AAPM Task Group 334: A guidance document to using radiotherapy immobilization devices and accessories in an MR environment

Use of magnetic resonance (MR) imaging in radiation therapy has increased substantially in recent years as more radiotherapy centers are having MR simulators installed, requesting more time on clinical diagnostic MR systems, or even treating with combination MR linear accelerator (MR-linac) systems. With this increased use, to ensure the most accurate integration of images into radiotherapy (RT), RT immobilization devices and accessories must be able to be used safely in the MR environment and produce minimal perturbations. The determination of the safety profile and considerations often falls to the medical physicist or other support staff members who at a minimum should be a Level 2 personnel as per the ACR. The purpose of this guidance document will be to help guide the user in making determinations on MR Safety labeling (i.e., MR Safe, Conditional, or Unsafe) including standard testing, and verification of image quality, when using RT immobilization devices and accessories in an MR environment.

Treatment of Recurrent Orbital Rhabdomyosarcoma with Exenteration and HDR Brachytherapy in a Custom Mold

PURPOSE/OBJECTIVE(S)

Rhabdomyosarcoma (RMS) is the most frequent cancer affecting the orbit in children. The orbit is classified as a favorable site for RMS as treatment with chemotherapy and radiation is effective. Local failure for patients with RMS of the orbit has ranged from 2-16% on IRS and COG protocols. In the event of local recurrence, survival is poor, and management is difficult. We report four patients with local recurrence of orbital RMS managed with orbital exenteration followed by high dose rate (HDR) brachytherapy.

MATERIALS/METHODS

Four patients were treated from 2016-2022. HDR brachytherapy with Ir-192 was delivered in a custom mold of the orbit made after the orbital exenteration procedure. Brachytherapy was given in 6-7 twice daily (BID) fractions starting 1 week after the orbital exenteration.

RESULTS

At the time of brachytherapy, patient ages were 3, 1, 7, and 7 years. Three patients had embryonal histology and underwent initial systemic therapy with ARST0331 regimen A. The fourth patient had alveolar, FOXO1 fusion positive RMS and was initially treated as per COG D9803 regimen A. All patients had received proton radiotherapy as part of initial treatment. Three received 50.40 Gy and one received 45 Gy. Patients developed biopsy-proven, recurrent disease an average of 56 weeks (range 38-77) after initial diagnosis. All patients received salvage chemotherapy before undergoing orbital exenteration at an average of 12 weeks after recurrence (range 5-16). Three patients received 30 Gy in 6 BID fractions, and one patient received 28 Gy in 7 fractions with HDR brachytherapy using an Ir-192 source. All four patients are alive without evidence of disease at an average of 27 months (range 6-70) from recurrence and 39 months (range 21-78) from initial diagnosis. All patients have acceptable orbit healing. Two patients have asymptomatic evidence of frontal lobe edema (and in one case possible necrosis) extending 1-2 cm above the orbit. This appears to be beyond the range of the brachytherapy dosimetry, but the combination of proton beam and brachytherapy are implicated. No other toxicities have occurred.

CONCLUSION

Orbital RMS has a favorable prognosis, but local failure after initial combined modality therapy can be fatal. Options for successful local salvage are limited. Orbital exenteration with HDR brachytherapy in a custom mold is an effective and safe procedure for local control in these difficult cases.

High-Dose-Rate Brachytherapy for Vaginal Rhabdomyosarcoma (RMS): Lessons Learned at a Single Institution

PURPOSE/OBJECTIVE(S)

Botryoid RMS is a rare pediatric tumor most commonly arising within the vaginal wall of girls under age three. Most patients are successfully treated with low-risk chemotherapy protocols but local treatment is required to minimize risk of local relapse. Intravaginal brachytherapy is an effective local therapy that can minimize sequelae in these very young patients.

MATERIALS/METHODS

We reviewed records of all patients with RMS who received intravaginal high-dose-rate brachytherapy from 2010-2022 at a single institution. All were treated with multiagent chemotherapy with or without minor surgical procedures, and had no gross disease prior to intravaginal brachytherapy. All patients underwent CT simulation under anesthesia and optimal-sized cylindrical applicators were chosen based on patient anatomy.

RESULTS

Twelve girls, median age 23 months (range 3-33), were treated with daily anesthesia. All were Stage 1 and 92% had Group III disease. A single patient had Group IIA disease based on up-front resection. Early in the series, 5 patients received 21 Gy in 7 fractions according to COG protocol guidelines. Subsequent patients received higher doses of 28-30 Gy in 7-10 fractions. Custom sized cylinders were used with diameters ranging from 1.2-1.6 cm and dose was prescribed to a median depth of 3 mm. Median mean dose to the rectum, bladder, uterus, and bilateral ovaries was 8.7 Gy, 7.2 Gy, 6.9 Gy, and 5.0 Gy, respectively. Median follow-up was 4 years (range 1-10). No acute or late side effects have occurred. At follow-up, three girls were of pubescent age, all three exhibited signs of puberty and two had reached menarche. Three girls (25%) suffered local relapse at a median of 15 months (range 5-16 months) after brachytherapy. One-year and five-year local control rates were 92% (95% CI 54-99%) and 70% (95% CI 32-89%), respectively. All relapses were in patients receiving 21 Gy and two were beyond full dose coverage of brachytherapy at the introitus and in the uterus. Subsequent patients receiving higher doses and full coverage of the vagina have had no local failures. Two of three patients who failed were cured with salvage therapy resulting in one-year and five-year overall survival rates of 100% and 86% (95% CI 33-98%), respectively.

CONCLUSION

Intravaginal high-dose-rate brachytherapy is an excellent option for local control of vaginal RMS with fewer long-term risks than external beam proton therapy or radical surgery. A dose of 28 Gy in 7 fractions prescribed to the entire vagina is necessary for optimal prevention of relapse. Longer follow-up is needed to confirm preservation of ovarian, reproductive, and sexual function.

Prospective Evaluation of MRI-Based Endoluminal Brachytherapy with Novel Applicator for Anorectal Cancer

PURPOSE/OBJECTIVE(S)

To present results of patients treated on a prospective dose escalation trial of MRI-based endoluminal high dose rate (HDR) brachytherapy (BT) and concurrent chemotherapy utilizing a novel double-balloon applicator for recurrent or inoperable rectal and anal cancer.

MATERIALS/METHODS

A total of 15 patients were enrolled on a prospective, institutional review board-approved dose escalation protocol evaluating endoluminal HDR-BT with concurrent chemotherapy. Inclusion criteria were histologically confirmed locally residual or recurrent cancer of the rectum or anus and prior pelvic external beam radiation therapy (EBRT). BT was delivered with a novel anorectal applicator consisting of an inner balloon, which supported 8 channels for the radioactive source, and a compliant outer balloon for optimal deformation against exophytic lesions. Applicator insertion and treatment delivery were performed under general anesthesia in 3 weekly sessions. MRI-based treatment planning was performed while under anesthesia during the first session only. Capecitabine (825 mg/m2 BID) was administered Monday-Friday on the weeks of BT. Efficacy and toxicity were evaluated by clinical assessment and MRI examinations at pre-defined intervals (3, 6, and 12 months for the first year) after the procedure.

