Iridium-192 Brachytherapy Research Articles

Radiochromic film dosimetry of HDR 192Ir source radiation fields

A radiochromic film based dosimetry system for high dose rate (HDR) Iridium-192 brachytherapy source was described. A comparison between calibration curves established in water and Solid Water™ was provided. Pieces of EBT-2 model GAFCHROMIC™ film were irradiated in both water and Solid Water™ with HDR (192)Ir brachytherapy source in a dose range from 0 to 50 Gy. Responses of EBT-2 GAFCHROMIC™ film were compared for irradiations in water and Solid Water™ by scaling the dose between media through Monte Carlo calculated conversion factor for both setups. To decrease uncertainty in dose delivery due to positioning of the film piece with respect to the radiation source, traceable calibration irradiations were performed in a parallel-opposed beam setup. The EBT-2 GAFCHROMIC™ film based dosimetry system described in this work can provide an overall one-sigma dose uncertainty of 4.12% for doses above 1 Gy. The ratio of dose delivered to the sensitive layer of the film in water to the dose delivered to the sensitive layer of the film in Solid Water™ was calculated using Monte Carlo simulations to be 0.9941 ± 0.0007. A radiochromic film based dosimetry system using only the green color channel of a flatbed document scanner showed superior precision if used alone in a dose range that extends up to 50 Gy, which greatly decreases the complexity of work. In addition, Solid Water™ material was shown to be a viable alternative to water in performing radiochromic film based dosimetry with HDR (192)Ir brachytherapy sources.

Comparison of high–dose rate prostate brachytherapy dose distributions with iridium-192, ytterbium-169, and thulium-170 sources

Purpose Recent studies have identified that among different available radionuclides, the dose characteristics and shielding properties of ytterbium-169 ( 169Yb) and thulium-170 ( 170Tm) may suit high–dose rate (HDR) brachytherapy needs. The purpose of this work was to compare clinically optimized dose distributions using proposed 169Yb and 170Tm HDR sources with the clinical dose distribution from a standard microSelectron V2 HDR iridium-192 ( 192Ir) brachytherapy source (Nucletron B.V., Veenendaal, The Netherlands). Methods and materials CT-based treatment plans of 10 patients having prostate volumes ranging from 17 to 92 cm 3 were studied retrospectively. Clinical treatment of these patients involved 16 catheters and a microSelectron V2 HDR 192Ir source. All dose plans were generated with inverse planning simulated annealing optimization algorithm. Dose objectives used for the 192Ir radionuclide source were used for the other two radionuclides. The dose objective parameters were adjusted to obtain the same clinical target (prostate) volume coverage as the original 192Ir radionuclide plan. A complete set of dosimetric indices was used to compare the plans from different radionuclides. A pairwise statistical analysis was also performed. Results and conclusions All the dose distributions optimized with specific 192Ir, 169Yb, and 170Tm sources satisfied the standard clinical criteria for HDR prostate implants, such as those for the Radiation Therapy Oncology Group clinical trial 0321, for combined HDR and external beam treatment for prostate adenocarcinoma. For equivalent clinical target volume dose coverage, the specific 169Yb and 170Tm sources resulted in a statistically significant dose reduction to organs at risk compared with microSelectron V2 HDR 192Ir source. This study indicates that a 170Tm or 169Yb radionuclide source may be an alternative to the 192Ir radionuclide sources in HDR brachytherapy.

Electronic brachytherapy as adjuvant therapy for early stage breast cancer: a retrospective analysis

