Long Term Clinical Outcome and Quality of Life of Children, Adolescents and Young Adults Treated with Pencil Beam Scanning Proton Therapy for Rhabdomyosarcoma

PURPOSE/OBJECTIVE(S)

To assess the long-term clinical outcomes of children, adolescents and young adults (CAYAs) with rhabdomyosarcoma (RMS) treated with pencil beam scanning proton therapy (pbsPT).

MATERIALS/METHODS

One hundred twenty-one RMS (embryonal, n = 102; 84.3%) patients treated between January 2000 and December 2020 were included in this analysis. The median age was 4.7 years (range, 0.1-35.3). All patients received systemic chemotherapy according to prospective protocols. The median total dose delivered was 54 Gy (RBE) (range, 41.4-74.0).

RESULTS

After a median follow-up time of 85.5 month (range,3.4-240.0), we observed 23 local/regional and 12 distant failures. The estimated 5-year local control (LC) and overall survival (OS) was 81.5% and 80%, respectively. For the subgroups of parameningeal (PM), orbital, urogenital and H&N non-PM the 5-year LC was 74.7%, 92%, 100% and 66.7%. The corresponding figures for OS were 68.8%, 100%, 100%, and 66.7, respectively. The 5-year non-ocular Grade 3 toxicity free survival was 78.9%. At the start of pbsPT children and their caregivers reported QoL significantly worse than the norm group. QoL improved however over the follow up period to normal values in nearly all domains. Median of PEDQOL PROXY reported QoL in Normgroup (children: 4- 18 yrs) and RMS patients (n = 27-42 answers per domain): CONCLUSION: Excellent clinical outcome was observed for CAYAs with RMS treated with pbsPT. Two thirds of treatment failures were local. High-grade late non-ocular toxicity was manageable. QoL improved towards normal scores in nearly all domains after therapy.

NTCP modelling for high-grade temporal radionecrosis in a large cohort of patients receiving pencil beam scanning proton therapy for skull base and head and neck tumors

PURPOSE/OBJECTIVES

To develop a normal tissue complication probability (NTCP) model including clinical and dosimetric parameters for high-grade temporal lobe radionecroses (TRN) after pencil beam scanning (PBS) proton therapy (PT).

MATERIALS/METHODS

Data of 299 patients with skull base and Head and Neck tumors treated with PBS PT with a total dose of ≥60 Gy_RBE from 05/2004-11/2018 were included. Patients with a ≥ grade (G) 2 TRN (CTCAE v5.0 criteria) were considered as having a high-grade TRN. Nine clinical and 27 dosimetric parameters were considered for structure-wise modelling. After elimination of strongly cross-correlated variables, logistic regression models were generated using penalized LASSO regression. Bootstrapping was performed to assess parameter selection robustness. Model performance was evaluated via cross-correlation by assessing the area under the curve of receiver operating characteristic curves (AUC-ROC) and calibration with a Hosmer-Lemeshow test statistic.

RESULTS

After a median radiological follow-up of 51.5 months (range, 4-190), 27 (9%) patients developed a ≥ G2 TRN. Eleven patients had bitemporal necrosis, resulting in 38 events in 598 temporal lobes for structure-wise analysis. During Bootstrapping analysis, the highest selection frequency was found for prescription dose (PD), followed by Age, V_40Gy[%], Hypertension (HBP) and D_1cc[Gy]. During cross validation Age*PD* D_1cc[Gy]*HBP was superior in all described test statistics. Full cohort structure wise and patient wise models were built with a maximum AUC-ROC of 0.79 (structure-wise) and 0.76 (patient-wise).

CONCLUSION

While developing a logistic regression NTCP model to predict ≥ G2 TRN, the best fit was found for the model containing Age, PD, D_1cc[Gy] and HBP as risk factors. External validation will be the next step to improve generalizability and potential introduction into clinical routine.

Outcomes, Prognostic Factors and Salvage Treatment for Recurrent Chordoma After Pencil Beam Scanning Proton Therapy at the Paul Scherrer Institute

AIMS

The outcome of chordoma patients with local or distant failure after proton therapy is not well established. We assessed the disease-specific (DSS) and overall survival of patients recurring after proton therapy and evaluated the prognostic factors affecting DSS.

MATERIALS AND METHODS

A retrospective analysis was carried out of 71 recurring skull base (n = 36) and extracranial (n = 35) chordoma patients who received adjuvant proton therapy at initial presentation (n = 42; 59%) or after post-surgical recurrence (n = 29; 41%). The median proton therapy dose delivered was 74 GyRBE (range 62-76). The mean age was 55 ± 14.2 years and the male/female ratio was about one.

