Monte Carlo simulation of the effect of magnetic fields on brachytherapy dose distributions in lung tissue material

The aim of this work was to use TOPAS Monte Carlo simulations to model the effect of magnetic fields on dose distributions in brachytherapy lung treatments, under ideal and clinical conditions. Idealistic studies were modeled consisting of either a monoenergetic electron source of 432 keV, or a polyenergetic electron source using the spectrum of secondary electrons produced by ¹⁹²Ir gamma-ray irradiation. The electron source was positioned in the center of a homogeneous, lung tissue phantom (ρ = 0.26 g/cm³). Conversely, the clinical study was simulated using the VariSource VS2000 ¹⁹²Ir source in a patient with a lung tumor. Three contoured volumes were considered: the tumor, the planning tumor volume (PTV), and the lung. In all studies, dose distributions were calculated in the presence or absence of a constant magnetic field of 3T. Also, TG-43 parameters were calculated for the VariSource and compared with published data from EGS-brachy (EGSnrc) and PENELOPE. The magnetic field affected the dose distributions in the idealistic studies. For the monoenergetic and poly-energetic studies, the radial distance of the 10% iso-dose line was reduced in the presence of the magnetic field by 64.9% and 24.6%, respectively. For the clinical study, the magnetic field caused differences of 10% on average in the patient dose distributions. Nevertheless, differences in dose-volume histograms were below 2%. Finally, for TG-43 parameters, the dose-rate constant from TOPAS differed by 0.09% ± 0.33% and 0.18% ± 0.33% with respect to EGS-brachy and PENELOPE, respectively. The geometry and anisotropy functions differed within 1.2% ± 1.1%, and within 0.0% ± 0.3%, respectively. The Lorentz forces inside a 3T magnetic resonance machine during ¹⁹²Ir brachytherapy treatment of the lung are not large enough to affect the tumor dose distributions significantly, as expected. Nevertheless, large local differences were found in the lung tissue. Applications of this effect are therefore limited by the fact that meaningful differences appeared only in regions containing air, which is not abundant inside the human.

Deployment and performance of model-based dose calculation algorithm in 192Ir shielded cylinder brachytherapy

PURPOSE

The purpose of the study was to integrate model-based dose calculation algorithm (MBDCA) and 3-D planning into our institutional capabilities for clinical cases with inherent heterogeneities, namely shielded cylinder cases, which were previously performed using templates.

METHODS AND MATERIALS

AcurosBV (Varian Medical Systems) was selected as MBDCA, and we compared results against the American Association of Physicists in Medicine working group (WG) reference Test Case #4, which contains a 36-mm-diameter 180-degree shielded cylinder. The last five clinically used template plans, as generated with ABACUS (Varian Medical Systems), were compared against MBDCA results. Clinical plans used 20-, 23-, and 26-mm-diameter cylinders, prescribed from 5 to 7 Gy, 50- to 110-mm active length, 7 to 21 dwell positions, with 5- or 10-mm spacing.

RESULTS

Compared with the WG reference plan, AcurosBV produced excellent agreement, within 1% at reference points. Larger deviations arose only within the applicator itself. Historical plans generated using ABACUS had higher point dose than AcurosBV by 3-4% or 2-3% using transport within medium at prescription points, with dose to medium or water, respectively.

CONCLUSIONS

To verify the accuracy of our MBDCA algorithm, we benchmarked against the WG data set available for shielded cylinders. We discovered a 3-4% difference in dose from our established historical templates, which is easily outweighed by daily positioning uncertainties. Dose distributions from MBDCA were used to assess and validate existing historical templates.

[Complications and effectiveness of treatment of patients with locally advanced prostate cancer after combined radiotherapy and radical prostatectomy with postoperative radiotherapy]

Treatment for prostate cancer remains a significant social problem due to the continuing trend of growth of morbidity and mortality in Russia from this disease. In recent years a real alternative to surgical treatment is radiotherapy. In treatment of locally advanced stages of prostate cancer radiotherapy plays a dominant role. At our institution from 2005 till 2011, 105 patients with locally advanced prostate cancer underwent complex and combined treatment comprising in the first group the concomitant radiotherapy with Ir-192 and the control group--radical prostatectomy followed by adjuvant remote radiotherapy. In patients treated with concomitant radiotherapy compared to the control group there were occurred fewer number of genitourinary complications according to the RTOG scale (5,8% vs. 32,7%). In patients who had undergone radical prostatectomy followed by adjuvant radiotherapy urinary incontinence was met significantly often.

Dose error from deviation of dwell time and source position for high dose-rate 192Ir in remote afterloading system

The influence of deviations in dwell times and source positions for (192)Ir HDR-RALS was investigated. The potential dose errors for various kinds of brachytherapy procedures were evaluated. The deviations of dwell time ΔT of a (192)Ir HDR source for the various dwell times were measured with a well-type ionization chamber. The deviations of source position ΔP were measured with two methods. One is to measure actual source position using a check ruler device. The other is to analyze peak distances from radiographic film irradiated with 20 mm gap between the dwell positions. The composite dose errors were calculated using Gaussian distribution with ΔT and ΔP as 1σ of the measurements. Dose errors depend on dwell time and distance from the point of interest to the dwell position. To evaluate the dose error in clinical practice, dwell times and point of interest distances were obtained from actual treatment plans involving cylinder, tandem-ovoid, tandem-ovoid with interstitial needles, multiple interstitial needles, and surface-mold applicators. The ΔT and ΔP were 32 ms (maximum for various dwell times) and 0.12 mm (ruler), 0.11 mm (radiographic film). The multiple interstitial needles represent the highest dose error of 2%, while the others represent less than approximately 1%. Potential dose error due to dwell time and source position deviation can depend on kinds of brachytherapy techniques. In all cases, the multiple interstitial needles is most susceptible.

Shielding effect of a customized intraoral mold including lead material in high-dose-rate 192-Ir brachytherapy for oral cavity cancer

A high-dose-rate (HDR) 192-Ir brachytherapy using a customized intraoral mold is effective for superficial oral cavity cancer, and the surrounding normal tissue is kept away from the radioactive source with gauze pads and/or mouth piece for reducing the dose on the normal tissues. In the Tokushima university hospital, the mold has a lead shield which utilizes the space prepared with sufficient border-molding by a specific dental technique using modeling compound. In HDR 192-Ir brachytherapy using a lead shielded customized intraoral mold, there are no reports measuring the absorbed dose. The purpose of the present study is to measure the absorbed dose and discuss the optimum thickness of lead in HDR 192-Ir brachytherapy using a customized intraoral mold with lead shield using a 1 cm thickness mimic mold. The thickness of lead in the mold could be changed by varying the arrangement of 0.1 cm thickness sheet of the acrylic resin plate and lead. The measured doses at the lateral surface of the mold with thermo-luminescence dosimeter were reduced to 1.12, 0.79, 0.57, 0.41, 0.31, 0.24 and 0.19 Gy and the ratios to the prescription dose were reduced to 56, 40, 29, 21, 16, 12 and 10 percent as lead thickness increased from 0 to 0.6 cm in 0.1 cm increments, respectively. A 0.3 cm thickness lead was considered to be required for a 1 cm thickness mold, and it was necessary to thicken the lead as much as possible with the constraint of limited space in the oral cavity, especially at the fornix vestibule.

Chronic total occlusion due to diffuse in‐stent restenosis: is brachytherapy the solution?

