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Li W, Padayachee J, Navarro I, Winter J, Dang J, Raman S, Kong V, Berlin A, Catton C, Glicksman R, Malkov V, McPartlin A, Kataki K, Lindsay P, Chung P. Practice-based training strategy for therapist-driven prostate MR-Linac adaptive radiotherapy. Tech Innov Patient Support Radiat Oncol 2023; 27:100212. [PMID: 37265510 PMCID: PMC10230256 DOI: 10.1016/j.tipsro.2023.100212] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 04/19/2023] [Accepted: 05/09/2023] [Indexed: 06/03/2023] Open
Abstract
Purpose To develop a practice-based training strategy to transition from radiation oncologist to therapist-driven prostate MR-Linac adaptive radiotherapy. Methods and materials In phase 1, 7 therapists independently contoured the prostate and organs-at-risk on T2-weighted MR images from 11 previously treated MR-Linac prostate patients. Contours were evaluated quantitatively (i.e. Dice similarity coefficient [DSC] calculated against oncologist generated online contours) and qualitatively (i.e. oncologist using a 5-point Likert scale; a score ≥ 4 was deemed a pass, a 90% pass rate was required to proceed to the next phase). Phase 2 consisted of supervised online workflow with therapists required no intervention from the oncologist on 10 total cases to advance. Phase 3 involved unsupervised therapist-driven workflow, with offline support from oncologists prior to the next fraction. Results In phase 1, the mean DSC was 0.92 (range 0.85-0.97), and mean Likert score was 3.7 for the prostate. Five therapists did not attain a pass rate (3-5 cases with prostate contour score < 4), underwent follow-up one-on-one review, and performed contours on a further training set (n = 5). Each participant completed a median of 12 (range 10-13) cases in phase 2; of 82 cases, minor direction were required from the oncologist on 5 regarding target contouring. Radiation oncologists reviewed 179 treatment fractions in phase 3, and deemed 5 cases acceptable but with suggestions for next fraction; all other cases were accepted without suggestions. Conclusion A training stepwise program was developed and successfully implemented to enable a therapist-driven workflow for online prostate MR-Linac adaptive radiotherapy.
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Affiliation(s)
- Winnie Li
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Jerusha Padayachee
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
| | - Inmaculada Navarro
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
| | - Jeff Winter
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Jennifer Dang
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
| | - Srinivas Raman
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Vickie Kong
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Alejandro Berlin
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Charles Catton
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Rachel Glicksman
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Victor Malkov
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Andrew McPartlin
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Kaushik Kataki
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
| | - Patricia Lindsay
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
| | - Peter Chung
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada
- Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada
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Berger D, Van Dyk S, Beaulieu L, Major T, Kron T. Modern Tools for Modern Brachytherapy. Clin Oncol (R Coll Radiol) 2023:S0936-6555(23)00182-6. [PMID: 37217434 DOI: 10.1016/j.clon.2023.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 03/28/2023] [Accepted: 05/04/2023] [Indexed: 05/24/2023]
Abstract
This review aims to showcase the brachytherapy tools and technologies that have emerged during the last 10 years. Soft-tissue contrast using magnetic resonance and ultrasound imaging has seen enormous growth in use to plan all forms of brachytherapy. The era of image-guided brachytherapy has encouraged the development of advanced applicators and given rise to the growth of individualised 3D printing to achieve reproducible and predictable implants. These advances increase the quality of implants to better direct radiation to target volumes while sparing normal tissue. Applicator reconstruction has moved beyond manual digitising, to drag and drop of three-dimensional applicator models with embedded pre-defined source pathways, ready for auto-recognition and automation. The simplified TG-43 dose calculation formalism directly linked to reference air kerma rate of high-energy sources in the medium water remains clinically robust. Model-based dose calculation algorithms accounting for tissue heterogeneity and applicator material will advance the field of brachytherapy dosimetry to become more clinically accurate. Improved dose-optimising toolkits contribute to the real-time and adaptive planning portfolio that harmonises and expedites the entire image-guided brachytherapy process. Traditional planning strategies remain relevant to validate emerging technologies and should continue to be incorporated in practice, particularly for cervical cancer. Overall, technological developments need commissioning and validation to make the best use of the advanced features by understanding their strengths and limitations. Brachytherapy has become high-tech and modern by respecting tradition and remaining accessible to all.