Purpose:This multicenter, retrospective study evaluated treatment and clinical outcomes of patients with early stage breast cancer who received adjuvant high-dose rate (HDR) electronic brachytherapy (EBT) treatment post-lumpectomy using the Axxent® EBT system. Dosimetric data from the EBT treatment plans were compared with those based on iridium-192 HDR brachytherapy.Material and methods:Medical records of 63 patients with early stage breast cancer (Tis, T1a, T1b, T1c, and T2) who were treated post-lumpectomy with EBT alone or in combination with external beam radiation therapy were reviewed. The prescribed EBT dose was 34 Gy (10 fractions over 5 days, 3.4 Gy each) to 1 cm from the balloon surface. Dosimetry data from 12 patients were compared with these of treatment plans using an iridium-192 source prepared for the same 12 patients.Results:The majority of patients (90.5%) were older than 50 years and had one or more risk factors for breast cancer (80.6%). Tumor sizes were 0.1 cm to 3.5 cm (mean 1.3 cm). Median follow-up was 7 months (1 to 18 months) post-EBT. Balloon applicators were implanted 0 to 85 days (mean 13.4 days) post-lumpectomy/re-excision. The most common adverse events were erythema, rash dermatitis, and pain or breast tenderness. No recurrences were reported. Dosimetric analyses demonstrated comparable target coverage, increased high-dose regions, and a significantly reduced dose to the ipsilateral breast and lungs as well as the heart with EBT as compared with the iridium-192 treatment plans.Conclusion:This retrospective, multicenter study showed that postsurgical adjuvant radiation therapy for early stage breast cancer can be administered using the EBT system with similar toxicity outcomes to those reported with iridium-192 brachytherapy. EBT offers a convenient, portable, nonisotope alternative to HDR brachytherapy using iridium-192.

SU‐FF‐T‐50: Clinical Implementation of New Endometrial Cylinder Applicator for Electronic Brachytherapy

Introduction: Cylindrical applicators for vaginal cuff irradiation are now commercially available for use with a 50 kV electronic brachytherapy (EB) source and are similar in size and shape to cylinders that have been long employed with iridium‐192 brachytherapy (IB). Although the insertion of the new applicator is relatively the same, the implementation from simulation to treatment can be quite different than conventional IB. This study describes the clinical implementation process of the first ever treatment of a patient using this applicator. Methods: The EB endometrial cylinder applicator (Axxent Vaginal Applicator) was supplied and manufactured by Xoft Inc., Sunnyvale, CA. Prior to treatment, a detailed analysis was performed to verify the position of dwell positions, dose distribution verification using gafchromic film and applicator geometry measurements to verify length and diameter. Finally, treatment plans were generated using PLATO software (Nucletron Corp., Columbia, MD) on CT scan data and verified using TLD data. Results: The results of the dwell position verification show that the dummy seed insert agree with the gafchromic film measurements. The distance from dwell position 1 and the surface of the apex of the applicator vary with cylinder size. The dose distribution can be verified at the point of prescription. Discussion: The results of this study show that the EB endometrial cylinder applicator can and has been implemented safely. It should be noted that this applicator has some differences from the traditional IB applicators and need to be accounted for.

Outcomes of high dose rate interstitial boost brachytherapy after external beam radiation therapy in head and neck cancer—An Indian (single institutional) learning experience

PurposeThis study is to assess efficacy and toxicity associated with external beam radiation therapy (EBRT) and high dose rate (HDR) interstitial Iridium-192 (192Ir) brachytherapy for the treatment of squamous carcinoma of the oropharynx and oral cavity. Methods and materialsBetween July 2004 and June 2006, 33 patients with oropharynx and oral cavity carcinomas were treated with 192Ir interstitial implants after EBRT at Medical College Hospital, Kolkata. Fifteen patients had early stage disease (Stage I and II) and 18 had advanced stage disease (Stage III and IV). All received EBRT to a median dose of 50Gy (range, 46–66Gy) to the primary tumor and regional lymph nodes before brachytherapy. Node-positive patients with residual neck disease also underwent neck dissection. Brachytherapy dose (HDR) in combination with EBRT varied from 14 to 21Gy, 3–3.5Gy per fraction, two fractions daily. Locoregional control, freedom from disease, and complications were assessed. ResultsFollowup duration was between 18 and 40 months. At the end of treatment with radiation, 79% achieved complete response (CR) (p<0.009), 21% achieved partial response (PR) and the ultimate control rate (including surgical salvage) was 100% and 78% for early and advanced disease, respectively (p<0.108). Three (9%) patients failed locally after CR. No distant metastasis was seen during followup. Grade 3 mucositis was seen in 12% cases. Transient hemorrhage occurred in 3 (9%) patients and local infection in 1 (3%) patient. Severe dysphagia was seen in 1 (3%) patient. 5/33 (15%) patients experienced xerostomia (Grade 3–4), but almost all patients had Grade 1–2 xerostomia. ConclusionOropharyngeal and oral cavity tumors can be effectively treated with 192Ir implant boost after EBRT. Local control is excellent and complication rates are acceptable.