Percutaneous coronary intervention of chronic total occlusions (CTO) is associated with a significantly higher incidence of reocclusion and restenosis compared with non-total occlusions. Randomized and observational trials have demonstrated the effectiveness of intracoronary brachytherapy (ICBT) for the prevention of recurrent in-stent restenosis. However, limited data are available on the effectiveness of ICBT in patients with totally occluded in-stent restenosis. The authors assessed the long-term outcome of patients treated with intracoronary gamma radiation for totally occluded in-stent restenotic lesions. Percutaneous coronary intervention and subsequent catheter-based irradiation with iridium-192 was performed in 100 patients (103 vessels) with diffuse in-stent restenosis. At baseline, CTO of the target vessel at the site of the stent was present in 15 vessels (14.5%). Follow-up data were collected during follow-up visits and from telephone interviews. Repeat coronary angiography was performed in symptomatic patients with clinical restenosis. Clinical and angiographic characteristics were similar between the two groups, although there was a trend towards more unstable angina at the index procedure in CTO patients (66.7% versus 41.4%; p = 0.12) compared with patients without non-total occlusions. A higher percentage of patients (53.3%) with CTO required longer radiation sources (14 seeds, covering a length of 55 mm), compared with 23.9% of patients with non-total occlusion (p = 0.04). With a mean follow-up period of 47.5 +/- 24.0 months, major adverse cardiac events (MACE) were observed in 10 of 15 patients (66.7%) with CTO compared with 25 out of 88 patients (28.4%) without CTO (p = 0.009). According to multivariate analysis, total occlusion of the target vessel at baseline was the single independent predictor of MACE at one-year follow-up (relative risk 16.2, 95% confidence interval 4.2-62.9; p < 0.0001). This study shows that the use of gamma radiation for the prevention of recurrence of in-stent restenosis in patients with CTO does not seem to be as effective as in patients with non-total occlusions. Furthermore, CTO was an independent predictor of worse outcome at long-term follow-up in this study.

CT-guided interstitial HDR brachytherapy for recurrent glioblastoma multiforme. Long-term results

BACKGROUND AND PURPOSE

Recurrences of glioblastoma multiforme (GBM) within previously irradiated volumes pose a serious therapeutic challenge. This retrospective study evaluates the long-term tumor control of recurrent GBM treated with interstitial high-dose-rate brachytherapy (HDR-BRT).

PATIENTS AND METHODS

Between 1995 and 2003, 84 patients were treated for recurrent cerebral GBM located within previously irradiated volumes. All patients had received adjuvant external radiotherapy following primary surgery, with a focal dose up to 60 Gy. The median recurrent tumor volume was 51 cm(3) (3-207 cm(3)), and the HDR-BRT consisted of an afterloading (192)Ir implant which delivered a median dose of 40 Gy (30-50 Gy). Catheter implantation was implemented using interactive computed tomography (CT) guidance under local anesthesia and sedoanalgesia.

RESULTS

After a median follow-up of 61 months, 5/84 patients (6%) were alive. The median post-BRT survival was 37 weeks, and the median overall survival 78 weeks. Moderate to severe complications occurred in 5/84 cases (6%).

CONCLUSION

For patients with recurrences of GBM within previously irradiated volumes, CT-guided interstitial HDR-BRT is a feasible treatment option that can play an important role in providing palliation.

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 iridium(192) 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 iridium(192) 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 iridium(192) 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.

[Application of interstitial brachytherapy via parapharynx involvement transnasal approach to enhance dose in radiotherapy for nasopharyngeal carcinoma]

BACKGROUND & OBJECTIVE

Although intracavitary irradiation (ICI) is usually applied to enhance dose in radiotherapy for early stage nasopharyngeal carcinoma (NPC), its use in parapharyngeal enhancing dose is limited because of dislocation and poor repetition of conventional catheterization. This study was to evaluate the application of a new technique, interstitial brachytherapy via parapharynx involvement transnasal approach, to enhance dose in radiotherapy for NPC.

METHODS

Twenty-three naive and recurrent NPC patients with tumor residue of more than 1 cm under nasopharyngeal mucosa or restricted tumor residue in the parapharyngeal space received interstitial brachytherapy between Sep. 2005 and Aug. 2006 via parapharynx involvement transnasal approach under the guidance of sinus endoscopy. The 3-dimensional (3D) planning system was used to delineate target volume, optimize dose distribution, and perform interstitial brachytherapy after CT scan. The depths of catheters under mucosa on the moment of inserting and pulling out were measured. The efficacy and complications were assessed.

RESULTS

All catheters were intubated into tumors successfully; the veracity of catheter location was 100%. The submucosa depths of catheters were (9.59+/-2.72) mm when inserted and (9.43+/-2.30) mm when pulled out, without significant difference (t = 0.23,P > 0.05); the shift length was (0.75+/-0.75) mm. The patients were followed up from 3 to 15 months (median, 6 months), and no one dropt out. Three cases of irradiation-associated turbinate adhesion occurred and were cured after lysis; no infection, serious bleeding, palatal perforation, nasopharyngeal necrosis, and other serious complications occurred. All tumors disappeared in 3 months after treatment. No local recurrence and distant metastasis occurred.

CONCLUSIONS

The nasopharyngeal and parapharyngeal catheterization with sinus endoscopy guidance is accurate, steady, safe, and feasible. Interstitial brachytherapy is effective for tumor residue in the nasopharynx or parapharyngeal space of NPC patients after radiotherapy without serious complications.

Treatment results and prognostic factors for cervical cancer patients treated by radiochemotherapy with weekly cisplatin

OBJECTIVE

This retrospective trial aims to report the treatment results of patients with locally advanced cervical cancer treated by concomitant radiochemotherapy with weekly cisplatin.

METHODS

Between October 1999 and December 2003, 81 patients with FIGO Stages IB-IVA were treated at Ege University Faculty of Medicine Department of Radiation Oncology by radiochemotherapy with weekly cisplatin (40 mg/m2). Intracavitary high-dose rate brachytherapy was applied to 76 patients (93.8%) and five patients (6.2%) were treated with external radiotherapy alone. Early and late side-effects of the treatment were analyzed according to RTOG-EORTC criteria.

RESULTS

Median age was 55 years and the most frequent histology was epidermoid carcinoma. Median follow-up time was 42 months. Five-year overall, disease-free and local relapse-free survival rates were 69%, 77%, and 82%, respectively. The presence of low Hgb level (< 12 g/dl), bulky tumor (> 4 cm), poor performance status, pelvic nodal involvement and limited early response to treatment had a significant impact on the local failure rate. Prognostic factors influencing disease-free survival were bulky tumor, performance status, pelvic nodal status, pretreatment Hgb level and limited early response to treatment. A significantly higher 5-year overall survival rate was observed in patients with good performance status, without pelvic nodal involvement, normal pretreatment Hgb level and complete response to treatment. Grade 3-4 side-effects were not observed in any patients. The most frequent acute side-effects were leukopenia, anemia, nausea and vomiting. Long-term side-effects were observed in 54% of patients.

CONCLUSION

This series suggests that radiochemotherapy with weekly cisplatin is an effective and a safe treatment in locally advanced cervical cancer.

Absolute depth-dose-rate measurements for an Ir192 HDR brachytherapy source in water using MOSFET detectors

Reported MOSFET measurements concern mostly external radiotherapy and in vivo dosimetry. In this paper, we apply the technique for absolute dosimetry in the context of HDR brachytherapy using an 192Ir source. Measured radial dose rate distributions in water for different planes perpendicular to the source axis are presented and special attention is paid to the calibration of the R and K type detectors, and to the determination of appropriate correction factors for the sensitivity variation with the increase of the threshold voltage and the energy dependence. The experimental results are compared with Monte Carlo simulated dose rate distributions. The experimental results show a good agreement with the Monte Carlo simulations: the discrepancy between experimental and Monte Carlo results being within 5% for 82% of the points and within 10% for 95% of the points. Moreover, all points except two are found to lie within the experimental uncertainties, confirming thereby the quality of the results obtained.

Monte Carlo calculation of the TG-43 dosimetric parameters of a new BEBIG Ir-192 HDR source

BACKGROUND AND PURPOSE

High dose rate (HDR) brachytherapy is a highly extended practice in clinical brachytherapy today. Quality dose rate distribution datasets of the HDR sources used in a clinical treatment are required. Because of the different source designs, a specific dosimetry dataset is required for each source model. In the recently published BRAPHYQS-ESTRO Report, an overview of available dosimetric data for all HDR Ir-192 sources is given, pointing out the lack of data for one of the sources that is used by the BEBIG MultiSource afterloading system (BEBIG GmbH, Germany). The purpose of this study is to obtain detailed dose rate distributions in liquid water media around this source.

MATERIAL AND METHODS

The Monte Carlo code GEANT4 was used to estimate dose rate in water and air-kerma strength around the Ir-192 source. All the details of the stainless steel encapsulated BEBIG HDR 1.1mm in external diameter has been included in the simulation.

RESULTS

A complete dosimetric dataset for the BEBIG Ir-192 HDR source is presented. TG43 dosimetric functions and parameters have been obtained as well as a 2D rectangular dose rate table, consistent with the TG43 dose calculation formalism. The dosimetric parameters and functions obtained for the BEBIG HDR source have been compared with that obtained in the literature for others HDR sources, showing that the use of specific datasets for this new source is justified.