RESULTS

From 1/2015 to 4/2018 15 patients at a median age of 65 years (43-86) with recurrent or residual cancer (9 rectal, 6 anal) were enrolled and treated at the initial dose level of 15 Gy in 3 fractions (n = 6), the intermediate dose level of 18 Gy in 3 fractions (n = 3), and the highest dose level of 21 Gy in 3 fractions (n = 6). Treatment was delivered as planned for 14 patients; 1 patient was treated with a single-channel Bougie applicator for the third fraction due to the development of severe circumferential narrowing that prevented insertion of the endorectal applicator. On first MRI imaging post-BT, 7 patients had a complete response, 5 patients had a partial response, 1 patient had progressive disease, and 2 patients had indeterminate imaging. At a median follow up of 26 months (7-88), 10 patients (6 rectal and 4 anal) have developed a local recurrence (2 also with distant disease) which were treated with surgery (4), systemic therapy (1), or no known therapy (3). Acute (<6 months post-RT) grade 2 and 3 toxicities were observed in 1 (rectal bleeding) and 2 (anorectal pain) patients, respectively, and the only late grade 3 toxicity observed was rectal bleeding in 1 patient.

CONCLUSION

Endoluminal HDR BT with MRI-based treatment planning and a novel double-balloon applicator was feasible up to a dose level of 21Gy in 3 fractions in patients with non-operable rectal or anal cancers and history of prior EBRT. The clinical efficacy and toxicity associated with this treatment should be more clearly defined with analyses of larger cohorts of patients.

Pre-Brachytherapy Diffusion-Weighted Magnetic Resonance Imaging (DW-MRI) Response as Predictor of Local Control in the Definitive Treatment of Cervical Cancer

PURPOSE/OBJECTIVE(S)

Chemoradiation consisting of external beam radiotherapy (EBRT) followed by brachytherapy (BT) is the standard of care for Stage IB2-IVA cervical cancer (CC). Multi-parametric MRI (mpMRI) is a valuable tool for initial staging, treatment planning and response assessment. In this study, we aim to explore the potential of mpMRI, in particular DW-MRI, to predict overall tumor control following chemoradiation in CC.

MATERIALS/METHODS

We identified 78 consecutive patients treated with chemoradiation for FIGO IB2-IVA CC between 2012-2020, who had an MRI at baseline (MRb) and post-EBRT prior to brachytherapy boost (MRpb) that included DW-MRI (b-value = 0 and 800 s/mm2). Median age was 53 years, most patients had squamous cell carcinoma (76.9%) and advanced-stage disease (56.4% stage IIIA-IVA). Median time from completion of EBRT to MRpb was 3 days. Regions of interest (ROI) in primary tumor were delineated on DW image (b = 0 s/mm2) using ITK-SNAP software. DW-MRI data were fitted to a monoexponential model to calculate apparent diffusion coefficient (ADC) values using in-house software platform (MRI-QAMPER). MRpb mean ADC values (n = 78) and relative changes (%) in mean ADC values between MRb and MRpb (n = 64) were correlated with outcomes, including local failure (LF), regional or distant failure (RDF), and failure at any site (FAS), with death without failure as a competing risk. Median follow-up time was 45 months (95% CI 38, 53).

RESULTS

At first post treatment assessment, 72 patients (92.3%) had a complete response (CR) in the cervix and 68 patients (87.2%) had CR in all disease sites. Of patients who had CR in the cervix (n = 72), only 1 patient had local recurrence. Of patients who had CR in all disease sites, 10 later recurred (1 LF only, 1 LF&RDF, 8 RDF only). Overall, 7 patients (9%) had LF, and 19 patients (24.4%) had FAS. A higher mean ADC value in MRpb was associated with LF (HR 4.3, 95% CI 1.32, 14.6; P = 0.016), but not with RDF (P = 0.4) or FAS (P = 0.5). A higher relative change in the mean ADC value between MRb and MRpb was associated with a lower risk of LF (HR 0.94, 95% CI 0.90, 0.98; P = 0.002), but not with RDF (P = 0.8) or FAS (P = 0.4).

CONCLUSION

Treatment response as measured on prebrachytherapy DW-MRI is a significant predictor of local control in patients undergoing chemoradiation for stage IB2-IVA CC. ADC values, a quantitative imaging biomarker on MRpb may be instrumental in dose intensification/de-escalation efforts in CC.

Feasibility and Safety of Diffusing Alpha-Emitter Radiation Therapy for Recurrent or Unresectable Skin Cancers

Importance

Patients with recurrent or unresectable skin cancers have limited treatment options. Diffusing alpha-emitter radiation therapy (DaRT), a novel solid tumor management strategy using alpha-particle interstitial brachytherapy, may address this challenge.

Objective

To evaluate the feasibility and safety of using DaRT to manage recurrent or unresectable skin cancers.

Design, Setting, and Participants

This prospective cohort study of patients who received a 2-week to 3-week treatment course and were followed up for 24 weeks after treatment during 2021 and 2022 at 2 sites in the US. Patients with malignant skin tumors or soft tissue tumors were recruited if they had limited treatment options for tumors recurrent after prior surgery or external beam radiotherapy or unresectable tumors.

Intervention

Patients underwent DaRT to deliver a physical dose of 10 Gy (equivalent weighted dose of 200 CGE) to the tumor.

Main Outcomes and Measures

Feasibility of the DaRT procedure was evaluated based on the ability of investigators to successfully deliver radiation to the tumor. Patients were followed up for adverse events (AEs) for 24 weeks and for tumor response by physicians' physical examination and imaging 12 weeks after device removal.

Results

This study included 10 participants with recurrent or unresectable skin cancer (median [IQR] age, 72 [68-75] years; 6 males [60%]; 4 females [40%]). Six patients (60%) had recurrent disease, and 4 (40%) had tumors that were deemed unresectable. Tumors were located on the nose, chin, eyelid, scalp, neck, trunk, and extremities. Median (range) tumor volume before treatment was 2.1 cm3 (0.65-12.65 cm3). The mean (SD) prescription dose coverage of the gross tumor volume was 91% (2.8%) with all tumors having coverage of 85% or more. No device-related grade 3 AEs were noted. Common AEs were grade 1 to 2 erythema, edema, and pruritus. At 12 weeks following treatment, there was a 100% complete response rate. Nine of 10 complete responses (90%) were confirmed by CT imaging.

Conclusions and Relevance

This cohort study suggests the feasibility and preliminary safety of DaRT in the management of recurrent or unresectable skin cancers. The favorable safety profile and high response rates are promising. A US trial for marketing approval based on this pilot study is under way.

Trial Registration

ClinicalTrials.gov Identifier: NCT04377360.

AAPM medical physics practice guideline 13.a: HDR brachytherapy, part A

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines (MPPGs) will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines: (1) Must and must not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. (2) Should and should not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances. Approved by AAPM's Executive Committee April 28, 2022.

