TEDDI: radiotherapy delivery in deep inspiration for pediatric patients - a NOPHO feasibility study

Paediatric CBCT protocols for image-guided radiotherapy; outcome of a survey across SIOP Europe affiliated countries and literature review

BACKGROUND

Implementation of daily cone-beam CT (CBCT) into clinical practice in paediatric image-guided radiotherapy (IGRT) lags behind compared to adults. Surveys report wide variation in practice for paediatric IGRT and technical information remains unreported. In this study we report on technical settings from applied paediatric CBCT protocols and review the literature for paediatric CBCT protocols.

METHODS

From September to October 2022, a survey was conducted among 246 SIOPE-affiliated centres across 35 countries. The survey consisted of 3 parts: 1) baseline information; technical CBCT exposure settings and patient set-up procedure for 2) brain/head, and 3) abdomen. Descriptive statistics was used to summarise current practice. The literature was reviewed systematically with two reviewers obtaining consensus RESULTS: The literature search revealed 22 papers concerning paediatric CBCT protocols. Seven papers focused on dose-optimisation. Responses from 50/246 centres in 25/35 countries were collected: 44/50 treated with photons and 10/50 with protons. In total, 48 brain/head and 53 abdominal protocols were reported. 42/50 centres used kV-CBCT for brain/head and 35/50 for abdomen; daily CBCT was used for brain/head = 28/48 (58%) and abdomen = 33/53 62%. Greater consistency was seen in brain/head protocols (dose range 0.32 - 67.7 mGy) compared to abdominal (dose range 0.27 - 119.7 mGy).

CONCLUSION

Although daily CBCT is now widely used in paediatric IGRT, our survey demonstrates a wide range of technical settings, suggesting an unmet need to optimise paediatric IGRT protocols. This is in accordance with the literature. However, there are only few paediatric optimisation studies suggesting that dose reduction is possible while maintaining image quality.

ESTRO-ACROP guideline: Recommendations on implementation of breath-hold techniques in radiotherapy

The use of breath-hold techniques in radiotherapy, such as deep-inspiration breath hold, is increasing although guidelines for clinical implementation are lacking. In these recommendations, we aim to provide an overview of available technical solutions and guidance for best practice in the implementation phase. We will discuss specific challenges in different tumour sites including factors such as staff training and patient coaching, accuracy, and reproducibility. In addition, we aim to highlight the need for further research in specific patient groups. This report also reviews considerations for equipment, staff training and patient coaching, as well as image guidance for breath-hold treatments. Dedicated sections for specific indications, namely breast cancer, thoracic and abdominal tumours are also included.

Baseline FDG PET/CT in free breathing versus deep inspiration breath-hold for pediatric patients with mediastinal lymphoma

INTRODUCTION

The prospective TEDDI protocol investigates the feasibility of radiotherapy delivery in deep inspiration breath-hold (DIBH) for pediatric patients. To secure optimal radiotherapy planning, a diagnostic baseline FDG PET/CT in free breathing (FB) and DIBH was acquired. The anatomical changes in the mediastinum and the effect on PET metrics between the two breathing conditions were assessed for pediatric patients with mediastinal lymphoma.

MATERIAL AND METHODS

Ten patients aged 5-17 were included and had a PET/CT in FB and DIBH. Metabolic active lymphoma volumes were manually delineated with a visually based segmentation method and the PET metrics were extracted. The anatomical lymphoma, lung and heart volumes were delineated on CT.

RESULTS

The lung volume increased while the heart was displaced caudally and separated from the lymphoma in DIBH compared to FB. Both the anatomical and the metabolically active lymphoma volumes appeared different regarding shape and configuration in the two breathing conditions. The image quality of the DIBH PET was equal to the FB PET regarding interpretation and delineation of lymphoma lesions. All PET metrics increased on the DIBH PET compared to the FB PET with the highest increase observed for the maximum standardized uptake value (33%, range 7-56%).

CONCLUSION

Diminished respiratory motion together with anatomical changes within the lymphoma increased all PET metrics in DIBH compared to FB. The anatomical changes observed in DIBH compared to FB are expected to reduce radiation doses to the heart and lungs in pediatric patients with mediastinal lymphoma referred for radiotherapy delivery in DIBH and, thereby, reduce their risk of late effects.

TRIAL REGISTRATION

The Danish Ethical Committee (H-16035870, approved November 24^th 2016), the Danish Data Protection Agency (2012-58-0004, approved 1 January 2017). Registered retrospectively at clinicaltrials.gov (NCT03315546, 20 October 2017).

Low dose cone beam CT for paediatric image-guided radiotherapy: Image quality and practical recommendations

PURPOSE

Cone beam CT (CBCT) is used in paediatric image-guided radiotherapy (IGRT) for patient setup and internal anatomy assessment. Adult CBCT protocols lead to excessive doses in children, increasing the risk of radiation-induced malignancies. Reducing imaging dose increases quantum noise, degrading image quality. Patient CBCTs also include 'anatomical noise' (e.g. motion artefacts), further degrading quality. We determine noise contributions in paediatric CBCT, recommending practical imaging protocols and thresholds above which increasing dose yields no improvement in image quality.

