Positive post-treatment biopsy after radiotherapy tied to higher risk of distant metastasis, death
Patients with a positive post-treatment biopsy after external beam radiotherapy are at higher risk of distant metastasis and prostate cancer-related death, suggests a recent study. Positive post-treatment biopsies are more frequent in the setting of external beam radiotherapy alone without androgen deprivation therapy or in the presence of high-risk disease.
“Patients with severe treatment effect classified biopsies have biological characteristics more like patients with a negative biopsy than a positive biopsy,” the investigators said.
Positive biopsy had a 30-percent prevalence, while treatment effect and negative biopsy had a rate of 22 percent and 48 percent, respectively. Androgen deprivation therapy omission and high-risk disease correlated with a 2.6- and 1.8-fold increase in the odds of positive post-treatment biopsy.
For prostate-specific antigen (PSA), the 15-year relapse rate associated with negative, severe treatment effect and positive post-treatment biopsies were 34 percent, 36 percent and 79 percent, respectively (p<0.001).
Distant metastasis was 2.6 times more likely to occur and cause-specific mortality was twice as high in patients with a positive biopsy (p<0.001) compared to those with negative and severe treatment effect biopsy outcomes (hazard ratio, 2.00; p=0.022) after controlling for known predictors.
This study included 382 patients who underwent a post-treatment biopsy after external beam radiotherapy for clinically localized prostate cancer. Post-treatment biopsies were categorized as positive (prostatic adenocarcinoma without typical radiation induced changes), negative (no evidence of carcinoma) or adenocarcinoma with a severe treatment effect. Median follow-up was 9 years.
The investigators examined associations between prognostic predictors and cause-specific mortality, distant metastasis and PSA failure using competing risks regression.