Yuko Iraha, Presenter: Nothing to Disclose

Masahiro Okada MD, Abstract Co-Author: Nothing to Disclose

Maho Tsubakimoto MD, Abstract Co-Author: Nothing to Disclose

Nanae Tsuchiya, Abstract Co-Author: Nothing to Disclose

Sadayuki Murayama MD, PhD, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to evaluate the volumetric changes in prostate gland before and after intensity-modulated radiotherapy (IMRT) and to assess the signal intensity changes of the peripheral zone (PZ) using MRI.

Fifty-two patients with localized prostate cancer were enrolled in this retrospective study, which was approved by our Institutional Review Board. All patients underwent IMRT, and all patients underwent MRI examination before and after IMRT. Forty-nine patients received androgen deprivation therapy (ADT) prior to IMRT. Median age of patients was 74 years (range 55-79). Mean prostate-specific antigen (PSA) level pre-IMRT was 2.3 ng/mL (range 0.01-70). Prostate volumes and signal intensity of the PZ on T2WI before and after IMRT, with 2 years of follow-up, were determined. Change in volume over time were calculated and compared with regard to age, pre-IMRT PSA level, ADT completion time, and initial prostate volume.

There were significant decreases in mean prostate volume after the completion of IMRT: a 14% decrease at 1 month and a 5% decrease at 4 to 5 months. There were significant increases in mean prostate volume after IMRT: a 3% increase at 1 year and a 9% increase at 2 years. The shrinking effect was significantly higher when the prostate volumes were initially larger and when pre-IMRT PSA levels were higher. The volume enlargement after 2 years of IMRT was significantly noticed when the prostate volumes were initially smaller, when pre-IMRT PSA levels were lower, when the patients completed ADT before the start of IMRT, and in patients under 70 years old. T2 signal intensity of the PZ decreased or stayed low 1 month after IMRT in most patients (49/52: 94%). T2 Signal intensity of the PZ increased gradually during 4th to 24th month after IMRT in most patients (47/54: 87%).

Patients undergoing IMRT show definite prostate shrinkage for the first 5 months, followed by a volume increase 2 years after the therapy. T2 signal intensity of the PZ decreased 1 month after IMRT, but increased gradually during 4th to 24th month after the therapy.

To understand the volumetric change and T2 signal intensity change of the prostate with long-term follow up after radiation therapy may useful for the evaluation of therapeutic effect.

Iraha, Y, Okada, M, Tsubakimoto, M, Tsuchiya, N, Murayama, S, Change in Prostate Gland Volume after Intensity-modulated Radiotherapy: MRI Evaluation.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14005392.html