METHODS AND MATERIALS

Sixty CBCTs including the thorax or abdomen/pelvis from 7 paediatric patients (aged 6-13 years) were acquired at a range of doses and used to simulate lower dose scans, totalling 192 scans (0.5-12.8 mGy). Noise measured in corresponding regions of each patient and a 10-year-old phantom were compared, modelling total (including anatomical) noise, and quantum noise contributions as a function of dose. Contrast-to-noise ratio (CNR) was measured between fat/muscle. Soft tissue registration was performed on the kidneys, comparing accuracy to the highest dose scans.

RESULTS

Quantum noise contributed <20% to total noise in all cases, suggesting anatomical noise is the largest determinant of image quality in the abdominal/pelvic region. CNR exceeded 3 in over 90% of cases ≥ 1 mGy, and 57% of cases at 0.5 mGy. Soft tissue registration was accurate for doses > 1 mGy.

CONCLUSION

Anatomical noise dominates quantum noise in paediatric CBCT. Appropriate soft tissue contrast and registration accuracy can be achieved for doses as low as 1 mGy. Increasing dose above 1 mGy holds no benefit in improving image quality or registration accuracy due to the presence of anatomical noise.

Advances in radiotherapy technology for pediatric cancer patients and roles of medical physicists: COG and SIOP Europe perspectives

Over the last two decades, rapid technological advances have dramatically changed radiation delivery to children with cancer, enabling improved normal-tissue sparing. This article describes recent advances in photon and proton therapy technologies, image-guided patient positioning, motion management, and adaptive therapy that are relevant to pediatric cancer patients. For medical physicists who are at the forefront of realizing the promise of technology, challenges remain with respect to ensuring patient safety as new technologies are implemented with increasing treatment complexity. The contributions of medical physicists to meeting these challenges in daily practice, in the conduct of clinical trials, and in pediatric oncology cooperative groups are highlighted. Representing the perspective of the physics committees of the Children's Oncology Group (COG) and the European Society for Paediatric Oncology (SIOP Europe), this paper provides recommendations regarding the safe delivery of pediatric radiotherapy. Emerging innovations are highlighted to encourage pediatric applications with a view to maximizing the therapeutic ratio.

Safely achieving single prolonged breath-holds of > 5 minutes for radiotherapy in the prone, front crawl position

OBJECTIVE

Breast cancer radiotherapy is increasingly delivered supine with multiple, short breath-holds. There may be heart and lung sparing advantages for locoregional breast cancer of both prone treatment and in a single breath-hold. We test here whether single prolonged breath-holds are possible in the prone, front crawl position.

METHODS

19 healthy volunteers were trained to deliver supine, single prolonged breath-holds with pre-oxygenation and hypocapnia. We tested whether all could achieve the same durations in the prone, front crawl position.

RESULTS

19 healthy volunteers achieved supine, single prolonged breath-holds for mean of 6.2 ± 0.3 min. All were able to hold safely for the same duration while prone (6.1 ± 0.2 min ns. by paired ANOVA). With prone, the increased weight on the chest did not impede chest inflation, nor the ability to hold air in the chest. Thus, the rate of chest deflation (mean anteroposterior deflation movement of three craniocaudally arranged surface markers on the spinal cord) was the same (1.2 ± 0.2, 2.0 ± 0.4 and 1.2 ± 0.4 mm/min) as found previously during supine prolonged breath-holds. No leakage of carbon dioxide or air was detectable into the facemask.

CONCLUSION

Single prolonged (>5 min) breath-holds are equally possible in the prone, front crawl position.

ADVANCES IN KNOWLEDGE

Prolonged breath-holds in the front crawl position are possible and have the same durations as in the supine position. Such training would therefore be feasible for some patients with breast cancer requiring loco-regional irradiation. It would have obvious advantages for hypofractionation.

Irradiating Residual Disease to 30 Gy with Proton Therapy in Pediatric Mediastinal Hodgkin Lymphoma

Background:

Local relapse is a predominant form of recurrence among pediatric patients with Hodgkin lymphoma (PHL). Although PHL radiotherapy doses have been approximately 20 Gy, adults with Hodgkin lymphoma receiving 30 to 36 Gy experience fewer in-field relapses. We investigated the dosimetric effect of such a dose escalation to the organs at risk (OARs).

Materials and Methods:

Ten patients with PHL treated with proton therapy to 21 Gy involved-site radiation therapy (ISRT_21Gy) were replanned to deliver 30 Gy by treating the ISRT to 30 Gy (ISRT_30Gy), delivering 21 Gy to the ISRT plus a 9-Gy boost to postchemotherapy residual volume (rISRT_boost), and delivering 30 Gy to the residual ISRT target only (rISRT_30Gy). Radiation doses to the OARs were compared.

Results:

The ISRT_30Gy escalated the dose to the target by 42% but also to the OARs. The rISRT_boost escalated the residual target dose by 42%, and the OAR dose by only 17% to 26%. The rISRT_30Gy escalated the residual target dose by 42% but reduced the OAR dose by 25% to 46%.