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Affiliation(s)
- D Berger
- International Atomic Energy Agency, Vienna International Centre, Vienna, Austria.
| | - S Van Dyk
- Radiation Therapy Services, Division of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia
| | - L Beaulieu
- Service de Physique Médicale et Radioprotection, et Axe Oncologie du Centre de Recherche du CHU de Québec, CHU de Québec, Québec, Canada; Département de Physique, de Génie Physique et d'Optique et Centre de Recherche sur le Cancer, Université Laval, Québec, Canada
| | - T Major
- Radiotherapy Centre, National Institute of Oncology, Budapest, Hungary; Department of Oncology, Semmelweis University, Budapest, Hungary
| | - T Kron
- Peter MacCallum Cancer Centre and Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Australia; Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia
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Cousins MM, Heckman P, Short E, Narayana V, Bryant AK, Evans C, Hixson G, Hurley P, McLaughlin PW. Rectal sparing in prostate radiotherapy with combination-brachytherapy and hydrogel spacer. Brachytherapy 2022; 21:300-307. [DOI: 10.1016/j.brachy.2021.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 10/11/2021] [Accepted: 11/09/2021] [Indexed: 11/25/2022]
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Prostate radiotherapy in the setting of bilateral hip prostheses: All commonly used photon-based radiation approaches are feasible. Med Dosim 2021; 46:404-410. [PMID: 34175156 DOI: 10.1016/j.meddos.2021.05.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 03/02/2021] [Accepted: 05/11/2021] [Indexed: 11/22/2022]
Abstract
The prevalence of hip prostheses is increasing. Prostate radiation delivery in the setting of hip prostheses is complicated by both imaging artifacts that interfere with volume delineation and dosimetric effects that must be addressed in the planning process. We hypothesized that with specialized planning, any photon-based definitive prostate radiotherapy approach may be utilized in patients with bilateral hip prostheses. Imaging data from sequential patients with prostate cancer and bilateral hip prostheses treated definitively with radiation were retrospectively reviewed. Bimodality imaging was used to define targets and organs at risk (OARs) along with specialized MRI sequences and/or orthopedic metal artifact reduction (OMAR) for MRI and CT artifact suppression, respectively. Multiple VMAT plans were generated for each set of patient images to include three fractionation schemes (conventional, hypofractionated, and SBRT), each with hip avoidance and with simulated normal hip. The ability to meet standard dose constraints was assessed for each plan type. Differences in target and OAR dosing between plans accounting for prosthetic hips via avoidance vs plans with simulated absence of prosthetic hip were also assessed. T-tests were used to compare dosimetric parameters. Ten patients with bilateral hip prostheses were identified, and 6 plans were created for each patient for a total of 60 radiation plans. Prosthetic hip avoidance did not result in failure to meet dose constraints for any patient. Hip avoidance resulted in minimal increases in high dose to the rectum and bladder (increases in mean V80%, V90%, and V95% ranged from 0.1% to 2.4%). Larger increases were seen at lower dose levels, with rectal V50% significantly increased in all three plan types with hip avoidance (conventional: 26.0% [standard deviation, SD 13.9] vs 16.9% [SD 10.2, p = 0.003]; hypofractionation: 26.4% [SD 13.3] vs 17.1% [SD 10.1, p = 0.002]; SBRT: 18.3% [SD 10.7] vs 10.5% [SD 6.9, p = 0.008]). Similarly, hip avoidance resulted in increases in bladder V50% to 31.7% (SD 16.8) vs 23.3% (SD 14.0, p = 0.001), 31.3% (SD 17.0) vs 23.3% (SD 13.8, p = 0.002), and 22.7% (SD 12.3) vs 16.5% (SD 12.6, p < 0.001) for conventional, hypofractionated, and SBRT plans, respectively. Hydrogel spacer resulted in reductions in rectal dose. For example, V70% for hip avoidance plans decreased with spacer presence to 8.3% (SD 6.7) vs 21.1% (SD 5.8, p = 0.021), 8.6% (SD 6.5) vs 21% (SD 5.7, p = 0.022), and 3.7% (SD 3.2) vs 15% (SD 8.2, p = 0.010) for conventional, hypofractionated, and SBRT plans, respectively. Any photon-based definitive prostate radiotherapy approach can be used with bimodality imaging for target and OAR definition and planning techniques to avoid dose attenuation effects of hip prostheses. Hydrogel spacer is a useful adjunct.