Salvage resection plus cesium-131 brachytherapy durably controls post-SRS recurrent brain metastases

BACKGROUND

Salvage of recurrent previously irradiated brain metastases (rBrM) is a significant challenge. Resection without adjuvant re-irradiation is associated with a high local failure rate, while reirradiation only partially reduces failure but is associated with greater radiation necrosis risk. Salvage resection plus Cs131 brachytherapy may offer dosimetric and biologic advantages including improved local control versus observation, with reduced normal brain dose versus re-irradiation, however data are limited.

METHODS

A prospective registry of consecutive patients with post-stereotactic radiosurgery (SRS) rBrM undergoing resection plus implantation of collagen-matrix embedded Cs131 seeds (GammaTile, GT Medical Technologies) prescribed to 60 Gy at 5 mm from the cavity was analyzed.

RESULTS

Twenty patients underwent 24 operations with Cs131 implantation in 25 tumor cavities. Median maximum preoperative diameter was 3.0 cm (range 1.1-6.3). Gross- or near-total resection was achieved in 80% of lesions. A median of 16 Cs131 seeds (range 6-30), with a median air-kerma strength of 3.5 U/seed were implanted. There was one postoperative wound dehiscence. With median follow-up of 1.6 years for survivors, two tumors recurred (one in-field, one marginal) resulting in 8.4% 1-year progression incidence (95%CI = 0.0-19.9). Radiographic seed settling was identified in 7/25 cavities (28%) 1.9-11.7 months post-implantation, with 1 case of distant migration (4%), without clinical sequelae. There were 8 cases of radiation necrosis, of which 4 were symptomatic.

CONCLUSIONS

With > 1.5 years of follow-up, intraoperative brachytherapy with commercially available Cs131 implants was associated with favorable local control and toxicity profiles. Weak correlation between preoperative tumor geometry and implanted tiles highlights a need to optimize planning criteria.

Safety practices and opportunities for improvement in brachytherapy: A patient safety practices survey of the American Brachytherapy Society membership

PURPOSE

Safe delivery of brachytherapy and establishing a safety culture are critical in high-quality brachytherapy. The American Brachytherapy Society (ABS) Quality and Safety Committee surveyed members regarding brachytherapy services offered, safety practices during treatment, quality assurance procedures, and needs to develop safety and training materials.

METHODS AND MATERIALS

A 22-item survey was sent to ABS membership in early 2019 to physicians, physicists, therapists, nurses, and administrators. Participation was voluntary. Responses were summarized with descriptive statistics and relative frequency distributions.

RESULTS

There were 103 unique responses. Approximately one in three was attending physicians and one in three attending physicists. Most were in practice >10 years. A total of 94% and 50% performed gynecologic and prostate brachytherapy, respectively. Ninety-one percent performed two-identification patient verification before treatment. Eighty-six percent performed a time-out. Ninety-five percent had an incident reporting or learning system, but only 71% regularly reviewed incidents. Half reviewed safety practices within the last year. Twenty percent reported they were somewhat or not satisfied with department safety culture, but 92% of respondents were interested in improving safety culture. Most reported time, communication, and staffing as barriers to improving safety. Most respondents desired safety-oriented webinars, self-assessment modules, learning modules, or checklists endorsed by the ABS to improve safety practice.

CONCLUSIONS

Most but not all practices use standards and quality assurance procedures in line with society recommendations. There is a need to heighten safety culture at many departments and to shift resources (e.g., time or staffing) to improve safety practice. There is a desire for society guidance to improve brachytherapy safety practices. This is the first survey to assess safety practice patterns among a national sample of radiation oncologists with expertise in brachytherapy.

Intraoperative implantation of a mesh of directional palladium sources (CivaSheet): Dosimetry verification, clinical commissioning, dose specification, and preliminary experience

PURPOSE

To present the clinical commissioning of a novel ¹⁰³Pd directional brachytherapy device (CivaSheet) for intraoperative radiation therapy.

METHODS AND MATERIALS

Clinical commissioning for the CivaSheet consisted of establishing: (1) source strength calibration capabilities, (2) experimental verification of TG-43 dosimetry parameters, (3) treatment planning system validation, and (4) departmental practice for dose specification and source ordering. Experimental verification was performed in water with radiochromic film calibrated with a 37 kVp X-ray beam. Percentage difference ([measurements - calculation]/calculation) and distance to agreement (difference between film-to-source distance and distance that minimized the percentage difference) were calculated. Nomogram values (in U/100 Gy) for all configurations (up to 20 × 20 sources) were calculated for source ordering. Clinical commissioning was used on patients enrolled in an ongoing Institutional Review Board-approved protocol.

RESULTS

A source calibration procedure was established, and the treatment planning system was commissioned within standard clinical uncertainties. Percentage dose differences (distances to agreement) between measured and calculated doses were 8.6% (-0.12 mm), 0.6% (-0.01 mm), -6.4% (0.22 mm), and -10.0% (0.44 mm) at depths of 2.3, 5.1, 8.0, and 11.1 mm, respectively. All differences were within the experimental uncertainties. Nomogram values depended on sheet size and spatial extent. A value of 2.4U/100 Gy per CivaDot was found to satisfy most cases, ranging from 2.3 to 3.3U/100 Gy. Nomogram results depended on elongation of the treatment area with a higher variation observed for smaller treatment areas. Postimplantation dose evaluation was feasible.

CONCLUSIONS

Commissioning and clinical deployment of CivaSheet was feasible using BrachyVision for postoperative dose evaluation. Experimental verification confirmed that the available TG-43 dosimetry parameters are accurate for clinical use.

Magnetic resonance imaging basics for the prostate brachytherapist

Magnetic resonance imaging (MRI) is increasingly being used in radiation therapy, and integration of MRI into brachytherapy in particular is becoming more common. We present here a systematic review of the basic physics and technical aspects of incorporating MRI into prostate brachytherapy. Terminology and MRI system components are reviewed along with typical work flows in prostate high-dose-rate and low-dose-rate brachytherapy. In general, the brachytherapy workflow consists of five key components: diagnosis, implantation, treatment planning (scan + plan), implant verification, and delivery. MRI integration is discussed for diagnosis; treatment planning; and MRI-guided brachytherapy implants, in which MRI is used to guide the physical insertion of the brachytherapy applicator or needles. Considerations and challenges for establishing an MRI brachytherapy program are also discussed.

Hip-related toxicity after prostate radiotherapy: Treatment related or coincidental?

BACKGROUND AND PURPOSE

To evaluate the incidence and predictors of hip toxicity postradiotherapy for localized prostate cancer.

METHODS AND MATERIALS

4067 prostate cancer patients were treated with external beam radiotherapy (EBRT; n=2569; 63%) or brachytherapy with or without supplemental EBRT (n=1508; 27%). 43% (n=1738) were treated with neo-adjuvant and concurrent ADT and 57% (n=2329) with radiotherapy alone. Hip toxicity was defined as moderate or severe pain upon ambulation with or without the need for hip-revision surgery. Median follow-up was 7years (range, 3-21years).