RESULTS

The median time to first failure after proton therapy was 30.8 months (range 3-152). Most patients (n = 59; 83%) presented with locoregional failure only. There were only 12 (17%) distant failures, either with (n = 5) or without (n = 7) synchronous local failure. Eight patients (11%) received no salvage therapy for their treatment failure after proton therapy. Salvage treatments after proton therapy failure included surgery, systemic therapy and additional radiotherapy in 45 (63%), 20 (28%) and eight (11%) patients, respectively. Fifty-three patients (75%) died, most often from disease progression (47 of 53 patients; 89%). The median DSS and overall survival after failure was 3.9 (95% confidence interval 3.1-5.1) and 3.4 (95% confidence interval 2.5-4.4) years, respectively. On multivariate analysis, extracranial location and late failure (≥31 months after proton therapy) were independent favourable prognostic factors for DSS.

CONCLUSION

The survival of chordoma patients after a treatment failure following proton therapy is poor, particularly for patients who relapse early or recur in the skull base. Although salvage treatment is administered to most patients with uncontrolled disease, they will ultimately die as a result of disease progression in most cases.

Development and prospective in-patient proof-of-concept validation of a surface photogrammetry + CT-based volumetric motion model for lung radiotherapy

PURPOSE

We develop and validate a motion model that uses real-time surface photogrammetry acquired concurrently with four-dimensional computed tomography (4DCT) to estimate respiration-induced changes within the entire irradiated volume, over arbitrarily many respiratory cycles.

METHODS

A research, couch-mounted, VisionRT (VRT) system was used to acquire optical surface data (15 Hz, ROI = 15 × 20 cm² ) from the thoraco-abdominal surface of a consented lung SBRT patient, concurrently with their standard-of-care 4DCT. The end-exhalation phase from the 4DCT was regarded as reference and for each remaining phase, deformation vector fields (DVFs) with respect to the reference phase were computed. To reduce dimensionality, the first two principal components (PCs) of the matrix of nine DVFs were calculated. In parallel, ten phase-averaged VRT surfaces were created. Surface DVFs and corresponding PCs were computed. A principal least squares regression was used to relate the PCs of surface DVF to those of volume DVFs, establishing a relationship between time-varying surface and the underlying time-varying volume. Proof-of-concept validation was performed during each treatment fraction by concurrently acquiring 30 s time series of real-time surface data and "ground truth" kV fluoroscopic data (FL). A ray-tracing algorithm was used to create a digitally reconstructed fluorograph (DRF), and motion trajectories of high-contrast, soft-tissue, anatomical features in the DRF were compared with those from kV FL.

RESULTS

For five of the six fluoroscopic acquisition sessions, the model out-performed 4DCT in predicting contour Dice coefficient with respect to fluoroscopy-derived contours. Similarly, the model exhibited a marked improvement over 4DCT for patch positions on the diaphragm. Model patch position errors varied from 5 to -15 mm while 4DCT errors ranged between 5 and -22.4 mm. For one fluoroscopic acquisition, a marked change in the a priori internal-external correlation resulted in model errors comparable to those of 4DCT.

CONCLUSIONS

We described the development and a proof-of-concept validation for a volumetric motion model that uses surface photogrammetry to correlate the time-varying thoraco-abdominal surface to the time-varying internal thoraco-abdominal volume. These early results indicate that the proposed approach can result in a marked improvement over 4DCT. While limited by the duration of the fluoroscopic acquisitions as well as the resolution of the acquired images, the DRF-based proof-of-concept technique developed here is model-agnostic, and therefore, has the potential to be used as an in-patient validation tool for other volumetric motion models.

Impact of regular magnetic resonance imaging follow-up after stereotactic radiotherapy to the surgical cavity in patients with one to three brain metastases

BACKGROUND

Administering stereotactic radiotherapy to the surgical cavity and thus omitting postoperative whole brain radiotherapy (WBRT) is a favored strategy in limited metastatic brain disease. Little is known about the impact of regular magnetic resonance imaging follow-up (MRI FU) in such patient cohorts. The aim of this study is to examine the impact of regular MRI FU and to report the oncological outcomes of patients with one to three brain metastases (BMs) treated with stereotactic radiosurgery (SRS) or hypo-fractionated stereotactic radiotherapy (HFSRT) to the surgical cavity.

METHODS

We retrospectively analyzed patients who received SRS or HFSRT to the surgical cavity after resection of one to two BMs. Additional, non-resected BMs were managed with SRS alone. Survival was estimated by the Kaplan-Meier method. Prognostic factors were examined with the log-rank test and Cox proportional hazards model. Regular MRI FU was defined as performing a brain MRI 3 months after radiotherapy (RT) and/or performing ≥1 brain MRI per 180 days. Primary endpoint was local control (LC). Secondary endpoints were distant brain control (DBC), overall survival (OS) and the correlation between regular MRI FU and overall survival (OS), symptom-free survival (SFS), deferment of WBRT and WBRT-free survival (WFS).

