Proton Bragg Peak FLASH Enables Organ Sparing and Ultra-High Dose-Rate Delivery: Proof of Principle in Recurrent Head and Neck Cancer

Pennock, Michael; Wei, Shouyi; Cheng, Charles Ching-An; Lin, Haibo; Hasan, Shaakir; Chhabra, Arpit; Choi, J. Isabelle; Bakst, Richard L.; Kabarriti, Rafi; Simone, Charles B.; Lee, Nancy Y.; Kang, Minglei; Press, Robert H.

doi:10.3390/cancers15153828

Cited by 10 publications

(13 citation statements)

References 68 publications

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“…For high doses delivered to small CTVs, clinical PBS plans showed superior dose uniformity compared to FLASH plans, which is consistent with previous findings in lung [45], liver [47], head-neck [46], and breast [48] cancer cases. Conventional PBS treatment plans rely on multiple energy layers, small weighting spots, and a denser spot map to achieve planning goals.…”

Section: Discussionsupporting

confidence: 90%

“…Wei et al [44] developed an in-house treatment planning system that incorporated spot placement, weighting, and dose rate optimization through the inverse algorithm. This technique has been successfully applied to treatment planning studies on Bragg peak proton FLASH-RT for lung [44,45], head and neck [46], liver [47], and breast [48] cases.…”

Section: Optimization Of Beam Parameters For Proton Flashmentioning

confidence: 99%

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Pencil Beam Scanning Proton Bragg Peak Conformal FLASH in Prostate Cancer Stereotactic Body Radiotherapy

Kaulfers,

Lattery,

Cheng

et al. 2024

Cancers

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Bragg peak FLASH radiotherapy (RT) uses a distal tracking method to eliminate exit doses and can achieve superior OAR sparing. This study explores the application of this novel method in stereotactic body radiotherapy prostate FLASH-RT. An in-house platform was developed to enable intensity-modulated proton therapy (IMPT) planning using a single-energy Bragg peak distal tracking method. The patients involved in the study were previously treated with proton stereotactic body radiotherapy (SBRT) using the pencil beam scanning (PBS) technique to 40 Gy in five fractions. FLASH plans were optimized using a four-beam arrangement to generate a dose distribution similar to the conventional opposing beams. All of the beams had a small angle of two degrees from the lateral direction to increase the dosimetry quality. Dose metrics were compared between the conventional PBS and the Bragg peak FLASH plans. The dose rate histogram (DRVH) and FLASH metrics of 40 Gy/s coverage (V40Gy/s) were investigated for the Bragg peak plans. There was no significant difference between the clinical and Bragg peak plans in rectum, bladder, femur heads, large bowel, and penile bulb dose metrics, except for Dmax. For the CTV, the FLASH plans resulted in a higher Dmax than the clinical plans (116.9% vs. 103.3%). For the rectum, the V40Gy/s reached 94% and 93% for 1 Gy dose thresholds in composite and single-field evaluations, respectively. Additionally, the FLASH ratio reached close to 100% after the application of the 5 Gy threshold in composite dose rate assessment. In conclusion, the Bragg peak distal tracking method can yield comparable plan quality in most OARs while preserving sufficient FLASH dose rate coverage, demonstrating that the ultra-high dose technique can be applied in prostate FLASH SBRT.

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Section: Discussionsupporting

confidence: 90%

Section: Optimization Of Beam Parameters For Proton Flashmentioning

confidence: 99%

Pencil Beam Scanning Proton Bragg Peak Conformal FLASH in Prostate Cancer Stereotactic Body Radiotherapy

Kaulfers,

Lattery,

Cheng

et al. 2024

Cancers

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“…For high doses delivered to small volumes, clinically refined IMPT plans did show superior dose uniformity compared to FLASH plans in superficial left breast and skin OARs, which is consistent with the previous observation in the lung [ 20 ], liver [ 31 ], and head–neck cases [ 41 ]. This is because the conventional IMPT plans use multiple energy layers.…”