RESULTS

One hundred twenty-one (2.7%) patients developed moderate-to-severe hip pain after radiotherapy affecting ambulation. Of these, 73 (60%) required hip replacement secondary to persistent hip pain. Among patients with baseline degenerative joint disease (DJD) changes on scans, 10-year incidence of hip-related toxicity was 11% versus 3% for those without such changes (P<.001). The only variables on multivariate analysis associated with hip-related toxicity post-radiotherapy were baseline DJD on imaging (P<.0001) and prolonged ADT for salvage therapy (P<.0001).

CONCLUSIONS

Prostate EBRT or brachytherapy is associated with low incidence of long-term hip-related toxicity. The only variables identified associated with hip toxicity posttherapy was the presence of baseline DJD and prolonged salvage ADT posttreatment for patients developing recurrence.

Impact of source position on high-dose-rate skin surface applicator dosimetry

PURPOSE

Skin surface dosimetric discrepancies between measured and treatment planning system predicted values were traced to source position sag inside the applicator and to source transit time. We quantified their dosimetric impact and propose corrections for clinical use.

METHODS AND MATERIALS

We measured the dose profiles from the Varian Leipzig-style high-dose-rate (HDR) skin applicator, using EBT3 film, photon diode, and optically stimulated luminescence dosimeter for three different GammaMedplus HDR afterloaders. The measured dose profiles at several depths were compared with BrachyVision Acuros calculated profiles. To assess the impact of the source sag, two different applicator orientations were considered. The dose contribution during source transit was assessed by comparing diode measurements using an HDR timer and an electrometer timer.

RESULTS

Depth doses measured using the three dosimeters were in good agreement, but were consistently higher than the Acuros dose calculations. Measurements with the applicator face up were significantly (exceeding 10%) lower than those in the face down position, due to source sag inside the applicator. Based on the inverse square law, the effective source sag was evaluated to be about 0.5 mm from the planned position. The additional dose during source transit was evaluated to be about 2.8% for 30 seconds of treatment with a 40700 U (10 Ci) source.

CONCLUSION

With a very short source-to-surface distance, the small source sag inside the applicator has a significant dosimetric impact. This effect is unaccounted for in the vendor's treatment planning template and should be considered before the clinical use of the applicator. Further investigation of other applicators with large source lumen diameter may be warranted.

High-dose-rate brachytherapy of rhabdomyosarcoma limited to the external auditory canal

PURPOSE

To report on the single-catheter high-dose-rate brachytherapy treatment of a 21-month-old girl child with an embryonal, botryoid-type, rhabdomyosarcoma limited to the external auditory canal (EAC).

METHODS AND MATERIALS

A 2.4-mm diameter catheter was inserted into the right EAC and placed against the tympanic membrane. A computed tomography simulation scan was acquired. A brachytherapy treatment plan, in which 21 Gy in seven fractions was prescribed to a 1-mm depth along the distal 2 cm of the catheter, was generated. Treatments were delivered under anesthesia without complication. A dosimetric comparison between this plan and an intensity-modulated radiation therapy (IMRT) plan was then conducted. A clinical target volume (CTV), which encompassed a 1-mm margin along the distal 2 cm of the catheter, was delineated for both plans. Given positioning uncertainty under image guidance, a planning target volume (PTV = CTV + 3-mm margin) was defined for the IMRT plan. The IMRT plan was optimized for maximal CTV coverage but subsequently normalized to the same CTV volume receiving 100% of the prescription dose (V₁₀₀) of the brachytherapy plan.

RESULTS

The IMRT plan was normalized to the brachytherapy CTV V₁₀₀ of 82.0%. The PTV V₁₀₀ of this plan was 34.1%. The PTV exhibited dosimetric undercoverage within the middle ear and toward the external ear. Mean cochlea doses for the IMRT and brachytherapy plans were 26.7% and 10.5% of prescription, respectively.

CONCLUSIONS

For rhabdomyosarcomas limited to the EAC, a standard brachytherapy catheter can deliver a highly conformal radiation plan that can spare the nearby cochlea from excess radiation.

Radiation safety of receptive anal intercourse with prostate cancer patients treated with low-dose-rate brachytherapy

PURPOSE

Prostate low-dose-rate (LDR) brachytherapy involves implantation of radioactive seeds permanently into the prostate gland. During receptive anal intercourse, the penis of the partner may come in close proximity to the implanted prostate gland. We estimate the potential intrarectal dose rates and suggest guidance on radiation precautions.

METHODS AND MATERIALS

One hundred two patients were included in the study. After implantation, with patients under anesthesia in the dorsal lithotomy position, a new set of ultrasound (US) images and a CT scan were obtained. The images were fused, radioactive seeds and US probe locations were determined on the CT, and prostate, bladder, and rectal contours were drawn on the US. Dose rates (cGy/h) were calculated for the portion of the US probe spanning the prostate for several dose-volume histogram parameters.

RESULTS

Twenty patients were treated with (125)I and 82 patients with (103)Pd. Average dose rates at Day 0 to the portion of the US probe spanning the prostate were 2.1 ± 1.3 cGy/h and 2.5 ± 0.8 cGy/h for patients treated with (125)I and (103)Pd, respectively. After 60 days, average calculated probe dose drops to 1.0 ± 0.6 cGy/h and 0.2 ± 0.1 cGy/h for (125)I and (103)Pd, respectively.

CONCLUSIONS

During the immediate weeks after prostate seed implant, the estimated intrarectal dose rates are higher in (103)Pd compared to (125)I. As (103)Pd decays faster than (125)I, 2 months after the implant, radiation exposure from (103)Pd becomes lower than (125)I. Receptive anal intercourse time should be kept as low as possible during 2 and 6 months after low-dose-rate brachytherapy of the prostate with (103)Pd and (125)I, respectively.

Long-term outcome of magnetic resonance spectroscopic image-directed dose escalation for prostate brachytherapy

PURPOSE

To report the long-term control and toxicity outcomes of patients with clinically localized prostate cancer, who underwent low-dose-rate prostate brachytherapy with magnetic resonance spectroscopic image (MRSI)-directed dose escalation to intraprostatic regions.

METHODS AND MATERIALS

Forty-seven consecutive patients between May 2000 and December 2003 were analyzed retrospectively. Each patient underwent a preprocedural MRSI, and MRS-positive voxels suspicious for malignancy were identified. Intraoperative planning was used to determine the optimal seed distribution to deliver a standard prescription dose to the entire prostate, while escalating the dose to MRS-positive voxels to 150% of prescription. Each patient underwent transperineal implantation of radioactive seeds followed by same-day CT for postimplant dosimetry.

RESULTS

The median prostate D90 (minimum dose received by 90% of the prostate) was 125.7% (interquartile range [IQR], 110.3-136.5%) of prescription. The median value for the MRS-positive mean dose was 229.9% (IQR, 200.0-251.9%). Median urethra D30 and rectal D30 values were 142.2% (137.5-168.2%) and 56.1% (40.1-63.4%), respectively. Median followup was 86.4 months (IQR, 49.8-117.6). The 10-year actuarial prostate-specific antigen relapse-free survival was 98% (95% confidence interval, 93-100%). Five patients (11%) experienced late Grade 3 urinary toxicity (e.g., urethral stricture), which improved after operative intervention. Four of these patients had dose-escalated voxels less than 1.0 cm from the urethra.