CONCLUSIONS

This dataset can be used as input in the TPS and to validate its calculations. As policy of BRAPHYQS-ESTRO task group, this dataset will be incorporated to the website: available to users in excel format.

Chest wall dose in MammoSite™ breast brachytherapy: Radiobiologic estimations of late complication risk based on dose–volume considerations

PURPOSE

To estimate the risk of late effects in women treated with MammoSite brachytherapy (MBT), the balloon catheters of which were placed near the ribs.

METHODS AND MATERIALS

Upon reviewing 93 plans, 16 patients (17%) treated with MBT were considered to have received a high chest wall dose (>or=120% isodose line in contact with a rib). A dose-volume histogram was generated for this rib, and its distance from the MBT balloon measured. Using the linear quadratic equation, the equivalent dose, delivered in 10 fractions, to the dose that causes a 5% and 50% risk of rib late effects at 5 years using 2Gy per fraction, was calculated to be 37 and 44Gy, respectively. The rib volume receiving greater than or equal to these doses (V37 and V44) was correlated to the balloon-to-rib distance. Chest wall signs, symptoms, and radiologic findings for all 16 patients were recorded.

RESULTS

The median balloon-to-rib distance was 4.8mm. The median values of V37 and V44 were 13.5% and 3.3%, respectively. All patients with a V37>or=15% and V44>or=5% had a minimum balloon-to-rib distance of <5mm. Two patients reported treatment-related chest wall tenderness (both had balloons placed <5mm from the chest wall), but neither presented with radiologic complications.

CONCLUSIONS

Sixteen patients considered to receive relatively high chest wall doses had less than one-third of their primary rib volume being exposed to the estimated TD 5/5 and TD 50/5 doses. Therefore, we estimate the risk of late effects in women treated with MBT, the balloon catheters of which placed near the ribs were negligible, and believe that MBT remains a safe and effective treatment for selected patients with early stage breast cancer.

Improving patient-specific dosimetry for intravascular brachytherapy

PURPOSE

Accurate patient-specific dosimetry in intravascular brachytherapy (IVBT) is generally difficult due to the extremely high-dose gradient, complexity of treatment device, and patient-specific geometry (e.g., calcification, stent, curvature, movement of target). The purpose of this study is to analyze quantitatively and systematically the dose effects of calcification, stent, guidewire, and source curvature on clinical dosimetry in an IVBT procedure, and propose a method that can be used to assess these effects in routine clinical practice.

METHODS AND MATERIALS

Monte Carlo techniques were used to calculate 3-D dose distribution in both homogeneous and inhomogeneous media for three most commonly used IVBT sources: (90)Sr beta (Novoste), (192)Ir gamma (Cordis/Best), and (32)P beta (Guidant). Dosimetric perturbations in the presence of metallic stents, calcified plaques, metallic guide wires, and source curvature were studied for situations commonly encountered in the clinic. The importance of each of these perturbations and their practical influence on patient-specific dosimetry were analyzed. Factors (plaque, stent, guidewire, and curvature) that may be used to correct/reduce these perturbations were introduced to prevent dosimetric cold spots during IVBT. Practical methods of using these correction factors are proposed.

RESULTS

Dose perturbations are significant due to the presence of source curvature, metallic stents, calcified plaques, and metallic guide wires, especially for beta sources. These perturbations can be as high as 30% under normal clinical conditions, although they can be much higher in extreme situations. Empirical relationships of plaque factor with the thickness of calcified plaque, stent factor with stent metallic surface area, guidewire with guidewire thickness, and curvature factor with the bending angle are derived. These relationships are found to be useful in improving clinical dose accuracy in IVBT treatment planning or dose evaluation after treatment.

CONCLUSIONS

Significant dose perturbations due to the presence of source curvature, metallic stents, calcified plaques, and guide wires have been found in IVBT for in-stent restenosis. Because it has been reported that, with the current prescriptions for IVBT, higher doses consistently improve treatment outcomes, the empirical method derived from this work can be used to assess cold spots dosimetrically, thus improving patient-specific dosimetry for IVBT.

Endobronchial brachytherapy in the treatment of malignant lung tumours

A prospective study was made to assess the short-term clinical and endoscopic response to high-dose-rate endobronchial brachytherapy (HDREB) in patients with malignant endobronchial tumours. From July 1995 to May 2000, 288 HDREB sessions were carried out on 81 patients. The mean patient age was 61.57 yrs (range 34-82); males were predominant (87.65%). Tumours were primary in 76 patients (93.82%) and metastatic in five patients (6.18%). The inclusion criteria were malignant endobronchial tumour and either palliative treatment for incurable disease or intent-to-cure treatment for residual malignancy on the bronchial resection surface after surgery or an inoperable tumour. The exclusion criteria were as follows: impediments to catheter placement, expected survival <2 months, Karnofsky index <60, or absence of informed consent. The clinical response of a symptom was categorised as complete (disappearance of the symptom), partial (less than complete) or absent. The endoscopic response was considered to be complete if lesions disappeared and biopsy findings remained negative 1 month after the last radiation session; partial if lesions improved to some extent, but the biopsy findings were positive; and absent if there was no change in relation to baseline. The technique consisted of delivering high-dose irradiation from an Ir192 source to a target volume using one or two endobronchial catheters inserted under optical or video bronchoscopic guidance. Four sessions were scheduled at weekly intervals and 500 cGy was applied per session over a length of 1-9 cm, measured 0.5-1 cm from the centre of the source. In total, 85% of the symptoms analysed (haemoptysis, cough, dyspnoea, expectoration, and stridor) disappeared with HDREB, which was categorised as a complete response. The endoscopic response was complete in 56.79% of patients, partial or less than complete in 40.74% and absent in 2.46%. One major complication occurred (bronchial fistula 1.2%), but no lethal haemoptysis. Minor complications (pneumonitis, bronchospasm and bronchial stenosis) each occurred in one patient (1.2%). High-dose-rate endobronchial brachytherapy is a good palliative treatment for endoluminal lung neoplasms, effectively alleviating symptoms and endoscopic evidence in many cases with an acceptable rate of complications. High-dose-rate endobronchial brachytherapy can be carried out as an intent-to-cure procedure in highly selected cases.

A Monte Carlo brachytherapy study for dose distribution prediction in an inhomogeneous medium

The purpose of this study was to present a theoretical analysis of how the presence of bone in interstitial brachytherapy affects dose rate distributions. This study was carried out using a Monte Carlo simulation of the dose distribution in homogeneous medium for 3 commonly used brachytherapy seeds. The 3 seeds investigated in this study are iridium-192 (192Ir) iodine-125 (125I), and palladium-103 (103Pd). The computer code was validated by comparing the specific dose rate (Lambda), the radial dose function g(r), and anisotropy function F(r,theta;) for all 3 seeds with the AAPM TG-43 dosimetry formalism and current literature. The 192Ir seed resulted in a dose rate of 1.115 +/- 0.001 cGy-hr(-1)-U(-1), the 125I seed resulted in a dose rate of 0.965 +/- 0.006 cGy/h(-1)/U(-1), and the 103Pd seed resulted in a dose rate of 0.671 +/- 0.002 cGy/h(-1)/U(-1). The results for all 3 seeds are in good agreement with the AAPM TG-43 and current literature. The validated computer code was then applied to a simple inhomogeneous model to determine the effect bone has on dose distribution from an interstitial implant. The inhomogeneous model showed a decrease in dose rate of 2% for the 192Ir, an increase in dose rate of 84% for 125I, and an increase in dose rate of 83% for the 103Pd at the surface of the bone nearest to the source.

High-dose rate brachytherapy for Stage I/II papillary serous or clear cell endometrial cancer

OBJECTIVE

To determine the efficacy of high-dose rate brachytherapy as adjuvant treatment for Stage I/II papillary serous or clear cell endometrial cancer.

METHODS

A retrospective study of all patients with Stage I/II papillary serous or clear cell endometrial cancer treated with high-dose rate brachytherapy between 1995 and 2001 was performed. Following surgical staging, which included hysterectomy with pelvic and aortic lymphadenectomy, all patients without extrauterine disease were treated with high-dose rate brachytherapy and followed for recurrence. The locations of recurrences were noted and were classified as local or distant.

