Methods and Materials: Megavoltage Cone-Beam CT (MV CBCT) refersto the reconstruction of a 3D image from a set of 2D projections, producedusing photons in the MeVenergy range. MV CBCT scans are obtained usinga medical linear accelerator equipped with an amorphous-silicon flat paneldetector. The acquisition and processing time for a MV CBCT scan is lessthan two minutes, and the dose delivered to the patient ranges between 2and 15 cGy. Since MV CBCT images are less affected by high atomicnumber materials, such as metal objects, they can complement theinformation provided by kV CT in images with metal-induced streakartifacts. To visualize the position of the catheters in MV CBCT images,metal wires are inserted into them. Different designs of the metal wireswere compared using a water phantom to select the most visible one.Results: We acquired MV CBCT images of two interstitial HDR patients:a gynecologic cancer patient with a hip prosthesis, and an oral tonguepatient with dental fillings. The MV CBCT images were overlaid with thekV CT images to obtain a common coordinate system, and both data setswere imported into the PLATO HDR planning system (Nucletron) todelineate anatomical structures and the position of the catheters. Themetal wires facilitated the digitalization of catheters on the MV CBCTimages. MV CBCT images were used to complement the anatomicalinformation where artifacts on the regular CT hindered the image quality.Conclusions: The MV CBCT system provides sufficient image quality andsoft-tissue resolution to help define anatomical structures, prosthetic devicesand the position of the catheters for CT-based HDR brachytherapy treatmentplanning. Our objective is to study the advantages of using the informationprovided by MV CBCT for planning purposes and to identify the categoriesof patients that would most benefit from this new technique. The catheterposition and organ segmentation obtained using kV CT will be comparedwith those obtained using MV CBCT images, and the dosimetricdifferences in the two treatment plans will be quantified.This project is sponsored by Siemens Oncology Care Systems

PLENARY

Thursday May 11, 2006

9:45 AM-10:45 AM

OR-24 Presentation Time: 9:45 AM

Long-term outcome and toxicity in a Phase I/II trial using HDR

multicatheter interstitial brachytherapy for T1-2 breast cancer

Seth A Kaufman, M.D.,1 Thomas A DiPetrillo, M.D.,1,2 Jennifer Bassett

Midle, M.P.H.,3 Lori Lyn Price, M.S.,3 David E Wazer, M.D.1,2 1Radiation

Oncology, Tufts-New England Medical Center, Boston, MA; 2Radiation

Oncology, Brown University-Rhode Island Hospital, Providence, RI;3Clinical Care Research, Tufts-New England Medical Center,

Boston, MA.

Purpose: To present an updated analysis of recurrence rate and toxicity fora cohort of women with early stage breast cancer treated with high-dose-rate(HDR) interstitial brachytherapy.Methods and Materials: From August 1997 to July 2001, a total of 32women with 33 breast cancers were treated with HDR interstitialbrachytherapy following breast conserving surgery as part of a multi-institutional phase I/II protocol. All patients had T1-2 tumors with <3axillary nodes positive (without extracapsular extension), non-lobularhistology, and negative surgical margins. A total of 34 Gy was deliveredin 10 fractions over 5 days. Toxicities (skin, subcutaneous tissue, pain, fatnecrosis) were evaluated by RTOG criteria; cosmesis was assessed usinga previously published scale. Toxicity scores were separated into fourfollowup intervals: <6 months, O6 months and <2 years, O2 and <5years, and O5 years.Results: The median age was 64 years (range: 38-77 years). Medianfollowup was 6.9 years (range: 4.5-8.4 years). The actuarial disease freesurvival (DFS) was 90.6% at 8.4 years with the last measured event at 5.8years. A total of 3 treatment failures were observed at 2.1, 3.3, and 5.8years of followup. All three were elsewhere failures within the treatedbreast. One patient died after 7.4 years of followup secondary toa subsequent small cell lung cancer. Fat necrosis was observed in 17 of33 treated breasts (53%) over the entire followup interval. Fat necrosiswas not seen up to 6 months after treatment, then appeared in 27.3% ofcases from 6 months to 2 years, 28.1% from 2-5 years, and 18.5% beyond

