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Published on: March 6, 2018
The importance of an exponential prostate-specific antigen decline after external beam radiotherapy for intermediate
Guila Delouya1, Gabriel Kaufman, Marie-Pierre Sylvestre
1Department of Radiation Oncology, Centre hospitalier de l'Université de Montréal, Québec, Canada.
Background:
To study the influence of an exponential prostate-specific antigen (PSA) decline on biochemical failure after external-beam radiotherapy (EBRT).
Methods:
We analyzed 114 patients with intermediate risk prostate cancer (Gleason≤6 and PSA 10-20 or Gleason 7 and PSA <10). Patients were randomized between EBRT doses of either 70.2 Gy or 79.2 Gy (1.8 Gy per day). All patients had a follow up of at least six PSA measurements post-EBRT. Exponential decline and PSA half life were included in a Cox regression analysis for factors associated with biochemical failure.
Results:
A total of 80/114 (70.2%) patterns were classified as having an exponential PSA decline. Both exponential decline (HR 0.115, 95%CI 0.03-0.44, p=0.0016) and PSA half life ratio were statistically significant predictors (HR 1.03 (95% CI 1.01-1.06)) of biochemical failure. In the model predicting for exponential decline, none of the factors were significant.
Conclusion:
Patients with an exponential PSA decline show a better biochemical outcome in the long term.
