The potential of MRI-guided online adaptive re-optimisation in radiotherapy of urinary bladder cancer

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• 作者：Anne Vestergaard^a ; ^b ; ¹ ; ^{annveste@rm.dk" class="auth_mail" title="E-mail the corresponding author} ; Shaista Hafeez^c ; Ludvig P. Muren^a ; Simeon Nill^b ; Morten Hø ; yer^d ; Vibeke N. Hansen^b ; Caroline Grø ; nborg^a ; Erik M. Pedersen^e ; Jø ; rgen B. Petersen^a ; Robert Huddart^c ; Uwe Oelfke^b
• 关键词：Adaptive radiotherapy ; Bladder cancer ; Re-optimisation ; Dose accumulation ; MRI guided
• 刊名：Radiotherapy and Oncology
• 出版年：2016
• 出版时间：January 2016
• 年：2016
• 卷：118
• 期：1
• 页码：154-159
• 全文大小：845 K

文摘

Adaptive radiotherapy (ART) using plan selection is being introduced clinically for bladder cancer, but the challenge of how to compensate for intra-fractional motion remains. The purpose of this study was to assess target coverage with respect to intra-fractional motion and the potential for normal tissue sparing in MRI-guided ART (MRIGART) using isotropic (MRIGARTiso), an-isotropic (MRIGARTanIso) and population-based margins (MRIGARTpop).

Materials and methods

Nine bladder cancer patients treated in a phase II trial of plan selection underwent 6–7 weekly repeat MRI series, each with volumetric scans acquired over a 10 min period. Adaptive re-planning on the 0 min MRI scans was performed using density override, simulating a hypo-fractionated schedule. Target coverage was evaluated on the 10 min scan to quantify the impact of intra-fractional motion.

Results

MRIGARTanIso reduced the course-averaged PTV by median 304 cc compared to plan selection. Bladder shifts affected target coverage in individual fractions for all strategies. Two patients had a v95% of the bladder below 98% for MRIGARTiso. MRIGARTiso decreased the bowel V25 with 15–46 cc compared to MRIGARTpop.

Conclusion

Online re-optimised ART has a considerable normal tissue sparing potential. MRIGART with online corrections for target shift during a treatment fraction should be considered in ART for bladder cancer.