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McLaughlin PW, Narayana V. Progress in Low Dose Rate Brachytherapy for Prostate Cancer. Semin Radiat Oncol 2020; 30:39-48. [DOI: 10.1016/j.semradonc.2019.08.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Glicksman R, Sanmamed N, Thoms J, Zlotta AR, Finelli A, van der Kwast T, Sweet J, Jewett M, Klotz LH, Rosewall T, Fleshner NE, Bristow RG, Warde P, Berlin A. A Phase 1 Pilot Study of Preoperative Radiation Therapy for Prostate Cancer: Long-Term Toxicity and Oncologic Outcomes. Int J Radiat Oncol Biol Phys 2019; 104:61-66. [PMID: 30625410 DOI: 10.1016/j.ijrobp.2018.12.054] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 12/22/2018] [Accepted: 12/30/2018] [Indexed: 12/30/2022]
Abstract
PURPOSE Neoadjuvant radiation therapy (RT) improves disease control in various cancers and has become an established oncologic treatment strategy. During 2001 to 2004, we conducted a phase 1 pilot study assessing the role of short-course preoperative RT (PreORT) for men with unfavorable intermediate- and high-risk localized prostate cancer. Herein, we present long-term follow-up toxicity and oncologic outcomes. METHODS AND MATERIALS Eligible patients had histologically proven prostate cancer, cT1-T2N0M0 disease, prostate-specific antigen >15 to 35 ng/mL regardless of Gleason score, or prostate-specific antigen 10 to 15 ng/mL with Gleason score ≥7. Patients received 25 Gy in 5 consecutive daily fractions (5 Gy per fraction) to the prostate only, followed by radical prostatectomy within 14 days after RT completion. Primary outcomes were intraoperative morbidity and late genitourinary (GU) and gastrointestinal toxicities. RESULTS In total, 15 patients were enrolled; 14 patients completed PreORT followed by radical prostatectomy, which also included bilateral lymph node dissections in 13 cases. Median follow-up was 12.2 years (range, 6.7-16.3). Late GU toxicity was common, with 2 patients (13.3%) experiencing G2 toxicity and 6 patients (40%) G3 toxicity. There were no patients with G4 to G5 late GU toxicity. Late gastrointestinal toxicity was infrequent, with only 1 patient (6.7%) experiencing transient G2 proctitis. At last follow-up, 8 (53.3%) and 6 (40%) patients experienced biochemical and metastatic disease recurrence, respectively. CONCLUSIONS The use of PreORT in men with high-risk prostate cancer is associated with unexpected high rates of late GU toxicity. Future studies examining the role of RT preradical prostatectomy must cautiously select RT technique and dose schedule. Importantly, long-term follow-up data are essential to fully determine the therapeutic index of PreORT in the management of localized disease.
