The effect of ionizing radiation on intraocular lenses.

BACKGROUND: The native crystalline lens is the principal shield against ultraviolet radiation (UV), damage to the human retina. Every year in the United States, more than one million patients undergo removal of the natural lens in the course of cataract surgery (phakectomy), at which time an intraocular lens (IOL) is placed in the lens capsule. The IOL thenceforth serves as the principal barrier to ultraviolet radiation over the life of the implant, potentially for decades. The synthetic organic molecules of which IOLs are composed offer little UV protection unless ultraviolet-absorbing chromophores are incorporated into the lens material during manufacture. However, chromophores are alkenes potentially subject to radiolytic degradation. It is unknown whether ionizing radiation at clinical doses (e.g., to the brain or in the head-and-neck region) affects the UV-absorbing capacity of chromophore-bearing IOLs and consequently exposes the retina to potentially chronic UV damage. In addition, the polymers of which IOLs are composed are themselves subject to radiation damage, which theoretically might result in optical distortion in the visible light range. OBJECTIVE: To determine whether megavoltage photon ionizing radiation alters the absorption spectra of ultraviolet-shielding polymethylmethacrylate (PMMA) and organopolysiloxane (silicone) intraocular lenses (IOLs) in the UV (280 nm < or = lambda < 400 nm), visible (400 nm < or = lambda < or = 700 nm), and low-end near-infrared (700 nm < lambda < or = 830 nm) ranges. DESIGN: Prospective, nonrandomized trial of dose-paired IOL cohorts. METHODS: Fourteen IOLs, seven of PMMA (Chiron 6842B) and seven of silicone (IOLAB L141U), were paired and examined for absorption spectra in 1-nm intervals over the range lambda = 280-830 nm on a Cary 400 deuterium and quartz halogen source-lamp UV/visible spectrophotometer before and after undergoing megavoltage ionizing irradiation to doses of 2, 5, 10, 20, 40, 60, and 100 Gray, respectively. Because of artifactual aberrations inherent in analyzing convex lenses on a conventional flat-plate spectrophotometer, post-irradiation absorption spectra were subsequently reanalyzed on a Cary 300 spectrophotometer outfitted with a Labsphere Diffused Reflectance Accessory (DRA-CA-30-I) incorporating a Spectralon-coated integrating sphere. MAIN OUTCOME MEASURES: Primary: Changes in UV absorbance after irradiation. Secondary: Changes in visible and low-end near-infrared absorbance after irradiation. RESULTS: Photon ionizing radiation in the 2-Gy to 100-Gy range produced no detectable alterations in the UV (280 nm < or = lambda < 400 nm), visible (400 nm < or = lambda < or = 700 nm), or low-end near-infrared (700 nm < lambda < or = 830 nm) absorption spectra of any of the lenses irradiated. However, silicone IOLs as a group revealed peak post-irradiation UV absorption at a shorter wavelength than did PMMA IOLs, with marginally greater UV transmission at the uppermost extreme of the UV spectrum (lambda = 384.5-400 nm). CONCLUSIONS: At clinically relevant doses used in radiation therapy, megavoltage photon ionizing radiation produces no significant alterations in the absorption spectra of PMMA and silicone IOLs over the range lambda = 280- 830 nm. These findings indicate that, even at supraclinical doses, the UV-absorbing capacity of chromophore-bearing PMMA and silicone IOLs remains unimpaired. It is not clear whether the lower UV peak of silicone lenses represents a radiation effect or a peculiarity of the chromophore used in the lenses tested.

Bullous pemphigoid masquerading as acute radiation dermatitis: case report.

We report the first case of bullous pemphigoid complicating radiation therapy for vulvar cancer. Shortly after completion of postoperative radiation therapy for a TIN1 vulvar carcinoma, the patient presented with a rash that started within, but continued to extend, well beyond the radiation field. A biopsy of the lesions confirmed the diagnosis of bullous pemphigoid, and she had prompt clinical resolution with systemic tetracycline and steroids.

Practical considerations in setting up an intracoronary brachytherapy program: results of a multicenter survey.