RESULTS

Three (13%) recurrences occurred among 24 patients with Stage I/II papillary serous or clear cell carcinoma. The risk of recurrence was similar for papillary serous and clear cell cancer (12% vs. 12%). Local control was achieved in 96%. The risk of recurrence for those with no myometrial invasion, less than 1/2, or more than 1/2 myometrial invasion was 0%, 10%, and 50%, respectively (P < 0.04). Two of the three recurrences were distant and all patients with recurrence died despite additional treatment.

CONCLUSIONS

High-dose rate brachytherapy (HDR) as the sole adjuvant treatment of Stage I/II papillary serous or clear cell carcinoma is associated with a 13% risk of recurrence. Although local control with HDR is excellent, the risk of distant recurrence is increased with deep myometrial invasion. High-dose rate brachytherapy is adequate for Stage IA cases, but more aggressive treatment combining chemotherapy with HDR should be evaluated for more advanced Stage I/II cases.

Favorable effect of ?-radiation for in-stent restenosis: Effect of diabetes on angiographic and clinical outcomes

The purpose of this study was to examine the effect of vascular brachytherapy with gamma-radiation (gamma-RT) in patients with diabetes mellitus (DM) with coronary in-stent restenosis (ISR). In the Washington Radiation for In-Stent Restenosis (WRIST) trial, 130 patients with ISR were treated with (192)Ir or placebo. Of the patients enrolled, 44 (34%) had DM (18 of them treated with gamma-RT and 26 with placebo). Gamma-radiation therapy of ISR in diabetics resulted in similar procedural success and in-hospital outcome compared to nondiabetics. At 6-month follow-up, both DM and non-DM patients treated with gamma-RT had significantly lower target lesion revascularization (TLR), target vessel revascularization, and major adverse cardiac event rates compared to placebo. DM remains a powerful predictor of TLR and major adverse cardiac events even after treatment of ISR with gamma-RT.

Gamma radiation for in-stent restenosis: effect of lesion length on angiographic and clinical outcomes

The relation between lesion length and effectiveness of gamma radiation treatment (gamma-RT) has not been well described. We evaluated the acute and long-term outcome according to baseline lesion length in 130 patients treated with (192)Ir in the Washington Radiation for In-Stent Restenosis Trial; 44 (35.5%) had baseline short in-stent restenosis (ISR) lesions (length < 15 mm) and 80 (64.5%) long ISR lesions (length > or = 15 mm). At 6-month follow-up after gamma-RT, the short ISR group had larger lumen dimensions and lower late loss than the long ISR group. Restenosis rate was significantly higher in patients with long ISR for both the placebo (74% vs. 39%; P = 0.01) and the gamma-RT arm (31% vs. 5.3%; P = 0.04). gamma-RT significantly improved the angiographic outcome in the short-lesion groups but had the more pronounced effect on the reduction of clinical events after treatment of long ISR group. Lesion length remains a powerful predictor of recurrent ISR and clinical events after treatment of ISR even with gamma-RT.

Impact of radiation dose on late clinical outcome after intracoronary radiation therapy: Three-year follow-up of Long WRIST

To determine the safety and efficacy, including the impact, on the late recurrence rate of an incremental gamma-radiation dose from 15 to 18 Gy, we report the 3-year clinical outcome of Washington Radiation for In-Stent Restenosis Trial for Long Lesions (Long WRIST). One hundred eighty patients with recurrent in-stent restenosis (ISR) were enrolled in the Long WRIST series and treated with (192)Ir with 1 month of antiplatelet therapy. Between 6 months and 3 years, the need for repeat revascularization was low and similar among the three groups. At 3 years, target lesion revascularization (TLR) and major adverse cardiac events (MACE) were less frequent in the 18 Gy group than in the 15 Gy group (P = 0.12 for TLR, P < 0.05 for MACE) and less frequent in the 15 Gy group as compared to the placebo group (P < 0.05 for TLR and MACE). At 3 years, a higher dose of 18 Gy with (192)Ir continues to improve the outcome of patients treated for ISR when compared to patients treated with 15 Gy or placebo.

Treatment of T3 and T4 anal carcinoma with combined chemoradiation and interstitial 192Ir implantation: a 10-year experience

PURPOSE

To report our experience in treating T3 and T4 anal carcinoma with combined external beam (EBRT) and chemotherapy, followed by interstitial (192)Ir implant boost.

METHODS AND MATERIALS

From 1990 to 2000, 31 patients with T3 and T4 anal carcinoma were treated with: 30 Gy EBRT (2 Gy fractions, 5 days/week) + 5-fluorouracil + mitomycin-C. Median implant dose was 31.3 Gy at 0.5 cm, delivered at a mean rate of 0.52 Gy/h.

RESULTS

Six patients had local persistence and 4 eventually developed local-regional recurrence. Eight underwent abdomino-perineal resection (APR). With the addition of APR in selected cases, the ultimate local-regional control after initial treatment was 84%. Distant metastases occurred in 10. Of the initial cohort, 55% is still alive and NED. Eight had radiation proctitis and 7 developed postimplant ulceration. Only 1 required surgical intervention.

CONCLUSIONS

Treatment of T3 and T4 anal cancer with combined chemotherapy and EBRT, followed by interstitial implant results in an ultimate local-regional control of 84%, after the inclusion of selected APR. It is well tolerated, with acceptable toxicity.

High dose rate192Ir afterloading brachytherapy for cancer of the vagina

We report results of brachytherapy for carcinoma of the vagina, utilizing a Nucletron high dose rate system for Delclos Vaginal Applicators (cylinder) and Syed Template Applicators (interstitial). The linear quadratic (LQ) model was used to determine the optimum time-dose-fractionation schedules. Interstitial doses were determined at the isodose line that included gross tumour. Cylinder doses were determined either at the vaginal surface (5 cases), at 0.5 cm depth (5 cases), or at 1.0 cm depth (1 case). For the first treatment (n=19), interstitial templates were utilized in 8 patients and vaginal cylinders in 11. 11 patients received second treatments: 6 templates and 5 cylinders. The median dose of external beam radiation (n=15) was 40.0 Gy followed, after a median 23 day interval, by high dose rate brachytherapy (HDRB) of 4 fractions in 30-42 h; then a median interval gap of 25 days, followed by repeat HDRB. The median total fractionated HDRB dose per patient was 23.0 Gy (range: 6.9 Gy to 40.4 Gy; calculated low dose rate equivalent of 29.8 Gy). Tumour histologies included 14 squamous cell carcinomas, 2 adenocarcinomas, 2 melanomas, and 1 small cell tumour. Three patients experienced early brachytherapy-related complications (diarrhoea, dysuria and labial dermatitis). Three patients (15.8%) developed serious/late complications including ureteral stenosis, painful vaginal necrosis and small bowel obstruction. The first of these patients received 2 templates, the second a cylinder followed by a template and a cylinder, and the third a single cylinder. The 2 year progression-free survival was 39.3% (median 15.7 months), while the 2 year overall survival was 66.1% (median 29.9 months). (192)Ir afterloading HDRB is a feasible approach to women with vaginal cancer with acceptable toxicity and tumour response. Potential advantages include patient preference, outpatient cost-effectiveness in the case of cylinder technique, and no radiation exposure to hospital personnel. Long-term follow-up is needed to further assess late complications, and larger studies are needed to confirm our results.

Treatment of bifurcation in-stent restenotic lesions with beta radiation using strontium 90 and sequential positioning pullback technique: procedural details and clinical outcomes

BACKGROUND

In-stent restenotic lesions have been problematic for many patients with the need for multiple repeat percutaneous coronary interventions (PCI). The need for repeat PCI has been significantly reduced in patients since the advent of vascular brachytherapy. In-stent restenosis resulting in bifurcation presents even more of a challenge. The use of radiation therapy for the treatment of this kind of lesion has not yet been reported. The purpose of this paper is to present five cases of radiation therapy in bifurcation in-stent restenotic lesions using the intraluminal beta radiation catheter delivery system (Beta-Cath System, Novoste Corporation, Norcross, Georgia).

METHODS

We reviewed the database of patients enrolled in our Compassionate Use Registry between August 1999 and April 2002. The data is reported for 5 patients who received radiation in both branches of bifurcation lesions with the Beta-Cath catheter system.