A Contura™ catheter provides dosimetric advantages over a MammoSite™ catheter for accelerated partial breast irradiation.

Abstract Abstract #5141 Purpose/Objective(s): With the new ConturaTM Multi-Lumen Balloon (MLB) catheter (SenoRx, Inc, Aliso Viejo, CA), one may achieve 2 dosimetric advantages over a MammoSiteTM catheter: 1) avoidance of a radiation “hot spot” in the skin which may improve cosmetic results, and 2) reduction of the size of an air/fluid pocket in the planning target volume for plan evaluation (PTV_EVAL) which may improve local control by increasing the radiation dose delivered to breast tissue at risk. The purpose of this study was to analyze the frequency with which a Contura catheter can satisfy the above 2 dosimetric goals relative to a MammoSite catheter.&amp;#x2028; Materials/Methods: From October 2007 to June 2008, 23 patients between the ages of 43 and 88 years (median, 57 years) with unifocal AJCC pathological T0, T1, or T2 (maximum, 3.0 cm; median, 1.0 cm), N0 ductal, papillary, or tubular carcinomas of the breast at least 1 mm from the inked edge of the lumpectomy specimen were treated with high-dose-rate iridium-192 brachytherapy using a Contura MLB catheter. Sixty-five percent of the cancers were estrogen-receptor positive. Brachytherapy was delivered to a total dose of 34 Gy in 10 fractions bid over 5-7 days. We prescribed the dose to a depth of 1.0 cm from the balloon surface. The Contura applicator allows one to load up to 5 source lumens: 4 lumens that are offset 0.5 cm circumferentially from a central lumen. The ability to choose from multiple lumens allows for greater control over where radiotherapy is delivered. The Contura catheter also has a sixth lumen through which air/fluid can be removed from around the balloon. This feature helps to improve tissue-balloon conformance. The minimum balloon-to-skin distance was 0.5 cm. In 39% of patients, the balloon-to-skin distance was 0.5-0.9 cm. The balloon volume was 30-55 cc, V150 was ≤ 33 cc, and V200 was ≤ 10 cc. Hypothetical MammoSite treatment plans were created using a CT scan of the breast prior to air/fluid removal. Only the central lumen was loaded for the hypothetical MammoSite plan. The 2 treatment planning goals were to keep the: 1) maximum skin dose ≤ 100% of the prescribed dose, and 2) volume of air/fluid around the balloon ≤ 3.0% of PTV_EVAL. A one-sided McNemar test was used to compare the % of Contura plans that satisfied both goals vs the % of MammoSite plans that satisfied both goals.&amp;#x2028; Results: The maximum skin dose was 100% of the prescribed dose with the Contura catheter vs 145% of the prescribed dose with a MammoSite catheter. The volume of air/fluid around the balloon was 4.4% ± 1.0% (mean ± standard error) of PTV_EVAL prior to suctioning vs 1.2% ± 0.3% after suctioning. Ninety-one percent of Contura plans satisfied both treatment planning goals vs only 48% of MammoSite plans (p=0.08).&amp;#x2028; Conclusion: A Contura applicator resulted in a trend towards dosimetric improvement over a MammoSite catheter. Patients will be followed long-term in order to determine their local control, disease-free survival, cosmetic results, and treatment-related toxicities. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5141.

