Presentation (CTI)

OBJECTIVES: The UK diagnostic pathway for clinically significant prostate cancer (csPCa) begins with a prostate-specific antigen (PSA) test followed by multi-parametric magnetic resonance imaging scanning (mpMRI). Men who score between 2-10 ng/mL are said to be in the PSA ‘grey zone’ with uncertainty around csPCa diagnosis. A mpMRI of >3 on the Likert scale results in referral for a biopsy, with negative biopsies associated with unnecessary costs and health-related quality of life (HRQoL) impacts. The Prostate Health Index (phi) test estimates the probability of csPCa by combining three tests, the PSA, free-PSA and p2PSA, into a single score. It has better specificity than the PSA test alone, which could decrease the number of mpMRI and biopsies.
METHODS: A 30-day decision tree model was constructed to compare a pathway of ‘phi>mpMRI’ with ‘mpMRI alone’ in a population of men in the PSA ‘grey zone’. The model focussed on csPCa and took an NHS perspective. All clinical input data (prevalence of csPCa, sensitivity/specificity of phi/mpMRI) were sourced from UK-specific studies. Resource use and HRQoL data were sourced from NICE NG131, while costs were from the National Cost Collection.
RESULTS: Both the deterministic and probabilistic per-person results showed that, at phi threshold 25 (sensitivity=96%, specificity=25%), phi>mpMRI led to a cost saving of £92 and a minor increase in QALYs. This was due to fewer mpMRI and biopsies being conducted in the phi>mpMRI arm.
CONCLUSIONS: The use of phi before an mpMRI for men in the PSA ‘grey zone’ could result in fewer mpMRI and biopsies being conducted. This reduces NHS resource use and prevents unnecessary risky and invasive procedures. This is offset by the increase in csPCa cases missed, however if PSA/phi tests are conducted regularly, it is unlikely that a man is not correctly diagnosed within 6 months of the original test.