Quality assessment of medical decision making in radiation oncology: variability in target volume delineation for brain tumours

The enormous developments in radiation technology open new horizons for improvements in local tumour control. However, the evolution from conventional external beam radiotherapy planning to conformal therapy might be hampered by the potential risk of over-reliance on the physician's capability of estimating the tumour extent from imaging modalities. The variability between 12 volunteering physicians in the delineation of tumour and target volume on the lateral orthogonal localisation radiograph from CT was assessed for 5 brain tumours. The estimated tumour and target sizes varied, respectively with a factor of 1.3-2.6 and with a factor of 1.3-2.1. The anatomical location of the volumes showed maximum variations from 11 to 27 mm in the cranio-caudal direction and from 14 to 21 mm in the fronto-occipital direction. For the 5 test cases, the tumour area on which all radiation oncologists agreed, represented only 25-73% of the corresponding mean tumour area. Although the introduction of computed tomography in radiation treatment planning was proved to be a major step forwards for treatment planning in many tumour sites, the results of the present study on brain tumours demonstrate that the subjective interpretation of the tumour extent based on CT images might be one of the largest factors contributing to the overall uncertainty in radiation treatment planning. Moreover, this study endorses the need for uncertainty analysis of the medical decision-making process. It may be that the process of making uncertainties explicit can contribute to the improvement of our present concept of radiation treatment planning.(ABSTRACT TRUNCATED AT 250 WORDS)