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Title: SU-F-T-404: Dosimetric Advantages of Flattening Free Beams to Prone Accelerated Partial Breast Irradiation

Abstract

Purpose: Prone accelerated partial breast irradiation (APBI) results in dose reduction to the heart and lung. Flattening filter free beams (FFF) reduce out of field dose due to the reduced scatter from the removal of the flattening filter and reduce the buildup region. The aim of this work is to evaluate the dosimetric advantages of FFF beams to prone APBI target coverage and reduction in dose to organs at risk. Methods: Fifteen clinical prone APBI cases using flattened photon beams were retrospectively re-planned in Eclipse-TPS using FFF beams. FFF plans were designed to provide equivalent target coverage with similar hotspots using the same field arrangements, resulting in comparable target DVHs. Both plans were transferred to a prone breast phantom and delivered on Varian-Edge-Linac. GafChromic-film was placed in the coronal plane of the phantom, partially overlapping the treatment field and extending into OARs to compare dose profiles from both plans. Results: FFF plans were comparable to the clinical plans with maximum doses of (108.3±2.3)% and (109.2±2.4)% and mean doses of (104.5±1.0)% and (104.6±1.2)%, respectively. Similar mean dose doses to the heart and contralateral lungs were observed from both plans, whereas the mean dose to the contra-lateral breast was (2.79±1.18) cGy andmore » (2.86±1.40) cGy for FFF and clinical plans respectively. However for both plans the error between calculated and measured doses at 4 cm from the field edge was 10%. Conclusion: The results showed that FFF beams in prone APBI provide dosimetrically equivalent target coverage and improved coverage in superficial target due to softer energy spectra. Film analysis showed that the TPS underestimates dose outside field edges for both cases. The FFF measured plans showed less dose outside the beam that might reduce the probability of secondary cancers in the contralateral breast.« less

Authors:
; ;  [1]
  1. NYU Langone Medical Center, New York, NY (United States)
Publication Date:
OSTI Identifier:
22649000
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; ENERGY SPECTRA; IRRADIATION; MAMMARY GLANDS; PHOTON BEAMS; RADIATION DOSES; RADIOTHERAPY