RESULTS

The mean diameter of the vessels was 3.1 mm 0.5 mm. The dose administered was from 18.3 to 23 Gy, with an overlap of 3.3 to 10.3 mm; the hinge angle between the branches went from 43.3 to 65.4 . Angiographic follow-up was obtained at 6 months in 4 patients, with a single patient showing a focal (< 5 mm) edge lesion treated by balloon angioplasty (TVR no TLR). No aneurysms or zones of ectasia were noted.

CONCLUSION

Beta radiation with the Beta-Cath catheter system appears to be safe, secure and clinically useful in in-stent restenotic bifurcation lesions.

The syed temporary interstitial iridium gynaecological implant: an inverse planning system

Patients with advanced gynaecological cancer are often treated with a temporary interstitial implant using the Syed template and Ir- 192 ribbons at the Memorial Sloan-Kettering Cancer Center. Urgency in planning is great. We created a computerized inverse planning system for the Syed temporary gynaecological implant, which optimized the ribbon strengths a few seconds after catheter digitization. Inverse planning was achieved with simulated annealing. We discovered that hand-drawn target volumes had drawbacks; hence instead of producing a grid of points based on target volume, the optimization points were generated directly from the catheter positions without requiring an explicit target volume. Since all seeds in the same ribbon had the same strength, the minimum doses were located at both ends of the implant. Optimization points generated at both ends ensured coverage of the whole implant. Inverse planning took only a few seconds, and generated plans that provide a good starting point for manual improvement.

Effect of catheter-based iridium-192 gamma brachytherapy on the added risk of restenosis from diabetes mellitus after intervention for in-stent restenosis (subanalysis of the GAMMA I Randomized Trial)

Catheter-based intracoronary radiation therapy using iridium-192 (Ir-192) has been shown to be effective in reducing recurrent coronary restenosis after initial percutaneous treatment of in-stent restenosis. Patients with diabetes mellitus (DM) have a higher risk of recurrent restenosis than nondiabetics for nonstented and in-stent restenosis coronary lesions. The use of Ir-192 for preventing recurrent restenosis in such patients remains undefined. The GAMMA I trial was a prospective, randomized, double-blind, multicenter trial of 252 patients with in-stent restenosis who underwent percutaneous coronary intervention and were assigned to receive either Ir-192 (131 patients) or catheter-based placebo (121 patients). DM was present in 79 patients (31%) (41 patients received Ir-192 and 38 patients received placebo) and was absent in 173 patients (90 patients received Ir-192 and 83 patients received placebo). At 6-month follow-up in the GAMMA I trial, the angiographic in-lesion binary restenosis rate was lower in the Ir-192 arm than in the placebo arm (32.4 vs 55.3, p = 0.01). When patients were stratified by the presence of DM, the antirestenosis effect of Ir-192 was larger for diabetic patients than for nondiabetic patients (absolute in-lesion restenosis rate was reduced by 40% for diabetics and 16% for nondiabetics). Thus, adjunctive Ir-192 intracoronary radiation therapy reduces recurrent restenosis after intervention for in-stent restenosis in patients with and without DM. The relative impact of this treatment is more pronounced in diabetic patients because it appears to neutralize the added risk of recurrent restenosis seen in proliferative diabetic lesions.

Fractionated intraluminal HDR 192Ir brachytherapy as palliative treatment in patients with endobronchial metastases from non-bronchogenic primaries

AIM

To evaluate the efficacy of iridium-192 high-dose rate (HDR) endobronchial brachytherapy for the palliation of symptoms caused by endobronchial metastases of non-bronchogenic primaries.

PATIENTS AND METHOD

Between 1991 and 1998, eleven patients (female n = 3, male n = 8; age: median 66 years, range 44-81 years) underwent intraluminal HDR brachytherapy for histologically confirmed endobronchial metastases from non-pulmonary primary tumors of various sites like urogenital tract (n = 5), gastrointestinal tract (n = 3), ear/nose/throat (n = 2) and breast (n = 1). The median time between diagnosis of the primary non-bronchogenic tumor and histopathological diagnosis of the endobronchial metastases was 39 months, range 1-99 months. A total dose of 15-20 Gy was delivered in three to four fractions of 5-6 Gy once a week. No palliative chemotherapy was added.

RESULTS

Median follow-up after palliative brachytherapy was 15 months (range 1.4-59 months). Objectively, complete endoscopic response was observed in three (27%) patients, and in five (46%) others partial opening of the initially obstructed airway was achieved. Treatment was judged unsuccessful in three (27%) patients. No patient showed up with local progression. At date of analysis five patients were alive with documented residual tumor (80%) or complete response (20%). Relief of symptoms occurred in the vast majority of patients (n = 8, 73%).

CONCLUSION

HDR intraluminal brachytherapy palliates symptoms in patients suffering from endobronchial metastases of non-pulmonary primary tumors. The applied treatment is a safe, effective and well tolerated palliative procedure leading to an improved patient quality of life.

Five-year clinical follow-up after intracoronary radiation: results of a randomized clinical trial

BACKGROUND

Several clinical trials indicate that intracoronary radiation is safe and effective for treatment of restenotic coronary arteries. We previously reported 6-month and 3-year clinical and angiographic follow-up demonstrating significant decreases in target lesion revascularization (TLR) and angiographic restenosis after gamma radiation of restenotic lesions. The objective of this study was to document the clinical outcome 5 years after treatment of restenotic coronary arteries with catheter-based iridium-192 (192Ir).

METHODS AND RESULTS

A double-blind, randomized trail compared 192Ir to placebo sources in patients with restenosis after coronary angioplasty. Over a 9-month period, 55 patients were enrolled; 26 were randomized to 192Ir and 29 to placebo. At 5-year follow-up, TLR was significantly lower in the 192Ir group (23.1% versus 48.3%; P=0.05). There were 2 TLRs between years 3 and 5 in patients in the 192Ir group and none in patients in the placebo group. The 5-year event-free survival rate (freedom from death, myocardial infarction, or TLR) was greater in 192Ir-treated patients (61.5% versus 34.5%; P=0.02).

CONCLUSIONS

Despite apparent mitigation of efficacy over time, there remains a significant reduction in TLR at 5 years and an improvement in event-free survival in patients treated with intracoronary 192Ir. The early clinical benefits after intracoronary gamma radiation with 192Ir seem durable at 5-year clinical follow-up.

Five-year clinical and angiographic follow-up after intracoronary iridium-192 radiation therapy

BACKGROUND

Ionizing gamma radiation has been shown to reduce neointimal formation and the incidence of restenosis after balloon angioplasty and stenting in clinical trials. However, the long-term effects of this therapy are unknown. The first cohort of patients to receive intracoronary gamma radiation after balloon angioplasty for the prevention of restenosis have completed a 5-year angiographic and clinical follow-up. The outcome of these patients is presented and discussed.

METHODS

Twenty-one patients with unstable angina (22 arteries) underwent standard balloon angioplasty. Intracoronary radiation therapy was performed immediately after the intervention using an Iridium-192 source wire hand-delivered to the angioplasty site. All patients were followed clinically and Quantitative Coronary Analysis (QCA) was performed at 6, 24, 36 and 60 months.

RESULTS

Target lesion revascularization occurred in six lesions, three of which were total occlusions (two early within 30 days and one occurred at 2 years), and one patient had a myocardial infarction attributable to a nontarget vessel. Serial QCA detected a binary restenosis rate of 28.6% (n=6) at 6 months. The late loss (0.29 mm) and loss index (0.25) remained low at 2, 3 and 5 years. Angiographic complications included four aneurysms (two procedure related and two occurring within 3 months). At 2 years, only one aneurysm increased in size (46 vs. 27 mm(2)); and at 3 and 5 years, all aneurysms remained unchanged. No other angiographic complications were observed.

CONCLUSION

The early clinical and angiographic effects of intracoronary gamma radiation were maintained at 5 years without further increase in the aneurysm formation or apparent new adverse effects related to the radiation therapy between 2 and 5 years.

The WRIST series--what have we learnt?

BACKGROUND

The evolution of the WRIST (Washington Radiation for In-Stent Restenosis Trial) series has reflected the progress that has been made in intracoronary radiation for In-stent restenosis of coronary artery and saphenous vein graft disease. We have enrolled over 1,500 patients in eleven WRIST series performed at the Washington Hospital Center, providing a unique and powerful data set that is pivotal in our understanding of vascular brachytherapy.

