Optimal timing of re-planning for head and neck adaptive radiotherapy

Gan, Yong; Langendijk, Johannes A.; Oldehinkel, Edwin; Lin, Zhixiong; Both, Stefan; Brouwer, Charlotte L.

doi:10.1016/j.radonc.2024.110145

Cited by 3 publications

References 38 publications

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Clinical advantages of incorporating predicted weekly anatomy in IMPT optimization with reduced setup error

Zhang,

Chan

2024

Medical Physics

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BackgroundIn head and neck (H&N) cancer treatment, a conventional setup error (SE) of 3mm is often used in robust optimization (cRO3mm). However, cRO3mm may lead to excessive radiation doses to organs at risk (OARs) and does not purposefully compensate for interfractional anatomy variations.PurposeThis study introduces a method using predicted images from an anatomical model and a reduced 1mm SE uncertainty for robust optimization (aRO1mm), aiming to decrease the dose to OARs without affecting the coverage of the clinical target volume (CTV).MethodsThis retrospective study involved 10 nasopharynx radiotherapy patients. Validation CT scans (vCT) from treatment weeks 1 to 6 were analyzed. A predictive anatomical model, designed to capture the average anatomical changes over time, provided predicted CT images for weeks 1, 3, and 5. We compared three optimization scenarios: (1) aRO1mm, using three predicted images with 1mm setup shift and 3% range uncertainty, (2) cRO3mm, with a robust 3mm setup shift and 3% range uncertainty, and (3) cRO1mm, a robust 1mm setup shift and 3% range uncertainty. The accumulated dose to CTVs and serial organs was evaluated under these uncertainties, while parallel OARs were assessed using the accumulated nominal dose (without errors).ResultsThe accumulated volume receiving 94% of the prescribed dose (V94) for CTVs in cRO3mm exceeded 98%, meeting the clinical goal. For high‐risk CTV, the minimum V94 was 96.44% in aRO1mm and 94.05% in cRO1mm. For low‐risk CTV, these values were 97.68% in aRO1mm and 97.15% in cRO1mm. When comparing aRO1mm to cRO3mm on OARs, aRO1mm reduced normal tissue complication probability (NTCP) for grade 2 xerostomia and dysphagia by averages of 3.67% and 1.54%, respectively.ConclusionaRO1mm lowers the radiation dose to OARs compared to the traditional approach, while maintaining adequate dose coverage on the target area. This method offers an improved strategy for managing uncertainties in radiation therapy planning for H&N cancer, enhancing treatment effectiveness.

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Clinical advantages of incorporating predicted weekly anatomy in IMPT optimization with reduced setup error

Zhang,

Chan

2024

Medical Physics

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Optimal Timing of Organs-at-Risk-Sparing Adaptive Radiation Therapy for Head-and-Neck Cancer under Re-planning Resource Constraints

Nosrat,

Dede,

McCullum

et al. 2024

Preprint

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Objective. The objective of this study was to determine personalized optimal timing for re-planning in adaptive organ-at-risk-sparing radiation therapy under limited re-planning resources in patients with head and neck cancer (HNC). Approach. A novel Markov decision process (MDP) model was developed to determine optimal timing of re-plannings based on the patients expected toxicity, characterized by normal tissue complication probability (NTCP), for four toxicities: xerostomia, dysphagia, parotid gland dysfunction, and feeding tube dependency at 6 months post-treatment. The MDP parameters were derived from a dataset comprising 52 HNC patients treated at the University of Texas MD Anderson Cancer Center between 2007 and 2013. Optimal re-planning strategies were obtained when the permissible number of re-plannings throughout the treatment was limited to 1, 2, and 3. Main results. Based on the MDP solution, it is optimal to re-plan when the difference between planned and actual NTCPs (ΔNTCP) was greater than or equal to 1%, 2%, 2%, and 4% at treatment fractions 10, 15, 20, and 25, respectively, exhibiting a temporally increasing pattern. The ΔNTCP thresholds remained constant across the number of re-planning allowances (1, 2, and 3). This result underscores the importance of re-planning for patients experiencing the slightest change in ΔNTCP at fraction 10. Significance. In contrast to prior work that relies on a single re-planning allowance or predetermined time intervals using a one-size-fits-all approach, the MDP model proposed in this paper offers a personalized, resource-aware, and scalable decision-making tool; it identifies optimal dynamic re-planning schedules tailored to individual needs, guided by changes in NTCP.

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Prediction and monitoring of adaptive radiation therapy timing using two-dimensional X-ray image-based water equivalent thickness

Hirotaki,

Moriya,

Tomizawa

et al. 2024

Preprint

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Background This study aimed to predict and monitor the optimal timing for implementing adaptive radiation therapy (ART) using two-dimensional X-ray image-based water equivalent thickness (2DWET). Methods The study included 40 patients with oropharyngeal and hypopharyngeal cancer who underwent CT rescanning during the treatment period. An adaptive score (AS) was proposed as a quantitative indicator to facilitate the decision regarding when to implement ART. The AS was derived from changes in four key dose indices: target coverage, spinal cord dose, parotid gland dose, and over-dose volume. Delivered dose distributions were reviewed by two oncologists specializing in head and neck radiation therapy, and the need for ART was evaluated using a four-point score. Logistic regression analysis was used to determine the AS cutoff value, and receiver operating characteristic analysis was used to assess 2DWET as a predictor of ART timing. Results The AS strongly correlated with the decisions made by the radiation oncologists, with Pearson correlation coefficients of 0.74 and 0.64. An AS cutoff value of 7.5 was identified as an indicator of the optimal time to implement ART, predicting two oncologists' decisions with sensitivities of 79.2% and 89.5% and specificities of 87.5% and 81.0%, respectively. The 2DWET method detected AS = 7.5 with a sensitivity of 63.2% and a specificity of 81.0%. Conclusions An adaptive score of 7.5 strongly correlated with the radiation oncologists' decision to implement ART and could therefore be used as a surrogate marker. Two-dimensional WET detected AS = 7.5 with high sensitivity and specificity and could potentially be used as a highly efficient and low-exposure tool for predicting and monitoring the optimal timing of ART implementation.

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Optimal timing of re-planning for head and neck adaptive radiotherapy

Cited by 3 publications

References 38 publications

Clinical advantages of incorporating predicted weekly anatomy in IMPT optimization with reduced setup error

Clinical advantages of incorporating predicted weekly anatomy in IMPT optimization with reduced setup error

Optimal Timing of Organs-at-Risk-Sparing Adaptive Radiation Therapy for Head-and-Neck Cancer under Re-planning Resource Constraints

Prediction and monitoring of adaptive radiation therapy timing using two-dimensional X-ray image-based water equivalent thickness

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