CONCLUSIONS

Low-dose-rate brachytherapy with MRSI-directed dose escalation to suspicious intraprostatic regions exhibits excellent long-term biochemical control. Patients with dose-escalated voxels close to the urethra were at higher risk of late urinary stricture.

High- and low-dose-rate intraoperative radiotherapy for thoracic malignancies resected with close or positive margins

PURPOSE

Local recurrence is a significant problem after surgical resection of thoracic tumors. As intraoperative radiotherapy (IORT) can deliver radiation directly to the threatened margin, we have used this therapy in an attempt to reduce local recurrence, using high-dose-rate (HDR) as well as low-dose-rate (LDR) techniques.

METHODS AND MATERIALS

We performed a retrospective review of patients undergoing LDR ((125)I) mesh placement or HDR ((192)Ir) afterloading therapy during lung tumor resection between 2001 and 2013 at our institution. Competing risks methods were used to estimate the cumulative incidence of local failure. We also assessed possible predictive factors of local failure.

RESULTS

Fifty-nine procedures (41 LDR and 18 HDR) were performed on 58 patients. Median follow-up was 55.1 months. Cumulative incidence of local failure at 1, 2, and 3 years was 28.5%, 34.2%, and 34.2%, respectively. Median overall survival was 39.9 months. There was no significant difference in local failure according to margin status, HDR vs. LDR, use of adjuvant external beam radiotherapy, or metastatic vs. primary tumor. Two patients (3.4%) experienced Grade 3+ toxicities likely related to brachytherapy. Additionally, 7 patients experienced Grade 3+ postsurgical complications unlikely related to brachytherapy.

CONCLUSIONS

IORT is associated with good local control after resection of thoracic tumors otherwise at very high risk for local recurrence. There is a low incidence of severe toxicity attributable to brachytherapy. HDR-IORT appears to have equivalent outcomes to LDR-IORT. HDR or LDR-IORT can, therefore, be considered in situations where the oncologic completeness of thoracic tumor resection is in doubt.

Intraoperative high-dose rate of radioactive phosphorus 32 brachytherapy for diffuse recalcitrant conjunctival neoplasms: a retrospective case series and report of toxicity

IMPORTANCE

Adjunct treatments for conjunctival malignancies are needed when standard therapy provides limited benefits or fails.

OBJECTIVE

To describe the results of patients with diffuse conjunctival neoplasms treated with radioactive phosphorus 32 (32P)-impregnated flexible film.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective case series between January 1, 2010, and January 1, 2013, was conducted at Memorial Sloan-Kettering Cancer Center, a tertiary referral center. The study was conducted on 7 eyes of 6 patients treated for diffuse conjunctival squamous cell carcinoma, sebaceous carcinoma, or lymphoma that had recurrent or residual disease after primary treatment.

INTERVENTIONS

Patients underwent mapping biopsies and detailed conjunctival drawings to delineate the pathologic extent of the disease. The brachytherapy film used for treatment was the RIC Conformal Source Model 100 (RIC-100, RI Consultants). The RIC-100 is a flexible, thin (approximately 0.5-mm) film made of a polymer chemically bound to 32P. The radioactive 32P film was placed intraoperatively, allowed to stay in place until the prescription dose was reached, and then removed. The median dose at the prescription point (1 mm from the surface of the film) was 15 Gy (range, 5-17 Gy).

MAIN OUTCOMES AND MEASURES

Patients were tested for best-corrected visual acuity, recurrence-free survival, and adverse events scored by using the Adult Comorbidity Evaluation-27 scale.

RESULTS

Between 2010 and 2013, 7 eyes of 6 patients were treated. The median age of patients was 70 years. All patients had a recurrent or persistent neoplasm. Four patients with squamous cell carcinoma, 1 with sebaceous carcinoma, and 1 with metachronous bilateral lymphomas were treated. The median treatment time was 19 minutes (range, 10-52 minutes). The median follow-up was 24.9 months (range, 3.1-38.2 months). Recurrence-free survival 24 months after brachytherapy was 75% (95% CI, 19-89.1). Two moderate adverse events and 1 severe adverse event occurred. Visual acuity was stable or improved in 5 of the 7 eyes (ie, better than 20/70 in the 5 patients who retained their treated eye).

CONCLUSIONS AND RELEVANCE

Our results show the use of an intraoperative high-dose rate of 32P brachytherapy in selected cases of recalcitrant diffuse conjunctival neoplasms. This technique offers a novel adjunct in the treatment of these cancers. Further follow-up and study are warranted.

Qualitative evaluation of fiducial markers for radiotherapy imaging

PURPOSE

To evaluate visibility, artifacts, and distortions of various commercial markers in magnetic resonance imaging (MRI), computer tomography (CT), and ultrasound imaging used for radiotherapy planning and treatment guidance.

METHODS

We compare 2 solid gold markers, 4 gold coils, and 1 polymer marker from 3 vendors. Imaging modalities used were 3-T and 1.5-T GE MRIs, Siemens Sequoia 512 Ultrasound, Phillips Big Bore CT, Varian Trilogy linear accelerator (cone-beam CT [CBCT], on-board imager kilovoltage [OBI-kV], electronic portal imaging device megavoltage [EPID-MV]), and Medtronic O-ARM CBCT. Markers were imaged in a 30 × 30 × 10 cm(3) custom bolus phantom. In one experiment, Surgilube was used around the markers to reduce air gaps. Images were saved in Digital Imaging and Communications in Medicine (DICOM) format and analyzed using an in-house software. Profiles across the markers were used for objective comparison of the markers' signals. The visibility and artifacts/distortions produced by each marker were assessed qualitatively and quantitatively.

RESULTS

All markers are visible in CT, CBCT, OBI-kV, and ultrasound. Gold markers below 0.75 mm in diameter are not visible in EPID-MV images. The larger the markers, the more CT and CBCT image artifacts there are, yet the degree of the artifact depends on scan parameters and the scanner itself. Visibility of gold coils of 0.75 mm diameter or larger is comparable across all imaging modalities studied. The polymer marker causes minimal artifacts in CT and CBCT but has poor visibility in EPID-MV. Gold coils of 0.5 mm exhibit poor visibility in MRI and EPID-MV due to their small size. Gold markers are more visible in 3-T T1 gradient-recalled echo than in 1.5-T T1 fast spin-echo, depending on the scan sequence. In this study, all markers are clearly visible on ultrasound.

CONCLUSION

All gold markers are visible in CT, CBCT, kV, and ultrasound; however, only the large diameter markers are visible in MV. When MR and EPID-MV imagers are used, the selection of fiducial markers is not straightforward. For hybrid kV/MV image-guided radiotherapy imaging, larger diameter markers are suggested. If using kV imaging alone, smaller sized markers may be used in smaller sized patients in order to reduce artifacts. Only larger diameter gold markers are visible across all imaging modalities.

