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Purpose/Objective: to evaluate the effect of the interval between surgery and radiotherapy (ICRT) in local failure in patients with breast cancer treated with conservative surgery and radiotherapy without chemotherapy. Materials and Methods: historical cohort study of 358 patients (pts) with breast cancer stages I-II treated with conservative surgery as well as radiotherapy without chemotherapy in our Unit from 1993 to 2009. Radiation therapy consisted of 50 Gy to whole breast in 25 fractions with or without inclusion of regional nodes followed or not by a boost to the primary tumor bed of 10 to 20 Gy in 5 to 10 fractions. 339 pts received also hormonal treatment. The patients were divided into two groups according to the ICRT: ≤ 3 months (237 pts) and > 3 months (121 ptes). Kaplan-Meier curves have been used for the statistical analysis of survival and the long-rank test for the comparison of the survivals. Prognostic factors such as age, primary tumor size, state of the margin, ICRT and type of hormonal therapy have been related to local failure free survival (LFFS), disease-free survival (DFS) and overall survival (OS) using Cox regression. Results: Median follow-up of 72 months (4-220). Local failure-free survival, disease-free and overall survival at 15 years of pts with ICRT ≤ 3 months was 99%, 93.8% and 91% and ICRT > 3 months 96.5%, 76% and 79% respectively. We did not find a significant difference in LFFS, DFS nor OS between ICRT ≤ 3 months vs. 3 months (p =0.22, p=0.60, p=0.95). After univariate and multivariate analysis of prognostic factors only age was associated significantly with the OS (p=0.018, HR 1.06; 95% IC 1.01-1.16). Conclusions: in our experience a delay in the start of radiotherapy of more than three months in patients with breast cancer treated with conservative surgery plus radiotherapy without chemotherapy was not associated with worse outcomes. EP-0995 DOSIMETRIC COMPARISION OF ELECTRON AND X-RAY FOR THE TREATMENT OF TUMOR BED BOOST IN BREAST CONSERVING SURGERY S. Park1, J. Kim1, J. Lee1, I. Park1 1 Kyungpook National University Hospital, Department of Radiation Oncology, Daegu, Korea Republic of Purpose/Objective: The objective of this study was to compare the dosimetric profiles of electron beams (EB) and x-ray beams (XB) and to establish a guideline of boost irradiation in breast conserving treatment. Materials and Methods: For 131 breast cancer patients treated with breast conserving surgery, plans for boost irradiation using both EB and XB were compared prospectively following whole breast irradiation. The clinical target volumes (CTVs) were delineated based on surgical clips or surgical scars. A boost dose 10-16 Gy in 2 Gy fraction was prescribed following a 50 Gy whole breast irradiation. Electron energy was chosen according to depth and thickness of CTV. Organs at risk (OARs) were cardiac chambers, coronary arteries, ipsilateral lung, and skin. The conformity index, inhomogeneity index, dose-volume parameters for CTVs and OARs were calculated. Results: XB plans showed significantly better conformity index (p = 0.014) and inhomogeneity index (p = 0.000) for CTVs than EB plans. Regarding ipsilateral lung and skin, XB provided increased mean dose, increased maximum dose, increased low-dose volume, and reduction of high-dose volume. In left-sided breast cancers, XB provided increased low-dose volume in cardiac chambers and coronary arteries, while high-dose volume to left ventricles and left anterior descending coronary arteries were reduced. In 33 patients whose radiation field included a nipple, inhomogeneity index was higher in EB (p = 0.010), whereas XB was not interfered by the presence of a nipple in the radiation field. Patients treated with EB showed increased risk of radiation pneumonitis on follow-up chest computed tomography (p = 0.026). Conclusions: XB plans were superior over EB plans in terms of CTV coverage (homogeneity and conformity) and high-dose volume sparing in OARs when used as boost irradiation in breast conserving surgery. Disadvantage of XB plan was an increase of low-dose volume in OARs (cardiac chambers and coronary arteries). Tailored plans with both XB and EB are mandatory to adapt patients' anatomic variance and geometric property of tumor bed correctly. EP-0996 NON-SURGICAL BREAST-CONSERVATION TREATMENT USING A NEW RADIOSENSITIZATION METHOD FOR STAGE I OR II BREAST CANCER Y. Ogawa1, K. Kubota1, N. Aoyama1, K. Ohgi1, Y. Kataoka1, M. Tadokoro1, T. Tamura1, S. Kariya1, M. Nogami1, A. Nishioka1
