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Title: Body radiation exposure in breast cancer radiotherapy: Impact of breast IMRT and virtual wedge compensation techniques

Abstract

Purpose: Recent reports demonstrate a dramatically increased rate of secondary leukemia for breast cancer patients receiving adjuvant high-dose anthracycline and radiotherapy, and that radiation is an independent factor for the development of leukemia. This study aimed to evaluate the radiation body exposure during breast radiotherapy and to characterize the factors associated with an increased exposure. Patients and Methods: In a prospective cohort of 120 women, radiation measurements were taken from four sites on the body at the time of adjuvant breast radiotherapy. Multiple regression analysis was performed to analyze patient and treatment factors associated with the amount of scattered radiation. Results: For standard 50 Gy breast radiotherapy, the minimal dose received by abdominal organs is on average 0.45 Gy, ranging from 0.06 to 1.55 Gy. The use of physical wedges as a compensation technique was the most significant factor associated with increased scattered dose (p < 0.001), resulting in approximately three times more exposure compared with breast intensity-modulated radiation therapy (IMRT) and dynamic wedge. Conclusions: The amount of radiation that is scattered to a patient's body is consistent with exposure reported to be associated with excess of leukemia. In accordance with the As Low As Reasonably Achievable (ALARA) principle, wemore » recommend using breast IMRT or virtual wedging for the radiotherapy of breast cancer receiving high-dose anthracycline chemotherapy.« less

Authors:
 [1];  [2];  [1];  [1];  [1];  [3];  [4]
  1. Department of Radiation Oncology, Sunnybrook and Women's College Health Sciences Centre, Toronto, Ontario (Canada)
  2. Department of Radiation Oncology, Sunnybrook and Women's College Health Sciences Centre, Toronto, Ontario (Canada). E-mail: Jean-Philippe.Pignol@sw.ca
  3. Department of Medical Physics, Sunnybrook and Women's College Health Sciences Centre, Toronto, Ontario (Canada)
  4. Department of Medical Oncology, Sunnybrook and Women's College Health Sciences Centre, Toronto, Ontario (Canada)
Publication Date:
OSTI Identifier:
20793455
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 65; Journal Issue: 1; Other Information: DOI: 10.1016/j.ijrobp.2005.11.023; PII: S0360-3016(05)02977-9; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ALARA; CHEMOTHERAPY; LEUKEMIA; MAMMARY GLANDS; PATIENTS; RADIATION DOSES; RADIOTHERAPY; SAFETY STANDARDS; WOMEN

