Quantifying the change in endorectal magnetic resonance imaging-defined tumor volume during neoadjuvant androgen suppression therapy in patients with prostate cancer.

OBJECTIVES To quantify the changes seen in the endorectal magnetic resonance imaging (erMRI)-defined prostate volume, predominant tumor volume, and secondary tumor volume during neoadjuvant total androgen suppression (TAS). METHODS Between July 1997 and April 2001, 152 consecutive patients with clinical Stage T1b-T3cNXM0 prostate cancer were treated with 6 months of TAS and external beam radiotherapy. erMRI was conducted before and after 2 months of neoadjuvant TAS. The median values and percentage of changes in the erMRI-measured prostate volume and primary and secondary tumor volumes during neoadjuvant TAS were calculated and compared, using the Wilcoxon matched-pairs signed-rank method, for the patients overall and stratified by pretreatment risk group. RESULTS All patients had a significant decline in their erMRI-defined median prostate volume (36.6 versus 25.7 cm(3), P <0.0001) during 2 months of neoadjuvant TAS. The median primary tumor volume decreased significantly in the intermediate-risk (0.77 versus 0.52 cm(3), P <0.0001) and high-risk (2.48 versus 0.83 cm(3), P <0.0001) patients. The median secondary tumor volume approached a significant decline in only the high-risk patients (0.45 versus 0.31 cm(3), P = 0.15). Fourteen percent of patients had an increase in their primary tumor volume during neoadjuvant TAS. CONCLUSIONS The erMRI-defined primary and secondary tumor volumes generally decreased in the study population during neoadjuvant TAS. However, 14% of patients had an increase in their primary tumor volume during androgen suppression therapy. The clinical significance of this awaits further study.