Differential attenuation of clavicle growth after asymmetric mantle radiotherapy

Auto-segmentation of important centers of growth in the pediatric skeleton to consider during radiation therapy based on deep learning

BACKGROUND

Routinely delineating of important skeletal growth centers is imperative to mitigate radiation-induced growth abnormalities for pediatric cancer patients treated with radiotherapy. However, it is hindered by several practical problems, including difficult identification, time consumption, and inter-practitioner variability.

PURPOSE

The goal of this study was to construct and evaluate a novel Triplet-Attention U-Net (TAU-Net)-based auto-segmentation model for important skeletal growth centers in childhood cancer radiotherapy, concentrating on the accuracy and time efficiency.

METHODS

A total of 107 childhood cancer patients fulfilled the eligibility criteria were enrolled in the training cohort (N = 80) and test cohort (N = 27). The craniofacial growth plates, shoulder growth centers, and pelvic ossification centers, with a total of 19 structures in the three groups, were manually delineated by two experienced radiation oncologists on axial, coronal, and sagittal computed tomography images. Modified from U-Net, the proposed TAU-Net has one main branch and two bypass branches, receiving semantic information of three adjacent slices to predict the target structure. With supervised deep learning, the skeletal growth centers contouring of each group was generated by three different auto-segmentation models: U-Net, V-Net, and the proposed TAU-Net. Dice similarity coefficient (DSC) and Hausdorff distance 95% (HD95) were used to evaluate the accuracy of three auto-segmentation models. The time spent on performing manual tasks and manually correcting auto-contouring generated by TAU-Net was recorded. The paired t-test was used to compare the statistical differences in delineation quality and time efficiency.

RESULTS

Among the three groups, including craniofacial growth plates, shoulder growth centers, and pelvic ossification centers groups, TAU-Net had demonstrated highly acceptable performance (the average DSC = 0.77, 0.87, and 0.83 for each group; the average HD95 = 2.28, 2.07, and 2.86 mm for each group). In the overall evaluation of 19 regions of interest (ROIs) in the test cohort, TAU-Net had an overwhelming advantage over U-Net (63.2% ROIs in DSC and 31.6% ROIs in HD95, p = 0.001-0.042) and V-Net (94.7% ROIs in DSC and 36.8% ROIs in HD95, p = 0.001-0.040). With an average time of 52.2 min for manual delineation, the average time saved to adjust TAU-Net-generated contours was 37.6 min (p < 0.001), a 72% reduction.

CONCLUSIONS

Deep learning-based models have presented enormous potential for the auto-segmentation of important growth centers in pediatric skeleton, where the proposed TAU-Net outperformed the U-Net and V-Net in geometrical precision for the majority status.

A novel inverse optimization based three-dimensional conformal radiotherapy technique in craniospinal irradiation

Our aim was to develop a novel inverse optimization-based three-dimensional conformal radiotherapy (i3DCRT) technique for craniospinal irradiation. The imaging data of 20 patients with medulloblastoma were used retrospectively. The first group included 10 pediatric patients with supine position treated under anesthesia/sedation, and the second group included 10 young adult/adult patients treated with prone position. Three different treatment plans were created for each patient via i3DCRT, forward-planned three-dimensional conformal radiotherapy (f3DCRT) and intensity-modulated radiotherapy (IMRT) techniques. A total dose of 36 Gy was prescribed in 20 fractions for all plans. The comparative evaluation was conducted by using the parameters of conformity-index, homogeneity-index, and doses to the target volumes and organs at risk (OARs). The plans created with i3DCRT technique achieved better conformity and homogeneity compared to f3DCRT. In terms of OARs sparing, we found pronounced dose reductions in esophagus and heart in i3DCRT compared to f3DCRT plans. i3DCRT technique also provided a well-conformed dose distribution not superior, but comparable, to IMRT without increase in the total monitor unit per fraction (MU/fx) with respect to f3DCRT. The average monitor unit per fraction (MU/fx) for i3DCRT, f3DCRT and IMRT plans were found as 379.3, 378.0 and 1051.7 MU for the first group and 577.4, 563.5 and 1368.7 MU for the second group, respectively. Novel i3DCRT technique solves the problems associated with field junctions and beam edge matching encountered in f3DCRT plans. Additionally, i3DCRT technique can create almost similar plans as with IMRT with lower total MU/fx.

