INCORPORATING EXTRINSIC GOALS INTO DECISION AND COST-EFFECTIVENESS ANALYSES

Purpose: We examine methods for including extrinsic goals in medical decision and cost-effectiveness analyses.

Methods: Extrinsic goals occurring at unique points in time, such as completing an important project or seeing a child graduate from college, are not easily expressed in terms of QALYs.  They have been posited as explanations for preferences inconsistent with the QALY model, such as the phenomenon of maximum endurable lifetime, and the unwillingness to trade away time or accept gambles to improve health.  We introduce GALYs, an extension QALYs that incorporates extrinsic goals, and use it to re-evaluate two previously published analyses where extrinsic goals may be  important: the management of unruptured intracranial arteriovenous malformations (Auger and Weibers 1992), and the evaluation of preventive strategies for BRCA+ women (Anderson et al 2006). 

Results: In our reanalysis of Anderson et al, we considered a 32-year-old BRCA1+ female.  Ignoring childbearing goals, the two strategies oophorectomy + mastectomy and oophorectomy alone dominate, with the latter having a CE ratio of $77,216/QALY compared to the former.  Including a childbearing goal represented by the willingness to trade off a hypothetical 5 years of subsequent life to guarantee 6 immediate years of childbearing potential, we found that three strategies oophorectomy + mastectomy, oophorectomy + mastectomy delayed 6 years, and mastectomy alone dominated, with the second strategy having a favorable $12,670/GALY ratio compared to the first, and the third having a favorable $30,963/GALY ratio compared to the second.  The two dominant strategies under the Cost/QALY analysis were themselves dominated in this Cost/GALY analysis.

Conclusions: Inclusion of relevant extrinsic goals can significantly affect cost-effectiveness  results.  Ad hoc modifications of a Cost/QALY analysis may not capture conclusions from the corresponding Cost/GALY analysis.  For example, as the results above indicate, the alternate naïve approach of adopting the Cost/QALY optimal strategy but delaying it until goal-achievement does not in general yield the Cost/GALY optimal strategy.  A second alternate approach, performing a Cost/QALY analysis with all goal-impeding strategies (e.g., immediate oophorectomy) removed, corresponds to assigning arbitrarily high weight to goal achievement, and will yield different results than a Cost/GALY analysis with moderate or low goal weights. So in general it is advisable to explicitly include relevant extrinsic goals using measures such as  GALYs.