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Affiliation(s)
- Rachel Glicksman
- Department of Radiation Oncology, University of Toronto, Toronto, Canada.
| | - Noelia Sanmamed
- Department of Radiation Oncology, University of Toronto, Toronto, Canada; Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - John Thoms
- Discipline of Oncology, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Canada
| | - Alexandre R Zlotta
- Division of Urology, Department of Surgery, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Antonio Finelli
- Division of Urology, Department of Surgery, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Theodorus van der Kwast
- Department of Pathology, Toronto General Hospital, University Health Network, Toronto, Canada
| | - Joan Sweet
- Department of Pathology, Toronto General Hospital, University Health Network, Toronto, Canada
| | - Michael Jewett
- Division of Urology, Department of Surgery, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Laurence H Klotz
- Department of Surgery (Urology), Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Canada
| | - Tara Rosewall
- Department of Radiation Oncology, University of Toronto, Toronto, Canada; Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Neil E Fleshner
- Division of Urology, Department of Surgery, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Robert G Bristow
- Manchester Cancer Research Centre, University of Manchester, Manchester, United Kingdom
| | - Padraig Warde
- Department of Radiation Oncology, University of Toronto, Toronto, Canada; Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Alejandro Berlin
- Department of Radiation Oncology, University of Toronto, Toronto, Canada; Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada; Techna Institute, University Health Network, Toronto, Canada.
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Grisotto S, Cerrotta A, Pappalardi B, Carrara M, Messina A, Tenconi C, Valdagni R, Fallai C. Pre-implant magnetic resonance and transrectal ultrasound imaging in high-dose-rate prostate brachytherapy: comparison of prostate volumes, craniocaudal extents, and contours. J Contemp Brachytherapy 2018; 10:285-290. [PMID: 30237811 PMCID: PMC6142648 DOI: 10.5114/jcb.2018.77947] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 08/17/2018] [Indexed: 11/17/2022] Open
Abstract
PURPOSE The purpose of this study was to compare the prostate contours drawn by two radiation oncologists and one radiologist on magnetic resonance (MR) and transrectal ultrasound (TRUS) images. TRUS intra- and inter-fraction variability as well as TRUS vs. MR inter-modality and inter-operator variability were studied. MATERIAL AND METHODS Thirty patients affected by localized prostate cancer and treated with interstitial high-dose-rate (HDR) prostate brachytherapy at the National Cancer Institute in Milan were included in this study. Twenty-five patients received an exclusive two-fraction (14 Gy/fraction) treatment, while the other 5 received a single 14 Gy fraction as a boost after external beam radiotherapy. The prostate was contoured on TRUS images acquired before (virtual US) and after (real US) needle implant by two radiation oncologists, whereas on MR prostate was independently contoured by the same radiation oncologists (MR1, MR2) and by a dedicated radiologist (MR3). Absolute differences of prostate volumes (│ΔV│) and craniocaudal extents (│Δdz│) were evaluated. The Dice's coefficient (DC) was calculated to quantify spatial overlap between MR contours. RESULTS Significant difference was found between Vvirtual and Vlive (p < 0.001) for the first treatment fractions and between VMR1 and VMR2 (p = 0.043). Significant difference between cranio-caudal extents was found between dzvirtual and dzlive (p < 0.033) for the first treatment fractions, between dzvirtual of the first treatment fractions and dzMR1 (p < 0.001) and between dzMR1 and dzMR3 (p < 0.01). Oedema might be responsible for some of the changes in US volumes. Average DC values resulting from the comparison MR1 vs. MR2, MR1 vs. MR3 and MR2 vs. MR3 were 0.95 ± 0.04 (range, 0.82-0.99), 0.87 ± 0.04 (range, 0.73-0.91) and 0.87 ± 0.04 (range, 0.72-0.91), respectively. CONCLUSIONS Our results demonstrate the importance of a multiprofessional approach to TRUS-guided HDR prostate brachytherapy. Specific training in MR and US prostate imaging is recommended for centers that are unfamiliar with HDR prostate brachytherapy.
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Affiliation(s)
- Simone Grisotto
- Medical Physics Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan
| | - Annamaria Cerrotta
- Radiotherapy 2 Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan
| | - Brigida Pappalardi
- Radiotherapy 2 Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan
| | - Mauro Carrara
- Medical Physics Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan
| | - Antonella Messina
- Diagnostic Imaging Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan
| | - Chiara Tenconi
- Medical Physics Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan
| | - Riccardo Valdagni
- Radiotherapy 1 Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan
- Prostate Program, Scientific Directorate, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan
- Department of Medicine and Surgery, Universita’ degli Studi, Milan, Italy
| | - Carlo Fallai
- Radiotherapy 2 Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan
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Use of magnetic resonance imaging in low-dose-rate and high-dose-rate prostate brachytherapy from diagnosis to treatment assessment: Defining the knowledge gaps, technical challenges, and barriers to implementation. Brachytherapy 2017; 16:672-678. [DOI: 10.1016/j.brachy.2017.01.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 01/31/2017] [Indexed: 01/03/2023]
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Zaorsky NG, Davis BJ, Nguyen PL, Showalter TN, Hoskin PJ, Yoshioka Y, Morton GC, Horwitz EM. The evolution of brachytherapy for prostate cancer. Nat Rev Urol 2017; 14:415-439. [PMID: 28664931 PMCID: PMC7542347 DOI: 10.1038/nrurol.2017.76] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Brachytherapy (BT), using low-dose-rate (LDR) permanent seed implantation or high-dose-rate (HDR) temporary source implantation, is an acceptable treatment option for select patients with prostate cancer of any risk group. The benefits of HDR-BT over LDR-BT include the ability to use the same source for other cancers, lower operator dependence, and - typically - fewer acute irritative symptoms. By contrast, the benefits of LDR-BT include more favourable scheduling logistics, lower initial capital equipment costs, no need for a shielded room, completion in a single implant, and more robust data from clinical trials. Prospective reports comparing HDR-BT and LDR-BT to each other or to other treatment options (such as external beam radiotherapy (EBRT) or surgery) suggest similar outcomes. The 5-year freedom from biochemical failure rates for patients with low-risk, intermediate-risk, and high-risk disease are >85%, 69-97%, and 63-80%, respectively. Brachytherapy with EBRT (versus brachytherapy alone) is an appropriate approach in select patients with intermediate-risk and high-risk disease. The 10-year rates of overall survival, distant metastasis, and cancer-specific mortality are >85%, <10%, and <5%, respectively. Grade 3-4 toxicities associated with HDR-BT and LDR-BT are rare, at <4% in most series, and quality of life is improved in patients who receive brachytherapy compared with those who undergo surgery.
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Affiliation(s)
- Nicholas G Zaorsky
- Department of Radiation Oncology, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, Pennsylvania 19111-2497, USA
| | - Brian J Davis
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Charlton Bldg/Desk R - SL, Rochester, Minnesota 5590, USA
| | - Paul L Nguyen
- Department of Radiation Oncology, Brigham and Women's Hospital, 75 Francis St BWH. Radiation Oncology, Boston, Massachusetts 02115, USA
| | - Timothy N Showalter
- Department of Radiation Oncology, University of Virginia, 1240 Lee St, Charlottesville, Virginia 22908, USA
| | - Peter J Hoskin
- Mount Vernon Cancer Centre, Rickmansworth Road, Northwood, Middlesex HA6 2RN, UK
| | - Yasuo Yoshioka
- Department of Radiation Oncology, Cancer Institute Hospital of the Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550, Japan
| | - Gerard C Morton
- Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Ave, Toronto, Ontario M4N 3M5, Canada
| | - Eric M Horwitz
- Department of Radiation Oncology, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, Pennsylvania 19111-2497, USA
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