Radiotherapy toxicity

Radiotherapy is used in >50% of patients with cancer, both for curative and palliative purposes. Radiotherapy uses ionizing radiation to target and kill tumour tissue, but normal tissue can also be damaged, leading to toxicity. Modern and precise radiotherapy techniques, such as intensity-modulated radiotherapy, may prevent toxicity, but some patients still experience adverse effects. The physiopathology of toxicity is dependent on many parameters, such as the location of irradiation or the functional status of organs at risk. Knowledge of the mechanisms leads to a more rational approach for controlling radiotherapy toxicity, which may result in improved symptom control and quality of life for patients. This improved quality of life is particularly important in paediatric patients, who may live for many years with the long-term effects of radiotherapy. Notably, signs and symptoms occurring after radiotherapy may not be due to the treatment but to an exacerbation of existing conditions or to the development of new diseases. Although differential diagnosis may be difficult, it has important consequences for patients.

A Road Map for Important Centers of Growth in the Pediatric Skeleton to Consider During Radiation Therapy and Associated Clinical Correlates of Radiation-Induced Growth Toxicity

With the increasing use of advanced radiation techniques such as intensity modulated radiation therapy, stereotactic radiation therapy, and proton therapy, radiation oncologists now have the tools to mitigate radiation-associated toxicities. This is of utmost importance in the treatment of a pediatric patient. To best use these advanced techniques to mitigate radiation-induced growth abnormalities, the radiation oncologist should be equipped with a nuanced understanding of the anatomy of centers of growth. This article aims to enable the radiation oncologist to better understand, predict, and minimize radiation-mediated toxicities on growth. We review the process of bone development and radiation-induced growth abnormalities and provide an atlas for contouring important growth plates to guide radiation treatment planning. A more detailed recognition of important centers of growth may improve future treatment outcomes in children receiving radiation therapy.

Mandibular growth in survivors of pediatric parotid gland carcinoma treated with interstitial brachytherapy

BACKGROUND

The aim of the study was to present long-term results of mandibular growth in pediatric parotid gland carcinoma survivors treated with interstitial brachytherapy.

PROCEDURE

Twenty-five survivors of pediatric parotid gland carcinoma treated with iodine-125 seed interstitial brachytherapy were included for quantitative analysis, including three dimensional (3D) cephalometry and measurement of mandibular volume.

RESULTS

3D cephalometry showed that the median fore-and-aft increments of the lengths of the condyle, the ramus, and the body of the mandible were 1.23, 0.19, and 1.66 mm for the affected side, respectively, and were 1.37, 1.95, and 3.42 mm for the unaffected side, respectively. The difference in increments of the ramus was statistically significant between the affected side and the unaffected side (P = 0.003; P < 0.05). Moreover, mandibular volume measurements showed that the median fore-and-aft increments of the volumes of the condyle, the ramus, and the body of the mandible were 290.62, 220.14, and 1706.40 mm³ for the affected side, respectively, and were 269.15, 370.40, and 1469.86 mm³ for the unaffected side, respectively. The difference in increments was statistically significant between the affected side and the unaffected side for the ramus (P = 0.005; P < 0.05) and the body (P = 0.043; P < .05).

CONCLUSION

Mandibular growth was affected by interstitial brachytherapy, especially for the ramus, in pediatric parotid gland carcinoma survivors treated with interstitial brachytherapy. Nevertheless, the impact was mild in these survivors.

Proton versus conventional radiotherapy for pediatric salivary gland tumors: Acute toxicity and dosimetric characteristics

PURPOSE

We evaluated acute toxicity profiles and dosimetric data for children with salivary gland tumors treated with adjuvant photon/electron-based radiation therapy (X/E RT) or proton therapy (PRT).

METHODS AND MATERIALS

We identified 24 patients who had received adjuvant radiotherapy for salivary gland tumors. Data were extracted from the medical records and the treatment planning systems. Toxicity was scored according to the Common Terminology Criteria for Adverse Effects 4.0.

RESULTS

Eleven patients received X/E RT and 13 PRT, with a median prescribed dose of 60 Gy in each group. In the X/E RT group, 54% of patients developed acute grade II/III dermatitis, 27% grade II/III dysphagia, and 91% grade II/III mucositis, and the median weight loss was 5.3% with one patient requiring feeding tube placement. In the PRT group, 53% had acute grade II/III dermatitis, 0% grade II/III dysphagia, and 46% grade II/III mucositis, with a median weight gain of 1.2%. Additionally, PRT was associated with lower mean doses to several normal surrounding midline and contralateral structures.

CONCLUSION

In this retrospective study of pediatric salivary tumors, PRT was associated with a favorable acute toxicity and dosimetric profile. Continued follow-up is needed to identify long-term toxicity and survival data.

