Original Research ARTICLE
Quantitative MRI changes during weekly ultra-hypofractionated prostate cancer radiotherapy with integrated boost
- 1The Netherlands Cancer Institute (NKI), Netherlands
- 2University Medical Center Utrecht, Netherlands
- 3Radboud University Nijmegen Medical Centre, Netherlands
Purpose: Quantitative MRI reflects tissue characteristics. As possible changes during radiotherapy may lead to treatment adaptation based on response, we here assessed if such changes during treatment can be detected.
Methods and Materials: In the hypoFLAME trial patients received ultra-hypofractionated prostate radiotherapy with an integrated boost to the tumor in 5 weekly fractions. We analyzed T2 and ADC maps of 47 patients that were acquired in MRI exams prior to and during radiotherapy, and performed rigid registrations based on the prostate contour on anatomical T2-weighted images. We analyzed median T2 and ADC values in 3 regions of interest (ROIs): the central gland (CG), peripheral zone (PZ) and tumor. We analyzed T2 and ADC changes during treatment and compared patients with and without hormonal therapy. We tested changes during treatment for statistical significance with Wilcoxon signed rank tests. Using confidence intervals as recommended from test-retest measurements, we identified persistent T2 and ADC changes during treatment.
Results: In the CG, median T2 and ADC values significantly decreased 12% and 8% respectively in patients that received hormonal therapy, while in the PZ these values decreased 17% and 18%. In the tumor no statistically significant change was observed. In patients that did not receive hormonal therapy, median ADC values in the tumor increased with 20%, while in the CG and PZ no changes were observed. Persistent T2 changes in the tumor were found in 2 out of 24 patients, while none of the 47 patients had persistent ADC changes.
Conclusions: Weekly quantitative MRI could identify statistically significant ADC changes in the tumor in patients without hormonal therapy. On a patient level few persistent T2 changes in the tumor were observed. Long-term follow-up is required to relate the persistentT2 and ADC changes to outcome and evaluate the applicability of quantitative MRI for response based treatment adaptation.
Keywords: quantitative MRI, Ultra-hypofractionated prostate radiotherapy, ADC mapping, MRI changes, Hormonal therapy (HT), T2 mapping
Received: 03 Jul 2019;
Accepted: 31 Oct 2019.
Copyright: © 2019 Schie, Houdt, Ghobadi, Pos, Walraven, Boer, Berg, Smeenk, Kerkmeijer and Heide. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Mr. Marcel v. Schie, The Netherlands Cancer Institute (NKI), Amsterdam, Netherlands, email@example.com