Comparison of weekly and daily online adaptation for head and neck intensity-modulated proton therapy

Abstract

The high conformality of intensity-modulated proton therapy (IMPT) dose distributions causes treatment plans to be sensitive to geometrical changes during the course of a fractionated treatment. This can be addressed using adaptive proton therapy (APT). One important question in APT is the frequency of adaptations performed during a fractionated treatment, which is related to the question whether plan adaptation has to be done online or offline. The purpose of this work is to investigate the impact of weekly and daily online IMPT plan adaptation on the treatment quality for head and neck patients. A cohort of ten head and neck patients with daily acquired cone-beam CT (CBCT) images was evaluated retrospectively. Dose tracking of the IMPT treatment was performed for three scenarios: base plan with no adaptation (BP), weekly online adaptation (OAW), and daily online adaptation (OAD). Both adaptation schemes used an in-house developed online APT workflow, performing Monte Carlo dose calculations on scatter-corrected CBCTs. IMPT plan adaptation was achieved by only tuning the weights of a subset of beamlets, based on deformable image registration from the planning CT to each CBCT. Although OAD mitigated random delivery errors more effectively than OAW on a fraction per fraction basis, both OAW and OAD achieved the clinical goals for all ten patients, while BP failed for six cases. In the high-risk CTV, accumulated values of D 98% ranged between 97.15% and 99.73% of the prescription dose for OAD, with a median of 98.07%. For OAW, values between 95.02% and 99.26% were obtained, with a median of 97.61% of the prescription dose. Otherwise, the dose to most organs at risk was similar for all three scenarios. Globally, our results suggest that OAW could be used as an alternative approach to OAD for most patients in order to reduce the clinical workload.

CT-on-Rails Versus In-Room CBCT for Online Daily Adaptive Proton Therapy of Head-and-Neck Cancers

“…For this retrospective study, we used the same patient cohort and treatment planning approach as for the work reported in [ 9 , 30 ]. The dataset included 10 H&N patients with tumors located in the oral cavity, oropharynx, and larynx.…”

“…We performed plan adaptation with an in-house developed online framework for adaptive proton therapy [ 9 ] based on fast GPU-accelerated Monte Carlo (gPMC) calculations [ 33 , 34 , 35 , 36 ]. For each daily vCT, contours were propagated by performing DIR from the planning CT to the vCT in Plastimatch using the same algorithm and metric as for vCT generation.…”

“…Two conceptually different daily adaptation approaches have been suggested. One adaptation workflow is based on fast GPU Monte Carlo dose calculation and Cone-Beam CT (CBCT) imaging [ 8 , 9 ]. Alternatively, an approach based on in-room CT imaging and analytical dose recalculation has been proposed [ 10 , 11 , 12 , 13 ].…”

Evaluation of alternative parameter settings for dose restoration and full plan adaptation in IMPT for prostate cancer

“…For such approaches the simplified optimization technique should be thoroughly compared to the original optimizer, as was done in our study by comparing RPM to 2p∊c. Another technique, described in [28,29], uses deformable image registration to obtain daily delineations. The method first calculates the dose for each pencil-beam on the new anatomy, and then performs a restoration by re-optimizing the intensity of a subset of spots using the planning objectives of the intended plan.…”

Magnetic resonance linear accelerator technology and adaptive radiation therapy: An overview for clinicians

“…This is primarily because the effort associated with the process is exceedingly time‐consuming with the current technology. Before sufficient support of that time and effort can be provided or more robust technologies become available, there should be commensurate compensation for the considerable additional time and effort associated with this work 42‐51 . Table 1 summarizes select prospective trials that have recently examined different adaptive strategies 35,37,38,41 …”