CT-Guided Interstitial Brachytherapy of Primary and Secondary Lung Malignancies

CT-guided interstitial brachytherapy of primary lung malignancies and pulmonary metastases represents a novel interventional technique, combining conventional high-dose-rate (HDR) iridium-192 (192Ir) brachytherapy with modern CT guidance for applicator positioning and computer-aided 3-D radiation treatment planning. The purpose of this study was to assess safety and efficacy of this technique. 30 patients with 83 primary or secondary lung malignancies were recruited in a prospective nonrandomized trial (Table 1). After catheter positioning under CT fluoroscopy, a spiral CT was acquired for treatment planning (Figure 1). All but two patients received a defined single dose (coverage > 99%) of at least 20 Gy from a 192Ir source in HDR technique. Adverse effects were nausea (n = 3, 6%), minor (n = 6, 12%) and one major pneumothorax (2%). Post intervention, no changes of vital capacity and forced expiratory volume could be detected. The median follow-up period was 9 months (1–21 months) with a local tumor control of 91% at 12 months (Figure 2). CT-guided interstitial brachytherapy proved to be safe and effective for the treatment of primary and secondary lung malignancies.

Clinical results of conformal high-dose-rate Iridium-192 brachytherapy combined with external beam radiotherapy for localized high-risk prostate cancer

Clinical results of conformal high-dose-rate Iridium-192 brachytherapy combined with external beam radiotherapy for localized high-risk prostate cancer

M1229 Comparative Outcomes for Biliary Papillomatosis Treated with Intraluminal Iridium-192 Brachytherapy Combined with External Radiotherapy and Conservative Treatment

M1229 Comparative Outcomes for Biliary Papillomatosis Treated with Intraluminal Iridium-192 Brachytherapy Combined with External Radiotherapy and Conservative Treatment

Angiosarcoma of the Eyelid and Periorbital Region. Experience in Leiden with Iridium192 Brachytherapy and Low-Dose Doxorubicin Chemotherapy

Aim: To report on the use of iridium192 brachytherapy and doxorubicin chemotherapy as adjuvant therapy in 6 patients with angiosarcoma of the eyelid and periorbital region. Material and Methods: Tumor localization and diameter, signs of inflammation, histology and treatment are discussed in this retrospective study of 6 patients (age 46–87 yrs.) presenting with primary angiosarcoma in the eyelid. Results: Six patients (4 elderly) with angiosarcoma localized in one or more eyelids, the face or multilocular were seen between 1987 and 2000. In one patient, a small nodular tumor did not recur within 4 years after radical excision. In another patient, the tumor was treated with surgery and iridium192 wire brachytherapy and did not recur in 17 years of follow-up. In four patients with large diffuse tumors that were treated with doxorubicin, partial regression was achieved. The follow-up was >3 years (median 5 years). Conclusion: If radical surgery for angiosarcoma of the eyelid and periorbital region is not possible, adjuvant iridium192 wire brachytherapy may prove beneficial. For widespread, diffusely growing tumors, and in elderly patients, low-dose (slowly, 20 mg i.v.) doxorubicin can be used weekly as adjuvant therapy, resulting in partial regression and longer survival rates than previously published by other authors.

Is the Treatment of Keloid Scars Still a Challenge in 2006?

Several options are described to treat keloid scars, none of them being 100% successful. Radiotherapy is suggested to have the most significant effect on recurrence rate. The aim of the study is to confirm the effectiveness of iridium brachytherapy combined with surgery and to evaluate patient satisfaction. We retrospectively enrolled 24 patients with 30 keloids, treated by surgical excision and iridium 192 high-dose-rate (HDR) brachytherapy. We observed a significant difference in scar thickness before and after the treatment (P < 0.001). With regard to patient satisfaction and complaints, 79.1% of them had no pain and irritation after treatment, 79.2% of patients would recommend this treatment to other patients, and 87.5% would undergo this treatment again if necessary. Our results confirm the effectiveness of surgical keloid excision followed by HDR brachytherapy in primary treatment or if other alternative methods have failed.

