472: The Value of Repeat Serum PSA Measurements in the Detection of Prostate Cancer - Experience from the Feasibility Phase of the UK Protect Study

[Prognostic significance of "sawtooth" PSA and "stepwise" PSA]

OBJECTIVE

To evaluate the risk of diagnosing prostate cancer on repeated biopsies in patients with fluctuating PSA values compared to patients with stable or regularly increasing PSA values.

MATERIAL

Retrospective study conducted on the 2000-2003 databases of 2 French teaching hospitals. Selected patients had a first negative prostatic biopsy, then at least one other series of prostatic biopsies. "Sawtooth" PSA was defined by a PSA value less than that of the previous assay. Other cases were described as "stepwise" PSA.

RESULTS

191 patients were included: 79 in the "sawtooth" group and 112 in the "stepwise" group. Prostate cancer was diagnosed in 53 patients (27.7%), on the second prostatic biopsy 39 cases. Prostate cancer was detected in 17 (21.5%) of the 79 patients of the "sawtooth" group. This proportion was not significantly different (p = 0.14) from that observed in patients of the "stepwise" group: 36/112 (32.1%). No significant difference in terms of age, stage, Gleason score and initial PSA was observed between patients with a diagnosis of prostate cancer in the "sawtooth" and "stepwise" groups.

CONCLUSION

In our study, the risk of diagnosing prostate cancer on repeated prostatic biopsies was not greater in patients with "stepwise" PSA compared to patients with "sawtooth" PSA.

The impact of reducing the prostate-specific antigen threshold and including isoform reflex tests on the performance characteristics of a prostate-cancer detection programme

OBJECTIVE

To assess the effects on the performance characteristics, in a prostate-cancer detection programme using prostate-specific antigen (PSA) levels, of a lower PSA threshold and the incorporation of reflex (free or complexed PSA) tests.

METHODS

We reviewed publications and extracted data on PSA distributions and performance characteristics of the PSA test and isoform tests from population-based surveys. We estimated the rate of biopsy, cancers detected, and cancers missed that would result from lowering PSA thresholds and including reflex testing.

RESULTS

Lowering the PSA threshold for biopsy referral to 2 ng/mL would increase the number of referrals from 110 to 230 per 1000 men tested, with most of the extra biopsies being among men with no cancer, i.e. an increase from 74 to 172 per 1000 men tested. However, this increased testing would result in an increase in the cancer-detection rate from 3.6% to 5.8%. Including a reflex test for men with moderately elevated PSA levels has little effect on programme performance, with only a modest (10-15%) reduction in unnecessary biopsies and a small increase in the numbers of missed cancers.

CONCLUSIONS

Lowering PSA thresholds, with or without the concurrent introduction of reflex tests, would increase both the numbers of cancers detected and the number of patients referred for biopsy procedures, of which most would be unnecessary. As the extra cancers detected are likely to be clinically localized, and with no evidence that their treatment improves the outcome of the disease, such changes place a possibly unjustified additional burden on the healthcare provider.