Citation Formats

Woo, Tony, Pignol, Jean-Philippe, Rakovitch, Eileen, Vu, Toni, Hicks, Deanna, O'Brien, Peter, and Pritchard, Kathleen. Body radiation exposure in breast cancer radiotherapy: Impact of breast IMRT and virtual wedge compensation techniques. United States: N. p., 2006. Web. doi:10.1016/J.IJROBP.2005.1.
Woo, Tony, Pignol, Jean-Philippe, Rakovitch, Eileen, Vu, Toni, Hicks, Deanna, O'Brien, Peter, & Pritchard, Kathleen. Body radiation exposure in breast cancer radiotherapy: Impact of breast IMRT and virtual wedge compensation techniques. United States. doi:10.1016/J.IJROBP.2005.1.
Woo, Tony, Pignol, Jean-Philippe, Rakovitch, Eileen, Vu, Toni, Hicks, Deanna, O'Brien, Peter, and Pritchard, Kathleen. Mon . "Body radiation exposure in breast cancer radiotherapy: Impact of breast IMRT and virtual wedge compensation techniques". United States. doi:10.1016/J.IJROBP.2005.1.
@article{osti_20793455,
title = {Body radiation exposure in breast cancer radiotherapy: Impact of breast IMRT and virtual wedge compensation techniques},
author = {Woo, Tony and Pignol, Jean-Philippe and Rakovitch, Eileen and Vu, Toni and Hicks, Deanna and O'Brien, Peter and Pritchard, Kathleen},
abstractNote = {Purpose: Recent reports demonstrate a dramatically increased rate of secondary leukemia for breast cancer patients receiving adjuvant high-dose anthracycline and radiotherapy, and that radiation is an independent factor for the development of leukemia. This study aimed to evaluate the radiation body exposure during breast radiotherapy and to characterize the factors associated with an increased exposure. Patients and Methods: In a prospective cohort of 120 women, radiation measurements were taken from four sites on the body at the time of adjuvant breast radiotherapy. Multiple regression analysis was performed to analyze patient and treatment factors associated with the amount of scattered radiation. Results: For standard 50 Gy breast radiotherapy, the minimal dose received by abdominal organs is on average 0.45 Gy, ranging from 0.06 to 1.55 Gy. The use of physical wedges as a compensation technique was the most significant factor associated with increased scattered dose (p < 0.001), resulting in approximately three times more exposure compared with breast intensity-modulated radiation therapy (IMRT) and dynamic wedge. Conclusions: The amount of radiation that is scattered to a patient's body is consistent with exposure reported to be associated with excess of leukemia. In accordance with the As Low As Reasonably Achievable (ALARA) principle, we recommend using breast IMRT or virtual wedging for the radiotherapy of breast cancer receiving high-dose anthracycline chemotherapy.},
doi = {10.1016/J.IJROBP.2005.1},
journal = {International Journal of Radiation Oncology, Biology and Physics},
number = 1,
volume = 65,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2006},
month = {Mon May 01 00:00:00 EDT 2006}
}
  • A forward planned intensity modulated technique was initiated for intact breasts radiotherapy (FPIMRT). Forty-three patients were selected to compare dose distributions achieved by FPIMRT to dose distributions produced by conventional wedge techniques (CW). For the simulation process, the treatment field margins were clinically defined by a physician, and a set of fiducial reference markers was placed on the patient. A computed tomography (CT) scan was then performed and the images were transferred to a 3-dimensional (3D) treatment planning system (TPS). The breast tissue was then contoured to allow for a quantitative dose volume analysis. The treatment plan was initially generatedmore » with conventional tangential beam arrangements and open fields. Multiple multileaf collimator (MLC) shaped segments were created for each tangential beam in an effort to produce dose homogeneity throughout the breast. 6-MV photon beams were used for treatment unless acceptable dose homogeneity could not be achieved due to large breast size. In this case, the beam energies of selected segments were modified to 15-MV. Once the FPIMRT plan was created, additional plans were generated using the same beam geometry and 2 tangential open fields with CW techniques and 15 deg. wedges (15DW), 30 deg. wedges (30DW), 45 deg. wedges (45 DW), and 60 deg. wedges (60DW). The dose distributions generated by the CW plans were then compared to the FPIMRT plan. This process was repeated for each patient, and the patient group was divided into 3 categories based on breast volume (small, medium, and large). Both point dose relationships, which compared global hot spot (GHS) magnitude and location and dose volume relationships, which compared breast volume coverage of the 105% and 110% isodose lines (IDL) relative to the prescribed dose (PD), were explored. For the patient group in our study, FPIMRT produced the smallest average GHS and the most evenly distributed location of GHS for all breast size categories when compared to all CW techniques. FPIMRT also produced the smallest average breast volume receiving greater than 105% of the PD (V{sub a105}) for the small- and medium-size breast patients and the smallest average breast volume receiving greater than 110% of the PD (V{sub a110}) for all breast size categories when compared to all CW techniques.« less
  • Purpose: In this project, we compared the conventional tangent pair technique to IMRT technique by analyzing the dose distribution. We also investigated the effect of respiration on planning target volume (PTV) dose coverage in both techniques. Methods: In order to implement IMRT technique a template based planning protocol, dose constrains and treatment process was developed. Two open fields with optimized field weights were combined with two beamlet optimization fields in IMRT plans. We compared the dose distribution between standard tangential pair and IMRT. The improvement in dose distribution was measured by parameters such as conformity index, homogeneity index and coveragemore » index. Another end point was the IMRT technique will reduce the planning time for staff. The effect of patient’s respiration on dose distribution was also estimated. The four dimensional computed tomography (4DCT) for different phase of breathing cycle was used to evaluate the effect of respiration on IMRT planned dose distribution. Results: We have accumulated 10 patients that acquired 4DCT and planned by both techniques. Based on the preliminary analysis, the dose distribution in IMRT technique was better than conventional tangent pair technique. Furthermore, the effect of respiration in IMRT plan was not significant as evident from the 95% isodose line coverage of PTV drawn on all phases of 4DCT. Conclusion: Based on the 4DCT images, the breathing effect on dose distribution was smaller than what we expected. We suspect that there are two reasons. First, the PTV movement due to respiration was not significant. It might be because we used a tilted breast board to setup patients. Second, the open fields with optimized field weights in IMRT technique might reduce the breathing effect on dose distribution. A further investigation is necessary.« less