High Dose Rate Iridium-192 Brachytherapy as a Component of Radical Radiotherapy for the Treatment of Localised Prostate Cancer

Aims To assess the treatment outcomes and toxicity of conformal high dose rate (HDR) brachytherapy boost as a means of radiation dose escalation in patients with localised prostate cancer. Materials and methods Between December 1998 and July 2004, 65 consecutive patients with localised prostate cancer (magnetic resonance imaging-staged T1–3 N0 M0) were treated with external beam radiation therapy (EBRT) followed by two fractions of HDR iridium-192 brachytherapy. The patients selected this treatment modality in preference to entering an ongoing randomised phase 3 trial. Any pre-treatment serum prostate-specific antigen (PSA) and Gleason score were included. The primary end point was biochemical disease-free progression. Late treatment-related morbidity was graded according to the Radiation Therapy Oncology Group and the European Organization for Research and Treatment of Cancer criteria. Results The median patient age was 67.3 years (range 47.9–80). Sixty patients (92.3%) had intermediate- to high-risk disease defined by clinical stage, presenting PSA and Gleason score/World Health Organisation (WHO) grade. With a median follow-up of 3.5 years (range 0.6–5.8), two patients had died of metastatic disease and another four patients had PSA relapse, giving a 3-year actuarial biochemical disease-free progression of 90.8%. Three patients (4.6%) had acute grade 3 genitourinary toxicity, in the form of urinary retention. Late grade 3 and 4 genitourinary toxicities occurred in four patients (6.2%) and one patient (1.5%), respectively. No late gastrointestinal toxicities were observed. Conclusions These results suggest that the combined modality of conformal HDR brachytherapy and EBRT is a feasible treatment modality with acceptable acute and late toxicities, comparable with those of EBRT alone. It offers an attractive conformal treatment modality with the potential of further dose escalation in the treatment of localised prostate cancer.

Accelerated partial breast irradiation using interstitial high dose rate 192iridium brachytherapy: Early Australian experience and review of the literature

Summary Accelerated partial breast irradiation (APBI) is an evolving new technique of adjuvant irradiation in selected women with early-stage breast cancer. We developed a pilot programme of APBI in 2000 and report end results in seven patients followed for a mean of 42.7 months (range 29-55 months). Good to excellent cosmesis and no loco-regional relapse or systemic metastases have occurred. The literature related to APBI is reviewed.

Three‐year results of treatment for prostate cancer with low‐dose rate temporary iridium‐192 brachytherapy

To report the 3-year treatment results of definitive irradiation by using a temporary interstitial implant with low-dose rate iridium-192 with or without external beam radiotherapy in the treatment of localized prostate cancer. One-hundred and forty-three patients with pathologically defined prostate carcinoma were treated from December 1997 to April 2003. The patients were classified into a low-risk group (T2, PSA<or=20 ng/mL and Gleason score<or=6) or a high-risk group (T3, PSA>20 ng/mL or Gleason score>or=7). Low-risk patients were treated with low-dose-rate iridium brachytherapy as monotherapy delivering 70 Gy. High-risk patients were treated with the combination of brachytherapy and external beam radiotherapy delivering 40 Gy and 36 Gy, respectively. Kaplan-Meier estimates of prostate-specific antigen (PSA) progression-free survival rate were analysed. To assess the treatment quality in different periods, PSA progression-free survival rates in late era (year of 2000 and after) and in early era (before 2000) were compared. Morbidity was graded according to the Radiation Therapy Oncology Group grading scale. One hundred and nineteen patients were analysed, of which 86 patients underwent monotherapy with an iridium implant, and 33 were treated with the combination of external beam radiotherapy. Twenty-four patients were excluded from the analysis because the classification of risk group did not suit the criteria. The total (n=119) PSA progression-free survival rate at 3 years was 80.3%. The PSA progression-free survival rate at 3 years for the monotherapy group (n=86) and the combination therapy group (n=33) were 78.2% and 86.9%, respectively. There were 23 patients who were followed for more than 36 to 63 months, and, during this period, only 1 patient who received the monotherapy was diagnosed as PSA failure at 50 months. The 3-year PSA progression-free survival rate of monotherapy in late era was significantly higher than that in early era; however, no significant difference was seen in the combination treatment. Morbidity for the combination treatment was low; however, for the monotherapy, three patients developed severe rectal ulcers, and colostomies were made. The PSA progression-free survival rate after low-dose rate iridium-192 brachytherapy with or without external beam radiotherapy can be satisfactory and longer follow up is necessary to compare the efficacy of other treatments.