(106)Ru plaque brachytherapy for uveal melanoma: factors associated with local tumor recurrence

PURPOSE

Plaque brachytherapy is a common form of treatment for uveal melanoma, and the Collaborative Ocular Melanoma Study (COMS) used (125)I. Recently, (106)Ru has been reintroduced for plaque brachytherapy in the United States. We reviewed our experience treating uveal melanoma with (106)Ru plaque brachytherapy using COMS planning techniques, hypothesizing that we would observe similar outcomes to those in the COMS.

METHODS AND MATERIALS

Medical records of patients undergoing (106)Ru plaque brachytherapy were reviewed retrospectively. Patient, tumor, and treatment characteristics were recorded. Outcomes including visual acuity, local tumor recurrence, salvage treatment, metastasis, and survival were recorded. Cox regression analyses were used to determine factors associated with local tumor recurrence and enucleation.

RESULTS

Twenty-eight patients were studied. Median age was 60 years, and 50% were men. Median tumor base diameter and height were 9.4 and 2.6 mm, respectively. Ophthalmic complications were rare. Local tumor recurrence and enucleation occurred in 13 and 4 patients, respectively. Local tumor recurrence was associated with low visual acuity in the tumor-bearing eye, posterior tumors, small plaque size, and difference in plaque-tumor diameter of <6 mm. Enucleation was associated with low visual acuity and posteriorly located tumor. Estimated 5-year rate of death and metastasis was 18.5% and 11.4%, respectively.

CONCLUSIONS

Among patients treated with (106)Ru plaque brachytherapy using COMS planning techniques, we found a greater than expected rate of local tumor recurrence. Planning (106)Ru plaque brachytherapy should be done carefully at centers that have previously used COMS protocols and (125)I.

A comparative dosimetric analysis of virtual stereotactic body radiotherapy to high-dose-rate monotherapy for intermediate-risk prostate cancer

PURPOSE

Stereotactic body radiotherapy (SBRT) is being used with increasing frequency as definitive treatment of early stage prostate cancer. Much of the justification for its adoption was derived from earlier clinical results using high-dose-rate (HDR) brachytherapy. We determine whether HDR's dosimetry can be achieved by virtual SBRT.

METHODS AND MATERIALS

Patients with intermediate-risk prostate cancer on a prospective trial evaluating the efficacy of HDR monotherapy treated to dose of 9.5Gy×4 fractions were used for this study. A total of 5 patients were used in this analysis. Virtual SBRT plans were developed to reproduce the planning target volume (PTV) HDR dose distributions. Both normal tissue- and PTV-prioritized plans were generated.

RESULTS

From the normal tissue-prioritized plan, HDR and virtual SBRT achieved similar PTV V100 (93.8% vs. 93.1%, p=0.20) and V150 (40.3% vs. 42.9%, p=0.69) coverage. However, the PTV V200 was not attainable with SBRT (15.2% vs. 0.0%, p<0.001). The rectal Dmax was significantly lower with HDR (94.2% vs. 99.42%, p=0.05). The rectal D2 cc was also lower (60.8% vs. 71.1%, p=0.07). Difference in D1 cc urethral dose was not significantly different (87.7% vs. 75.2%, p=0.33). Comparing the PTV-prioritized plans, the rectal Dmax (94.2% vs. 111.1%, p=0.05) and mean dose (27.1% vs. 33.3%, p=0.03) were significantly higher using SBRT, and the rectal D2 cc was higher using SBRT (60.8% vs. 81.8%, p=0.07).

CONCLUSIONS

HDR achieves significantly higher intraprostatic doses while achieving a lower maximum rectal dose compared with our virtual SBRT treatment planning. Future studies should compare clinical outcomes and toxicity between these modalities.

Intraoperative and percutaneous iridium-192 high-dose-rate brachytherapy for previously irradiated lesions of the spine

PURPOSE

Advances in stereotactic radiosurgery have improved local control of spine metastases, but local failure is still a problem and repeat irradiation is limited by normal tissue tolerance. A novel high-dose-rate (HDR) brachytherapy technique has been developed to treat these previously irradiated lesions.

METHODS AND MATERIALS

Five patients with progressive disease at previously irradiated sites in the spine who were not amenable to further external beam radiation were treated. Catheters were placed intraoperatively in 2 patients and percutaneously implanted in 3 patients with image-guided techniques. Conformal plans were generated to deliver dose to target tissues and spare critical structures. Patients received single-fraction treatment using HDR iridium-192 brachytherapy.

RESULTS

Median dose was 14 Gy (range, 12-18 Gy) with a median gross total volume D90 of 75% (range, 31-94%); spinal cord/cauda equina dose constraints were met. At a median followup of 9 months, no local progression of disease has been observed. Four patients had reduction in pain 1-4 weeks after treatment. No brachytherapy-related complications have been observed.

CONCLUSIONS

Intraoperative and percutaneous iridium-192 HDR spine brachytherapy techniques were not associated with complications or acute toxicity. There has been no local progression at treated sites, and most patients experienced reduction in cancer-related pain.

Endoluminal high-dose-rate brachytherapy for early stage and recurrent esophageal cancer in medically inoperable patients

PURPOSE

The management of superficial primary and recurrent esophageal cancer (EC) in medically inoperable patients is complex. Endoluminal high-dose-rate (HDR) brachytherapy has shown mixed results in terms of toxicity and local control. In this study, we examined the outcomes and toxicities in a set of patients with superficial primary and recurrent EC treated with a consistent HDR technique.

METHODS AND MATERIALS

Between 8/2008 and 7/2011, 14 patients were treated with HDR intraluminal brachytherapy, 10 (71.4%) with recurrent disease, and 4 (28.6%) with previously unirradiated lesions. Patients received three weekly fractions to a median dose of 12 Gy (range, 10-15 Gy); dose was prescribed to 7-mm median depth with mucosal dose limited to 8-10 Gy using a 12-14-mm applicator.

RESULTS

Median followup was 15.4 months. Overall freedom from failure (OFFF) and overall survival (OS) at 18 months were 30.8% (95% confidence interval [CI]: 5.2, 56.4) and 72.7% (95% CI: 45.3, 100), respectively. For patients with recurrent disease, OFFF and OS at 18 months were 11.1% (95% CI: 0, 32.1) and 55.6% (95% CI: 15.4, 95.8), respectively. For patients with previously unirradiated disease, OFFF and OS at 18 months were 75.0% (95% CI: 31.6, 100) and 100.0%, respectively. Eight (57.1%) patients had Grade 1 acute adverse effects; 6 (42.9%) patients had chronic Grade 1 adverse effects; 1 (7.1%) patient developed Grade 2 stricture. Grade 3 tracheoesophageal fistula occurred in 1 (7.1%) patient. One patient died before completion of treatment of unrelated causes.

CONCLUSIONS

HDR endoluminal brachytherapy is a well-tolerated treatment for superficial primary and recurrent EC in medically inoperable patients.

