Anussara Songthong MD, Presenter: Nothing to Disclose

Danita Kannarunimit MD, Abstract Co-Author: Nothing to Disclose

Chakkapong Chakkabat MD, Abstract Co-Author: Nothing to Disclose

Chawalit Lertbutsayanukul MD, Abstract Co-Author: Nothing to Disclose

Simultaneous integrated boost intensity modulated radiation therapy (SIB-IMRT) is widely used in treatment of nasopharyngeal carcinoma (NPC). Higher dose per fraction leads to increased tumor control probability despite higher risk of normal tissue complications. The purpose of this study is to investigate acute and late toxicities comparing SEQ-IMRT versus SIB-IMRT in patient with NPC.

Newly diagnosed stage I-IVB NPC patients were stratified and randomized to receive SEQ-IMRT or SIB-IMRT. SEQ-IMRT consisted of two sequential radiation treatment plans; 2Gy x 25 fractions to low-risk planning target volume (PTV-LR) followed by 2Gy x 10 fractions to high-risk planning target volume (PTV-HR). In contrast, SIB-IMRT consisted of only one treatment plan; 2.12Gy and 1.7Gy x 33 fractions to PTV-LR and PTV-HR, respectively. All patients received concurrent weekly cisplatin followed by three cycles of adjuvant cisplatin and 5FU. Dosimetric data was compared between two IMRT plans. Toxicities were evaluated according to CTCAE version 4.03.

Between October 2010 and November 2013, 130 eligible patients were randomized between SEQ-IMRT (59 patients) and SIB-IMRT (71 patients). Dosimetric data showed significant difference in PTV-LR dose as well as median one parotid gland dose. With median follow-up time of 460 days (17-1211 days), there was no significant difference in toxicities between both IMRT techniques. During chemoradiation, the most common grade 3-5 acute toxicities were mucositis (14% vs 13.2%, SEQ vs SIB, p=0.897) followed by dysphagia (8.8% vs 10.3%, p=0.774) and xerostomia (8.8% vs 7.4%, p=0.512). During adjuvant chemotherapy period, 23.8% and 34.6% experienced grade 3 weight loss in SEQ-IMRT and SIB-IMRT (p=0.255). At 1 year, grade 3 weight loss was not significantly different between two arms. One-year overall survival (OS) and progression-free survival (PFS) were 93.9% and 96% in SEQ-IMRT and 98% and 88.8% in SIB-IMRT, respectively (p =0.406 for OS and 0.053 for PFS).

This randomized phase III trial comparing SIB-IMRT versus SEQ-IMRT in NPC showed no statistically significant difference between both IMRT techniques in terms of acute and late adverse events. Short-term tumor control and survival outcome were promising.

SIB-IMRT (dose painting technique) resulted in similar  adverse events compared with SEQ-IMRT (shrinking field technique) in NPC.  

Songthong, A, Kannarunimit, D, Chakkabat, C, Lertbutsayanukul, C, A Randomized Phase III Study of Adverse Events between Sequential (SEQ) versus Simultaneous Integrated Boost (SIB) Intensity Modulated Radiation Therapy (IMRT) in Nasopharyngeal Carcinoma; Preliminary Result.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14003605.html