AIM

This review is intended to give an overview of the individual trials, summarize pertinent lessons that have been learned and give insight into future of intracoronary radiation.

Present status of endovascular brachytherapy in peripheral arteries

BACKGROUND

Peripheral artery disease based on atherosclerosis is one of the major problems in angiology. Endovascular brachytherapy has shown to be a promising new treatment method for prevention of restenosis after femoropopliteal angioplasty.

METHOD

Brachytherapy for peripheral arteries is performed by using an iridium-192 gamma source delivered with a remote controlled afterloading unit. Semiflexible 5F radiation catheter without centering possibility and specially designed 7F centering radiation delivery catheter with segmented balloons are available. After angioplasty patient is transported to the brachytherapy unit equipped with specific shielded walls. For treatment planning the whole length of intervention (interventional length = IL) plus safety margins is assumed to be the target. Dose should be related to a certain radial depth (2 mm) from the vessel lumen into vessel wall as proposed in the EVA GEC ESTRO Recommendations. Treatment planning is performed based on the vessel lumen diameter, IL safety margins and reference isodose length (RIL).

RESULTS

First clinical experience with endovascular brachytherapy was obtained in Frankfurt and showed significant improvement of arterial patency even after a long follow-up period. The Vienna-2 study was the first prospective, randomized trial proofing 48% relative reduction of restenosis in the brachytherapy arm. The results of ongoing trials using centering catheter (Vienna-3, PARIS) are soon expected and will definitely determine the role of endovascular brachytherapy for restenosis prevention after angioplasty.

Patient effective dose from endovascular brachytherapy with 192Ir sources

The growing use of endovascular brachytherapy has been accompanied by the publication of a large number of studies in several fields, but few studies on patient dose have been found in the literature. Moreover, these studies were carried out on the basis of Monte Carlo simulation. The aim of the present study was to estimate the effective dose to the patient undergoing endovascular brachytherapy treatment with 112Ir sources, by means of experimental measurements. Two standard treatments were taken into account: an endovascular brachytherapy of the coronary artery corresponding to the activity x time product of 184 GBq.min and an endovascular brachytherapy of the renal artery (898 GBq.min). Experimental assessment was accomplished by thermoluminescence dosemeters positioned in more than 300 measurement points in a properly adapted Rqndo phantom. A method has been developed to estimate the mean organ doses for all tissues and organs concerned in order to calculate the effective dose associated with intravascular brachytherapy. The normalised organ doses resulting from cronary treatment were 2.4 x 10(-2) mSv.GBq(-1).min(-1) for lung, 0.9 x 10(-2) mSv.GBSq(-1).min(-1) for oesophagus and 0.48 x 10(-2) mS.GBq(-1).min(-1) for bone marrow. During brachytherapy of the renal artery, the corresponding normalised doses were 4.2 x 10(-2) mS.GBq(-1).min(-1) for colon, 7.8 x 10(-2) mSv.GBq(-1).min(-1) for stomach and 1.7 x 10(-2) mSv.GBq(-1).min(-1) for liver. Coronary treatment iJnvlled an efl'fective dose of (0.046 mSv.GBq(-1).min(-1), whereas the treatment of the renal artery resulted in an effective dose of 0.15 mSv.GBq(-1).min(-1); there were many similarities with data from former studies. Based on these results it can be concluded that the dose level of patients exposed during brachytherapy treatment is low.

Required treatment margin for coronary endovascular brachytherapy with iridium-192 seed ribbon

PURPOSE

Preliminary clinical trials (SCRIPPS I, WRIST and Gamma 1) employing catheter-based endovascular brachytherapy (EVBT) with iridium-192 (Ir-192) seeds show promising results in reducing restenosis after coronary intervention. Failure analysis of these studies showed a significant number of restenosis at the treatment margin called "edge effect." The objective of this study is to investigate the factors that contribute to the adequacy of treatment margin.

METHODS AND MATERIALS

The factors contributing to the margins are penumbra effect at the end of the seed train, uncertainty in target localization, longitudinal seed movement during cardiac cycle and barotrauma due to stent deployment. The magnitudes of the penumbra effect, which refers to the tapering off the prescribed isodose line near the ends of the source train, were calculated for various source lengths of Ir-192 seed ribbon using AAPM TG-43 algorithm. Uncertainty in target localization refers to the fact that the visual estimation of proximal and distal extent of the injury is not accurate, and this can be obtained by comparing the "estimate" from the interventional cardiologist with careful review of the cine-angiogram. Longitudinal seed movements relative to the coronary vessel during the cardiac cycle were determined by frame-by-frame reviewing cine-angiograms of 30 patients. The proximal and distal source points were measured in reference to branching vessels during the contrast phase of the cine-angiogram. The maximum proximal and distal longitudinal movement was captured and source displacement was measured from the closest proximal and distal branching vessel. Barotrauma, additional injury to the vessel arising from the stent deployment balloon, was obtained by reviewing specifications from commercially available stent delivery systems.

RESULTS

The penumbra effect ranges from 3.9 to 4.5 mm for 6-22 Ir-192 seed ribbons. The uncertainty in target localization is within 3 mm for our interventional cardiologists. The results of seed movements were categorized by three major coronary vessels and by proximal versus distal ends. The mean and standard deviation of seed movement are 1.1 and 0.8 mm, respectively. The average length of barotrauma beyond the stent margins for reviewed stents was 1.7 mm, ranging from 0.5 to 2.5 mm.

CONCLUSION

A minimum of 8-mm treatment margin is recommended for coronary vascular brachytherapy with Ir-192 seed ribbon. This was derived by considering the above contributing factors. Excessive margins should be avoided due to possible increase risk of late effect. By providing adequate treatment margins, one can avoid geographic miss; hence, one can further improve the effect of EVBT in reducing restenosis.

High dose rate afterloading 192 iridium prostate brachytherapy

Since the evolution of prostate-specific antigen testing for prostate cancer, men have been diagnosed with earlier staged disease. Earlier staged cancer is amenable to local therapy. Over the last decade, new technology has evolved in the treatment of localized prostate cancer. High dose rate afterloading 192 Iridium prostate brachytherapy is a new innovative technique utilizing state of the art equipment and highly specialized computers to achieve precise treatment of prostate cancer with radiation. We present our initial experience with this innovative technique.

[Advanced hepatocellular carcinoma--feasibility and clinical impact of high-dose-rate brachytherapy on the treatment of lesions growing into biliary trees, portal veins and the vena cava]

This study was performed to evaluate the feasibility and clinical impact of intraluminal and endovascular high-dose-rate iridium-192 brachytherapy on the treatment of HCC lesions growing into biliary trees, portal veins and the inferior vena cava. HCCs involving biliary trees in 2 patients, the main and/or first-order portal veins in 3 patients, and the inferior vena cava in 2 patients. Brachytherapy was percutaneously performed with a 5F applicator, which was placed adjacent to the lesions. A mean total dose of 23 Gy (range, 5-7 Gy/fr) was irradiated (at a 5 mm radius) to the biliary or the portal venous tumors. A total dose of 10 Gy (5 Gy/fr) was given to the caval tumors. External-beam radiotherapy was combined in 2 patients with caval lesions, stent placement in 2 patients with biliary lesions and hepatic arterial infusion chemotherapy in 5 patients. There was no major complication except hemobilia, which ceased after placing a PTCD tube in the bile duct in one patient. All tumors were significantly reduced in size and remained controlled during the period of patients' survival. Complete tumor necrosis was histologically proved in 2 autopsy cases having biliary lesions. The median survival was 13 months. Intraluminal and endovascular high-dose-rate brachytherapy appears to be a feasible, and effective procedure to treat advanced HCCs invading biliary trees, portal veins and the vena cava.

Comparison of traditional low-dose-rate to optimized and nonoptimized high-dose-rate tandem and ovoid dosimetry

PURPOSE

Few dose specification guidelines exist when attempting to perform high-dose-rate (HDR) dosimetry. The purpose of this study was to model low-dose-rate (LDR) dosimetry, using parameters common in HDR dosimetry, to achieve the "pear-shape" dose distribution achieved with LDR tandem and ovoid applications.

METHODS AND MATERIALS

Radiographs of Fletcher-Suit LDR applicators and Nucletron "Fletcher-like" HDR applicators were taken with the applicators in an idealized geometry. Traditional Fletcher loadings of 3M Cs-137 sources and the Theratronics Planning System were used for LDR dosimetry. HDR dosimetry was performed using the Nucletron Microselectron HDR UPS V11.22 with an Ir-192 source. Dose optimization points were initially located along a line 2 cm lateral to the tandem, beginning at the tandem tip at 0.5-cm intervals, ending at the sail, and optimized to 100% of the point A dose. A single dose optimization point was also placed laterally from the center of each ovoid equal to the radius of the ovoid (ovoid surface dose). For purposes of comparison, dose was also calculated for points A and B, and a point located 1 cm superior to the tandem tip in the plane of the tandem, (point F). Four- and 6-cm tandem lengths and 2.0-, 2.5-, and 3.0-cm ovoid diameters were used for this study. Based on initial findings, dose optimization schemes were developed to best approximate LDR dosimetry. Finally, radiographs were obtained of HDR applications in two patients. These radiographs were used to compare the optimization schemes with "nonoptimized" treatment plans.

RESULTS

Calculated doses for points A and B were similar for LDR, optimized HDR, and nonoptimized HDR. The optimization scheme that used tapered dose points at the tandem tip and optimized a single ovoid surface point on each ovoid to 170% of point A resulted in a good approximation of LDR dosimetry. Nonoptimized HDR resulted in higher doses at point F, the bladder, and at points lateral to the tandem tip than both the optimized plan or the LDR plan.

CONCLUSION

Optimized HDR allows specification of dose to points of interest, can approximate LDR dosimetry, and appears superior to nonoptimized HDR treatment planning, at least at the tandem tip. An optimization scheme is presented that approximates LDR dosimetry.

Edge stenosis and geographical miss following intracoronary gamma radiation therapy for in-stent restenosis

OBJECTIVES

We sought to determine the relationship between geographical miss (GM) and edge restenosis (ERS) following intracoronary radiation therapy.

BACKGROUND

Edge restenosis may be a limitation of intracoronary irradiation to prevent in-stent restenosis (ISR). Inadequate radiation source coverage of the injured segment (GM) has been proposed as a cause of ERS. We studied the relationship between GM and ERS following 192Ir treatment of ISR.

METHODS

There were 100 patients with native vessel ISR in WRIST (Washington Radiation for In-Stent Restenosis Trial), in which patients with ISR were first treated with conventional techniques and then randomized to gamma irradiation (192Ir) or placebo. Geographical miss was defined as segments proximal or distal to the treated lesion that were subjected to injury during primary intervention but were not covered by the radiation source.

RESULTS

Geographical miss was documented in 56 of 164 edges (34%). Edge restenosis was noted at eight of 80 radiated edges and in four of 84 placebo edges. In the irradiated group, ERS was observed in 21% of edges with GM and in 40% of edges without GM (p = 0.035). In contrast, in the placebo group, ERS was observed in only 7% of edges with GM and in 4% of edges without GM (p = NS). The late edge lumen loss was higher in the irradiated group with GM as compared to placebo with GM (0.74 +/- 0.57 vs. 0.41 +/- 0.50 mm, p = 0.016).

CONCLUSIONS

Edge restenosis following gamma irradiation treatment of ISR is related to GM: a mismatch between the segment of artery injured during the primary catheter-based intervention and the length of the radiation source.

PSA kinetics after external beam radiotherapy alone or combined with an iridium brachytherapy boost to deliver 85 grays to prostatic adenocarcinoma

PURPOSE

Increasing the dose to prostatic adenocarcinoma in conformal external beam therapy (EBT) has resulted in increased levels of PSA normalization and increased percentage of biochemical disease-free survival rates. However technical problems due to prostate motion inside the pelvis or patients' set-up make difficult the realization of the EBT boost fields above 72 Gy. Brachytherapy which overcomes these problems was investigated to deliver the boost dose to achieve 85 Gy. PSA nadir which has been identified as the strongest independent predictor of any failure in many studies has been used as the end point for early evaluation of this work.

PATIENTS AND METHODS

In a retrospective way we report on 163 patients' PSA kinetics after EBT alone to 68 Gy or EBT first and a brachytherapy boost up to 75 or 85 Gy.

RESULTS

At 12 months follow-up, PSA nadirs percentage < or = 0.5 or < or = 1 ng/ml increased from 7.5 and 20.7% after 68 Gy EBT to 49.8 and 71.2% after a brachytherapy boost to deliver 85 Gy (p < 0.0001). In the Cox PH model analysis, the total dose remained the most important factor for predicting PSA normalization.

CONCLUSIONS

These results are in accordance with the most recent results published after conformal EBT at the same 80 Gy level of dose. If confirmed on a higher number of patients they could place brachytherapy among the most accurate methods of boosting in the radiation treatment of prostatic carcinoma.

[The brachytherapy with low dose-rate iridium for prostate cancer]

PURPOSE

Brachytherapy as an option for the treatment of prostate cancer has been commonly performed in USA. As the permanent seeding of the radioactive materials is strictly restricted by the law in Japan, brachytherapy must be performed by the temporary implant. This treatment has been performed at a few facilities in Japan mostly using high dose-rate iridium. Only our facility has been using low dose-rate iridium (LDR-Ir) for prostate cancer. This study evaluates the clinical results of the treatment.

PATIENTS AND METHODS

Since December 1997 to December 1999, 26 patients with histologically diagnosed as prostate cancer (Stage B, 92%; Stage C, 8%) underwent brachytherapy. Twenty-two patients received brachytherapy alone, three were treated with a combination of brachytherapy and external beam radiotherapy (ERT) and one was treated with a combination of brachytherapy and neoadjuvant endocrine therapy. Patients ranged in age from 61 to 84 (median 76) years old. Treatment was initiated with perineal needle placement. From 10 to 14 needles were placed through the holes on the template which was fixed to the stabilizer of the transrectal ultrasound probe. After the needle placement. CT scan was performed to draw distribution curves for the treatment planning. LDR-Ir wires were introduced to the sheath and indwelled during the time calculated from dosimetry. Peripheral dose was 70 Gy for the monotherapy of brachytherapy. For the combination therapy, 40 Gy was given by brachytherapy and 36 Gy with ERT afterwards. LDR-Ir wires were removed after completion of the radiation and patients were followed with serum PSA level and annual biopsy.

RESULTS

During 2 to 26 (median 12) months follow-up, 8 out of 9 patients with initial PSA level above 20 ng/ml showed PSA failure. All 13 patients with initial PSA level lower than 20 ng/ml were free from PSA failure. Eight out of 11 patients with Gleason's score 7 or higher showed PSA failure, and all 14 patients (including three patients with combined therapy) with Gleason's score 6 or less were free from PSA failure. Annual biopsy was performed in 8 patients, and 4 patients histologically revealed tumor free and 4 patients (two of them showed PSA failure) were tumor positive. No major complication was observed, however, some minor side-effect as irritability was seen in 65% of the patients.

CONCLUSIONS

The results showed that brachytherapy with LDR-Ir was an acceptable treatment as long as the patients were selected strictly with PSA level and Gleason's score. A good candidate for this treatment is the patient whose PSA level is lower than 20 ng/ml and Gleason's score is 6 or less. The treatment is effective and safe, but further observation is necessary to reach the conclusion.

[Inhibition of ERK1/2 activity and c-fos mRNA after coronary artery balloon injury by intracoronary radiation in swine]

The effect of intracoronary radiation on extracellular signal regulated kinase 1/2 (ERK1/2) activity and c-fos mRNA after coronary artery balloon injury was investigated in swine. Twenty three swines were randomly divided into a radiation group and a control group after coronary balloon over stretch. The dilated segments in the radiation group were exposed to a dose of 20 Gy by a catheter based radiation system. The animals were sacrificed at 3 (6 swines from each group) and 30 days (6 swines from radiation group and 5 from control group) after the operation. The injured segments were processed to examine c-fos gene expression by reverse transcription polymerase chain reaction (RT PCR) and to measure the activity of ERK1/2 biochemically. Intracoronary radiation decreased significantly the ERK1/2 activity and gene expression of c-fos in the radiation treated animals 3 days after coronary balloon injury (20.5%,P<0.01; 47.7%,P<0.05), but neither ERK1/2 activity nor c-fos gene expression was significantly affected by endovascular radiation in animals 30 days after balloon injury. Therefore, both ERK1/2 and c-fos may be involved in inhibiting restenosis.