Impairments that influence physical function among survivors of childhood cancer

Children treated for cancer are at increased risk of developing chronic health conditions, some of which may manifest during or soon after treatment while others emerge many years after therapy. These health problems may limit physical performance and functional capacity, interfering with participation in work, social, and recreational activities. In this review, we discuss treatment-induced impairments in the endocrine, musculoskeletal, neurological, and cardiopulmonary systems and their influence on mobility and physical function. We found that cranial radiation at a young age was associated with broad range of chronic conditions including obesity, short stature, low bone mineral density and neuromotor impairments. Anthracyclines and chest radiation are associated with both short and long-term cardiotoxicity. Although numerous chronic conditions are documented among individuals treated for childhood cancer, the impact of these conditions on mobility and function are not well characterized, with most studies limited to survivors of acute lymphoblastic leukemia and brain tumors. Moving forward, further research assessing the impact of chronic conditions on participation in work and social activities is required. Moreover, interventions to prevent or ameliorate the loss of physical function among children treated for cancer are likely to become an important area of survivorship research.

Survivors of childhood and adolescent cancer: life-long risks and responsibilities

Survival rates for most paediatric cancers have improved at a remarkable pace over the past four decades. In developed countries, cure is now the probable outcome for most children and adolescents who are diagnosed with cancer: their 5-year survival rate approaches 80%. However, the vast majority of these cancer survivors will have at least one chronic health condition by 40 years of age. The burden of responsibility to understand the long-term morbidity and mortality that is associated with currently successful treatments must be borne by many, including the research and health care communities, survivor advocacy groups, and governmental and policy-making entities.

Children's Oncology Group's 2013 blueprint for research: radiation oncology

Radiation therapy (RT) is used to treat children with CNS tumors, solid tumors or Hodgkin lymphoma. Pediatric radiation oncologists have provided critical input into the development and implementation of concepts for clinical trials to further define the modality's role and test newer methods to reduce side effects or intensify therapy. The quality of pediatric oncology clinical trials that include radiation therapy is linked to the quality of guidelines. Radiation oncology is an adult medical specialty; thus, pediatric radiation oncologists are uniquely positioned to work with adult cancer investigators in the reorganized US National Cancer Institute Clinic Trials Network.

Proton radiotherapy for pediatric bladder/prostate rhabdomyosarcoma: clinical outcomes and dosimetry compared to intensity-modulated radiation therapy

PURPOSE

In this study, we report the clinical outcomes of 7 children with bladder/prostate rhabdomyosarcoma (RMS) treated with proton radiation and compare proton treatment plans with matched intensity-modulated radiation therapy (IMRT) plans, with an emphasis on dose savings to reproductive and skeletal structures.

METHODS AND MATERIALS

Follow-up consisted of scheduled clinic appointments at our institution or direct communication with the treating physicians for referred patients. Each proton radiotherapy plan used for treatment was directly compared to an IMRT plan generated for the study. Clinical target volumes and normal tissue volumes were held constant to facilitate dosimetric comparisons. Each plan was optimized for target coverage and normal tissue sparing.

RESULTS

Seven male patients were treated with proton radiotherapy for bladder/prostate RMS at the Massachusetts General Hospital between 2002 and 2008. Median age at treatment was 30 months (11-70 months). Median follow-up was 27 months (10-90 months). Four patients underwent a gross total resection prior to radiation, and all patients received concurrent chemotherapy. Radiation doses ranged from 36 cobalt Gray equivalent (CGE) to 50.4 CGE. Five of 7 patients were without evidence of disease and with intact bladders at study completion. Target volume dosimetry was equivalent between the two modalities for all 7 patients. Proton radiotherapy led to a significant decrease in mean organ dose to the bladder (25.1 CGE vs. 33.2 Gy; p=0.03), testes (0.0 CGE vs. 0.6 Gy; p=0.016), femoral heads (1.6 CGE vs. 10.6 Gy; p=0.016), growth plates (21.7 CGE vs. 32.4 Gy; p=0.016), and pelvic bones (8.8 CGE vs. 13.5 Gy; p=0.016) compared to IMRT.

CONCLUSIONS

This study provides evidence of significant dose savings to normal structures with proton radiotherapy compared to IMRT and is well tolerated in this patient population. The long-term impact of these reduced doses can be tested in future studies incorporating extended follow-up, objective outcome measures, and quality-of-life analyses.