Intraoperative 32P High-Dose Rate Brachytherapy of the Dura for Recurrent Primary and Metastatic Intracranial and Spinal Tumors

BACKGROUND:

Treatment of spinal and intracranial tumors with dural involvement is complicated by radiation tolerance of sensitive structures, especially in the setting of previous treatment.

OBJECTIVE:

To evaluate whether intraoperative brachytherapy with short-range sources allows therapeutic dose delivery without damaging sensitive structures.

METHODS:

The median doses of previous treatment were 3000 cGy (range, 1800-7200 cGy) for 8 patients with primary/recurrent and 17 patients with metastatic spinal tumors and 5040 cGy (range, 1300-6040 cGy) for 5 patients with locally recurrent and 2 patients with metastatic intracranial tumors. Patients underwent gross total or maximal resection of the tumor and were then treated with an intraoperative brachytherapy plaque consisting of a flexible silicone film incorporating 32P. A dose of 1000 cGy was delivered to a depth of 1 mm; the percent depth dose was less than 1% at 4 mm from the prescription depth. Median postoperative radiation doses of 2700 cGy (range, 1800-3000 cGy) were delivered to 15 spinal tumor patients and 3000 cGy (range, 1800-3000 cGy) to 3 intracranial tumor patients. The median follow-up was 4.4 months (range, 2.6-23.3 months) for spinal tumor patients and 5.3 months (range, 0.7-16.2) for intracranial tumor patients.

RESULTS:

At 6-month follow-up, for all spinal tumor patients, local progression-free survival and overall survival rates were both 83.3% (95% confidence interval [CI]: 62.3%-94.3%); for all intracranial tumor patients, the local progression-free survival rate was 62.5% (95% CI: 23.8%-90.9%) and the overall survival rate was 66.7% (95% CI: 26.7%-92.9%). There were no intraoperative or postoperative complications secondary to radiotherapy.

CONCLUSION:

Use of the 32P brachytherapy plaque is technically simple and not associated with increased risk of complications, even after multiple radiation courses. Local control rates were more than 80% in patients with proven radiation-resistant spinal disease.

American Brachytherapy Society consensus guidelines for high-dose-rate prostate brachytherapy

PURPOSE

A well-established body of literature supports the use of high-dose-rate (HDR) brachytherapy as definitive treatment for localized prostate cancer. Most of the articles describe HDR as a boost with adjuvant external beam radiation, but there is a growing experience with HDR monotherapy.

METHODS AND MATERIALS

The American Brachytherapy Society has convened a group of expert practitioners and physicists to develop guidelines for the use of HDR in the management of prostate cancer. This involved an extensive literature review and input from an expert panel.

RESULTS

Despite a wide variation in doses and fractionation reported, HDR brachytherapy provides biochemical control rates of 85-100%, 81-100%, and 43-93% for low-, intermediate-, and high-risk prostate cancers, respectively. Severe toxicity is rare, with most authors reporting less than 5% Grade 3 or higher toxicity. Careful attention to patient evaluation for appropriate patient selection, meticulous technique, treatment planning, and delivery are essential for successful treatment.

CONCLUSION

The clinical outcomes for HDR are excellent, with high rates of biochemical control, even for high-risk disease, with low morbidity. HDR monotherapy, both for primary treatment and salvage, are promising treatment modalities.

A comparison of the impact of isotope ((125)I vs. (103)Pd) on toxicity and biochemical outcome after interstitial brachytherapy and external beam radiation therapy for clinically localized prostate cancer

PURPOSE

To compare biochemical outcomes and morbidity associated with iodine-125 ((125)I) and palladium-103 ((103)Pd) brachytherapy as part of combined modality therapy for clinically localized prostate cancer.

METHODS AND MATERIALS

Between October 2002 and December 2008, 259 patients underwent prostate brachytherapy ((125)I prescription dose, 110Gy: n=199; (103)Pd prescription dose, 100Gy: n=60) followed by external beam radiotherapy (median dose, 50.4Gy). Eighty-seven patients also received neoadjuvant androgen deprivation therapy. Toxicities were recorded with CTCAE v 3.0, International Prostate Symptoms Score (IPSS), and International Index of Erectile Function questionnaires.

RESULTS

Overall, acute Grade ≥2 genitourinary toxicity occurred in 21% and 30% of patients treated with (125)I and (103)Pd, respectively (p=0.16). There were no significant differences in IPSS change or urinary quality-of-life scores between the isotopes at 4, 6, or 12 months (p=0.20, 0.21, and 1.0, respectively). IPSS resolution occurred at a median of 11 and 6 months for (125)I and (103)Pd patients, respectively (p=0.03). On multivariate analysis, only the use of neoadjuvant androgen deprivation therapy was predictive of time to IPSS resolution (p=0.046). Late Grade ≥2 gastrointestinal toxicity occurred in 7% of (125)I patients and 6% of patients treated with (103)Pd. Of 129 potent patients at baseline, there was better erectile function in patients who received (103)Pd (p=0.02); however, the followup was shorter for these patients. The 5-year prostate-specific antigen relapse-free survival for (125)I and (103)Pd patients was 95.2% and 98.2% (p=0.73), respectively.

CONCLUSION

There were no differences in acute or long-term genitourinary or gastrointestinal toxicity between (125)I and (103)Pd in combined modality therapy for prostate cancer. There may be less erectile toxicity with the use of (103)Pd; however, additional followup of these patients is needed. There was no significant difference in 5-year prostate-specific antigen relapse-free survival between (103)Pd and (125)I.

Intraoperative real-time planned conformal prostate brachytherapy: Post-implantation dosimetric outcome and clinical implications

PURPOSE

To report the dosimetric outcome of patients with clinically localized prostate cancer treated with I-125 permanent implantation using an intraoperative real-time conformal planning technique.

METHODS AND MATERIALS

Five hundred and sixty-two patients with prostate cancer were treated with I-125 permanent interstitial implantation using a transrectal ultrasound-guided approach. Real-time intraoperative treatment planning software that incorporates inverse planning optimization was used. Dose-volume constraints for this inverse-planning system included: prostate V100 >or=95%, maximal urethral dose <or=120%, and average rectal dose <80% of the prescription dose. Day zero computed tomography scans were acquired for post-implantation dosimetric evaluation.

RESULTS

The median V100 and D90 to the prostate target were 96% and 166 Gy, respectively. In 91% of cases a D90 of >or=140 Gy was achieved. In these patients, the V100 and D90 values did not have a significant influence on PSA relapse-free survival outcomes. The median maximum rectal dose and urethral doses were 104 Gy (72% of the prescription dose) and 187 Gy (130% of the prescription dose). The average and maximum rectal doses exceeding 100% of the prescription dose were less than 1% and 10% of patients, respectively. Average and maximum urethral doses exceeding 150% of the prescription dose were noted in 3% and 24% of patients, respectively. Average and maximum urethral doses exceeded 120% of the prescription dose in 21% and 58% of patients, respectively. Among patients where >or=2.5 cm(3) of the rectum was exposed to the prescription dose, the incidence of late grade 2 toxicity rectal toxicity was 9% compared to 4% for smaller volumes of the rectum exposed to similar doses (p=0.003). No dosimetric parameter in these patients with tight dose confines for the urethra influenced acute or late urinary toxicity.

