ESTRO 2023 - Abstract Book

S996

Digital Posters

ESTRO 2023

Conclusion PROs demonstrated detectability of time- and between-and within-groups-specific therapy-induced HRQOL changes. A further detailed exploration of EQ-5D-5L responsiveness for H&N cancer patients is required.

PO-1243 Local tumor extension and proposed clinical target volume delineation in nasopharyngeal carcinoma

W. yin 1 , Z. wu 2 , B. qi 1 , F. lin 3 , L. zhang 2 , Q. he 2 , F. li 4 , H. wang 2 , Y. Han 2

1 Affiliated Cancer Hospital & Institute of Guangzhou Medical University, Department of Radiation Oncology, guangzhou, China; 2 Hunan Cancer Hospital & the Affiliated Cancer Hospital of Xiangya School of Medicine, Department of Radiation Oncology, changsha, China; 3 Sun Yat-sen University Cancer Center, Department of Radiation Oncology, guangzhou, China; 4 Hunan Cancer Hospital & the Affiliated Cancer Hospital of Xiangya School of Medicine, Department of Imaging, changsha, China Purpose or Objective This research aims to summarize the characteristics of local extension of the eccentric and central nasopharyngeal carcinoma (NPC) by magnetic resonance imaging (MRI) and to improve clinical target volume (CTV) delineation. Materials and Methods MRIs of 870 newly diagnosed NPC patients were reviewed. According to the tumor distribution feature, the NPCs were divided into eccentric and central lesions. The central NPCs were defined as tumors whose main body located in the midline region of nasopharynx; while the remaining tumors were eccentric NPCs. Results All local invasions presented as continuous invasion from gross lesions and structures adjacent to the nasopharynx are more likely to be invaded; meanwhile, the most frequently invaded skull base foramina were foramen lacerum (47.1%), pterygopalatine fossa (27.0%). There were 240 (27.6%) and 630 (72.4%) cases with central and eccentric lesions, respectively. The spread of eccentric lesions centered on the ipsilateral Rosenmüller’s fossa; and most anatomic sites had significantly higher invasion rates in ipsilateral side than the contralateral side (P < 0.05); however, they were at low risk of concurrent bilateral tumor invasion (<10%) except the prevertebral muscle (15.4%). The extension of central NPCs centered on the nasopharyngeal superior-posterior wall and was more common in superior-posterior direction; furthermore, the bilateral tumor invasion into the anatomical sites was common. Conclusion Local invasion of NPC was characterized by continuous invasion from proximal to distal sites. The eccentric and central lesions showed different invasion features. Individual CTV delineation in NPC should be based on the distribution characteristics of tumors. The eccentric lesion had very low probability of invasion into the contralateral tissue, thus routine prophylactic radiation of contralateral parapharyngeal space and skull base foramina may not be necessary. 1 Sahlgrenska University Hospital, Department of Medical Physics and Biomedical Engineering, Gothenburg, Sweden; 2 University of Gothenburg, Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy, Gothenburg, Sweden; 3 University of Gothenburg, Department of Health and Rehabilitation/Physiotherapy, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden; 4 Sahlgrenska University Hospital, Department of Physical Therapy, Gothenburg, Sweden; 5 University of Gothenburg, Department of Oncology, Institute of Clinical Sciences, Sahlgrenska Academy, Gothenburg, Sweden; 6 Sahlgrenska University Hospital, Department of Oncology, Gothenburg, Sweden; 7 Regional Cancer Centre West, Research and development, Gothenburg, Sweden; 8 Chalmers University of Technology, Department of Technology Management and Economics, Centre for Healthcare Improvement, Gothenburg, Sweden; 9 Jönköping University, Department of Nursing, School of Health and Welfare, Jönköping, Sweden Purpose or Objective Since introduced more than two decades ago, Deep Inspiration Breath Hold (DIBH) has been widely used to spare the heart and ipsilateral lung in breast cancer radiation therapy. Three different DIBH maneuvers for breast cancer radiation therapy can be found in the scientific literature; spontaneous, abdominal, and thoracic DIBH (1-3). The results from different studies investigating DIBH are, however, not consistent. For instance, it has been concluded that abdominal DIBH combined with IMRT is the best option for sparing the heart (2), but it has also been concluded that a more pronounced thoracic DIBH is more beneficial with regard to sparing the heart (3). So, even though DIBH is a widely used treatment technique today, documented coaching strategies for optimal DIBH are still lacking (4). The aim of this study is to investigate the dosimetric effects for the heart and ipsilateral lung for different DIBH maneuvers in left-sided whole breast tangential 3D conformal radiation therapy (3DCRT) using MRI. Materials and Methods This study has ethical approval from the Swedish Ethical Review Board (reg no. 2020-00029). Four healthy female research participants were enrolled. Poster (Digital): Breast PO-1244 Is there an optimal DIBH maneuver in breast cancer radiation therapy? – A pilot study A. Karlsson 1,2 , N. Pham 2 , M. Fagevik Olsén 3,4 , D. Lundstedt 5,6 , F. Smith 7,8 , M. Giovinazzo Brovall 9,5 , M. Sohlin 1,2