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Kochi Medical School, Dept. of Radiation Oncology & Diagnostic Radiology, Nankoku, Japan Purpose/Objective: Tumor tissue can be re-oxygenated by inactivating peroxidase/catalase in the tumor tissue through the application of hydrogen peroxide. This hydrogen peroxide is then degraded to produce oxygen. In this way, low-linear energy transfer (LET) radioresistant tumors can be transformed into radiosensitive ones. The purpose of the present study was to establish a non-surgical breast-conservation treatment (BCT) utilizing KORTUC II radiosensitization treatment. Materials and Methods: A new radiosensitizing agent containing 0.5% hydrogen peroxide and 0.83% sodium hyaluronate (a CD44 ligand) has been developed for intra-tumoral injection into various tumors. This new method, named KORTUC II, was approved by our local ethics committee for the treatment of breast cancer. A total of 39 earlystage breast cancer patients (stage I, 12 patients; stage II, 27 patients) were enrolled in the KORTUC II trial after providing fully informed consent. A maximum of 6 ml of the agent was injected into breast tumor tissue twice a week under ultrasonographic guidance, just prior to each administration of radiotherapy. The injection was started immediately prior to the 6th fraction of radiotherapy. Concerning radiotherapy, hypofraction radiotherapy was administered using a tangential fields approach and field-in-field method; the energy level was 4 MV and the total radiation dose was 44 Gy administered as 2.75 Gy/fraction. An electron boost of 3 Gy was added three times just following the 14th, 15th and 16th administrations of 4-MV X-ray irradiation. From a needle biopsy specimen, hormonal status (estrogen and progesterone receptors), HER-2 antigen, and CD44 receptor status were examined by immunohistochemistry. Results: Treatment was well tolerated with minimal adverse effects in all 39 patients. A total of 36 patients achieved clinically complete response according to dynamic magnetic resonance imaging, and the study has not yet been performed for the remaining 3 patients. No patients showed any significant complications (excluding mild dermatitis: Grade I, 24 patients; Grade II, 15 patients), and cosmetic results were excellent/good for 35 patients. Fifteen patients under 75 years old with stage II breast cancer underwent induction chemotherapy (EC and/or taxane) prior to KORTUC II treatment, and 36 patients with estrogen receptor-positive tumors also received hormonal therapy following KORTUC II. The mean duration of followup as of the end of September 2011 was 30.1 months, at which time all 39 patients were alive without any distant metastases. Only 1 patient had local recurrence, which was discovered after 34 months of follow-up. Conclusions: Non-surgical KORTUC-BCT can be performed using KORTUC II, which has three major characteristics: image-guidance by ultrasonography; enzyme-targeting of peroxidase/catalase; and targeting of breast cancer stem cells via the CD44 receptor. KORTUCBCT offers great potential as a viable noninvasive replacement for surgical BCT (Ogawa Y et al. Int J Oncol 39: 553-560, 2011).
EP-0997 ADJUVANT HYPOFRACTIONATED RADIOTHERAPY AFTER CONSERVING SURGERY FOR EARLY BREAST CANCER IN ELDERLY WOMEN A. Di Russo1, S. Tomatis2, V. Cosentino2, F. Soncini1, A.M. Cerrotta1, S. Morlino1, C. Chiruzzi1, D. Posté2, P. Pittoni3, L. Lozza1 1 Fondazione IRCCS "Istituto Nazionale Tumori", SC Radioterapia, Milano, Italy 2 Fondazione IRCCS "Istituto Nazionale Tumori", SC Fisica Sanitaria, Milano, Italy 3 Casa di Cura Multimedica, SC Radioterapia, Sesto S. Giovanni, Italy Purpose/Objective: This prospective study aims to evaluate feasibility, acute and late-term toxicity in a hypofractionated wholebreast irradiation schedule in elderly patients. Materials and Methods: From July 2009 to October 2011, 157 consecutive patients (pts) aged ≥70 (median age 75) affected by breast cancer were treated with conservative surgery (lumpectomy) followed by sentinel-node biopsy in 55.6%, sampling of axillary nodes in 11.3%, axillary dissection in 22,6%. No axillary node surgery was performed in 10.5% of cases. Hystology was as follows: infiltrating ductal carcinoma 73%, infiltrating lobular carcinoma 5%, CDI and CLI 15%, CDI associated to DCIS 5%, others 2%. Stage was as follows: pT1 in 98 pts (85,2%), pT2 22 pts (14,1%). Negative nodes in 77 pts (67%). 70,4% of pts received adjuvant hormone therapy and 13% of pts received chemotherapy respectively.