Single Fraction Elderly Breast Irradiation (SiFEBI)

Breast Cancer

Single fraction, Elderly, Breast Irradiation

Irradiation and Accelerated Partial Breast (IPAS) to this day remains a therapeutic concept whose validity is being assessed on its non-inferiority in terms of local control compared to whole breast irradiation. At least eight phase III trials attempting to answer this question and thus provide a sufficient level of evidence to make this concept a new standard of care for sub-groups of patients well defined (1). However, without waiting for the final results of these randomized trials (which will not be fully valid with a drop of at least ten years), the American societies (ASTRO) and European (ESTRO) radiotherapy have all two proposed classification (very similar) into 3 groups according to the risk to the patient in terms of local recurrence after IPAS. And are defined by the ESTRO: * The low-risk group (suitable for ASTRO) * The intermediate-risk group (cautionary in ASTRO) * The high-risk group (not suitable for ASTRO) (2.3). Therefore, it is possible to propose to a patient a randomized clinical tria IPAS, to subject it belongs to the group low risk. The results of phase II trials as a long-term analysis of the matched team of William Beaumont Hospital (4) and the phase III trial using intra-operative radiation photons in low energy X whose results were recently published (5) confirm the value of this new therapeutic concept for post-operative breast cancer at low risk of local recurrence. In France, the therapists were quickly directed to a sub-population for which the IPAS could represent a real improvement in the therapeutic management in significantly reducing the number of irradiation sessions of thirty in 6 weeks 5 days at 10 in a single view (6). Several French phase II trials were started specifically targeting the female population aged using a balloon catheter (MammoSite ®) (7) or by intra-operative radiation électronthérapie (8). The results of the test using the GERICO-03 brachytherapy with high dose rate (promoter: FNCLCC, National Federation of Anti Cancer Centres , recently merged into Group Health Cooperation entitled UNICANCER) are currently submitted to Journal Green Radiotherapy (Radiotherapy and Oncology from 09/11/11) (9). On a technical level, two main approaches are used (10): * Irradiation intraoperative electron or low-energy photons, * Radiation after surgery The advantage of intraoperative irradiation is the optimal reduction of total processing time radio-surgery because the patient is irradiated during the lumpectomy. However, 15-20% of these patients receive partial breast irradiation, as histo-prognostic criteria provided in the histologically final report, confirm the non-adapted indication of IPAS (5). In contrast, the post-operative IPAS can treat only patients meeting all criteria for IPAS but treatment-related travel are about 5 treatments for bi-fractionated (2 sessions per days separated by at least 6 hours).

Single dose intraoperative issued by electrontherapy or low energy photons (50 Kv) is 21 Gy (5.11). However, these doses reported in the irradiated volume are not equivalent. Indeed, with electrontherapy, it is a complete volume of mammary parenchyma that is irradiated, whereas with low energy photon therapy (X 50 KV) is a shell of 5 mm thick which is treated knowing that to 10 mm from the surface of the sphere of treatment, the gland received only 50% of the dose initially prescribed. On interstitial brachytherapy with high dose rate, it has a dose escalation due to intrinsic volumes located within the irradiated area that will receive a higher dose than prescribed (12). It is this variation in dose within the target volume which can be efficiency, but also which can induce the toxicity of interstitial brachytherapy. The linear quadratic model to calculate the biological equivalence of 2 Gy irradiation scheme most often hypofractionned, is theoretically applicable for doses per fraction less than 8 Gy. Nevertheless, the authors using the IPAS intra-operative (electrons, photons) apply this method of calculation for doses of 21 Gy in one fraction. In our study, we propose to treat these patients with a total dose of 16 Gy in one fraction. This dose is calculated taking into account a report alpha/beta for the breast, on the order of 3.4 Gy for late toxicity and 4.6 Gy for local control (13). Applying the linear-quadratic model with alpha/beta for the breast of 4, 16 Gy in one fraction is calculated as radio-biologically equivalent to 53 Gy in conventional fractionation (14,15). Biological Equivalence of this dose is between the dose in the protocols IPAS intraoperative electron or X-ray photons of 50 kV (21 Gy in one fraction, 87 Gy EQD2 alpha/beta 4.6) (5.8) and the post-operative irradiation of 34-38 Gy in 10 fractions, 5 days (42 Gy EQD2 alpha/beta 4.6.

France

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