Two systematic reviews and an individual patient data meta-analysis reported clinically significant increases in risk of severe (grade ≥3) fluoropyrimidine (FP)-related toxicity in patients with DPYD gene variants c.1905+1G>A, c.2846A>T, c.1679T>G, or c.1236G>A/Hap B3. No clinically significant increase in risk of severe toxicity was found in patients with DPYD variant c.1601G>A.
Four cohort studies – two prospective and two retrospective – explored the feasibility and effects of DPYD genetic testing in routine clinical practice.
- All four studies reported successful implementation of DPYD genetic testing, with subsequent individualisation of FP dose for patients with clinically relevant DPYD variants.
- The two comparative prospective studies demonstrated a significant reduction in risk of severe (grade ≥3) treatment-related toxicity in patients with DPYD variants treated with reduced doses of FP compared with historical cohorts receiving a full dose.
- In one of the prospective studies the frequency of treatment-related severe (grade ≥3) toxicity in patients with DPYD variant c.1905+1G>A, receiving reduced doses of FP, was similar to that of wild-type variant patients receiving a full FP dose. In the second prospective study, despite FP dose reduction, the risk of severe toxicity remained elevated in patients with DPYD variants c.1236G>A or c.2846A>T compared with wild-type variant patients
Four published costing studies found that a pre-treatment testing strategy for DPYD gene variants is likely to be cost saving compared to reactive testing.
SHTG conducted an economic analysis using Scottish incidence and cost data. The model compared the costs and adverse events associated with a strategy of prospective DPYD genetic testing for patients eligible for FP based chemotherapy versus a strategy of no testing.
- Prospective testing was the dominant strategy. This meant it was less costly and led to fewer adverse events and associated hospital admissions compared to a no-testing strategy.
- The model predicted that up to 24 serious adverse events could be averted for every 1,000 patients tested.
- The incremental costs of DPYD testing are expected to be offset by lower expenditure on acute and in-patient care for patients experiencing adverse events.
What were we asked to look at?
We were asked to determine the economic case for routine pretreatment DPYD genetic testing for patients who are prescribed fluoropyrimidine-based chemotherapy.
Why is this important?
Fluoropyrimidines are chemotherapy drugs frequently used in the treatment of several types of cancer. Approximately 10% to 30% of patients treated with fluoropyrimidines experience severe (grade≥3) treatment-related toxicities. Changes to the DPYD gene can lead to dihydropyrimidine dehydrogenase (DPD) enzyme deficiency, which can lead to the accumulation of cytotoxic chemotherapy compounds in the body and cause severe side effects. Pre-treatment genetic testing could facilitate the delivery of tailored chemotherapy dosing schedules and reduce severe fluoropyrimidine-related toxicity in patients.
NHS National Services Scotland