Section: Discussionsupporting

confidence: 88%

Pencil Beam Scanning Bragg Peak FLASH Technique for Ultra-High Dose Rate Intensity-Modulated Proton Therapy in Early-Stage Breast Cancer Treatment

Lattery,

Kaulfers,

Cheng

et al. 2023

Cancers

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Bragg peak FLASH-RT can deliver highly conformal treatment and potentially offer improved normal tissue protection for radiotherapy patients. This study focused on developing ultra-high dose rate (≥40 Gy × RBE/s) intensity-modulated proton therapy (IMPT) for hypofractionated treatment of early-stage breast cancer. A novel tracking technique was developed to enable pencil beaming scanning (PBS) of single-energy protons to adapt the Bragg peak (BP) to the target distally. Standard-of-care PBS treatment plans of consecutively treated early-stage breast cancer patients using multiple energy layers were reoptimized using this technique, and dose metrics were compared between single-energy layer BP FLASH and conventional IMPT plans. FLASH dose rate coverage by volume (V40Gy/s) was also evaluated for the FLASH sparing effect. Distal tracking can precisely stop BP at the target distal edge. All plans (n = 10) achieved conformal IMPT-like dose distributions under clinical machine parameters. No statistically significant differences were observed in any dose metrics for heart, ipsilateral lung, most ipsilateral breast, and CTV metrics (p > 0.05 for all). Conventional plans yielded slightly superior target and skin dose uniformities with 4.5% and 12.9% lower dose maxes, respectively. FLASH-RT plans reached 46.7% and 61.9% average-dose rate FLASH coverage for tissues receiving more than 1 and 5 Gy plan dose total under the 250 minimum MU condition. Bragg peak FLASH-RT techniques achieved comparable plan quality to conventional IMPT while reaching adequate dose rate ratios, demonstrating the feasibility of early-stage breast cancer clinical applications.

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“…Such use case is relevant for ultra-high dose rate delivery (FLASH-RT), where the need for a high beam current imposes a low number of relatively high MU spots, thus making their positions critical. Optimizing the spot positions could be exploited further using a range modulator or ridge filter (Weber and Kraft 1999) to benefit from the Bragg peak distribution, (Kang et al 2022, Pennock et al 2023 reducing or eliminating distal doses. For conventional dose-rate, plan quality improvements are also expected when optimizing the spot positions of IMPT plans made of multiple energy layers.…”

Section: Conventional Imptmentioning

confidence: 99%

Combined optimization of spot positions and weights for better FLASH proton therapy

Lansonneur,

Magliari,

Rosa

et al. 2024

Phys. Med. Biol.

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Objective: In Intensity Modulated Proton Therapy (IMPT), the weights of individual pencil-beams or spots are optimized to fulfil dosimetric constraints. Theses spots are usually located on a regular lattice and their positions are fixed during optimization. In many cases, the range of spot weights may however be limited, leading sometimes to sub-optimal plan quality. An emblematic use case is the delivery of a plan at ultra-high dose rate (FLASH-RT), for which the spot weights are typically constrained to high values. Approach: To improve further the quality of IMPT FLASH plans, we propose here a novel algorithm to optimize both the spot weights and positions directly based on the objectives defined by the treatment planner. Main results: For all cases considered, optimizing the spot positions lead to an enhanced dosimetric score, while maintaining a high dose rate. Significance: Overall, this approach resulted in a substantial plan quality improvement compared to optimizing only the spot weights, and in a similar execution time.

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Proton Bragg Peak FLASH Enables Organ Sparing and Ultra-High Dose-Rate Delivery: Proof of Principle in Recurrent Head and Neck Cancer

Cited by 10 publications

References 68 publications

Pencil Beam Scanning Proton Bragg Peak Conformal FLASH in Prostate Cancer Stereotactic Body Radiotherapy

Pencil Beam Scanning Proton Bragg Peak Conformal FLASH in Prostate Cancer Stereotactic Body Radiotherapy

Pencil Beam Scanning Bragg Peak FLASH Technique for Ultra-High Dose Rate Intensity-Modulated Proton Therapy in Early-Stage Breast Cancer Treatment

Combined optimization of spot positions and weights for better FLASH proton therapy

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