RESULTS

Overall, 75 patients were enrolled. One, 2 and 3 BMs were seen in 63 (84%), 11 (15%) and 1 (1%) patients, respectively. Forty (53%) patients underwent MRI FU 3 months after RT and 38 (51%) patients received ≥1 brain MRI per 180 days. Median OS was 19.4 months (95% CI: 13.2-25.6 months). Actuarial LC, DBC and OS at 1 year were 72% (95% CI: 60-83%), 60% (95% CI: 48-72%) and 66% (95% CI: 53-76%), respectively. A planning target volume > 15 cm³ (p = 0.01), Graded Prognostic Assessment (GPA) score (p = 0.001) and residual tumor after surgery (p = 0.008) were prognostic for decreased OS in multivariate analysis. No significant correlation between MRI FU at 3 months and OS (p = 0.462), SFS (p = 0.536), WFS (p = 0.407) or deferment of WBRT (p = 0.955) was seen. Likewise, performing ≥1 MRI per 180 days had no significant impact on OS (p = 0.954), SFS (p = 0.196), WFS (p = 0.308) or deferment of WBRT (p = 0.268).

CONCLUSION

Our results regarding oncological outcomes consist with the current data from the literature. Surprisingly, regular MRI FU did not result in increased OS, SFS, WFS or deferment of WBRT in our cohort consisting mainly of patients with a single and resected BM. Therefore, the impact of regular MRI FU needs prospective evaluation.

TRIAL REGISTRATION

Project ID: 2017-00033, retrospectively registered.

Contour scanning for penumbra improvement in pencil beam scanned proton therapy

Proton therapy, especially in the form of pencil beam scanning (PBS), allows for the delivery of highly conformal dose distributions for complex tumor geometries. However, due to scattering of protons inside the patient, lateral dose gradients cannot be arbitrarily steep, which is of importance in cases with organs at risk (OARs) in close proximity to, or overlapping with, planning target volumes (PTVs). In the PBS approach, physical pencil beams are planned using a regular grid orthogonal to the beam direction. In this work, we propose an alternative to this commonly used approach where pencil beams are placed on an irregular grid along concentric paths based on the target contour. Contour driven pencil beam placement is expected to improve dose confirmation by allowing the optimizer to best enhance the penumbra of irregularly shaped targets using edge enhancement. Its effectiveness has been shown to improve dose confirmation to the target volume and reduce doses to OARs in head-and-neck planning studies. Furthermore, the deliverability of such plans, as well as the dosimetric improvements over conventional grid-based plans, have been confirmed in first phantom based verifications.

Perception of artificial stereoscopic stimuli from an incorrect viewing point

The present study investigates the distortions in the perception of artificial stereoscopic displays seen from an inappropriate distance and/or orientation. Stereoscopic displays represent 3-D information correctly, provided they are seen from the correct station point. The viewing point may differ from the correct station point in its distance or in its orientation to the screen. These differences lead to distortions that can be predicted mathematically. However, the perceptual function may be different from the predictions, since people may possibly compensate for the distortions. To test the degree of this compensation, participants saw anaglyphic stereoscopic stimuli that showed angles in the horizontal plane, and their perception of the configuration was tested for various orientations and distances. The estimates were compared with the values predicted from the mathematical functions, and participants' virtual positions were reconstructed via nonlinear regressions. The analyses revealed a moderate compensation for viewing orientations and a systematically overestimation of the viewing distances. These results indicate that people compensate partially for distortions in stereopsis, given that the relevant information is available.

Mothers' lay models of the causes and treatment of fever

Mothers' intuitive models concerning the causes of fever in their children and their beliefs about the effects of different treatments were compared to modern, folk and ancient models of the subject. A questionnaire was devised, presenting statements that were generated from the responses in a preliminary study, and from ancient, folk and modern views about fever. This questionnaire was answered by 147 mothers whose youngest child was up to eight years old. The sample consisted of four groups, who differed in their educational background: less than 10 years, 10-12 years and more than 12 years of schooling, and a group of professional nurses. Results reveal a complex picture. Unlike in physics, naive understanding does not duplicate ancient models. With increasing education, the views held by the ancient and contemporary folk beliefs are rejected. Many results of modern science are known throughout the population, and this is true both for practical recommendations and for their rationale. Even so, the medical model is only partly accepted, and is assimilated in a somewhat distorted form.

Duration estimates and users' preferences in human-computer interaction

Two experiments assessed the effect of various static and dynamic computer 'wait' message displays on (1) subjective estimates of the duration of intervals during which a subject had to wait for the computer's response, and (2) subjective preferences among the different displays. All the static displays led to identical duration estimates. For dynamic displays a direct relation between the rate of changes and the estimate was found. Faster rates led in most cases to increased estimates of duration, and slow-changing graphic displays appeared to have the shortest duration. Subjects preferred epigrams to all other displays, and cumulative graphic displays to a blinking or static WAIT. The rate of change did not affect preference ratings for the graphic displays, whereas slower blink rates were preferred for the WAIT. The results demonstrate that the findings and models from earlier basic research on time estimation are relevant for predicting the subjective assessment of wait-periods. However, users' satisfaction with the displays depends not only on the apparent duration of the wait period, but also on other variables. These should be considered when choosing the display that is shown while users wait for the system to complete a task.