Postoperative Proton Radiotherapy for Localized and Locoregional Breast Cancer: Potential for Clinically Relevant Improvements?
To study the potential reduction of dose to organs at risk (OARs) with intensity-modulated proton radiotherapy (IMPT) compared with intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT) photon radiotherapy for left-sided breast cancer patients.
Comparative treatment-planning was performed using planning computed tomography scans of 20 left-sided breast cancer patients. For each patient, three increasingly complex locoregional volumes (planning target volumes [PTVs]) were defined: whole breast (WB) or chest wall (CW) = (PTV1), WB/CW plus medial-supraclavicular (MSC), lateral-supraclavicular (LSC), and level III axillary (AxIII) nodes = (PTV2) and WB/CW+MSC+LSC+AxIII plus internal mammary chain = (PTV3). For each patient, 3D-CRT, IMRT, and IMPT plans were optimized for PTV coverage. Dose to OARs was compared while maintaining target coverage.
All the techniques met the required PTV coverage except the 3D-CRT plans for PTV3-scenario. All 3D-CRT plans for PTV3 exceeded left-lung V20. IMPT vs. 3D-CRT: significant dose reductions were observed for all OARs using IMPT for all PTVs. IMPT vs. IMRT: For PTV2 and PTV3, low (V5) left lung and cardiac doses were reduced by a factor >2.5, and cardiac doses (V22.5) were by a factor of >20 lower with IMPT compared with IMRT.
When complex-target irradiation is needed, 3D-CRT often compromises the target coverage and increases the dose to OARs; IMRT can provide better results but will increase the integral dose. The benefit of IMPT is based on improved target coverage and reduction of low doses to OARs, potentially reducing the risk of late-toxicity. These results indicate a potential role of proton-radiotherapy for extended locoregional irradiation in left breast cancer.
Available from: Thomas F Delaney
- "Given the increasing availability of proton radiation in both academic and private sectors, it is critical to evaluate potential benefits and techniques for the treatment of additional malignancies, such as breast cancer, for which the defined range of the proton might reduce normal tissue radiation dose, allow concurrent chemotherapy or some combination thereof for an improvement in patient outcome. Comparative planning studies hypothesize that protons will provide a decrease in acute and late cardiopulmonary toxicities for patients requiring RT for advanced or left sided breast cancer, but no clinical experience has been reported to date for this group of patients [3-5]. We report dosimetric comparisons for eleven patients with left sided breast cancer requiring post-mastectomy radiation therapy (PMRT) planned with 3D CRT, partially wide tangent fields (PWTF), and a mixed photon electron (P/E) technique to compare target coverage and conformality across these treatment modalities. "
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The delivery of post-mastectomy radiation therapy (PMRT) can be challenging for patients with left sided breast cancer that have undergone mastectomy. This study investigates the use of protons for PMRT in selected patients with unfavorable cardiac anatomy. We also report the first clinical application of protons for these patients.
Methods and materials
Eleven patients were planned with protons, partially wide tangent photon fields (PWTF), and photon/electron (P/E) fields. Plans were generated with the goal of achieving 95% coverage of target volumes while maximally sparing cardiac and pulmonary structures. In addition, we report on two patients with unfavorable cardiac anatomy and IMN involvement that were treated with a mix of proton and standard radiation.
PWTF, P/E, and proton plans were generated and compared. Reasonable target volume coverage was achieved with PWTF and P/E fields, but proton therapy achieved superior coverage with a more homogeneous plan. Substantial cardiac and pulmonary sparing was achieved with proton therapy as compared to PWTF and P/E. In the two clinical cases, the delivery of proton radiation with a 7.2 to 9 Gy photon and electron component was feasible and well tolerated. Akimbo positioning was necessary for gantry clearance for one patient; the other was treated on a breast board with standard positioning (arms above her head). LAO field arrangement was used for both patients. Erythema and fatigue were the only noted side effects.
Proton RT enables delivery of radiation to the chest wall and regional lymphatics, including the IMN, without compromise of coverage and with improved sparing of surrounding normal structures. This treatment is feasible, however, optimal patient set up may vary and field size is limited without multiple fields/matching.
Radiation Oncology 03/2013; 8(1):71. DOI:10.1186/1748-717X-8-71 · 2.55 Impact Factor
Available from: Zelig Tochner
- "Data with regard to use of proton therapy in treatment of breast cancer are relatively limited. Some dosimetric justification may exist for delivery of " boost " radiation to the tumor bed after radiation to the intact breast (Toscas et al., 2010), and for use of IMPT for delivery of whole breast radiation for patients with left sided breast cancer (Ares et al., 2010). This technique may allow improved dose delivery to the whole breast with sparing of heart and lung; however, it must be employed with great caution to avoid under-dosing of the chest wall and proximal breast tissue during normal respiration. "
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ABSTRACT: Proton therapy is associated with significant benefit in terms of normal tissue sparing and potential radiation dose escalation for many patients with malignant diseases. Due to recognition of these qualities, the availability of this technology is increasing rapidly, both through increased availability of large centers, and with the possibility of smaller, lower cost proton therapy centers. Such expansion is associated with increased opportunity to provide this beneficial technology to larger numbers of patients; however, the importance of careful treatment planning and delivery, deliberate patient selection, rigorous scientific investigation including comparison to other technologies when possible, and mindfulness of ethical issues and cost effectiveness must not be forgotten. The obligation to move forward responsibly rests on the shoulders of radiation oncologists around the world. In this article, we discuss current use of proton therapy worldwide, as well as many of the factors that must be taken into account during rapid expansion of this exciting technology.
Frontiers in Oncology 09/2011; 1:24. DOI:10.3389/fonc.2011.00024
Available from: Catharine ML West
- "Proton treatment is being used increasingly, with more facilities becoming available worldwide. Proton therapy allows for high-dose radiation to be deposited very accurately at a fixed depth, and is particularly advantageous when the target lies close to critical normal tissue structure, such as in the treatment of the brain stem and in pediatric malignancies . Protons have also been used in the treatment of prostate cancer to achieve dose escalation while minimizing doses to normal tissues . "
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ABSTRACT: Radiotherapy is involved in many curative treatments of cancer; millions of survivors live with the consequences of treatment, and toxicity in a minority limits the radiation doses that can be safely prescribed to the majority. Radiogenomics is the whole genome application of radiogenetics, which studies the influence of genetic variation on radiation response. Work in the area focuses on uncovering the underlying genetic causes of individual variation in sensitivity to radiation, which is important for effective, safe treatment. In this review, we highlight recent advances in radiotherapy and discuss results from four genome-wide studies of radiotoxicity.
Genome Medicine 08/2011; 3(8):52. DOI:10.1186/gm268 · 5.34 Impact Factor
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