A comparative study of planning and dosimetry in locally advanced head-and-neck cancer: sequential versus simultaneous integrated boost methods in intensity-modulated radiotherapy

Abstract

Objective: A head-and-neck cancer (HNC) comprises one-third load of India's cancer burden. We aim to compare the target coverage and the normal tissue sparing between sequential intensity-modulated radiotherapy (IMRT) and simultaneously integrated boost (SIB)-IMRT plan for patients of locally advanced HNCs. We evaluate dosimetric parameters of two plans for a single patient and compare target coverage and conformity index (C. I.) and also assess the differences in dose received by organs at risk (OAR) by two plans. Materials and Methods: After recording the detailed history, performing a thorough clinical examination and the relevant investigations, the patients who were staged as locally advanced squamous cell carcinoma of oropharynx, hypopharynx, and supraglottic regions were chosen for the study. An informed consent was taken before enrolling them in study. Results: A total of 30 patients were enrolled in the study. Three patients were female, whereas the remaining 27 were male. Of the 30 patients 19 patients (63.34%) had oropharyngeal disease and 11 had hypopharyngeal disease (36.66%). The present study reported that 24 patients had moderately differentiated squamous cell carcinoma, two patients had well differentiated tumor, and in four patients, it was poorly differentiated carcinoma. The minimum dose, maximum dose, and the mean dose volumes of planning target volume (PTV) 1 and PTV2 which were designated as D100, Dmax and Dmean, respectively, were analyzed by both SIB and SEQ-B IMRT plans. The C. I. was derived by Radiation Therapy Oncology Group (RTOG) 90-05 (34). The C. I. for PTV1 and PTV2 by SEQ-B and SIB IMRT plans was 0.96 versus 0.95 and 0.97 versus 0.95, respectively. The mean maximum dose to brain stem was 4230.02 cGy with SEQ-B and 4305.52 cGy with SIB plan. On analyzing the mean maximum dose received by mandible, a statistically significant sparing was seen with SIB technique. Conclusion: In the present study, as no significant difference was observed in OAR sparing except mandible in both the plans. Hence, in view of the results and comparative studies, both the plans are clinically acceptable, although taking into account the tumor coverage, the sequential boost IMRT plan arm gave better results.