Role of positron emission tomography in the treatment of occult disease in head-and-neck cancer: a modeling approach.
OBJECTIVE
To determine under what conditions positron emission tomography (PET) imaging will be useful in decisions regarding the use of radiotherapy for the treatment of clinically occult lymph node metastases in head-and-neck cancer.


METHODS
A decision model of PET imaging and its downstream effects on radiotherapy outcomes was constructed using an influence diagram. This model included the sensitivity and specificity of PET, as well as the type and stage of the primary tumor. These parameters were varied to determine the optimal strategy for imaging and therapy for different clinical situations. Maximum expected utility was the metric by which different actions were ranked.


RESULTS
For primary tumors with a low probability of lymph node metastases, the sensitivity of PET should be maximized, and 50 Gy should be delivered if PET is positive and 0 Gy if negative. As the probability for lymph node metastases increases, PET imaging becomes unnecessary in some situations, and the optimal dose to the lymph nodes increases. The model needed to include the causes of certain health states to predict current clinical practice.


CONCLUSIONS
The model demonstrated the ability to reproduce expected outcomes for a range of tumors and provided recommendations for different clinical situations. The differences between the optimal policies and current clinical practice are likely due to a disparity between stated clinical decision processes and actual decision making by clinicians.
Phillips
Mark H
MH
Department of Radiation Oncology, University of Washington Medical Center, Seattle, WA 98195, USA. markp@u.washington.edu
Smith
Wade P
WP
Parvathaneni
Upendra
U
Laramore
George E
GE
D001499:Bayes Theorem; D003661:Decision Support Techniques; D003663:Decision Trees; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008198:Lymph Nodes / Q000000981:diagnostic imaging*; D015182:Lymphatic Irradiation / Q000379:methods*; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D010157:Palatal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D010160:Palate, Soft / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D011879:Radiotherapy Dosage; D012680:Sensitivity and Specificity; D014062:Tongue Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy