Abstract Book

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ESTRO 37

mastectomy or modified radical mastectomy, and its relation with the type of the treatment planning. Material and Methods One hundred and thirty eight patients undergoing RT in our hospital for breast cancer were retrospectively analyzed. Patients were divided into three groups: three- dimensional conformal radiotherapy (3D- CRT) group, forward intensity-modulated radiotherapy (F- IMRT) group and inverse IMRT (I-IMRT) group. The IMC were contoured according to Radiation Therapy Oncology Group (RTOG) concensus,and were not include into the planning target volume (PTV).The mean doses ( D mean) and the volumes receiving equal or more than 20 Gy, 30 Gy, 40 Gy, 50 Gy (V 20 , V 30 , V 40 , V 50 ) to IMC were analyzed. Results The Dmean to IMC was 32.85 Gy for all patients, and the dose delivered to IMC showed no difference in CRT, F- IMRT and I-IMRT(33.80 Gy, 29.65 Gy and 32.95 Gy). For the IMC dose in the first three intercostal spaces (ICS1-3), there were no difference to the three treatment plannings. The Dmean,V 20 ,V 30 ,V 40 and V 50 of the ICS2 and ICS3 were all obviously superior than ICS1 for all these three plannings 。 Moderate positive correlation was founded between Dmean for IMC and Dmean for heart for patients underwent CRT (r=0.338, P=0.01). Whereas for F-IMRT and I-IMRT groups, positive correlation were founded between Dmean for IMC and Dmean and V 20 for ipsilateral lung. Conclusion The Dmean to IMC was 32.85 Gy for all patients, and the dose delivered to IMC showed no difference in CRT, F- IMRT and I-IMRT(33.80 Gy, 29.65 Gy and 32.95 Gy). For the IMC dose in the first three intercostal spaces (ICS1-3), there were no difference to the three treatment plannings. The Dmean,V 20 ,V 30 ,V 40 and V 50 of the ICS2 and ICS3 were all obviously superior than ICS1 for all these three plannings 。 Moderate positive correlation was founded between Dmean for IMC and Dmean for heart for patients underwent CRT (r=0.338, P=0.01). Whereas for F-IMRT and I-IMRT groups, positive correlation were founded between Dmean for IMC and Dmean and V 20 for ipsilateral lung. EP-1311 Self-reported work ability in breast cancer patients during and after breast cancer treatment. M. Gregorowitsch 1 1 UMC Utrecht, Radiation Oncology, Utrecht, The Netherlands Purpose or Objective Early detection and advances in breast cancer treatment has led to an improved survival. As a result understanding the long-term effects of various breast cancer treatments is important. Returning to work after treatment and maintaining employment is relevant, since work is intrinsically rewarding, an important source of income and generates social interactions. Knowledge of disease characteristics and treatment factors associated with poor work ability allows adequate information of patients on what to expect and to offer targeted interventions. This may contribute to improved quality of life (QoL) after breast cancer treatment. Material and Methods This study was conducted within the Dutch UMBRELLA cohort, i.e. prospective observational cohort including breast cancer patients indicated to receive post- operative radiotherapy at the department of Radiation Oncology at the University Medical Centre Utrecht. All working-aged breast cancer patients (<67 years) within the Dutch UMBRELLA cohort were selected. Work ability and QoL were measured by the Work Ability Index (WAI) [Ilmarinen J, 2007] and EORTC QLQ-C30 questionnaire, respectively. The WAI score, ranging from 7 to 49, was calculated. Higher scores reflect better work ability and

scores were categorized in low (7-36) and good/excellent (37-49). Mean work ability scores were stratified for treatment strategies and compared with scores of the age-matched Dutch reference population. Results Between October 2013 and November 2016, 844 patients were enrolled. In total 527 patients (62%) responded to at least one of the questionnaires and were employed at the time of assessment. Of the responders, 65% had permanent employment, 14% were freelancer, 9% had temporary contracts and 12% reported another form of employment. Mean age of the study population was 52 years. At baseline, before start of radiotherapy, the mean WAI score was 30.8, which was substantially lower than the reference population score of 42. Low work ability at baseline was reported by 68% (n=360) of the patients. At 6 and 18 months, mean work ability scores increased to 33.2 and 37.5, resp. and the proportion of patients with suboptimal work ability decreased over time (60% at 6 months and 36% at 18 months). Patients who reported a low work ability at baseline were significantly younger (51 years vs. 53 years in patients with good/excellent work ability p= 0.004). Work ability was lower in patients treated with mastectomy compared to breast-conserving surgery (Fig. 1A), after locoregional compared to local radiotherapy (Fig. 1B) and when treated with (neo)adjuvant systemic therapy (Fig. 1C), at all time points (i.e. baseline, 6 and 18 months). Patients with excellent work ability reported a better QoL during follow-up compared to patients with poor work ability.

Conclusion Compared to the Dutch population, breast cancer patients report a lower work ability. Work ability was lowest after surgery, during radiotherapy and chemotherapy, and improved gradually over time. EP-1312 Improved treatment prone positioning in 3D whole-breast irradiation D. Hernández González 1 , P. Castro Tejero 1 , M. Roch González 1 , S. Martín Juárez 2 , J.D. Arango Garrote 2 , P. Castañón García 1 , M.T. Murillo González 3 , L. Pérez González 1 1 H.U. La Princesa, Medical Physics, Madrid, Spain 2 H.U. LA PRINCESA, Radiation TherapisTs, Madrid, Spain 3 H.U. LA PRINCESA, Radiation Oncology, Madrid, Spain