PURPOSE: To identify logistic issues faced by radiation oncologists in initiating intracoronary radiation therapy (RT) and to delineate their role in these procedures. MATERIALS AND METHODS: Radiation oncologists from 12 sites (with combined experience of >500 cases) that participated in a randomized, double-blinded study of intracoronary RT completed a questionnaire that included demographics and experience, regulatory issues, scheduling and interaction with patients, time commitment, involvement of the radiation oncologist, and ideas for overcoming hurdles. RESULTS: Licensing was perceived as a substantial hurdle; Nuclear Regulatory Commission approval took more than 5 months at five of 12 sites. At two higher-volume sites, 10-20 procedures were performed per week; 75% of these radiation oncologists did not see the patient prior to the procedure and were not involved in obtaining informed consent. The mean time spent per case was 30-90 minutes; however, there were major concerns about case scheduling (<50% had any input in case scheduling) and after-hours coverage. Radiation oncologists performed fluoroscopy and cineangiography at most centers (92% and 83%); they also performed intracoronary contrast material injections (67%), interpreted intravascular ultrasonographic images (42%), and repositioned the intracoronary RT catheter (33%). CONCLUSION: The authors identify several issues that need to be addressed before intracoronary RT becomes a part of widespread clinical practice. Close collaboration between cardiologists and radiation oncologists at various levels is required to ensure that patients derive maximal benefit from this new technology.

Current therapy in the management of heterotopic ossification of the elbow: a review with case studies.

Heterotopic ossification, or the appearance of ectopic bone in para-articular soft tissues after surgery, immobilization, or trauma, complicates the surgical and physiatric management of injured joints. The chief symptoms of heterotopic ossification are joint and muscle pain and a compromised range of motion. Current therapies for prevention or treatment of heterotopic ossification include surgery, physical therapy, radiation therapy, and medical management. Unlike heterotopic ossification of the hip, heterotopic ossification of the elbow has not been extensively investigated, leaving its optimal management ill-defined. To remedy this deficiency, we review risk factors, clinical anatomy, physical findings, proposed mechanisms, and current practice for treatment and prevention of heterotopic ossification. We then consider and draw conclusions from four cases of elbow injury treated at our institutions (three complicated by heterotopic ossification) in which treatment included surgery, radiation therapy, physical therapy, and medical therapy. We summarize our institutional practices and conclude with a call for a randomized clinical trial to better define optimal management of heterotopic ossification of the elbow.

Radiation therapy to prevent stenosis of peripheral vascular accesses.

Postangioplasty vascular restenosis is a major clinical problem. There has been an upsurge in interest in the use of postangioplasty endovascular brachytherapy in preventing vascular restenosis. Much of the work in this field is being driven by the interventional cardiology community, and there has been a tendency to use a one-size-fits-all approach. This article reviews the application of vascular radiation therapy to prevent postangioplasty dialysis access restenosis. We identify the key features of dialysis accesses that distinguish them from other clinical situations of postangioplasty restenosis. The implications for interventional radiation therapy in this setting are discussed at length, including the need for a centering device, the issues involved in isotope selection, and the advantages offered by external-beam radiation therapy.

External beam radiation therapy to prevent postangioplasty dialysis access restenosis: a feasibility study.

PURPOSE: To evaluate the feasibility and short-term side-effects of postangioplasty external beam radiation for patients with compromised arteriovenous dialysis accesses. MATERIALS AND METHODS: Ten patients with compromised arteriovenous dialysis accesses were studied. Following confirmation of access compromise by an angiogram, patients were treated by a standard angioplasty +/- stent deployment. The target volume incorporated a margin of 1 cm beyond the angioplastied segment. The first 5 patients were treated to a dose of 12 Gy in two 6-Gy fractions spaced 48 h apart, whereas the next 5 patients were treated to 8 Gy in two similarly separated 4-Gy fractions. Five of the patients had at least one prior access that had failed. The current access had been in use for 6-52 months, and 5 of the 10 patients had at least one episode of compromise involving the current access. The length of stenosis ranged from 2 to 9 cm (mean 4.4 cm). All patients were followed clinically for adequacy of dialysis; a radiological follow-up with a fistulogram was performed for all in 3-monthly intervals. Follow-up ranged from 4 to 10 months, with a median follow-up of 6 months. RESULTS: There were no procedure-related complications. Three patients developed a restenosis at the site of the original stenosis, and one patient developed a restenosis at the edge of the stent. As part of the natural history of this process, five patients have also developed new lesions elsewhere in the proximal veins requiring radiological intervention. None of the patients showed any radiation-related side effects, either in the skin/ soft tissues, or in the vasculature on follow-up angiograms. CONCLUSIONS: Several different radiotherapeutic approaches are being currently investigated to prevent postangioplasty restenosis. There are several issues involved with the use of endovascular brachytherapy in these patients. On the other hand, given the superficial location of the dialysis access, we believe that external beam radiation offers a safe and simple method of radiation therapy in this setting. The clinical efficacy of this modality needs to be established through a randomized phase III trial.

