The initial literature search identified 568 publications, of which 44 duplicates were removed. Of the 524 unique publications, 459 were excluded following title and abstract screening (Fig. 1). The remaining 65 studies underwent full text review, with 39 meeting the inclusion criteria. Studies were stratified by stage (II or III) and the AC strategies being investigated, with some studies found to examine multiple strategies or report aggregated stage II and III results.
3.1 General characteristics
Table 2 summarises the main characteristics and key results of the identified evaluations. Where applicable, we provided the cost-effectiveness judgement reported by the author(s) and the willingness-to-pay (WTP) threshold per health outcome.
Table 2: Summary of the study characteristics and key findings of the final sample of economic evaluations
(Uploaded as separate file due to size)
Of the 39 studies, 35 (90%) were full economic evaluations with 22 cost-utility analysis (CUA), 4 cost-minimisation analysis (CMA), 3 cost-effectiveness analysis (CEA), 4 combined CUA and CEA, 1 combined CUA and budget impact analysis, and 1 cost-consequence (CC) study. There were 4 partial evaluations that only considered costs.
3.2 Perspective and costs
Regarding the perspective on costs, 22 studies (56%) adopted a healthcare payer perspective, 12 (31%) a societal perspective, which considers additional patient-related costs, and 5 (13%) a healthcare sector perspective.
All studies considered the AC drugs and administration costs, 29 (74%) considered costs from adverse events (AEs) that did not result in hospitalisation, 33 (85%) hospitalisations from AEs, 24 (62%) cancer surveillance, 22 (56%) treatment of recurrence, 12 (31%) patient travel costs, and 13 (33%) costs due to loss of productivity.
Of the studies that costed adverse events (n = 33), 21 (64%) specifically costed the management of treatment-related febrile neutropenia, 21 (64%) diarrhoea, and 19 (58%) nausea and vomiting. Twelve studies (36%) considered the cost of additional AEs with the most common being oxaliplatin-related neurotoxicity (8 of 24 studies that included oxaliplatin), stomatitis/mucositis (n = 8) and palmar-plantar erythrodysesthesia (PPE; n = 6).
3.3 Health utility values
The most common measure of health outcomes were quality-adjusted life years (QALYs), reported by 27 economic evaluations. In measuring QALYs, 21 (78%) of these studies utilised health utility values (HUVs) from literature with the remaining measuring HUVs directly from recruited patients. Nineteen of the evaluations relying on published HUV utilised values measured in the 1990s.12, 13 Notably, all studies comparing AC duration adopted utilities derived from patient surveys collected alongside the SCOT study, a phase III clinical trial randomising patients to 3 or 6 months AC.14
3.4 Quality of reporting
On average, the evaluations reported 89% of applicable items on the CHEERS checklist (range: 74–100%). The mostly poorly reported CHEERS items were the abstract (60%) due to incomplete reporting of uncertainty analyses, model parameters (66%), and conflict of interest (66%). The detailed scoring is available in the Supplemental Material.
3.5 AC vs. No AC
All studies reported that AC was cost-effective compared to no AC in stage II (n = 3) and stage III (n = 5). 15–20All studies only considered single agent AC aside from one study that concluded doublet AC was cost-effective in stage III patients.18
3.6 Oral vs. intravenous AC
Of the 9 full economic evaluations comparing capecitabine to 5FU in stage III, 6 (67%) concluded capecitabine dominates 5-FU (being less costly and more effective) and 1 (11%) reported cost-effectiveness (more costly but more effective).21–38 Of the two remaining studies, Soni et al. utilised data from a retrospective cohort study, noting patients receiving capecitabine were older (mean age: 73 vs. 67 years) and less fit (ECOG 2–4: 14.6% vs. 6.3%).30 Accordingly, these patients were less likely to receive full intensity of treatment with the authors concluding that capecitabine would be cost-effective if treatment intensity approached 100%. In the remaining study, the cost of capecitabine acquisition was reported as almost 10 times the cost of 5-FU, which is substantially higher than reported in other studies.32 Notably, there was no full evaluation comparing capecitabine to 5FU in stage II CRC.
Further analyses demonstrated that CAPOX reduced costs compared to FOLFOX with one CUA reported cost-effectiveness in a combined cohort of high-risk stage II and stage III patients.23, 31, 36, 37
3.7 Oxaliplatin-based AC
There was only one evaluation of oxaliplatin-based therapy in stage II patients, concluding that FOLFOX was not cost-effective compared to 5-FU.15 Amongst stage III studies, 7 of 8 (88%) full economic evaluations determined that FOLFOX was cost-effective compared to 5-FU alone.22, 26, 30, 32, 34, 39–43 The remaining study modelled strategies that included different treatments for metastatic recurrence, limiting the assessment of AC alone.32
Additionally, Pandor et al. concluded that FOLFOX dominates capecitabine in stage III.39 Conversely, Soni et al. concluded that 5-FU dominates CAPOX but as previously noted, capecitabine-treated patients in this study were less likely to receive the full intensity of treatment, limiting efficacy.30
3.8 Three vs. six month duration
Three studies were modelled on data from the SCOT trial, a randomised controlled trial of 3 versus 6 months of oxaliplatin-based doublet AC in a cohort of high-risk stage II and stage III patients.44–47 Two of these studies concluded that 3 months of AC dominates 6 months. The remaining study assumed partial prescription of shortened AC duration based on a survey of physicians (stage II: 18%; stage III: 50%) but despite this limited uptake, a 3-month treatment duration was still cost-effective.47
Jongeneel et al. analysed AC in high-risk stage II patients by specific regimen, concluding that 3 months of CAPOX dominates 6 months but that 3 months of FOLFOX was not cost-effective.44 Importantly, they considered T4 staging and microsatellite stability (MSS) as high-risk histological features compared to the more expansive definition of high risk disease utilised in the SCOT trial.14
3.9 Biomarker vs. SOC
Two studies evaluated the use of OncotypeDx, a clinically validated and commercially available tumour-based genomic assay, in stage II patients with T3 and pMMR tumours. Compared to SOC patient selection, both studies reported an absolute decrease in AC prescription based on assay use (17 to 22%), concluding that Oncotype Dx reduces cost whilst improving health outcomes.48, 49
To et al. modelled the use of post-operative circulating tumour DNA (ctDNA) in unselected stage II CRC patients. Assigning AC to patients with detectable ctDNA alone resulted in a 13% absolute reduction in AC prescription compared to SOC.50 Furthermore, they considered a scenario in which some ctDNA negative patients would also receive AC. Both complete and incomplete adherence to ctDNA testing resulted in ctDNA dominating SOC.50
Jongeneel et al. compared several AC selection strategies in stage II cancers that were T4, and MSS tumours utilising a biomarker approach based on the presence of BRAF and KRAS mutations.51 The study concluded that AC prescription based on molecular biomarkers (4.8%) dominates no patients receiving AC. Patients in this model could have received either 3-months of CAPOX or 6-months of 5FU or FOLFOX, with the biomarker strategy retaining cost-effectiveness in scenarios in which only capecitabine-based AC was prescribed.
Alarid-Escudero et al. modelled a biomarker approach in stage II patients with T3 tumours, assigning FOLFOX to CDX2 negative patients only (7.2% of tested patients).52 Compared to no patients receiving AC, this biomarker approach was cost-effective in the base-case scenario and in > 88% of scenarios in which the effectiveness of AC was varied.