5 years. Moderate to severe skin toxicity was observed in 6.1%, 3.0%,3.1%, and 7.4% of cases at each successive time interval. Moderate tosevere subcutaneous toxicity was seen in 15.2%, 18.2%, 18.8%, and37.0% of cases successively. Less than excellent cosmetic outcome wasseen in 21.2%, 21.2%, 21.9%, and 11.1% of treated breasts successively.Pain scored as more than mild was seen in only one case. The percentageof cases with any degree of pain was 30.3%, 33.3%, 18.8%, and 18.5%over the sequential study intervals.Conclusions: Our series showed a 90.6% actuarial DFS at 8.4 years, whichis comparable to that seen in conventional whole breast series. Fat necrosiswas found in more than half the cohort. Fat necrosis, pain, and cosmesisappeared to improve with followup beyond 5 years, while skin andsubcutaneous toxicities worsened.

OR-25 Presentation Time: 10:00 AM

Androgen deprivation therapy does not impact cause-specific or

overall survival following permanent prostate brachytherapy

Gregory S Merrick, M.D.,1 Wayne M Butler, Ph.D.,1 Kent E Wallner,

M.D.,2 Robert W Galbreath, Ph.D.,1,3 Zachariah A Allen, M.S.,1 Edward

Adamovich, M.D.4 1Schiffler Cancer Center, Wheeling Hospital, Wheeling,

WV; 2Puget Sound Healthcare Corporation, Group Health Cooperative,

University of Washington, Seattle, WA; 3Ohio University Eastern, St.

Clairsville, OH; 4Pathology, Wheeling Hospital, Wheeling, WV.

Purpose: To determine if androgen deprivation therapy (ADT) impactscause-specific, biochemical progression-free, or overall survival followingprostate brachytherapy.Methods and Materials: From April 1995 through June 2002, 938consecutive patients underwent brachytherapy for clinical stage T1b-T3a(2002 AJCC) prostate cancer. All patients underwent brachytherapy morethan 3 years prior to analysis. Three hundred eighty-two (40.7%) patientsreceived ADT with a duration of <6 months in 277 and O6 months in105. The median follow up was 5.4 years. Multiple clinical, treatment anddosimetric parameters were evaluated as predictors of cause-specific,biochemical progression-free, and overall survival.Results: The 10-year cause-specific, biochemical progression-free andoverall survival rates for the entire cohort were 96.4%, 95.9% and 78.1%,respectively. Except for biochemical progression-free survival in high-riskpatients, ADT did not statistically impact any of the three survivalcategories. A Cox linear regression analysis demonstrated that Gleasonscore was the best predictor of cause-specific survival while precentpositive biopsies, prostate volume and risk group predicted forbiochemical progression-free survival. Patient age and tobacco use werethe strongest predictors of overall survival. One hundred two patientshave died with 80 of the deaths as a result of cardiovascular disease (54)and second malignancies (26). To date, only 12 patients have died ofmetastatic prostate cancer.Conclusions: Following brachytherapy, androgen deprivation therapy didnot impact cause-specific or overall survival and its influence onbiochemical progression-free survival was restricted to high-risk patients.Cardiovascular disease and second malignancies far outweighted prostatecancer as competing causes of death.

OR-26 Presentation Time: 10:15 AM

Vienna experience in 145 cervical cancer patients treated by

systematic MRI-based intracavitary G interstitial brachytherapy

from 1998-2003: Impact on local control

Richard Potter, M.D., Ph.D.,1 Johannes Dimopoulos, M.D.,1 Christian

Kirisits, Sc.D.,1 Petra Georg, M.D.,1 Thomas Knocke, M.D.,1 Claudia

Waldhausl, Sc.D.,1 Hajo Weitmann, M.D.,1 Alexander Reinthaller, M.D.,2

Stefan Wachter, M.D.1 1Radiotherapy and Radiobiology, Medical

University of Vienna, Vienna, Austria; 2Gynecology and Obstetrics,

Medical University of Vienna, Vienna, Austria.

Purpose: To evaluate, if systematic MRI based intracavitary G interstitialcervical cancer brachytherapy adds to local control, without increasinglate side effects. Two patient cohorts, treated within the same clinicalsetting, in two consecutive time periods with evolving approaches, wereanalysed.

