IGRT 2016 Madrid

Post operative margins

S. Gill et al. / Radiotherapy and Oncology 107 (2013) 1

• 547 daily CBCT from 15 pts

that not all cli bed deformatio and largest ad week of radiot the prostate be RTTs and ROs possible, the Pl These data sup statectomy sett There are s localization var was taken as a seen on the sa touring guideli 5 mm below t the CTV from t instructed to e the penile bulb same distance suggests that t touring guideli be taken as re where vesico-u usually the cas mend that if s should be used the vesico-uret the penile bulb get, we recom penile bulb ide This study also credentialing f tocols are empl able cutoff ma >50% of the an has previously ingful action th tact prostate ra This study c comparison of answer. A dosi dose fall-off ou dependent and Our data do po

Fig. 4. Distance between RTT volume and reference answer volume (in mm) in the SI, AP and LR directions that would required to cover the entire reference answer selected adaptive CTV volume for all 165 test answers.

Discussion

Ghilezan et al. reviewed IGART techniques and clinical out- comes in prostate cancer recently and found that adaptive radio- therapy in prostate cancer enabled better target coverage and reduced rectal dose with clinical follow-up demonstrating encour- aging clinical outcomes [19] . In the intact prostate setting, Liu et al. compared a multiple replan rolling-average adaptive strategy to a single replan adaptive strategy and IGRT alone and found that mul- tiple replanning was superior but significantly more complex [20] . The framework and techniques used in on-line IGART in the intact prostate setting have been fairly broad and range from direct beam aperture modification [21] to online adaptive inverse re-planning [22] . The post-prostatectomy target however undergoes noticeably more deformation than the intact prostate and adaptive techniques in the post-prostatectomy setting are sparse in the literature. The results of this study confirm that a ‘‘plan of the day’’ online strategy for IGART is feasible in the post-prostatectomy setting, because the difference in isocentre location and volume selection was small, and can be accounted for in a clinically acceptable CTV to PTV mar- gin. At the moment, we have insufficient evidence to suggest that margins can yet be reduced with IGART with the current protocol. The conventional margin for post-prostatectomy radiotherapy rec-

Ost P, IJROBP 2011 Gill S, Radiother Oncol 2013

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