There is considerable variation in diagnostic tests used for response evaluation after chemoradiotherapy (CRT) in patients with oropharyngeal cancer. An example of such a diagnostic test is examination under general anesthesia (EUA). This is an invasive procedure during which biopsies are taken in areas treated with CRT. Other options are imaging tests which are less invasive but cannot replace EUA because pathological confirmation is required. However, they could be used to select those patients with a high risk of residual disease for further diagnostic workup with EUA. This would reduce the number of patients that have to undergo (unnecessary) invasive diagnostic procedures. We evaluated four response evaluation strategies in terms of diagnostic accuracy and cost-effectiveness.
Strategies in the decision-analytic model
We considered EUA for all patients as the reference strategy. Furthermore, we evaluated three imaging strategies consisting of diffusion-weighted MRI (DW-MRI), 18-FDG-PET-CT, or both DW-MRI and 18-FDG-PET-CT followed by EUA in patients with a positive imaging test. We developed a decision-analytic model using trial data of forty-six patients and scientific literature to calculate for each strategy the proportion of correct diagnoses, costs concerning diagnostic instruments and the proportion of unnecessary EUAs. The impact of uncertainty was assessed in sensitivity analyses.
Health benefit, treatment burden and costs
In the EUA strategy, 96% of patients was correctly diagnosed. Expected costs were 468 Euros whereas 89% of the EUAs were futile. The DW-MRI strategy was the least costly strategy, but also led to the lowest proportion of correct diagnoses, i.e. 93%. The PET-CT strategy and combined imaging strategy were dominated by the EUA strategy due to an equal or smaller proportion of correct diagnoses, at higher costs. However, the combination of PET-CT and DW-MRI had the highest sensitivity. All imaging strategies considerably reduced (unnecessary) EUA indications and its associated burden compared to the EUA strategy.
Strategy of choice
Because the combined PET-CT and DW-MRI strategy costs only an additional €927 per patient, it is preferred over immediate EUA since it reaches the same diagnostic accuracy in detecting local residual disease while leading to substantially less unnecessary EUA indications. However, if healthcare resources are limited, DW-MRI is the strategy of choice because of lower costs while still providing a large reduction in unnecessary EUA indications.
Greuter MJE, Schouten CS, Castelijns JA et al. Cost-effectiveness of response evaluation after chemoradiation in patients with advanced oropharyngeal cancer using 18F-FDG-PET-CT and/or diffusion-weighted MRI. BMC Cancer. 2017;17:256.