86 Abstracts / Brachytherapy 5 (2006) 78–117

Methods and Materials: One hundred forty-five consecutive cervicalcancer pts who received definitive radiotherapy (45 Gy EBRT) Gcisplatin based chemotherapy (5 � 40 mg m2) at our department from1998–2003, were evaluated. FIGO stage distribution was: I 5 14 II–87,III 5 37, IVA 5 7. Tumor size was O5 cm in 78 pts. Brachytherapy wasintracavitary in 116 pts and intracavitary 1 interstitial in 29. 4 � 7 Gywas prescribed to point A from 98–2000 (group A: 73 pts) and to highrisk-CTV (Haie-Meder et al. R&O 2005) from 2001–2003 (group B: 72pts), respectively (84 Gy EQD2 (a/b 10).MRI based treatment planning was carried out in all pts, 1–2 out of 4fractions in group A, all in group B. In group B, a systematic approachwith contouring of GTV, HR-CTV and OAR and prospective evaluationof DVH-parameters using the LQ model was used (Potter et al. R&O 2006).Late adverse side effects were evaluated according to LENT-SOMA score.Kaplan-Meier method and log-rank test were used for statistical analysis (at3/2005).Results: Complete response was achieved in 138 pts (95%). Fifteen localrecurrences (LR) occurred in the true pelvis: group A 11, group B 4(median follow up 39 months).The local control (LC) rate at 3 yrs was 85% (22 LR). Continuous completeremission (CCR) rate was 88% (15 LR), 83% (11 LR) in group A and 95% (4LR) in group B. CCR for tumors !5 cm was 96% (1 LR) in group A and100% in group B. CCR was 80% (14 LR) for tumors O5 cm, CCR was72% (10 LR) in group A and 91% (4 LR) in group B.The results for group B were significant and for group A slightly better thanthose in Vienna 93–97 (189 pts) without MRI based treatment planning andinterstitial brachytherapy with overall 78% pelvic control, 90% for tumors!5 cm, 67% for tumors O5 cm) (Potter et al. 2000).Overall 8 grade 3 and 4 genitourinary and digestive adverse late side effectswere observed, 6 in group A and 2 in group B.Conclusions: Systematic individualized MRI-based treatment planningwith interstitial brachytherapy in advanced cervical cancer significantlyimproves local control and continuous complete remission, while the rateof late side effects remains low.

OR-27 Presentation Time: 10:30 AM

The meaning of prescription dose and D90 in permanent seed

prostate brachytherapy

Wayne M Butler, Ph.D.,1 Gregory S Merrick, M.D.,1 Kent E Wallner, M.D.2

1Schiffler Cancer Center, Wheeling Hospital, Wheeling, WV; 2Puget Sound

Health System, Department of Veterans Affairs, Seattle, WA.

Purpose: To investigate the range of dosimetric quality parameters that maybe encompassed by a monotherapeutic prescribed dose of 145 Gy or 125 Gyfor I-125 or Pd-103 permanent seed prostate implants, respectively, and toestimate radiobiological survival differences at constant D90, theminimum dose encompassing 90% of the planning target volume (PTV).Methods and Materials: Several seed strengths ranging from 0.4 to 1.0 Ufor I-125 and from 2.5 to 6.0 U for Pd-103 were applied in designingideal implants for a single prostate. Each design was required to have aV100 for the PTV between 99.5% and 100%, a D90 of 125% G 0.5%, aurethral V150 < 0.1%, and the volume covered by the prescription dose tobe the same within 0.5 cm3. Dose volume histograms and other summarydosimetric quality parameters (arithmetic mean, geometric mean, andharmonic mean doses) were calculated for the various implant designs.Using commonly accepted values for radiobiological parameters in thelinear quadratic formulation, tumor control probabilities (TCP) werederived from the DVHs.Results: For the ideal implants, 122 seeds were used for the low seedstrength implants of both radionuclides and 64 seeds for the highest seedstrengths. The mean dosimetric margins from the PTV to the 100%isodose line were nearly the same, 3.9 G 0.1 mm. At constant D90 of125%, V150 varied from 42% to 66% for I-125 and from 58% to 76% forPd-103 over the range of strengths studied. The arithmetic mean doseranged from 225% for low strength seed implants to 300% for highstrength implants while the harmonic means varied from 210% to 245%for low strength and high strength seeds, respectively. However, the TCPwas 18% less for high strength I-125 seeds than for low strength seeds. Asimilar advantaged5% higher TCP for low strength over highstrengthdwas seen for Pd-103. These TCP differences arose from the

