Dosimetric evaluation and systematic review of radiation therapy techniques for early stage node-negative breast cancer treatment

Cancer Management and Research Dovepress open access to scientific and medical research Review Cancer Management and Research downloaded from https://www.dovepress.com/ by 5.135.254.153 on 21-Dec-2018 For personal use only. Open Access Full Text Article Dosimetric evaluation and systematic review of radiation therapy techniques for early stage nodenegative breast cancer treatment This article was published in the following Dove Press journal: Cancer Management and Research Tabitha Y Chan 1 Johann I Tang 1 Poh Wee Tan 1 Neill Roberts 2 1 Department of Radiation Oncology, National University Cancer Institute, Singapore, Singapore; 2Faculty of Health and Wellbeing, Sheffield Hallam University, Sheffield, UK Introduction Correspondence: Tabitha Y Chan Department of Radiation Oncology, National University Cancer Institute, Singapore, 5 Lower Kent Ridge Road, 119074, Singapore Tel +65 6 772 8381 Fax +65 6 734 2986 Email An early stage node-negative breast cancer (ESNNBC) offers a good prognosis.1 Improved surgical techniques, systemic therapy options, and radiation therapy (RT) have resulted in significant improvement in long-term cause-specific survival.2,3 Increasing use of RT has resulted in significant increase in long-term survival,2,3 translating to more women at risk of developing long-term treatment-related toxicities. Hence, it is contradictory that the benefits of improved survival, due to the successful delivery of RT for ESNNBC, are negated by RT-induced toxicities. Dosimetry planning for whole breast external beam radiotherapy (WBEBRT) typically involves a pair of tangential fields to homogenously treat the entire breast while avoiding adjacent vital organs, like the lungs, heart, and left anterior descending artery (LAD).4 Cardiac toxicity studies demonstrate increased mortality and morbidity from heart disease,5–8 especially left-sided WBEBRT patients, 10–15 years after receiving irradiation compared to right-sided WBEBRT patients. Recent imaging studies demonstrate consistent occurrence of perfusion defects, microvascular disease, stenosis, and atherosclerosis where the heart and coronary arteries are included in the radiation field and validate the need to reduce cardiac dose.6,7,9 Lung toxicity studies have demonstrated increased risk of secondary lung cancers and mortality for radiation-induced lung cancer post WBEBRT.5 Grantzau and Overgaard found that ≥5 years after breast cancer diagnosis, RT was significantly associ4853 submit your manuscript | www.dovepress.com Cancer Management and Research 2018:10 4853–4870 Dovepress © 2018 Chan et al. This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms. php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (https://www.dovepress.com/terms.php). http://dx.doi.org/10.2147/CMAR.S172818 Powered by TCPDF (www.tcpdf.org) Abstract: Radiation therapy (RT) is essential in treating women with early stage breast cancer. Early stage node-negative breast cancer (ESNNBC) offers a good prognosis; hence, late effects of breast RT becomes increasingly important. Recent literature suggests a potential for an increase in cardiac and pulmonary events after RT. However, these studies have not taken into account the impact of newer and current RT techniques that are now available. Hence, this review aimed to evaluate the clinical evidence for each technique and determine the optimal radiation technique for ESNNBC treatment. Currently, six RT techniques are consistently used and studied: 1) prone positioning, 2) proton beam RT, 3) intensity-modulated RT, 4) breathhold, 5) partial breast irradiation, and 6) intraoperative RT. These techniques show dosimetric promise. However, limited data on late cardiac and pulmonary events exist due to challenges in long-term follow-up. Moving forward, future studies are needed to validate the efficacy and clinical outcomes of these current techniques. Keywords: early stage, breast cancer, radiation technique, dosimetric Dovepress Cancer Management and Research downloaded from https://www.dovepress.com/ by 5.135.254.153 on 21-Dec-2018 For personal use only. Chan et al ated with an increased risk of radiation-induced lung cancer relative risk (RR) of 1.39 (95% CI 1.28–1.51).10 Radiation pneumonitis (RP) arises from irradiation of the adjacent ipsilateral lung in breast cancer. It has been reported to be related to 1) the amount of lung irradiated within the tangential fields, 2) use of supraclavicular field, 3) prior exposure to chemotherapy, 4) high-dose chemotherapy, and 5) concurrent tamoxifen medication and smoking habits.11 Current literature suggests new advanced radiation techniques vis-a-vis delivering and quantifying radiation doses to the organs at risk (OAR).12 Such techniques include 1) maneuvers to achieve maximum separation of the heart from the chest wall (ie, synchronizing RT with the patients’ respiratory cycle or prone positioning),13–15 2) designing and utilizing cardiac blocks to minimize radiation damage to the heart while avoiding over shielding,16 3) utilizing advanced technologies for RT delivery (ie, intensity-modulated radiation therapy [IMRT] or proton beam radiation therapy [PBT]),17,18 and (4) moving away from whole breast volume to partial breast volume treatment (accelerated partial breast irradiation [APBI] or intraoperative radiation therapy [IORT]).19,20 This review aimed to evaluate the evidence for each technique by 1) identifying the different breast RT techniques for ESNNBC, 2) collate the dosimetric outcomes for each breast RT technique, and 3) identify the best dosimetric technique. Methods Eligible articles include articles about 1) breast cancer RT; 2) RT-associated toxicities, and 3) published in an English language peer-reviewed journal. A systematic search using MEDLINE/PubMed and MeSH headings was used to identify articles addressing RT techniques. The headings were breast cancer, radiation therapy, intensity modulated, prone, partial breast, breath-hold (BH), gating, intraoperative, side effects, heart, cardiac, lung, and pulmonary. Articles were excluded if they provided pilot data, descriptions of a study design, articles on non-breast cancer data, post-mastectomy radiation, lymph node irradiation, exclusive evaluation of patients with pectus excavatum, bilateral breast irradiation, articles not having heart, LAD, and/or lung dosimetric data or non-English language articles. Articles were reviewed specifically for data from patients whose left breast was trea (...truncated)