Salvage treatment for inoperable neck nodes in head and neck cancer using combined iridium-192 brachytherapy and surgical reconstruction.

The results of debulking surgery and re-irradiation with radioactive implants (brachytherapy) are reported for 39 patients with inoperable metastatic neck nodes from primary head and neck cancers. For 13 patients conventional salvage by partial debulking surgery and brachytherapy proved effective, with 68 per cent control at 1 year, but six patients suffered severe radiation fibrosis, necrosis and contractures. Some 26 patients were treated by combined tumour debulking, skin resurfacing and brachytherapy implant. Initial tumour control and freedom from serious toxicity was achieved in 24 patients. Local control was achieved in 63 per cent of patients at 1 year, with a serious morbidity rate of 12 per cent.

Dose-volume impact in high-dose-rate Iridium-192 brachytherapy as a boost to external beam radiotherapy for localized prostate cancer- a phase II study

Background and purpose Evaluation of dose-volume–time-related factors in 64 patients treated with high-dose-rate brachytherapy (HDR-BT) as a boost to external beam radiotherapy (EBRT) for localized prostate cancer. Patients and methods Clinical parameters were correlated with morbidity scores of the EPIC (Expanded Prostate Cancer Index) questionnaire. Median time after radiotherapy (HDR-BT up to 18 Gy in two fractions and EBRT up to a median dose of 50.4 Gy) was 1.5 and 3 years (first and second questionnaire). Results A significant impact of a urethra D1 exceeding 15 Gy in at least one HDR fraction concerning urinary morbidity and a rectum D1 exceeding 6 Gy to the rectal mucosa in the first and second HDR fraction concerning the rectal bleeding rate was found. A higher number of needles was associated with lower urinary and bowel scores after 1.5 years. A prostate length >4.8 cm and a longer duration of EBRT (independently of the dose) predisposed for lower urinary and bowel scores. In contrast to a urethra D1>15 Gy as an independent factor, a rectum D1>6 Gy per HDR fraction correlated with a higher number of needles and an increased prostate length. Conclusions To minimize morbidity in HDR-BT for prostate cancer, a maximum dose to the urethra of 15 Gy and a maximum dose to the rectal mucosa of 6 Gy is advisable. Treatment- and patient-related factors have a major impact on toxicity.

Results of high-dose rate iridium-192 brachytherapy boost to external beam radiation therapy for prostate cancer in Japanese men

4776 Background: Afterloading brachytherapy is the sole modality of interstitial radiotherapy currently available in Japan for treating prostate cancer. This technique has several advantages over permanent seed implantation, including absence of radiation protection and safety issues for patient. Also dosimetry can be based on images with the needles in situ, making it easy to optimize the dose. Currently several clinical trials reported that HDR brachytherapy is also appropriate for high risk (unfavorable) prostate cancer. To aim of this study is to evaluate treatment outcome of HDR brachytherapy and EBRT combined with or without neoadjuvant/adjuvant androgen ablation for patients with prostate cancer. Methods: From June 1999 to April 2003, 108 patients with clinically localized or locally extensive prostate carcinoma (T1N0M0-T3N0M0) were treated with HDR iridium-192 brachytherapy followed by 30 Gy EBRT. The whole prostate and any tumor extension beyond the capsule were irradiated five times over 3 days using an HDR Ir-192 source with a nominal activity of 370 GBq and each single dose was 7.5 Gy. Three days after HDR fraction, 3D conformal radiation was given using a fractionation of five times 3.0 Gy per week, specified at the isocenter, for 2 weeks. After June 2000, patients in the high risk group were given 6 months’ of neoadjuvant endocrine therapy followed by 36 months’ of adjuvant endocrine therapy following radiation therapy. The recommendations of the consensus panel of the ASTRO were followed for assessing biochemical failure. Results: The median age of the 108 patients was 70.5 years (range 50–84 years). Low risk patient was found in 20, intermediate risk in 30 and high risk in 58 patients, with a median follow-up was 31.5 months (range: 12–58months). The overall actuarial biochemical control rate (bNED) was 81.5%. The bNED in 36 months for low risk, intermediate risk, and high risk patient was 95.0%, 77.4% and 74.7%, respectively. Conclusions: HDR brachytherapy and EBRT combined with or without neoadjuvant/adjuvant androgen ablation is an effective treatment modality for prostate cancer and encouraging biochemical control rates after a median follow-up of 31.5 months. No significant financial relationships to disclose.

