ESTRO 2024 - Abstract Book

S1414

Clinical - Head & neck

ESTRO 2024

2618

Digital Poster

Pattern of Local Failure In Oropharyngeal Cancer After Radical Intensity Modulated Radiation Therapy

Mangesh Ikhe 1 , Ashwini Budrukkar 1 , Sheetal Kashid 1 , Monali Swain 1 , Sarbani Ghosh-Laskar 1 , Shwetabh Sinha 1 , Anuj Kumar 1 , Amit Janu 2 , Shrikant Kale 3 , Rituraj Upreti 3 , Jai Praksh Agarwal 1 1 Tata Memorial Hospital, Radiation oncology, Mumbai, India. 2 Tata Memorial Hospital, Radiodiagnosis, Mumbai, India. 3 Tata Memorial Hospital, Medical physics, Mumbai, India

Purpose/Objective:

To study the patterns of local failure for primary site with respect to clinical target volume (CTV-P1 and CTV-P2) in patients with oropharyngeal cancers treated using IMRT technique

Material/Methods:

One hundred and eight nine patients of histologically proven oropharyngeal cancers treated with radical intent IMRT from January 2013 to December 2019 at Tata Memorial Hospital Mumbai were analysed. CTV was generated by giving 5-10mm margin as per the discretion of treating clinician at the time of planning. For the purpose of this study CTV-P1 and CTV-P2 were generated by successive 5 mm margins to primary gross tumour volume (GTV) in the planning CT in patients who had local failure (LF). LF was defined as either persistence of disease post radiation therapy or reappearance of tumor at either primary site which was histologically or radiologically proven. LF was delineated on recurrent diagnostic scan for each patient and coregistered either using rigid or deformable registration with treatment planning computed tomography scans. Each recurrence was analyzed with three methods i.e volumetric approach given by Dawson et al and Chao et al and centre of mass approach (COM) given by Raktoe et al. At a median follow up of 33 months , out of 189 patients ,59 patients had LF either in form of persistent residual disease or local recurrence . The median time to LF from index disease was 5 months that included patients who had persistent residual disease at first response assessment. Out of 59 patients , 39 patients had only LF,12 patients had persistent primary and nodal disease ,3 patients had persistent primary , nodal and distant failure , 3 patients had local and regional recurrence while 2 patients had local and distant failure. Seven patient had regional recurrence , 6 patients had distant failure while 1 patient had regional and distant failure . Fourty four patients in whom scans at the time of recurrence were available in our institute were analysed for pattern of LF . With respect to 95% prescription isodose, 39(89%) patients had in field recurrence while 5(11%) patients had marginal recurrence. With respect to CTV-P1,23 (52%) patients had in field recurrence ,19 (43%) patients had marginal and 2(5%) patients had out of field recurrence . With respect to CTV-P2, 32 (73%) patients had in field recurrence , 11 (25%)patients had marginal recurrence while 1 (2%) patient had out of field recurrence . According to COM methodology, with respect to CTV-P1, 41 patients (93%) had in field LF and 3 patients(7%) had out of field Results: