The evolving role of positron emission tomography-computed tomography in organ-preserving treatment of head and neck cancer.

The introduction of image-guided radiation therapy and intensity-modulated radiation therapy has led to unparalleled advances in achieving precise dose conformality in radiation therapy and ushered in new possibilities in organ preservation. Without the ability to meticulously delineate radiation treatment volumes, these advantages would be clinically irrelevant. Positron emission tomography (PET)/computed tomography (CT) has revolutionized the management of head and neck cancers in all areas, including diagnosis, staging, radiation treatment planning, and response evaluation. It has been shown to have a superior sensitivity for defining primary disease and both higher sensitivity and specificity for nodal disease in comparison with CT or magnetic resonance imaging during treatment planning. Thus, PET/CT frequently leads to an alteration of gross tumor volume/clinical target volume/planning target volume and often changes a patient's tumor, nodes, metastases staging. According to our data, the addition of PET to CT alone led to a modification in treatment planning in 55% of patients studied. PET/CT also helps to standardize radiation therapy between institutions and decreases interobserver variability. PET/CT is a powerful predictor of outcome after treatment. Although technical obstacles do exist and PET/CT does have small inherent inaccuracies, these can usually be overcome with careful planning and specification of setup error/margins, thereby allowing PET/CT to remain an essential and necessary tool in our fight against head and neck cancers.