The potential of biology-guided radiation therapy in thoracic cancer: A preliminary treatment planning study.

Purpose: We investigated the feasibility of biology-guided radiotherapy (BgRT), a technique that utilizes real-time positron emission imaging to minimize tumor motion uncertainties, to spare nearby organs at risk. Methods: Volumetric modulated arc therapy (VMAT), intensity-modulated proton (IMPT) therapy, and BgRT plans were created for a paratracheal node recurrence (case 1; 60 Gy in 10 fractions) and a primary peripheral left upper lobe adenocarcinoma (case 2; 50 Gy in four fractions). Results: For case 1, BgRT produced lower bronchus V40 values compared to VMAT and IMPT. For case 2, total lung V20 was lower in the BgRT case compared to VMAT and IMPT. Conclusions: BgRT has the potential to reduce the radiation dose to proximal critical structures but requires further detailed investigation.

Young Adult Populations Face Yet Another Barrier to Care With Insurers: Limited Access to Proton Therapy.

PURPOSE: Young patients, including pediatric, adolescent, and young adult (YA) patients, are most likely to benefit from the reduced integral dose of proton beam radiation therapy (PBT) resulting in fewer late toxicities and secondary malignancies. This study sought to examine insurance approval and appeal outcomes for PBT among YA patients compared with pediatric patients at a large-volume proton therapy center. METHODS AND MATERIALS: We performed a cross-sectional cohort study of 284 consecutive patients aged 0 to 39 years for whom PBT was recommended in 2018 through 2019. Pediatric patients were defined as aged 0 to 18 years and YA patients 19 to 39 years. Rates of approval, denials, and decision timelines were calculated. Tumor type and location were also evaluated as factors that may influence insurance decisions. RESULTS: A total of 207 patients (73%) were approved for PBT at initial request. YA patients (n = 68/143, 48%) were significantly less likely to receive initial approval compared with pediatric patients (n = 139/141; 99%) (P < .001). Even after 47% (n = 35 of 75) of the PBT denials for YA patients were overturned, YAs had a significantly lower final PBT approval (72% vs pediatric 99%; P < .001). The median wait time was also significantly longer for YA patients (median, 8 days; interquartile range [IQR] 3-17 vs median, 2 days; IQR, 0-6; P < .001). In those patients requiring an appeal, the median wait time was 16 days (IQR, 9-25). CONCLUSION: Given the decades of survivorship of YA patients, PBT is an important tool to reduce late toxicities and secondary malignancies. Compared with pediatric patients, YA patients are significantly less likely to receive insurance approval for PBT. Insurance denials and subsequent appeal requests result in significant delays for YA patients. Insurers need to re-examine their policies to include expedited decisions and appeals and removal of arbitrary age cutoffs so that YA patients can gain easier access to PBT. Furthermore, consensus guidelines encouraging greater PBT access for YA may be warranted from both medical societies and/or AYA experts.

Characterization of a new physical phantom for testing rigid and deformable image registration.

The purpose of this study was to describe a new user-friendly, low-cost phantom that was developed to test the accuracy of rigid and deformable image registration (DIR) systems and to demonstrate the functional efficacy of the new phantom. The phantom was constructed out of acrylic and includes a variety of inserts that simulate different tissue shapes and properties. It can simulate deformations and location changes in patient anatomy by changing the rotations of both the phantom and the inserts. CT scans of this phantom were obtained and used to test the rigid and deformable registration accuracy of the Velocity software. Eight rotation and translation scenarios were used to test the rigid registration accuracy, and 11 deformation scenarios were used to test the DIR accuracy. The mean rotation accuracies in the X-Y (axial) and X-Z (coronal) planes were 0.50° and 0.13°, respectively. The mean translation accuracy was 1 mm in both the X and Y direction and was tested in soft tissue and bone. The DIR accuracies for soft tissue and bone were 0.93 (mean Dice similarity coefficient), 8.3 and 4.5 mm (mean Hausdouff distance), 0.95 and 0.79 mm (mean distance), and 1.13 and 1.12 (mean volume ratio) for soft tissue content (DTE oil) and bone, respectively. The new phantom has a simple design and can be constructed at a low cost. This phantom will allow DIR systems to be effectively and efficiently verified to ensure system performance.

Prescribing radiation dose to lung cancer patients based on personalized toxicity estimates.

INTRODUCTION: The lung radiosensitivity of the most sensitive patients limits doses that can be given to the majority of lung cancer patients. The purpose of the current study was to illustrate the concept of personalizing prescription dose by performing a retrospective study in which the prescription is determined using an individualized dose-volume constraint that is calculated from a toxicity prediction model. We test whether using a model-generated personalized lung-dose limit results in a clinically significant change to the prescription. METHODS: A model consisting of a dose-volume component and a genetic component (single-nucleotide polymorphism information) was used to determine iso-risk mean lung-dose (MLD) limits for each patient. The prescription dose for each patient was scaled according to the individualized MLD constraint and population-based constraints for the cord, esophagus, and heart. The difference between the model-determined prescription dose and the prescription the patient was originally treated with was evaluated. RESULTS: For 59% of the patients the change in prescription using the model-determined limit was greater than 5 Gy (either dose escalation or de-escalation). For 96% of the patients who developed radiation pneumonitis the model predicted that the prescription should have been lowered. CONCLUSIONS: Our results indicate that using a model-generated personalized MLD results in a clinically different (≥ 5 Gy) prescription. A model used in the manner described by the study can help physicians further personalize radiation therapy and aid them in determining how much dose can safely be delivered to the tumor and normal tissues.

Automated volumetric modulated Arc therapy treatment planning for stage III lung cancer: how does it compare with intensity-modulated radio therapy?

PURPOSE: To compare the quality of volumetric modulated arc therapy (VMAT) or intensity-modulated radiation therapy (IMRT) plans generated by an automated inverse planning system with that of dosimetrist-generated IMRT treatment plans for patients with stage III lung cancer. METHODS AND MATERIALS: Two groups of 8 patients with stage III lung cancer were randomly selected. For group 1, the dosimetrists spent their best effort in designing IMRT plans to compete with the automated inverse planning system (mdaccAutoPlan); for group 2, the dosimetrists were not in competition and spent their regular effort. Five experienced radiation oncologists independently blind-reviewed and ranked the three plans for each patient: a rank of 1 was the best and 3 was the worst. Dosimetric measures were also performed to quantitatively evaluate the three types of plans. RESULTS: Blind rankings from different oncologists were generally consistent. For group 1, the auto-VMAT, auto-IMRT, and manual IMRT plans received average ranks of 1.6, 2.13, and 2.18, respectively. The auto-VMAT plans in group 1 had 10% higher planning tumor volume (PTV) conformality and 24% lower esophagus V70 (the volume receiving 70 Gy or more) than the manual IMRT plans; they also resulted in more than 20% higher complication-free tumor control probability (P+) than either type of IMRT plans. The auto- and manual IMRT plans in this group yielded generally comparable dosimetric measures. For group 2, the auto-VMAT, auto-IMRT, and manual IMRT plans received average ranks of 1.55, 1.75, and 2.75, respectively. Compared to the manual IMRT plans in this group, the auto-VMAT plans and auto-IMRT plans showed, respectively, 17% and 14% higher PTV dose conformality, 8% and 17% lower mean lung dose, 17% and 26% lower mean heart dose, and 36% and 23% higher P+. CONCLUSIONS: mdaccAutoPlan is capable of generating high-quality VMAT and IMRT treatment plans for stage III lung cancer. Manual IMRT plans could achieve quality similar to auto-IMRT plans if best effort was spent.