Abstract Book

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ESTRO 37

mode, associated to significantly higher measurements in both lungs, contralateral breast, heart, liver, esophagus and thyroid. Maximal radiation dose was related to dosimetry of contralateral lung, contralateral breast and heart while laterality was: contralateral lung, heart and esophagus. The modality of primary axillary treatment in these women did not influence the dosimetry of the risk organs with the exception of contralateral breast that showed higher when radiating levels I-IV. However in the multivariate analysis, only radiation therapy modality and maximal dose were significantly associated with this The primary axillary treatment does not influence the dosimetry of the risk organs . Only laterality, max. dose and specially the modality of radiotherapy regimen influence dosimetry in risk organs. parameter. Conclusion EP-1353 Breast Cancer In Young Women: A Retrospective Study C. Sousa 1 , L. Pinto 2 , N. Saraiva 2 , I. Rego 2 , J. Paulo 2 , J. Bastos 3 , M. Mariano 2 , G. Sousa 2 , D. Roda 1 , C. Miranda 1 , G. Melo 1 , M. Cruz 1 , S. Martins 1 , P. Kayla 1 1 Instituto Português de Oncologia Coimbra Francisco Gentil- EPE, Radiation Oncology, Coimbra, Portugal 2 Instituto Português de Oncologia Coimbra Francisco Gentil- EPE, Medical Oncology, Coimbra, Portugal 3 Instituto Português de Oncologia Coimbra Francisco Gentil- EPE, Regional Oncology Registry of the Centre, Coimbra, Portugal Purpose or Objective Breast cancer in young patients represents a particular issue that needs attention. The increasing number of cases and poorer outcomes results due in part to the special clinical-pathological characteristics and the superior risk for disease recurrence and death. Despite an increased risk of local recurrence, age is not a contraindication to breast conserving therapy. The aim of this study is to analyze the characteristics, therapeutic procedures and the profile of radiodermitis (RD) on this group. Material and Methods Retrospective review of patients with breast cancer under 40 years treated between January 2009 and December 2013 in our institution - Portuguese Institute of Oncology of Coimbra. Multivariate statistical analyses and survival evaluation was performed. Results A total of 208 female patients were included, with a median age of 35.9 years (y) (22-39y). At the diagnosis 98.6% had ECOG-PS of 0. 6.3% were bilateral tumors. Gynecological history included a median menarche age of 12.5y (9-17y), 21.1% of nulliparous woman. The median age of first pregnancy was 26,1y (13-36y), 68.8% breastfed. Oral contraceptive were taken in 90.4%. 63% of the patients had BMI<25 kg/m 2 . Histological examination of the tumors revealed mostly invasive ductal carcinoma with grade 2 differentiation in 63% and grade 3 in 19.2% of the cases. Considering the subtype and characteristics of breast cancer we had 24.5% luminal A, 28.4% luminal B non-HER2, 23% HER2 positive and 24.1% patients had triple negative breast cancer. The TNM staging evaluation revealed 4.8% in stage I, 17.8% stage IIA, 33.7% with stage IIB, 36.1% stage III and 9.7% patients were diagnosed in stage IV. 204 patients were submitted to surgery and 70% (n=143) of them performed radiotherapy. Taking into account the absence of 15 registries, 55% (n=69) of patients developed grade (G) 1 RD. Most patients had a body mass index (BMI) of 18,5- 24,9kg/m 2 (n=81), and did not developed RD in 33% (n=27). Patients with BMI 25-29,9kg/m 2 developed G1 RD in 58% (n=19) and G2 RD in 30% (n=10). Patients with BMI 30-34,9kg/m 2 developed G1 RD in 92% (n=12). There is a correlation between BMI and RD, with the most severe RD

Conclusion DIBH reduces the dose to the heart subvolumes and IL globally. There is a significant dose reduction to the heart subvolumes in left breasts, and in the IL in right breasts. In patients with treated regional nodes, the reduction is lower than without them. EP-1352 Dosimetric Variations In Oars In The Radiotherapy Of Breast Cancer Pn1 With Or Without Alnd. M.D. De las Peñas-Cabrera 1 , M. Miguel Hernández 1 , E. Amaya Escobar 1 , P.M. Samper Ots 1 , R. Garcia-Marcos 1 , R. Polo Cezón 1 , M. Medina Cespedes 1 , P. Jimenez López 1 1 Hospital Rey Juan Carlos, Radiation Oncology, Mostoles - Madrid, Spain Purpose or Objective To evaluate the influence of regional nodal irradiation axillary level I-IV vs level III-IV on dosimetry of the risk organs by using a multivariate approach in women with breast cancer, SNB positive to either 1 or 2 nodes and sentinel lymph nodes biopsy alone or ALND. (ACOSOG Z0011 trial). Material and Methods Design: Preliminary report on an ongoing prospective longitudinal cohort study. Of a total of 2707 patients, 639 are breast cancer. 23.60%. There were cT1-2 cN0: 7.82%. In total, 50 women allocated in two groups were studied. 20 were treated by SNB (ACOSOG) and in the remained 30 lymphadenectomy was performed. Since October 2012 we began to apply the recommendation after ACOSOG Z0011 study, and AMAROS, not to perform ALND in patients with infiltrating breast cancer, cT1-T2 cN0, submitted to SNB, which after histological study, were pN1 independent of the type of surgery, conservative or mastectomy. In patientswith either 1 or 2 affected nodes at SNB, we irradiated axillary levels I-IV. Those who undertook ALND, level III-IV were only irradiated. Written informed consent was obtained all patients. Age histology, laterality, cTNM, pTNM, stages, inmunophenotipe were similar in both groups. Dosimetric comparisons of the treatment plans were performed based on the following parameters extracted from DVHs: V5, 10, V20 and mean lung dose (MLD) for the bilateral lungs; V25, V30, and mean heart dose (MHD) for the heart; V10, mean dose for the contralateral breast; esophagus, spinal cord, liver, thyroid, and brachial plexus and maximum dose for the skin. Results were shown as number and percentages for categorical variables (mean and SD) for numerical variables as distribution were normal. Comparisons were done by using chi squared, Student’s t test. Multiple lineal regression was used when several variables showed significance in the univariate analysis. Particularly the influence of laterality, total radiation dose (50 vs 60 Gy SIB), VMAT vs 3DCRT and axillary treatment on dosimetry were evaluated. Significance level was set at 95% (p < 0.05). Results In the univariate analysis the most influencer parameter on dosimetry of the risk organs was radiation therapy