Early clinical experience on inverse planned high dose rate interstitial brachytherapy in the treatment of locally advanced cervical cancer

To report treatment outcomes of cervical cancer patients treated with external beam radiotherapy (EBRT) and inverse planned high dose rate (HDR) interstitial implants. Thirty-four patients with newly-diagnosed cervical cancer treated with inverse planned interstitial HDR brachytherapy between March 2001 and July 2003 were retrospectively reviewed. During this period, patients with locally advanced tumor extending beyond coverage of the intracavitary brachytherapy system and early stage disease with unfavorable anatomy were treated with interstitial HDR brachytherapy boost. Twenty-nine patients who were medically fit for chemoradiation were treated with a cisplatin-based regimen. Patients generally received 45 Gy to the whole pelvis and some received 50 Gy to the true pelvis. The median EBRT dose was 48 Gy (range 29–54 Gy). Brachytherapy was initiated during or shortly after the completion of EBRT. All implants were performed using a freehand transrectal ultrasound guided interstitial implant technique. All patients underwent CT based treatment planning and dwell time optimization using inverse planning simulated annealing (IPSA). HDR Iridium-192 brachytherapy was given in 2–5 fractions delivered in doses of 6.0 to 9.5 Gy per fraction using 1–2 implants, with an interfraction interval of at least 6 hours. The median overall treatment time was 47 days (range 31–112 days). Total radiation doses (TRDs) combining EBRT and HDR doses were calculated using biologically equivalent doses with a/b of 10 to convert to 1.8 Gy fractionation. The median TRD was 82 Gy (range 53–93 Gy). The local control rates (LC), rates of regional failure (RF) and distant metastases (DM), and disease-specific (DSS) and overall survival (OS) probabilities were calculated using the Kaplan-Meier method. Univariate analyses were performed using the log rank test to evaluate patient, tumor and treatment related factors. Multivariate analyses were performed using Cox proportional hazard model to identify independent predictors of outcome. The median follow up time was 14 months. The median age was 51 years old. AJCC Stage distribution was: Stage I (3), Stage II (5), Stage III (14), Stage IV (12). Eleven patients had N1 and 6 had M1 disease. The 2-year LC was 71%. The 2-year RF and DM were 12% and 18%, respectively. The 2-year DSS and OS were 77% and 61%, respectively. Multivariate analyses showed that age was a prognostic factor for local recurrence (p = 0.04). Chemotherapy (no vs. yes) and TRD (<85 vs. ≥ 85 Gy) were prognostic for overall survival (p = 0.02 and 0.04 respectively). For patients with TRDs ≥ 85 Gy, 1 out of 10 patients failed locally, whereas, 6 out of 24 patients who received < 85 Gy had local failures (p = 0.11). The only patient who failed after receiving ≥ 85 Gy completed her treatment over 112 days. There were two cases (6%) of grade 3 or 4 acute toxicities. One patient developed deep vein thrombosis and another patient developed a uterine abscess. One patient developed a fistula in the setting of local recurrence. No other grade 3 or 4 late toxicities have occurred. Analysis of the dose-volume histograms showed that the median target volume (TV) was 157 cc. With each fraction of HDR brachytherapy, the median % of TV receiving 90% of the prescribed dose (PD) was 95%. The median % of TV receiving 100% of the PD was 88%. The median % of TV receiving 150% of the PD was 43%. The median doses to 2 and 5 cc of the bladder were 6.2 and 5.4 Gy, respectively. The median doses to 2 and 5 cc of the rectum were 6.0 and 5.4 Gy, respectively. The median doses to 2 and 5 cc of the bowel were 4.8 and 4.4 Gy, respectively. The median dose to 0.1 cc of the urethra was 4.4 Gy. Interstitial HDR brachytherapy using a freehand technique and inverse planning is well tolerated with minimal acute and late complications. Although there was not a statistically significant difference for local failure, we recommend delivering combined EBRT and HDR doses of at least 85 Gy in 1.8 Gy fractionation for locally advanced cervical cancer

MammoSite and interstitial brachytherapy for accelerated partial breast irradiation: factors that affect toxicity and cosmesis.

