Mid-treatment PSA measurement indicates posttreatment outcome
MedWire News: Mid-treatment prostate-specific antigen (midPSA) measurements can indicate the likely outcome of combined-modality prostate cancer treatment, show US study results.
Men whose midPSA is less than their pretreatment PSA survive longer than those whose midPSA is the same or higher than before treatment, with the longest survival observed among men whose midPSA decreased by 25% or more, say the researchers.
"Pretreatment PSA has been associated with posttreatment outcome," comment Sam Brown (The Radiation Medicine Center, Totowa, New Jersey) and colleagues in the International Journal of Radiation Oncology Biology Physics.
However, "Less information is available regarding PSA during therapy," they add.
To address this, the team investigated survival outcomes in a cohort of 717 prostate cancer patients treated with external beam radiotherapy (EBRT) followed by transperineal low-dose-rate brachytherapy (LDR).
The median age of the cohort was 71 years, and 512 patients received androgen therapy in addition to radiotherapy.
In all, 91% of patients experienced a decrease in PSA level when baseline (pretreatment) measurements were compared with those taken after EBRT (midPSA). The median decrease was 6.1 ng/ml, and 84% of the entire cohort had a midPSA decrease of 25% or more.
The median overall survival for patients who experienced a midPSA decrease was 9.8 years, compared with 7.4 years among patients whose PSA remained constant or increased mid-treatment.
Furthermore, overall survival was longer among patients whose midPSA decreased by 25% or more from baseline than those whose decreased by less than 25%, at 10.0 versus 7.4 years. The same trend was noted for disease-free survival and midPSA, at 9.8 versus 7.4 years for a decrease of at least 25% versus less than 25%.
After stratifying results according to androgen therapy status, Brown and team observed no difference in the direction or strength of these associations.
They suggest that the decrease in midPSA could represent a response to treatment, and/or that a stable PSA could indicate a patient harboring metastatic disease.
"We have shown that midPSA is predictive for outcome and remains significant even when accounting for use of androgen blockade," writes the team.
"The value of this is that, because therapy is not yet completed, it may be possible to adjust the remainder of therapy based on midPSA risk stratification," they conclude.
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By Sarah Guy