Role of PET CT in Radiotherapy Planning of Head and Neck Cancers

Abstract

Introduction: The use of new imaging modalities and combined chemoradiotherapy has resulted in significant improvements in treatment outcome for head and neck cancer patients. Presently, 3-D planning is standard in head and neck cancers and tissue volumes are delineated using computed tomography (CT) images. Role of positron emission tomography (PET) in radiotherapy planning is evolving. The PET/CT in radiotherapy planning may improve tumor delineation in terms of primary and nodal. The present study is designed to evaluate the role of PET-CT in radiotherapy planning of head and neck cancer and compare the dosimetric parameters for tumor and organs at risk between CT scan planning and PET-CT fusion planning.

Material and Methods: The present prospective study is of head and neck cancers was conducted in the department from August 2022 to January 2024. Histopathology proved squamous cell carcinoma head and neck cancers with age > 18 years and normal liver and kidney functions and not previously treated were selected. All patients were planned and delivered standard radiotherapy at a dose of 70 Gy in 35 fractions over 7 weeks. Two treatment plans were generated based on CT (group 1) and PET-CT (group 2) contours using intensity modulated radiotherapy technique (IMRT). Various dosimetric parameters of planning target volumes (PTV) and organs at risk (OAR) were evaluated for both groups. Collected data was analysed using standard statistical methods and the unpaired t-test was used to compare the means of both groups. p-value <0.05 was taken to be statistically significant.

Results: In the present study of 35 patients, majority of the patients were in the 7th decade of life with male predominance The commonest site involved was oropharynx (n = 13; 37.1%). T stage, N stage and overall stage, 17.1% cases were downstaged in PET CT. Total CTV (361.89 vs 355.96) and total PTV (692.33 vs 686.49) along with other PTV dosimetric parameters were slightly different in CT and PET CT which were not statistically significant. Similarly, various organs at risk did not show statistical difference in dosimetric parameters of both groups.

Conclusion: PET-CT supplementing radiotherapy planning contrast CT scan for tumor volume delineation has shown no statistical advantage in identifying the tumor more precisely in head and neck cancers. Cost-effectiveness and logistics associated with PET CT should be considered for radiotherapy planning.