Citation Formats

Galavis, P, Barbee, D, and Jozsef, G. SU-F-T-404: Dosimetric Advantages of Flattening Free Beams to Prone Accelerated Partial Breast Irradiation. United States: N. p., 2016. Web. doi:10.1118/1.4956589.
Galavis, P, Barbee, D, & Jozsef, G. SU-F-T-404: Dosimetric Advantages of Flattening Free Beams to Prone Accelerated Partial Breast Irradiation. United States. doi:10.1118/1.4956589.
Galavis, P, Barbee, D, and Jozsef, G. 2016. "SU-F-T-404: Dosimetric Advantages of Flattening Free Beams to Prone Accelerated Partial Breast Irradiation". United States. doi:10.1118/1.4956589.
@article{osti_22649000,
title = {SU-F-T-404: Dosimetric Advantages of Flattening Free Beams to Prone Accelerated Partial Breast Irradiation},
author = {Galavis, P and Barbee, D and Jozsef, G},
abstractNote = {Purpose: Prone accelerated partial breast irradiation (APBI) results in dose reduction to the heart and lung. Flattening filter free beams (FFF) reduce out of field dose due to the reduced scatter from the removal of the flattening filter and reduce the buildup region. The aim of this work is to evaluate the dosimetric advantages of FFF beams to prone APBI target coverage and reduction in dose to organs at risk. Methods: Fifteen clinical prone APBI cases using flattened photon beams were retrospectively re-planned in Eclipse-TPS using FFF beams. FFF plans were designed to provide equivalent target coverage with similar hotspots using the same field arrangements, resulting in comparable target DVHs. Both plans were transferred to a prone breast phantom and delivered on Varian-Edge-Linac. GafChromic-film was placed in the coronal plane of the phantom, partially overlapping the treatment field and extending into OARs to compare dose profiles from both plans. Results: FFF plans were comparable to the clinical plans with maximum doses of (108.3±2.3)% and (109.2±2.4)% and mean doses of (104.5±1.0)% and (104.6±1.2)%, respectively. Similar mean dose doses to the heart and contralateral lungs were observed from both plans, whereas the mean dose to the contra-lateral breast was (2.79±1.18) cGy and (2.86±1.40) cGy for FFF and clinical plans respectively. However for both plans the error between calculated and measured doses at 4 cm from the field edge was 10%. Conclusion: The results showed that FFF beams in prone APBI provide dosimetrically equivalent target coverage and improved coverage in superficial target due to softer energy spectra. Film analysis showed that the TPS underestimates dose outside field edges for both cases. The FFF measured plans showed less dose outside the beam that might reduce the probability of secondary cancers in the contralateral breast.},
doi = {10.1118/1.4956589},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • Purpose: To compare dosimetrically four different techniques of accelerated partial breast irradiation (APBI) in the same patient. Methods and Materials: Thirteen post-lumpectomy interstitial brachytherapy (IB) patients underwent imaging with preimplant computed tomography (CT) in the prone and supine position. These CT scans were then used to generate three-dimensional conformal radiotherapy (3D-CRT) and prone and supine helical tomotherapy (PT and ST, respectively) APBI plans and compared with the treated IB plans. Dose-volume histogram analysis and the mean dose (NTD{sub mean}) values were compared. Results: Planning target volume coverage was excellent for all methods. Statistical significance was considered to be a pmore » value <0.05. The mean V100 was significantly lower for IB (12% vs. 15% for PT, 18% for ST, and 26% for 3D-CRT). A greater significant differential was seen when comparing V50 with mean values of 24%, 43%, 47%, and 52% for IB, PT, ST, and 3D-CRT, respectively. The IB and PT were similar and delivered an average lung NTD{sub mean} dose of 1.3 Gy{sub 3} and 1.2 Gy{sub 3}, respectively. Both of these methods were statistically significantly lower than the supine external beam techniques. Overall, all four methods yielded similar low doses to the heart. Conclusions: The use of IB and PT resulted in greater normal tissue sparing (especially ipsilateral breast and lung) than the use of supine external beam techniques of 3D-CRT or ST. However, the choice of APBI technique must be tailored to the patient's anatomy, lumpectomy cavity location, and overall treatment goals.« less
  • Purpose: Accelerated partial breast irradiation (APBI) is an effective treatment for early stage breast-cancer. Irradiation in a prone position can mitigate breast motion and spare heart and lung. In this study, a comprehensive study is performed to evaluate various treatment techniques for prone APBI treatment including: 3D-CRT, IMRT, co-planar and non-coplanar partial arcs treatment. Methods: In this treatment planning study, a left breast patient treated in prone position in our clinic was imported into Varian Eclipse TPS. Six beams tangential to chest wall were used in both 3D-CRT and IMRT plans. These six beams were coplanar in a transactional planemore » achieved by both gantry and couch rotation. A 60-beam IMRT plan was also created to explore the maximum benefit of co-planar IMRT. Within deliverable couch rotation range (±30°), partial arc treatment plans with one and up to ten couch positions were generated for comparison. For each plan, 30Gy in 6 fractions was prescribed to 95% PTV volume. Critical dosimetric parameters, such as conformity index, mean, maximum, and volume dose of organ at risk, are evaluated. Results: The conformity indexes (CI) are 3.53, 3.17, 2.21 and 1.08 respectively to 3D-CRT, 6-beam IMRT, 60-beam IMRT, and two-partial-arcs coplanar plans. However, arc plans increase heart dose. CI for non-coplanar arc plans decreases from 1.19 to 1.10 when increases couch positions. Maximum dose in ipsilateral lung (1.98 to 1.13 Gy), and heart (0.62 to 0.43 Gy) are steadily decreased with the increased number of non-coplanar arcs. Conclusions: The dosimetric evaluation results show that partial arc plans have improved CIs compared to conventional 3D-CRT and IMRT plans. Increasing number of partial arcs decreases lung and heart dose. The dosimetric benefit obtained from non-coplanar arcs should be considered with treatment delivery time.« less
  • Purpose: The unique dosimetric features of proton radiotherapy make it an attractive modality for normal tissue sparing. We present our initial experience with protons for three-dimensional, conformal, external-beam accelerated partial breast irradiation (3D-CPBI). Methods and Materials: From March 2004 to June 2005, 25 patients with tumors {<=}2 cm and negative axillary nodes were treated with proton 3D-CPBI. The prescribed dose was 32 Cobalt Gray Equivalents (CGE) in 4 CGE fractions given twice daily. One to three fields were used to provide adequate planning target volume (PTV) coverage and dose homogeneity. Results: Excellent PTV coverage and dose homogeneity were obtained inmore » all patients with one to three proton beams. The median PTV receiving 95% of the prescribed dose was 100%. Dose inhomogeneity exceeded 10% in only 1 patient (4%). The median volume of nontarget breast tissue receiving 50% of the prescribed dose was 23%. Median volumes of ipsilateral lung receiving 20 CGE, 10 CGE, and 5 CGE were 0%, 1%, and 2%, respectively. The contralateral lung and heart received essentially no radiation dose. Cost analysis suggests that proton 3D-CPBI is only modestly more expensive (25%) than traditional whole-breast irradiation (WBI). Conclusion: Proton 3D-CPBI is technically feasible, providing both excellent PTV coverage and normal tissue sparing. It markedly reduces the volume of nontarget breast tissue irradiated compared with photon-based 3D-CPBI, addressing a principle disadvantage of external-beam approaches to PBI. As proton therapy becomes more widely available, it may prove an attractive tool for 3D-CPBI.« less
  • Purpose: To report the 5-year results of a prospective trial of three-dimensional conformal external beam radiotherapy (3D-CRT) to deliver accelerated partial breast irradiation in the prone position. Methods and Materials: Postmenopausal patients with Stage I breast cancer with nonpalpable tumors <2 cm, negative margins and negative nodes, positive hormone receptors, and no extensive intraductal component were eligible. The trial was offered only after eligible patients had refused to undergo standard whole-breast radiotherapy. Patients were simulated and treated on a dedicated table for prone setup. 3D-CRT was delivered at a dose of 30 Gy in five 6-Gy/day fractions over 10 daysmore » with port film verification at each treatment. Rates of ipsilateral breast failure, ipsilateral nodal failure, contralateral breast failure, and distant failure were estimated using the cumulative incidence method. Rates of disease-free, overall, and cancer-specific survival were recorded. Results: One hundred patients were enrolled in this institutional review board-approved prospective trial, one with bilateral breast cancer. One patient withdrew consent after simulation, and another patient elected to interrupt radiotherapy after receiving two treatments. Ninety-eight patients were evaluable for toxicity, and, in 1 case, both breasts were treated with partial breast irradiation. Median patient age was 68 years (range, 53-88 years); in 55% of patients the tumor size was <1 cm. All patients had hormone receptor-positive cancers: 87% of patients underwent adjuvant antihormone therapy. At a median follow-up of 64 months (range, 2-125 months), there was one local recurrence (1% ipsilateral breast failure) and one contralateral breast cancer (1% contralateral breast failure). There were no deaths due to breast cancer by 5 years. Grade 3 late toxicities occurred in 2 patients (one breast edema, one transient breast pain). Cosmesis was rated good/excellent in 89% of patients with at least 36 months follow-up. Conclusions: Five-year efficacy and toxicity of 3D-CRT delivered in prone partial breast irradiation are comparable to other experiences with similar follow-up.« less
  • Purpose: The dosimetric results from our institution's trials of prone accelerated partial breast irradiation are compared with the dosimetric requirements of RTOG-0413. Methods and Materials: Trial 1 and Trial 2 are 2 consecutive trials of prone-accelerated partial breast irradiation. Eligible for both trials were stage I breast cancer patients with negative margins after breast-conserving surgery. The planning target tumor volume (PTV) was created by extending the surgical cavity 2.0 cm for Trial 1 and 1.5 cm for Trial 2, respectively. Contralateral breast, heart, lungs, and thyroid were contoured. Thirty Gray was delivered in five daily fractions of 6 Gy bymore » a three-dimensional conformal radiation therapy technique in Trial 1 and were by image-guided radiation therapy/intensity-modulated radiation therapy in Trial 2. Dosimetric results from the trials are reported and compared with RTOG 0413 requirements. Results: One hundred forty-six consecutive plans were analyzed: 67 left and 79 right breast cancers. The plans from the trials complied with the required >90% of prescribed dose covering 90% of PTV{sub E}VAL (=generated from the PTV by cropping 0.5 cm from the skin edge and excluding the chest wall): V90% was 98.1 {+-} 3.0% (with V100% and V95%, 89.4 {+-} 12.8%, 96.4 {+-} 5.1%, respectively). No significant difference between laterality was found (Student's t test). The dose constraints criteria of the RTOG-0413 protocol for ipsilateral and contralateral lung (V30 <15% and Dmax <3%), heart (V5 <40%), and thyroid (Dmax <3%) were satisfied because the plans showed an average V5% of 0.6% (range, 0-13.4) for heart, an average V30% of 0.6% (range, 0-9.1%) for ipsilateral lung, and <2% maximum dose to the thyroid. However, our partial breast irradiation plans demonstrated a higher dose to contralateral breast than that defined by RTOG constraints, with a median value of maximum doses of 4.1% (1.2 Gy), possibly as a result of contouring differences. Conclusions: Our technique for prone accelerated partial breast irradiation generally satisfied RTOG-0413 requirements.« less