Can We Advance Proton Therapy for Prostate? Considering Alternative Beam Angles and Relative Biological Effectiveness Variations When Comparing Against Intensity Modulated Radiation Therapy

Underwood, Tracy; Giantsoudi, D.; Moteabbed, M.; Zietman, Anthony L.; Efstathiou, Jason A.; Paganetti, Harald; Lu, Hsiao‐Ming

doi:10.1016/j.ijrobp.2016.01.018

Cited by 40 publications

(42 citation statements)

References 40 publications

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“…We demonstrated previously that, for a cohort without rectal spacers, AO proton beams were not robust to modeled elevations in proton RBE: use of such beams could result in unacceptably high rectal doses [8]. Here we show that for cases with rectal spacers, it is typically (9 times of 10) possible to generate AO proton plans with a uniform 5 mm CTV to PTV margin expansion that are robust to variable RBE modeling.…”

Section: Discussionmentioning

confidence: 61%

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Hydrogel rectum-prostate spacers mitigate the uncertainties in proton relative biological effectiveness associated with anterior-oblique beams

et al. 2017

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Section: Discussionmentioning

confidence: 61%

“…For a cohort of patients without rectal spacers, we recently demonstrated that AO proton beam plans that appeared dosimetrically suitable assuming a fixed RBE of 1.1 no longer fulfilled rectal dose constraints when variable RBE weighted (vRBEw) dose models were applied [8]. In this work we studied the impact of rectal spacers upon AO proton beam plans.…”

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confidence: 99%

Hydrogel rectum-prostate spacers mitigate the uncertainties in proton relative biological effectiveness associated with anterior-oblique beams

et al. 2017

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“…These endpoints were selected because both tumor control and necrosis can be considered related to RBE values obtained from in vitro cell survival data. In addition, it has been suspected that elevated RBE values for low a/b tumors, such as prostate, could impact the interpretation of ongoing clinical trials comparing proton and photon treatments [18]. As far as toxicities are concerned, concerns have been raised that the elevated LET at the end of range of protons beams leads to incidents of necrosis in ependymoma patients where beams typically range out in the brainstem [13,19,20].…”

Section: Introductionmentioning

confidence: 99%

Relating the proton relative biological effectiveness to tumor control and normal tissue complication probabilities assuming interpatient variability in α/β

Paganetti

2017

Acta Oncologica

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Background: Proton therapy uses a constant relative biological effectiveness (RBE) of 1.1. The use of variable RBE values has been suggested but is currently not feasible due to uncertainties. The impact of variable RBE has solely been studied using dosimetric indices. This work elucidates the impact of RBE variations on tumor control and normal tissue complication probabilities (TCP/NTCP). Methods: Models to estimate TCP and NTCP were used in combination with an empirical proton RBE model. Variations in outcome as a function of linear-quadratic model parameters for cellular radiosensitivity were determined for TCP in prostate and ependymoma. In addition, NTCP analysis was done for brainstem necrosis. Results: Considering a variable proton RBE as a dose-modifying factor for prescription doses and dose constraints is misleading, as TCP/NTCP do not simply scale with RBE. The dependency of RBE on a/b cannot be interpreted independent of TCP/NTCP because variations in radiosensitivity affect both photon and proton treatments. Assuming interpatient variability in radiosensitivity results in lower TCP for patients with low a/b. In proton therapy, the magnitude of TCP variations is reduced due to an RBE increase as a/b decreases. The TCP in proton therapy is less affected by interpatient variability in a/b. On the other hand, patients with a lower a/b would have a lower complication probability, which is counteracted by an increase in RBE as a/b decreases. Toxicities in proton therapy would be more affected by a/b variations compared to photon therapy. Conclusions: Assessment of variable RBE in proton therapy should be based on TCP and NTCP. Potential interpatient variability in radiosensitivity causes a smaller variance in TCP but a larger variance in NTCP for proton patients. The relative TCP as a function of a/b was found to be higher than the RBE, whereas the relative NTCP was lower than a calculated RBE.

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“…Typically, the variations are largest at the distal end of the beams, where little averaging of the LET d over multiple spots and beam directions occurs. This may have implications for the choice of beam angles . RBE variations can also perturb the dose inside the target volume if the treatment is delivered in the presence of intrafractional motion .…”

Section: Biological‐based Planningmentioning

confidence: 99%

Advanced Treatment Planning

et al. 2018

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Treatment planning for protons and heavier ions is adapting technologies originally developed for photon dose optimization, but also has to meet its particular challenges. Since the quality of the applied dose is more sensitive to geometric uncertainties, treatment plan robust optimization has a much more prominent role in particle therapy. This has led to specific planning tools, approaches, and research into new formulations of the robust optimization problems. Tools for solution space navigation and automatic planning are also being adapted to particle therapy. These challenges become even greater when detailed models of relative biological effectiveness (RBE) are included into dose optimization, as is required for heavier ions.

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Can We Advance Proton Therapy for Prostate? Considering Alternative Beam Angles and Relative Biological Effectiveness Variations When Comparing Against Intensity Modulated Radiation Therapy

Cited by 40 publications

References 40 publications

Hydrogel rectum-prostate spacers mitigate the uncertainties in proton relative biological effectiveness associated with anterior-oblique beams

Hydrogel rectum-prostate spacers mitigate the uncertainties in proton relative biological effectiveness associated with anterior-oblique beams

Relating the proton relative biological effectiveness to tumor control and normal tissue complication probabilities assuming interpatient variability in α/β

Advanced Treatment Planning

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