Robust Optimization for Spot Scanning Proton Therapy based on Dose-Linear Energy Transfer (LET) Volume Constraints
arxiv(2024)
摘要
Purpose: Historically, spot scanning proton therapy (SSPT) treatment planning
utilizes dose volume constraints and linear-energy-transfer (LET) volume
constraints separately to balance tumor control and organs-at-risk (OARs)
protection. We propose a novel dose-LET volume constraint (DLVC)-based robust
optimization (DLVCRO) method for SSPT in treating prostate cancer to obtain a
desirable joint dose and LET distribution to minimize adverse events (AEs).
Methods: DLVCRO treats DLVC as soft constraints controlling the joint
distribution of dose and LET. Ten prostate cancer patients were included with
rectum and bladder as OARs. DLVCRO was compared with the conventional robust
optimization (RO) method using the worst-case analysis method. Besides the
dose-volume histogram (DVH) indices, the analogous LETVH and
extra-biological-dose (xBD)-volume histogram indices were also used. The
Wilcoxon signed rank test was used to measure statistical significance.
Results: In nominal scenario, DLVCRO significantly improved dose, LET and xBD
distributions to protect OARs (rectum: V70Gy: 3.07% vs. 2.90%, p = .0063, RO
vs. DLVCRO; LET_max (keV/um): 11.53 vs. 9.44, p = .0101;
xBD_max (Gy·keV/um): 420.55 vs. 398.79, p = .0086; bladder:
V65Gy: 4.82% vs. 4.61%, p = .0032; LET_max 8.97 vs. 7.51, p =
.0047; xBD_max 490.11 vs. 476.71, p = .0641). The physical dose
distributions in targets are comparable (D2
CTV D2
DLVCRO robustly enhanced OAR while maintaining the similar plan robustness in
target dose coverage and homogeneity.
Conclusion: DLVCRO upgrades 2D DVH-based to 3D DLVH-based treatment planning
to adjust dose/LET distributions simultaneously and robustly. DLVCRO is
potentially a powerful tool to improve patient outcomes in SSPT.
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