Irradiation of the prostate and pelvic lymph nodes with an adaptive algorithm

Abstract

Adaptive morphing with and without segment weight optimization can be used to compensate for the independent motion of the prostate and lymph nodes when combined with daily imaging or other methods to track the prostate motion. This method allows the delivery of the correct dose to both the prostate and lymph nodes with only small changes to the dose delivered to the target volumes.

Adaptive radiotherapy strategies for pelvic tumors – a systematic review of clinical implementations

“…Deformable image registration was more frequently applied in the in silico studies, mostly for online re-planning/re-optimization [59,61,67,71,86,87,94] and offline re-planning/re-optimization strategies [60,63,66,69,75,107] but also applied for online MLC/field adjustments [77,89]. To facilitate adaptations, especially for online execution, modifications of the planning system or automatic activation/selection of plans was applied in 50% of the in silico studies [58][59][60][61][67][68][69]71,72,[74][75][76][77][78][79][80][82][83][84][85][86][87][88][92][93][94]. In view of the increasing speed of optimization algorithms, limited in-room imaging quality together with manual (re-)contouring remains the biggest bottlenecks for clinical implementation of many of the ART strategies and certainly limiting online applications.…”

‘Compromise position’ image alignment to accommodate independent motion of multiple clinical target volumes during radiotherapy: A high risk prostate cancer example

“…To date, two image alignment approaches for this common clinical scenario have been evaluated in the literature. Firstly, image alignment to the position of the prostate (or radio‐opaque surrogate) was found to deliver acceptable doses to the PLN using simulated prostate motion, but not when evaluated using actual patient data . Conversely, image alignment to the position of the pelvic bones (as a surrogate for PLN), has been shown to result in significant reduction to the dose received by the prostate …”

“…Whereas increasing the lymph node PTV would increase the volume of small bowel irradiated, increasing the risk of toxicity with either approach. Some authors suggest that the only effective method to concurrently incorporate two independent CTVs, is to use sophisticated adaptive techniques to modify the distribution every day before treatment . Unfortunately, this approach is not currently practical for the vast majority of cancer clinics.…”

“…Firstly, image alignment to the position of the prostate (or radio-opaque surrogate) was found to deliver acceptable doses to the PLN using simulated prostate motion, 8 but not when evaluated using actual patient data. [9][10][11][12][13][14] Conversely, image alignment to the position of the pelvic bones (as a surrogate for PLN), has been shown to result in significant reduction to the dose received by the prostate. 10,13,[15][16][17][18] All of these authors identified the challenges of correcting for motion of multiple CTVs, but few suggested a clinically achievable solution.…”

“…[9][10][11][12][13][14] Conversely, image alignment to the position of the pelvic bones (as a surrogate for PLN), has been shown to result in significant reduction to the dose received by the prostate. 10,13,[15][16][17][18] All of these authors identified the challenges of correcting for motion of multiple CTVs, but few suggested a clinically achievable solution. Although the size of the planning target volume (PTV) margins could be increased to accommodate the geometric mismatch caused by aligning to a different structure, increasing the prostate PTV would increase the volume of bladder and rectum irradiated.…”