The SCRIPPS trial--catheter-based radiotherapy to inhibit coronary restenosis

The SCRIPPS trial is a randomized, double-blind, placebo-controlled trial evaluating the impact of gamma radiation to inhibit in-stent restenosis. Fifty-five patients were enrolled; twenty-six were assigned to receive catheter-based radiation with Ir-192 and 29 were treated with placebo. Angiographic restenosis in the Ir-192-treated patients was significantly reduced at six months (17% vs. 54%; p = 0.01), with the results sustained at 3-year follow-up (33.3% vs. 63. 6%; p<0.05). Likewise, the composite clinical endpoint of death, myocardial infarction or target lesion revascularization was also commensurately lower in the treated group as compared to the placebo group (23.1% vs. 55.2%; p = 0.01). Late angiography revealed no perforation, aneurysm or pseudoaneurysm or special safety issues unique to radiotherapy.

Curved angiocatheter metal guide for the implantation in velo-tonsillar carcinomas

Brachytherapy in velo-tonsillar region is not applied in all the institutions because of difficulties to learn it. For the implantation of wires in the soft palate, the Reverdin needle is replaced by a curved guide of angiocatheter 14 Gauge. This technique is easy and reduces the risk of tear mucosa.

Feasibility study combining low dose rate (192)Ir brachytherapy and external beam radiotherapy aiming at delivering 80-85 Gy to prostatic adenocarcinoma

BACKGROUND

Increasing the radiation dose to prostatic adenocarcinoma has provided higher local control rates. A total of 80 Gy seem necessary to achieve this goal but patient set-up and prostate motion remain difficult problems to solve in conformal radiotherapy. Brachytherapy which overcomes these points could be an alternative way to external beam boost fields. We wanted to transpose the irradiation models largely used in cervix cancer treatment combining external beam radiotherapy and low dose rate brachytherapy.

MATERIALS AND METHODS

In 71 patients with 19.5 and 13 ng/ml mean and median PSA levels, respectively, a dose escalation from 74 to 85 Gy was performed in four groups.

RESULTS

Shifting from intraoperative placement of sources vectors (Group I) to positioning under ultrasound controls (groups II-IV), improving the implantation shape and optimizing radiation delivery to urethral bed have reduced the total dose to rectal wall under 65 Gy and to urethra under 100 Gy. Rectal/prostate dose ratio was lowered from 0.7 (Groups I-II) to 0.58 (Groups III-IV) while avoiding problems resulting from pelvic bone arch interference, prostate volume or seminal vesicles location. The mean and median follow-up periods are 28 and 18 months. In Groups III and IV 85% of patients without hormonotherapy treated with 80-85 Gy normalized PSA under 1 ng/ml within 6 months. No severe late effect has been noted for patients implanted under echographic control.

CONCLUSIONS

The method described allows to deliver 85 Gy. Longer follow-up is however needed but the levels of dose delivered are not expected to induce prohibitive side effects.

Interstitial iridium-192 implantation for recurrent and/or locally advanced head and neck cancer

We report our experience with the use of interstitial iridium-192 implantation in the management of patients with recurrent and locally advanced squamous cell carcinoma of the head and neck. Between June 1992 and July 1998 this technique was employed in the management of two groups of patients: (1) a primary group, comprising 42 patients who had presented for the first time with advanced head and neck disease, and had therefore not undergone any previous treatment; and (2) a salvage group of 16 patients with recurrent disease previously treated with external beam radiotherapy (four received therapy to the neck, one to the cheek, eight to the tongue and three to the floor of the mouth). The follow-up in each group was short, ranging from 3 to 56 months. The overall response in the primary group was 38/42 (90%). A complete response was achieved in 35/42 (83%). In the salvage group, the overall response was 13/16 (81%); 4/16 (25%) showed a complete response and 9/16 (56%) a partial response. The estimated percentage surviving at 1 year for patients with primary disease is 70% (95% confidence interval (CI) 54-86). For those receiving salvage therapy the estimated percentage surviving at 1 year is 45% (95% CI 19-71).

Size and positioning reproducibility of an 192Ir brachytherapy stepping source

In this paper we describe techniques for measuring the dimensions and position reproducibility of an 192Ir brachytherapy stepping source. Measurements were carried out using a 0.25x10x152 mm3 collimator placed in front of a detector of our own design. The brachytherapy source was translated past the collimator in 0.025 mm increments using a stepper motor. The source was found to be 3.58 mm long and 0.69 mm wide, which is in good agreement with the manufacturer's values of 3.5x0.6 mm2. The source position was reproducible to within 0.12 mm.

Percutaneous brachytherapy for small-sized non-small cell lung cancer

A patient with a small-sized pulmonary adenocarcinoma was successfully treated by percutaneous high dose rate interstitial brachytherapy alone. The patient, who had an adenocarcinoma with 12-mm diameter in the lingular lobe of left lung, was judged to be inoperable because of poor pulmonary function due to emphysema and extensive pleural adhesion. The tumor was punctured with a 21-gauge fine applicator needle followed by the introduction of an iridium 192 (192Ir) radioactive source through the applicator needle using a remote afterloader. The tumor was irradiated for 225.1 s in one fraction. The tumor was in the inside of the iso-dose line of 40 Gy. The delivered doses calculated at nine reference points, which were 12.5 mm distant from the center of the tumor, distributed between 19.225 and 32.169 Gy, with a mean of 24.8 Gy. No apparent side effect including pneumothorax and hemoptysis was observed. The tumor shrank and showed no increment of the size for about 2 years.

Scatter and attenuation measurements at distances greater than 10 cm from an 192Ir source

Most algorithms developed by various investigators for use in brachytherapy treatment planning have typically been designed to calculate the dose within a 10 cm range of a radiation source. These algorithms predict the dose well at distances < 10 cm from the source but were not developed and should not be utilized to predict the dose at distances > 10 cm. On the contrary, treatment planning systems and manual calculations will produce erroneous results when dose points > 10 cm are calculated using these algorithms. The spread in the data generated by the above algorithms is 16% at 15 cm and 42% at 20 cm. Physical measurements were performed at distances between 5 and 50 cm from a high activity 192Ir source in water. The measured data correlated well with the predicted data from 5 to 10 cm, which had a 5% spread. Beyond 10 cm the measured data fell central to the range of the predicted data, with the spread of the predicted data increasing from 5% to 80% with increasing distance from the source. The measured data was fitted with a model incorporating a buildup factor and an attenuation factor. The best fit values are in reasonable agreement with those obtained by two of the investigators, Thomason and Tripathi.

Interstitial brachytherapy in carcinoma of the penis

AIM

Keeping in line with the increasing emphasis on organ preservation, we at the Tata Memorial Hospital have evaluated the role of Ir-192 interstitial implant as regards local control, functional and cosmetic outcome in early as well as locally recurrent carcinoma of the distal penis.

PATIENTS AND METHODS

From October 1988 to December 1996, 23 patients with histopathologically proven cancer of the penis were treated with radical radiation therapy using Ir-192 temporary interstitial implant. Our patients were in the age group of 20 to 60 years. The primary lesions were T1 in 7, T2 in 7 and recurrent in 9 patients. Only 7 patients had palpable groin nodes at presentation, all of which were pathologically negative. The median dose of implant was 50 Gy (range 40 to 60 Gy), using the LDR afterloading system and the Paris system of implant rules for dosimetry. Follow-up ranged from 4 to 117 months (median 24 months).

RESULTS

At last follow-up 18 of the 23 patients remained locally controlled with implant alone. Three patients failed only locally, 2 locoregionally and 1 only at the groin. Of the 5 patients who failed locally, 4 were successfully salvaged with partial penectomy and remained controlled when last seen. Local control with implant alone at 8 years was 70% by life table analysis. The patients had excellent functional and cosmetic outcome. We did not record any case of skin or soft-tissue necrosis. Only 2 patients developed meatal stenosis, both of which were treated endoscopically.

CONCLUSION

Our results lead us to interpret that interstitial brachytherapy with Ir-192 offers excellent local control rates with preservation of organ and function. Penectomy can be reserved as a means for effective salvage.