greater conformality of dose to the PTV when using a larger number oflow strength seeds rather than the converse. The harmonic mean dose ofan implant is more sensitive to areas of low dose and correlates betterwith TCP than the arithmetic mean or geometric mean dose.Conclusions: The prescribed dose is a poor indicator of the nature ofa prostate implant. Likewise, the D90 value is inadequate as a singleparameter to describe implant quality. Assuming random microscopicspread of disease throughout the PTV, TCP depends critically on theshape of the DVH curve at values less than D90. Harmonic mean doses orD99 values would be a valuable adjunct to implant quality reporting.

BREAST

Thursday May 11, 2006

4:00 PM–5:20 PM

OR-28 Presentation Time: 4:00 PM

Persistent seroma after intraoperative placement of MammoSite for

APBI: Incidence, pathological anatomy, and contributing factors

Suzanne B Evans, M.D., M.P.H.,1 Seth A Kaufman, M.D.,1 Lori Lyn Price,

M.S.,2 Gene A Cardarelli, M.S., M.P.H.,3 Thomas Dipetrillo, M.D.,1,3

David E Wazer, M.D.1,2 1Radiation Oncology, Tufts-New England Medical

Center, Boston, MA; 2Biostatitics Research Center, Tufs-New England

Medical Center, Boston, MA; 3Radiation Oncology, Rhode Island

Hospital, Brown University, Providence, RI.

Purpose: To investigate the incidence of and factors associated with seromaformation after intra-operative placement of the MammoSite� catheter foraccelerated partial breast irradiation (APBI).Methods and Materials: The study evaluated 38 patients who had intra-operative MammoSite� catheter placement at the time of lumpectomy orre-excision followed by APBI with 34 Gy in 10 fractions. Data werecollected regarding dosimetric parameters including V100, V150, V200,DHI, and maximum dose at the surface of the applicator. Clinical andtreatment-related factors were analyzed including patient age, weight,history of diabetes and smoking, use of re-excision, elapsed time betweensurgery and radiotherapy, total duration of catheter placement, totalexcised specimen volume, and the presence or absence of post-proceduralinfection. Seroma was verified by clinical exam, mammogram, and/orultrasonography. Persistent seroma was defined as seroma that wasclinically detectable more than 6 months after completion of radiotherapy.Results: After a median followup of 17 months, the overall rate of anydetectable seroma was 76.3%. Persistent seroma (O6 months) occurred in68.4% of cases of which 46% experienced at least modest discomfort atsome point during followup. Of these symptomatic patients, 3 requiredbiopsy or complete cavity excision, revealing squamous metaplasia,foreign body giant cell reaction, fibroblasts, and active collagendeposition. Of the analyzed dosimetric, clinical, and treatment-relatedvariables, only body weight was associated with persistent seromaformation (p 5 0.04). Post-procedural infection was significantly(p 5 0.05) associated with a reduced risk of seroma formation. Seromawas associated with sub-optimal cosmetic outcome as excellent scoreswere achieved in 61.5% with seroma as compared to 83% without seroma(p 5 0.03).Conclusions: Intra-operative placement of the MammoSite� catheter forAPBI is associated with a high rate of clinically detectable seroma thatadversely affects cosmetic outcome. Seroma risk is positively associatedwith body weight and negatively associated with post-procedural infection.

OR-29 Presentation Time: 4:10 PM

Interstitial high-dose-rate (HDR) brachytherapy for early stage

breast cancer

Rufus J Mark, M.D.,1,2 Paul J Anderson, M.D.,1 Thomas R Neumann,

M.D.,1,2 Murali Nair, Ph.D.,1 Scott Akins, M.D.1,2 1Radiation Oncology,

Joe Arrington Cancer Center, Lubbock, TX; 2Radiation Oncology, Texas

Tech University Medical Center, Lubbock, TX.

Purpose: External beam radiation therapy (EBRT) has been the standard ofcare for breast conservation radiation therapy. Recent data indicates thatInterstitial Implant and High-dose-rate (HDR) radiation afterloading

87Abstracts / Brachytherapy 5 (2006) 78–117