CONCLUSION

Real-time intraoperative planning was associated with a 90% consistency of achieving the planned intraoperative dose constraints for target coverage and maintaining planned urethral and rectal constraints in a high percentage of implants. Rectal volumes of >or=2.5 cm(3) exposed to the prescription doses were associated with an increased incidence of grade 2 rectal bleeding. Further enhancements in imaging guidance for optimal seed deposition are needed to guarantee optimal dose distribution for all patients. Whether such improvements lead to further reduction in acute and late morbidities associated with therapy requires further study.

High-dose-rate interstitial brachytherapy in recurrent and previously irradiated head and neck cancers—Preliminary results

PURPOSE

Although high-dose-rate brachytherapy (HDRBT) offers significant advantages over low dose rate brachytherapy, there are scant data on improved local control (LC) and treatment-related complications in patients with recurrent head and neck (H&N) cancers. We report our preliminary results in patients with recurrent H&N cancers treated with interstitial HDRBT.

METHODS AND MATERIALS

Thirty patients with recurrent H&N cancers were treated with HDRBT between September 2003 and October 2005. Seventy-seven percent (23/30) of the patients had either local or regional recurrence in the area of previous external beam radiation therapy. The treatment sites were oral cavity/oropharynx (11/30), neck (10/30), face/nasal cavity (6/30), and parotid bed (3/30). Whereas 18 patients underwent surgical resection followed by HDRBT, 3 patients were treated with combined external beam radiation and HDRBT, and the remaining 9 were treated with HDRBT alone. The dose and fractionation schedules used were 3.4Gy twice per day (b.i.d.) to 34Gy for postoperative cases, 4Gy b.i.d. to 20Gy when combined with 40-50Gy external beam, and 4Gy b.i.d. to 40Gy for definitive treatment. HDRBT was initiated 5 days after catheter placement to allow for tissue healing.

RESULTS

With a median followup of 12 months, 6 local recurrences were observed 1-10 months after the procedure. The 2-year LC and overall survival outcomes for the entire group were 71% and 63%, respectively. Patients treated with surgical resection and HDRBT had an improved 2-year LC compared to the patients treated with HDRBT+/-external beam radiation alone (88% vs. 40%, p=0.05). Six Grade II and four Grade III complications were noted in five patients, all observed in the postoperative HDRBT group.

CONCLUSION

The preliminary results of HDRBT indicate an acceptable LC and morbidity in recurrent H&N cancers. A planned surgical resection followed by HDRBT is associated with improved tumor control in these high-risk patients. Based on these encouraging results, prospective clinical trials are warranted using HDRBT in recurrent H&N cancers to decrease late toxicity.

Five-year outcome of intraoperative conformal permanent I-125 interstitial implantation for patients with clinically localized prostate cancer

PURPOSE

To report the 5-year tumor control and toxicity outcomes for patients with localized prostate treated with I-125 permanent implantation using an intraoperative real-time conformal planning technique.

METHODS AND MATERIALS

Between January 1998 and June 2002, 367 patients with prostate cancer were treated with I-125 permanent interstitial implantation using a transrectal ultrasound-guided approach. Real-time intraoperative treatment planning which incorporated inverse planning optimization was used. The median follow-up time was 63 months.

RESULTS

The median V100 and D90 were 96% and 173 Gy, respectively. In 96% of cases a D90 of >140 Gy was achieved. The median urethral and rectal doses were 100% and 33% of the prescription doses, respectively. The 5-year PSA relapse-free survival outcomes for favorable and intermediate risk patients according to the ASTRO definition were 96% and 89%, respectively. In these patients no dosimetric parameter was identified which influenced the biochemical outcome. Of 38% who developed acute Grade 2 urinary symptoms, 63% had resolution of their symptoms within a median time of 6 months. The incidence of late rectal and urinary Grade 3 or higher toxicities were 1% and 4%, respectively. Seven percent (n = 27) developed late rectal bleeding (Grade 2) and 19% experienced late Grade 2 urinary symptoms.

CONCLUSION

Real-time intraoperative planning consistently achieved optimal coverage of the prostate with the prescription dose with concomitant low doses delivered to the urethra and rectum. Biochemical control outcomes were excellent at 5 years and late toxicity was unusual. These data demonstrate that real-time planning methods can consistently and reliably deliver the intended dose distribution to achieve an optimal therapeutic ratio between the target and normal tissue structures.

Calibration procedures for seeds preloaded in cartridges

Radioactive seeds preloaded in sterilized cartridges or needles are commonly obtainable from manufacturers. Under the US regulations for control of radioactive materials, seed users are required to account for all seeds and independently verify their air kerma strength (SK). As a result, the viability of inspection schemes that rely on measurement of aggregate seeds is of interest. In this paper we consider the conditions (if any) under which cartridge inspection can satisfy regulatory requirements and still provide practical benefit (i.e., time savings) against the regular single-seed assay. The standards for comparison are the recommendations of AAPM TG40, AAPM TG56, and ACR's "Standard for the Performance of Manually Loaded Brachytherapy Sources." The practical benefit is judged in comparison to the effort required to apply the 10% assay recommendation of TG40 to seeds in cartridges. Two specific cartridge inspection schemes are considered: (a) measuring the SK of each cartridge in a batch; (b) measuring a single cartridge sampled at random from the batch. Unlike the 10% assay, which is defined (imperfectly, in our view) without reference to the prevalence of in-calibration seeds, the estimation of the relative merits of cartridge inspection methods must necessarily include such information and, as such, is manufacturer specific. In this paper results are provided for Oncura model 6711 125I seeds in shielded and unshielded Mick cartridges. We show that the only practically useful cartridge inspection scheme is the batch scheme applied to unshielded cartridges. The false positive rates associated with the other schemes are such that we expect to open a cartridge (and perform the 10% assay) at least 80% of the time. While anything less than 100% of the time is theoretically an improvement, this neglects the additional effort required to assay the cartridges.

Combining pattern discovery and discriminant analysis to predict gene co-regulation

MOTIVATION

Several pattern discovery methods have been proposed to detect over-represented motifs in upstream sequences of co-regulated genes, and are for example used to predict cis-acting elements from clusters of co-expressed genes. The clusters to be analyzed are often noisy, containing a mixture of co-regulated and non-co-regulated genes. We propose a method to discriminate co-regulated from non-co-regulated genes on the basis of counts of pattern occurrences in their non-coding sequences.

METHODS

String-based pattern discovery is combined with discriminant analysis to classify genes on the basis of putative regulatory motifs.

RESULTS

The approach is evaluated by comparing the significance of patterns detected in annotated regulons (positive control), random gene selections (negative control) and high-throughput regulons (noisy data) from the yeast Saccharomyces cerevisiae. The classification is evaluated on the annotated regulons, and the robustness and rejection power is assessed with mixtures of co-regulated and random genes.