In interstitial brachytherapy (IB), cosmesis and toxicity correlate with volume of tissue irradiated, dose homogeneity index (DHI), and adjuvant doxorubicin/cyclophosphamide based chemotherapy (ACCT). MammoSite brachytherapy (MSB) irradiates smaller volumes than IB, and lower dose homogeneity does not appear to affect toxicity. However, clinical experience suggests that other factors may also play an important role in cosmesis and toxicity with MSB. We reviewed our prospectively maintained data base of women who underwent accelerated partial breast irradiation (APBI) to assess this issue. Beginning in September 1995, 115 women were enrolled in a trial evaluating APBI as monotherapy after lumpectomy. The first 75 eligible patients received IB, and the most recent 28 eligible patients received MSB. All patients received 34 gray (Gy) in 10 twice-daily fractions through high-dose rate iridium-192 brachytherapy; 19% of patients in the IB group and 0% of patients in the MSB group received ACCT. At 1 year after treatment, MSB caused significantly less Grade 2-4 subcutaneous fibrosis (as graded by a radiation oncologist according to the Radiation Therapy Oncology Group/Eastern Cooperative Oncology Group system) compared with IB (10.7% vs. 32%; P = 0.04). However, when only ACCT-naïve patients in the IB group were compared with patients in the MSB group, this finding became nonsignificant. Among the patients who received MSB, significantly smaller volumes were irradiated, and the DHI was lower. Current studies suggest an improved toxicity profile with MSB compared with IB that is attributed to lower irradiated volumes with MSB. When only chemotherapy-naïve patients were compared, however, toxicity and cosmesis were found to be similar between MSB and IB, suggesting a more complex interplay between irradiated volumes, DHI, and chemotherapy. The relation of ACCT to toxicity in this scenario is intriguing and warrants further investigation.

Development of multi-channel radiofrequency (RF) interstitial hyperthermia system compatible with high-dose rate iridium-192 brachytherapy

9694 Background: We have developed a multi-channel RF interstitial hyperthermia system compatible with the high-dose rate Iridium-192 remote after loading system (Ir-192 RALS). The purpose of this presentation is to evaluate the heating characteristics of the system. Methods: The system is composed of eight channel RF signal generators, which can be controlled individually. Each RF generator consists of two types of electrodes: 1) an internal electrode made of stainless steel, which is originally an Ir-192 RALS applicator; and 2) a shared rectangular external electrode made of copper plate. For the computer simulation, we used simulation software (e-m CAD system, MAFIA ver. 3.20, CST, Germany) to calculate RF field distribution, magnetic field distribution and the specific absorption rate (SAR) distribution, in an arrangement using 4 needles inserted in a square-like formation, 2cm in distance from one another. For the experiments using the agar phantom, we generated a 5W 13.56 MHz RF signal for 5 minutes for 4 electrodes in the same square fashion. Results: The results from the computer simulation showed that SAR distribution outside each electrode was elevated, but the area inside the 4 electrodes did not show temperature elevation. The results from the experiments using the agar phantom showed a temperature increase in the center of the area surrounded by the 4 electrodes. Conclusions: Using an independently controlled RF signal, the results from the experiments with the agar phantom showed satisfactory temperature rise. The RF interstitial system we developed can provide greater heating volume compared to using a single internal electrode or multiple electrodes with a single generator. In addition, our system is compatible with the Ir-192 RALS, allowing for less-invasive interstitial hyperthermoradiotherapy by eliminating the trauma of needle re-insertion. No significant financial relationships to disclose.