Advances in dose/volume/outcome (or normal tissue complication probability, NTCP) modeling since the seminal Emami paper from 1991 are reviewed. There has been some progress with an increasing number of studies on large patient samples with three-dimensional dosimetry. Nevertheless, NTCP models are not ideal. Issues related to the grading of side effects, selection of appropriate statistical methods, testing of internal and external model validity, and quantification of predictive power and statistical uncertainty, all limit the usefulness of much of the published literature. Synthesis (meta-analysis) of data from multiple studies is often impossible due to sub-optimal primary analysis, insufficient reporting and variations in the models and predictors analyzed. Clinical limitations to the current knowledge-base includes the need for more data on the effect of patient-related co-factors, interactions between dose-distribution and cytotoxic or molecular targeted agents, and the effect of dose fractions and overall treatment time in relation to non-uniform dose distributions. Research priorities for the next 5 to 10 years are proposed.

Implementation of these guidelines in the daily practice of radiation oncology should contribute to reduce treatment variations from clinicians to clinicians, facilitate the conduct of multi-institutional clinical trials, and contribute to improved care of patients with head and neck carcinoma.

stage, induction chemotherapy use, dose/ fractionation, mode of detection of recurrence, salvage therapy, and number and modality of scans were recorded. Deaths from disease recurrence or from other causes were also recorded. Imaging costs were calculated based on the 2016 Medicare fee schedule. Results: A total of 1508 patients were included. Median overall survival was 99 months (range: 6-199). Mean imaging follow-up period was 70 months. Of the total, 190 (12.6%) patients had disease recurrenced107 locoregional (LR) and 83 distant. Of the relapsed group, 119 (62.6%) were symptomatic and/or had an adverse clinical finding associated with recurrence. Majority (80%) of LR relapses presented with a clinical finding, while 60% of distant relapses were detected via imaging alone in asymptomatic patients. There was no difference between the successful salvage rates and overall survival between those with relapses detected clinically or via imaging alone. Seventy percent of relapses occurred within the first 2 years posttreatment. In those who relapsed after 2 years, the median time to relapse was 51 months (2 LR and 11 distant relapses). After 2 years, the average cost for detecting a salvageable recurrence for image-detected group was $395,223.09, and the cost for preventing 1 recurrence-related death for image-detected disease was $474,267.70. The number of scans required to detect a salvageable recurrence in an asymptomatic patient after 2 years was 1539. Conclusion: Surveillance imaging in asymptomatic patients without clinically suspicious findings beyond 2 years requires judicious consideration.

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