152 Chapter 9 Can we reliably determine whether a treated aneurysm is ‘adequately’ occluded and longer follow-up not required? The classification of Roy and Raymond (R&R)77 (figure 2) is used in nearly all studies to describe the occlusion status of coiled aneurysms. R&R Class 1 R&R Class 2 R&R Class 3 Figure 2 Aneurysm occlusion classification by Roy and Raymond The relationship between this classification, based on morphology, and risk of late rebleed or recanalization requiring retreatment, is not clearly defined. A pragmatic use of the R&R classification could be as follows: Class 1: stable, follow-up no longer needed; Class 2: small neck remnant, no need for treatment but prolonged follow-up required; Class 3: recanalization requiring treatment. This is not the way the R&R classification is interpreted in the studies described in Chapter 1 and in the LOTUS study: class 2 is mostly considered as ‘stable’ or ‘adequate’, while class 3 is used for ‘unstable’ or ‘inadequate’ occlusions. About half of these inadequately occluded aneurysms are treated in practice,78 and the other half probably need prolonged follow-up.74 The R&R class 2 occlusions only require longer follow-up if there is a tendency to recanalize or rebleed at a later stage. As described in Chapter 7, we found no correlation in our data or in the LOTUS study data between R&R class 2 occlusion status and later recanalization. These findings are in line with other studies comparing six to 18 or 24 months follow-up results.62,79 Thus, we conclude that aneurysms with occlusion status R&R class 1 or 2 at six months are adequately occluded and do not need prolonged follow-up. Contrary to R&R class 1 and 2 occlusion, the distinction between R&R class 2 and 3 occlusion remains significant. A problem with such morphologic classifications however, lies in the initial size of the aneurysm. For example, if there is a large aneurysm with a small remnant after coiling this will usually be regarded as class 2. If the initial aneurysm was small (say 3 or 4mm), the same remnant will appear proportionally much larger, and may be classified as Class 3. Based on our findings described in Chapter 7 we suggest a simplification of occlusion classification of coiled aneurysms at six months follow-up. Proposal 9. Occlusion status of coiled aneurysms at six months follow-up can be described as adequate (class 1 or 2 of Roy and Raymond classification) or inadequate (class 3). Inadequately occluded aneurysms at six months require either retreatment or prolonged follow-up. Cost-effectiveness The Markov decision model can be used to calculate quality-adjusted life-years (QALYs) as outcome for different management strategies. Using costs as input parameters in this model, the effects of different management strategies on total costs can be calculated as well.80-82 In Chapter 8 we used both these outcomes to compare the cost-effectiveness of different imaging strategies in patients with a SAH. In an earlier study, Schaafsma et al. compared the cost-effectiveness of MRA versus DSA in the follow- up of patients with coiled intracranial aneurysms.83 This cost-effectiveness study supports our
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