on the planning CT with radio-opaque clips is 153 cm3

(range: 6e560 cm3, SD of 190 cm3). The average GTV volume ratio forthe first radiation oncologist is 0.49 (range 0.04e1.52, SD 0.47) and forthe second is 1.55 (range 0.04e5.39, SD 1.79). The relative longitudinalmiss for the first radiation oncologist is 0.53 (range 0e1, SD 0.34) andfor the second 0.4 (range 0e1, SD 0.39).Conclusions: Delineation of tumor on CT scans without clip placementleads to under- or overestimation of the tumor volume by 50%. It alsoleads to an average longitudinal miss of 50%. Radio-opaque clipplacement increases significantly the accuracy of tumor mapping duringHDRBT and the contribution of geographic miss during of radiationtreatment planning in the local recurrence of patients with esophagealcancer.

PO68

Diagnostic advantages of sublobar resection with vicryl mesh I-125

brachytherapy for early stage non-small cell lung cancer

Matthew Manning, M.D.1 Patrick Burney, M.D.2 Elizabeth Carey, M.S.1

Mohamed Mohamed3 1Radiation Oncology, Moses Cone Health System,

Greensboro, NC; 2Cardiovascular and Thoracic Surgeons (CVTS), Moses

Cone Health System, Greensboro, NC; 3Medical Oncology, Moses Cone

Regional Cancer Center, Greensboro, NC.

Purpose: For patients with early stage NSCLC and pulmonary dysfunction,emerging radiotherapeutic options include stereotactic radiotherapy (SRT)and sub-lobar resection with brachytherapy (SLR-B). A potentialadvantage of SLR-B is the diagnostic information from surgical

pathology. This study describes the pathology findings from SLR-B ina clinical series to help characterize the incidence of treatment-alteringfindings, which may go unrecognized with SRT.Methods and Materials: Between 7/06 and 3/07, 16 consecutive patientswith peripherally located clinical stage IA NSCLC based on PET-CT,underwent SLR-B. All patients would have been eligible for SRT.Intraoperatively, histology/margins were verified and lymph nodes weresampled. Then, I-125 seeds embedded in a vicryl mesh were applied tothe site of resection to deliver a dose of 100e120 Gy at a depth of 5 mm.Results: At surgery, 11/16 (69%) patients were confirmed to have stage IAdisease, and more advanced disease was discovered in 5/16 (31%). Theseincluded: 2eT2, 1eT3, 1eT4, and 1 metastasise M1. These patientsreceived individualized intensive adjuvant therapy, includingchemotherapy. With a median followup of 16 weeks (range 3e26) thelocal control, disease free survival and overall survival are 100%, 94%,and 94%.Conclusions: The diagnostic information derived from SLR-B may lead torecognition of more advanced subclinical disease overlooked by non-invasive ablative techniques such as SRT. In a significant proportion ofpatients, this may alter subsequent treatment recommendations. Theclinical benefit of customized stage-based adjuvant therapy followingSLR-B will require further study.

PO69

Development of a new Cf-252 source for remote afterloading neutron

brachytherapy: Implications and applications

Chris Wang, Ph.D.1 Rodger Martin, Ph.D.2 Jim Fontanesi, M.D.3 Mike

Joiner, Ph.D.4 Alvaro A. Martinez, M.D.3 Robert Ebling, B.S.5 1Nuclear &

Radiological Engineering and Medical Physics, Georgia Institute of

Technology, Atlanta, GA; 2Oak Ridge National Laboratory, Oak Ridge,

TN; 3Radiation Oncology, William Beaumont Hospitals, Detroit, MI;4Radiation Oncology, Wayne State University, Detroit, MI; 5Isotron Inc.,

Boston, MA.

Purpose: Advantages of neutrons in treating radioresistant tumors make252Cf an attractive alternative to traditional brachytherapy sources.However, clinical applications have been limited by large source sizes,manual handling during application, and the limited amount of 252Cf persource. In 1997 we began to determine if existing 252Cf sources, knownas ‘‘AT’’, could be miniaturized and made compatible with modern HDRtechnology.Methods and Materials: The active Pd-Cf2O3 ‘‘cermet’’ material includedin the AT sources made at Savannah River Laboratory (SRL) contain !0.1wt% 252Cf. The Radiochemical Engineering Development Center (REDC)at Oak Ridge National Laboratory (OR.N.L) increased the 252Cf contentin the cermet material. Instead of sintering at 1300�C, the pellet is heatedto 1600�C, melting the Pd-Cf2O3 mixture. For commercial sales, 1.1 mmsquare cermet wires are routinely fabricated at REDC with a nominalloading of 500 mg 252Cf per inch (O0.1 wt% 252Cf). Recently, undera CRADA with Isotron, Inc., REDC developed a new wire shapingmethod in which the wire is fed through a ‘‘shaper’’ unit, wherepneumatically activated collets squeeze the wire to smaller diameters. Awire diameter of ! 0.6 mm with uniform cross-section was obtained afterrepeated working at pressures between 40e100 psia.Results: In 2002, a batch of seven high activity miniature source seeds wassuccessfully encapsulated. The outside dimensions of the source capsule are1.1� 8 mm. The active length of the source is 5 mm. The average quantityof 252Cf per source was ~90 mg, which is O3 times that in the existing ATsources. In addition, the new source is 20 times smaller in volume thanthe AT source. A prototype remote afterloader has also been developed.Both the new sources and the remote afterloader are currently undergoingcalibration and characterization at Georgia Tech.Conclusions: Barriers impeding the use of 252Cf in brachytherapy havebeen overcome with the development of this new source. This will allowneutrons’ unique advantage in treating radioresistant tumors to berealized. The first HDR unit is scheduled for delivery in late 2008. Thereare additional plans for a multi-source HDR unit which will allowa single machine to house several types of brachytherapy sources, e.g.192Ir, 169Yb, and 252Cf.