Conclusion:

Boosting the postchemotherapy residual target dose to 30Gy can allow for dose escalation with a slight OAR dose increase. Treating the residual disease for the full 30Gy, however, would reduce the OAR dose significantly compared with ISRT_21Gy. Studies should evaluate these strategies to improve outcomes and minimize the late effects.

The Feasibility of Implementing Deep Inspiration Breath-Hold for Pediatric Radiation Therapy

PURPOSE

Radiation therapy delivery during deep inspiration breath-hold (DIBH) reduces the irradiation of the heart and lungs and is therefore recommended for adults with mediastinal lymphoma. However, no studies have addressed the use of DIBH in children. This pilot study investigates the feasibility of and compliance with DIBH in children.

METHODS AND MATERIALS

Children from the age of 5 years were recruited to a training session to assess their ability to perform DIBH. No children received radiation therapy. The children were placed in a potential radiation therapy position. The DIBH was voluntary and monitored using an optical surface system providing visual feedback. Children who performed 3 stable DIBHs of 20 seconds each and remained motionless were deemed DIBH compliant. Compliance, equipment suitability, and coaching were further assessed in a semistructured interview.

RESULTS

We included 33 children (18 healthy and 15 hospitalized children with cancer) with a mean age of 8.5 years (range, 5-15). A total of 28 (85%) children were DIBH compliant. Twenty children were deemed immediately DIBH compliant, and 8 were deemed conditionally DIBH compliant, as DIBH compliance was presumed with custom-made immobilization and/or additional DIBH training. Mean age of the DIBH-compliant and the non-DIBH-compliant children was 8.9 years (range, 5-15) and 6 years (range, 5-9), respectively. Only 1 of 15 hospitalized children was not DIBH compliant and only 1 of all 33 children was unable to grasp the DIBH concept. The available DIBH equipment was suitable for children, and 94% reported that they were happy with training and performing DIBH.

CONCLUSIONS

This pilot study demonstrated that children from the age of 5 years can potentially comply with the DIBH technique and perform stable and reproducible DIBHs suitable for radiation therapy. Custom-made immobilization and adequate training will potentially increase DIBH compliance. A prospective clinical trial (NCT03315546), investigating the dosimetric benefit of radiation therapy delivery in DIBH compared with free breathing with pediatric patients, has been initiated.

Risk and Response Adapted Treatment Guidelines for Managing First Relapsed and Refractory Classical Hodgkin Lymphoma in Children and Young People. Recommendations from the EuroNet Pediatric Hodgkin Lymphoma Group

The objective of this guideline is to aid clinicians in making individual salvage treatment plans for pediatric and adolescent patients with first relapse or refractory (R/R) classical Hodgkin lymphoma (cHL). While salvage with standard dose chemotherapy followed by high dose chemotherapy and autologous stem cell transplant is often considered the standard of care in adult practice, pediatric practice adopts a more individualized risk stratified and response adapted approach to salvage treatment with greater use of non-transplant salvage. Here, we present on behalf of the EuroNet Pediatric Hodgkin Lymphoma group, evidence and consensus-based guidelines for standardized diagnostic, prognostic and response procedures to allocate children and adolescents with R/R cHL to stratified salvage treatments.

The feasibility, safety and optimization of multiple prolonged breath-holds for radiotherapy

BACKGROUND & PURPOSE

Multiple, short breath-holds are now used in single radiotherapy treatment sessions. Here we investigated the feasibility and safety of multiple prolonged breath-holds in a single session. We measured how long is a second breath-hold if we prematurely terminate a single, prolonged breath-hold of >5 min either by using a single breath of oxygen (O₂), or by reintroducing preoxygenation and hypocapnia. We also investigated the feasibility and safety of undertaking 9 prolonged breath-holds in a row.

MATERIALS & METHODS

30 healthy volunteers with no previous breath-holding experience were trained to perform single prolonged breath-holds safely.

RESULTS

Their mean single, prolonged breath-hold duration was 6.1 ± 0.3 se minutes (n = 30). In 18/18 subjects, premature termination (at 5.1 ± 0.2 min) with a single breath of 60% O₂, enabled a 2nd safe breath-hold lasting 3.3 ± 0.2 min. In 18/18 subjects, premature termination at 5.3 ± 0.2 min) by reintroducing preoxygenation and hypocapnia, enabled a 2nd safe breath-hold lasting 5.8 ± 0.3 min. 17/17 subjects could safely perform 9 successive prolonged breath-holds, each terminated (at 4.3 ± 0.2 min) by reintroducing preoxygenation and hypocapnia for 3.1 ± 0.2 min. The 9th unconstrained breath-hold (mean of 6.0 ± 0.3 min) lasted as long as their single breath-hold.

CONCLUSIONS

Multiple prolonged breath-holds are possible and safe. In a ∼19 min treatment session, it would therefore be possible to have ∼13 min for radiotherapy treatment (3 breath-holds) and ∼6 min for setup and recovery. In a 65 min session, it would be possible to have 41 min for radiotherapy and 25 min for setup and recovery.