Patients with advanced oropharyngeal cancer are often treated with chemoradiation in order to preserve organ function and quality of life. Thorough follow-up is warranted to detect residual tumour. However, there is considerable variation in the diagnostic tests used for local response evaluation. The most reliable procedure, i.e. examination under general anesthesia (EUA) with biopsies in all patients, is invasive and the yield is low. Furthermore, it may induce substantial morbidity and has considerable impact on scarce health care resources.

Potential of imaging

The burden and costs of response evaluation might be reduced by using non-invasive imaging tests for response evaluation. Imaging cannot completely replace EUA because pathological confirmation is required before further treatment. Nevertheless, it could be used to select those patients with a high risk of residual disease for further diagnostic workup with EUA.

Study aim

To assess the effects and costs of four response evaluation strategies to detect local residual disease, namely EUA for all patients, PET-CT-based selection for EUA, DW-MRI-based selection for EUA and a combination of PET-CT and DW-MRI to select for EUA.

Methods

We built a decision-analytic model using trial data of forty-six patients and scientific literature. We estimated for four strategies the proportion of correct diagnoses, costs concerning diagnostic instruments and the proportion of unnecessary EUA indications.

Results

• The EUA strategy led to 96% correct diagnoses and expected costs of € 468 per patient. 89% of the EUA indications were unnecessary.
• All imaging strategies considerably reduced (unnecessary) EUA indications and its associated burden compared to the EUA strategy.
• The DW-MRI strategy was the least costly strategy but also led to the lowest proportion of correct diagnoses (93%).
• The combination of PET-CT and DW-MRI had the highest sensitivity. This strategy led to an equal proportion of correct diagnoses as the EUA strategy, but at higher costs.

Figure 1. Total number of EUA indications, number of unnecessary EUA indications and expected costs per patient per strategy for 1,000 patients.

Conclusion

The combined PET-CT and DW-MRI strategy reaches the same diagnostic accuracy in detecting local residual disease as the EUA strategy. As the former costs only an additional €927 per patient while substantially lowering the number of unnecessary, invasive EUA indications, the combined strategy is preferred over immediate EUA. 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.

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