  • Purpose: To evaluate dosimetric impact of two axillary nodes (AX) boost techniques: (1) posterior-oblique optimized field boost (POB), (2) traditional posterior-anterior boost (PAB) with field optimization (O-PAB), for a postmastectomy breast patient with positive axillary lymph nodes. Methods: Five patients, 3 left and 2 right chest walls, were included in this study. All patients were simulated in 5mm CT slice thickness. Supraclavicular (SC) and level I/II/III AX were contoured based on the RTOG atlas guideline. Five treatment plans, (1) tangential chest wall, (2) oblique SC including AX, (3) PAB, O-PAB and POB, were created for each patient. Three plan sumsmore » (PS) were generated by sum one of (3) plan with plan (1) and (2). The field optimization was done through PS dose distribution, which included a field adjustment, a fractional dose, a calculation location and a gantry angle selection for POB. A dosimetric impact was evaluated by comparing a SC and AX coverage, a PS maximum dose, an irradiated area percentage volume received dose over 105% prescription dose (V105), an ipsi-laterial mean lung dose (MLD), an ipsi-laterial mean humeral head dose (MHHD), a mean heart dose (MHD) (for left case only) and their DVH amount these three technique. Results: O-PAB, POB and PAB dosimetric results showed that there was no significant different on SC and AX coverage (p>0.43) and MHD (p>0.16). The benefit of sparing lung irradiation from PAB to O-PAB to POB was significant (p<0.004). PAB showed a highest PS maximum dose (p<0.005), V105 (p<0.023) and MLD (compared with OPAB, p=0.055). MHHD showed very sensitive to the patient arm positioning and anatomy. O-PAB convinced a lower MHHD than PAB (p=0.03). Conclusion: 3D CT contouring plays main role in accuracy radiotherapy. Dosimetric advantage of POB and O-PAB was observed for a better normal tissue irradiation sparing.« less
  • Purpose: To explore the correlations between anatomic features and dose-volumetric parameters in 3DCRT and eComp whole breast irradiation and identify the feasibility of anatomic parameters to predict the planning method selection. Methods: We compared the effectiveness between conventional three-dimensional conformal radiotherapy (3DCRT) and electronic tissue compensation (eComp) for whole breast irradiation. 3DCRT and eComp planning techniques were used to generate treatment plans for 60 whole breast patients, respectively. The planning goal was to cover 95% of the planning target volume (PTV) with 95% of the prescription dose while minimizing dose to lung, heart, and skin. Statistical analyses were performed betweenmore » critical organ doses and patient anatomic features, i.e., central lung distance (CLD), maximal heart distance (MHD), maximal heart length (MHL) and breast separation (BS). Results: Comparing to 3DCRT plans, on the average, eComp treatment planning process was about 7 minutes longer, but resulted in lower lung V20Gy, lower mean skin dose, with similar heart dose. The benefits were more pronounced for larger breast patients. To keep the lung V20Gy lower than 20% and mean skin dose lower than 85% of the prescription dose, eComp was the preferred method for patients with more than 2.3 cm CLD or larger than 22.5 cm BS. Conclusion: The study results may be useful in providing a handy criterion in clinical practice allowing us to easily choose between different planning techniques to satisfy the planning goal with minimal increase in complexity and cost. This study was supported by National Natural Science Foundation of China (NO. 31420103915) and Chongqing Health and Family Planning Commission Project (2015MSXM012).« less
  • Purpose: This study was to investigate the dosimetric benefit of a novel intensity modulated radiation therapy (IMRT) technique for irradiating the left breast and regional lymph node (RLN). Methods: The breast and RLN (internal mammary node and periclavicular node) and normal tissue were contoured for 16 consecutive left-sided breast cancer patients previously treated with RT after lumpectomy. Nine equi-spaced fields IMRT (9 -field IMRT), tangential multi-beam IMRT (tangential-IMRT) and IMRT with fixed-jaw technique (FJT-IMRT) were developed and compared with three-dimensional conformal RT (3DCRT). Prescribed dose was 50 Gy in 25 fractions. Dose distributions and dose volume histograms were used tomore » evaluate plans. Results: All IMRTs achieved similar target coverage and substantially reduced heart V30 and V20 compared to the 3DCRT. The average heart mean dose had different changes, which were 9.0Gy for 9-field IMRT, 5.7Gy for tangential-IMRT and 4.2Gy for FJT-IMRT. For the contralateral lung and breast, the 9-field IMRT has the highest mean dose; and the FJT-IMRT and tangential-IMRT had similar lower value. For the thyroid, both 9-field IMRT and FJT-IMRT had similar V30 (20% and 22%) and were significantly lower than that of 3DCRT (34%) and tangential-IMRT (46%). Moreover, the thyroid mean dose of FJT-IMRT is the lowest. For cervical esophagus and humeral head, the FJT-IMRT also had the best sparing. Conclusion: All 9-field IMRT, tangential-IMRT and FJT-IMRT had superiority for targets coverage and substantially reduced the heart volume of high dose irradiation. The FJT-IMRT showed advantages of avoiding the contralateral breast and lung irradiation and decreasing the thyroid, humeral head and cervical esophagus radiation dose at the expense of a slight monitor units (MUs) increasing.« less