The American Brachytherapy Society perspective on intravascular brachytherapy.

BACKGROUND: Recent clinical studies indicate that intravascular brachytherapy (IVB) can reduce the rate of restenosis substantially after angioplasty procedures. However, no clinical guidelines exist for optimal therapy. METHODS: The members of the IVB Subcommittee of the American Brachytherapy Society (ABS) identified the areas of consensus and controversies in IVB to issue the ABS perspective on IVB, based on analysis of published reports and the clinical experience of the members in brachytherapy. RESULTS: IVB is still experimental. The long-term efficacy, toxicity, the target tissue, and dose required for IVB are not established. The ABS recommends that IVB procedures must be performed, with careful attention to radiation-related issues, in the context of controlled multidisciplinary clinical trials with the approval of the institutional review board, the Nuclear Regulatory Commission, the Food and Drug Administration, and under an Investigational Device Exemption. The therapeutic radiologist, with a qualified radiation physicist, is responsible for dose prescription and delivery and needs to be present during the IVB procedure as part of this multidisciplinary team. The long-term outcome from these studies should be reviewed critically and published in peer-reviewed journals. The ABS endorsed the dosimetric guidelines of the American Association of Physicists in Medicine Task Group 60 (AAPM TG-60) report. The ABS recommends that dose specification be defined clearly; to allow comparisons between studies, the dose should be prescribed at 2 mm from the source for intracoronary brachytherapy and at an average luminal radius of +2 mm for peripheral vascular brachytherapy. The prescription doses at the above point is generally in the 12-18 Gy range. Comprehensive procedures for quality assurance, radiation protection, and emergencies should be in place before initiating an IVB program. Higher energy beta sources, lower energy gamma sources, dose-volume histograms, and correlation of three-dimensional reconstructions of delivered dose with patterns of failure are areas for further research. CONCLUSION: The ABS perspective on IVB is presented to assist the interventional team in developing protocols for the use of IVB in the prevention of restenosis. Long-term outcome data with a standardized reporting system are needed to establish the role of brachytherapy in preventing vascular restenosis. Endovascular brachytherapy is a new and evolving modality, and these recommendations are subject to modifications as new data become available.

Current issues in techniques of prostate brachytherapy.

Adenocarcinoma of the prostate is the most common malignancy diagnosed among men in the United States today. Brachytherapy permits conformal radiotherapy and dose escalation, and it offers the convenience of a single-day outpatient procedure which is very attractive to patients with a busy life-style. The reported potency preservation rates with brachytherapy are superior to both external beam radiation therapy (EBRT) and surgery. The older retropubic techniques have been replaced by ultrasound or CT-guided transperineal techniques. Prostate brachytherapy may be temporary or permanent, and the planning techniques for either approach are similar. This review briefly discusses the advantages and limitations of each. Temporary techniques may be used with low dose rate or high dose rate applications. The basic steps include assessing prostate volume by any diagnostic modality (CT or ultrasonography), determining total activity needed to encompass the gland and deliver the appropriate minimum peripheral dose, and determining the pattern of placement of the seeds within the gland. Preplanning may be done either by ultrasound or by CT. The operative technique requires the visualization of the prostate in three dimensions and is performed using combination of ultrasound and fluoroscopy or fluoroscopy in two axes. The New York Hospital technique employs CT-based preplanning along with ultrasound and fluoroscopy during the operative procedure. Special circumstances that necessitate neoadjuvant hormonal therapy include interference from the pubic arch and large volume glands. An analysis of patients with stage T2a disease treated at the New York Hospital-Queens, from 1990-1995, reveals an actuarial clinical freedom from relapse of 79% at 5 years and a 5-year biochemical freedom from relapse of 64% which is comparable to that reported for similar risk groups of disease by other centers. Potency is preserved in greater than 80% of patients in our series. Patient selection criteria include the pre-treatment prostate-specific antigen (PSA) level, tumor grade (Gleason), stage of disease, and presence or absence of bilateral positive biopsies and/or perineural invasion. Based on our review of the literature and our clinical results, we have divided patients with prostate cancer into good, intermediate and poor risk groups. We recommend brachytherapy as the sole procedure for good risk patients, and a combination of external beam radiation therapy (EBRT) and brachytherapy for the intermediate risk group. Future avenues for research include a search for improved imaging techniques and possibly newer isotopes.