Benign-looking adnexal masses on ultrasound: less is more–a cost-effectiveness analysis of the IOTA5 conservative model

Abstract STUDY QUESTION Is conservative management of benign-looking adnexal masses on ultrasound cost-effective compared with universal surgery, from the perspective of the Italian National Health Service (NHS)? SUMMARY ANSWER In this model-based analysis, conservative management of benign-looking adnexal masses was less costly and associated with fewer unnecessary surgical procedures than universal surgery scenario, with net savings exceeding €4.1 million per 1,919 patients over two years and consistent results across all deterministic sensitivity analyses. WHAT IS KNOWN ALREADY The International Ovarian Tumour Analysis Phase 5 (IOTA 5) prospective multicentre cohort demonstrated that conservative management of benign-looking adnexal masses on ultrasound is clinically safe, with cumulative 2-year rates of invasive malignancy, torsion and cyst rupture each below 0.5%. Spontaneous resolution occurred in 20.2% of newly diagnosed masses, suggesting that a substantial proportion of women managed surgically under a universal-surgery strategy would undergo unnecessary intervention. Despite this evidence, the economic implications of systematically adopting conservative management have not been formally evaluated: no cost-effectiveness analysis applying incremental cost-effectiveness ratio (ICER) methodology has been conducted for this clinical scenario. STUDY DESIGN, SIZE, DURATION Cost-effectiveness analysis from the Italian NHS payer perspective, based on published aggregate 2-year outcome data from the IOTA5 prospective cohort (1,919 patients with a newly diagnosed adnexal mass classified as benign on subjective ultrasound assessment). Two management strategies were compared over a 2-year time horizon: Scenario A (universal surgery) and Scenario B (IOTA5 conservative model: surgery in 16.1% of cases plus three post-baseline ultrasound examinations for the remaining 83.9%) using surgeries avoided as the intermediate effectiveness outcome. PARTICIPANTS/MATERIALS, SETTINGS, METHODS Clinical outcome data were derived from the published IOTA5 2-year interim analysis. Cost inputs were based on Italian NHS DRG (Diagnosis-Related Group) national tariffs (DRG 358/359 for adnexal surgery) and the NHS outpatient ultrasound tariff (code 88.78.2: €41.20). A weighted mean surgery cost of €2,700 was applied (85% DRG 359 at €2,550; 15% DRG 358 at €3,551). Three post-baseline ultrasound examinations were modelled for conservatively managed patients, consistent with the IOTA5 follow-up protocol (scans at 3, 6, and 12 months from recruitment; Froyman et al., 2019). Surgical complication costs were included as a supplementary analysis, applying published complication rates (overall 13.3%; major 0.6%) from the IOTA5 surgical cohort (Froyman et al., 2019). Event rates and tariffs were taken from published aggregate data and official tariff schedules, whereas the DRG case-mix, the unit costs of complications and the number of follow-up scans were assumptions made by the authors and were not derived from patient-level resource-use data. The ICER was calculated as net cost difference per surgery avoided. Uncertainty was explored using deterministic one-way and multi-way sensitivity analyses; probabilistic sensitivity analysis was not possible because individual patient data were not available. MAIN RESULTS AND THE ROLE OF CHANCE Scenario A (universal surgery) incurred total costs of €5,260,363 versus €1,112,359 for Scenario B, yielding net savings of €4,148,004 (79% cost reduction) over two years. Including surgical complication costs increased savings to €4,286,004. The base-case ICER was −€2,576 per surgery avoided, placing conservative management in the dominant south-east quadrant of the cost-effectiveness plane (less costly and more appropriate). One-way sensitivity analysis confirmed dominance across all parameter ranges tested (ICER range: −€2,512 to −€3,513 per surgery avoided). The break-even surgery rate, at which the conservative strategy would cease to dominate, was approximately 95%, far above the 16.1% observed in IOTA5. LIMITATIONS, REASONS FOR CAUTION This analysis was based on published aggregate rather than individual patient data; consequently, only deterministic sensitivity analyses could be performed. These assess robustness across the tested parameter ranges but do not replace formal probabilistic sensitivity analysis. The effectiveness outcome was intermediate rather than final, so the ICER cannot be compared with conventional cost-per-QALY thresholds. In addition, the DRG case mix and complication unit costs were based on author-defined assumptions rather than observed data. The downstream costs and health consequences of delayed cancer diagnosis were not incorporated into the primary model; therefore, the finding of economic dominance should be interpreted within the assumptions of the model. Finally, because cost estimates were derived from Italian NHS tariffs, their generalisability to other healthcare systems may be limited. WIDER IMPLICATIONS OF THE FINDINGS Conservative management of adnexal masses classified as benign on ultrasound appears to be both clinically safe and substantially less costly than universal surgery, with projected savings exceeding €4.1 million per 1919 patients over 2 years in the Italian NHS setting. Standardisation of gynaecological ultrasound training, a prerequisite for safe implementation, represents a modest investment relative to the potential clinical and economic benefits. Confirmation in a cost-utility framework, using prospectively collected quality-of-life data and patient-level resource use, is required before these findings can be regarded as definitive. FUNDING No external funding was received for this study. DISCLOSURES The authors have no conflicts of interest to declare. TRIAL REGISTRATION NUMBER N/A. This is a secondary analysis of published aggregate data from the IOTA5 study (ClinicalTrials.gov, NCT01698632).