Radiation-related treatment effects across the age spectrum: differences and similarities or what the old and young can learn from each other

Radiation related effects in children and adults limit the delivery of effective radiation doses and result in long-term morbidity affecting function and quality of life. Improvements in our understanding of the etiology and biology of these effects, including the influence of clinical variables, dosimetric factors, and the underlying biological processes have made treatment safer and more efficacious. However, the approach to studying and understanding these effects differs between children and adults. Using the pulmonary and skeletal organ systems as examples, comparisons are made across the age spectrum for radiation related effects, including pneumonitis, pulmonary fibrosis, osteonecrosis, and fracture. Methods for dosimetric analysis, incorporation of imaging and biology as well a length of follow-up are compared, contrasted, and discussed for both organ systems in children and adults. Better understanding of each age specific approach and how it differs may improve our ability to study late effects of radiation across the ages.

Treatment planning and delivery of external beam radiotherapy for pediatric sarcoma: the St. Jude Children's Research Hospital experience

PURPOSE

To describe and review the radiotherapy (RT) treatment planning and delivery techniques used for pediatric sarcoma patients at St. Jude Children's Research Hospital. The treatment characteristics serve as a baseline for future comparison with developing treatment modalities.

PATIENTS AND METHODS

Since January 2003, we have prospectively treated pediatric and young-adult patients with soft-tissue and bone sarcomas on an institutional Phase II protocol evaluating local control and RT-related treatment effects from external-beam RT (conformal or intensity-modulated RT; 83.4%), low-dose-rate brachytherapy (8.3%), or both (8.3%). Here we describe the treatment dosimetry and delivery parameters of the initial 72 patients (median, 11.6 years; range, 1.4-21.6 years).

RESULTS

Cumulative doses from all RT modalities ranged from 41.4 to 70.2 Gy (median, 50.4 Gy). Median D(95) and V(95) of the planning target volume of external-beam RT plans were, respectively, 93.4% of the prescribed dose and 94.6% of the target volume for the primary phase and 97.8% and 99.2% for the cone-down/boost phase. The dose-volume histogram statistics for 27 critical organs varied greatly. The spinal cord in 13 of 36 patients received dose >45 Gy (up to 52 Gy in 1 cc) because of tumor proximity.

CONCLUSIONS

Planning and delivery of complex multifield external beam RT is feasible in pediatric patients with sarcomas. Improvements on conformity and dose gradients are still desired in many cases with sensitive adjacent critical structures. Long-term follow-up will determine the risk of local failure and the benefit of normal tissue avoidance for this population.

Estimating differences in volumetric flat bone growth in pediatric patients by radiation treatment method

PURPOSE

To estimate potential differences in volumetric bone growth in children with sarcoma treated with intensity-modulated (IMRT) and conformal (CRT) radiation therapy using an empiric dose-effect model.

METHODS AND MATERIALS

A random coefficient model was used to estimate potential volumetric bone growth of 36 pelvic bones (ischiopubis and ilium) from 11 patients 4 years after radiotherapy. The model incorporated patient age, pretreatment bone volume, integral dose >35 Gy, and time since completion of radiation therapy. Three dosimetry plans were entered into the model: the actual CRT/IMRT plan, a nontreated comparable IMRT/CRT plan, and an idealized plan in which dose was delivered only to the planning target volume. The results were compared with modeled normal bone growth.

RESULTS

The model predicted that by using the idealized, IMRT, and CRT approaches, patients would maintain 93%, 87%, and 84%, respectively (p = 0.06), of their expected normal growth. Patients older than 10 years would maintain 98% of normal growth, regardless of treatment method. Those younger than 10 years would maintain 87% (idealized), 76% (IMRT), or 70% (CRT) of their expected growth (p = 0.015). Post hoc testing (Tukey) revealed that the CRT and IMRT approaches differed significantly from the idealized one but not from each other.

CONCLUSIONS

Dose-effect models facilitate the comparison of treatment methods and potential interventions. Although treatment methods do not alter the growth of flat bones in older pediatric patients, they may significantly impact bone growth in children younger than age 10 years, especially as we move toward techniques with high conformity and sharper dose gradient.

Final results of a prospective clinical trial with VAMP and low-dose involved-field radiation for children with low-risk Hodgkin's disease

PURPOSE

To evaluate outcome and assess complications in children and adolescents with low-risk Hodgkin's disease treated with vinblastine, doxorubicin, methotrexate, and prednisone (VAMP) chemotherapy and low-dose, involved-field radiation therapy (IFRT).

PATIENTS AND METHODS

One hundred ten children with low-risk Hodgkin's disease were treated with four cycles of VAMP and 15 Gy IFRT for those who achieved a complete response (CR) or 25.5 Gy for those with a partial response after two cycles of VAMP.

RESULTS

With median follow-up of 9.6 years (range, 1.7 to 15.0), 5- and 10-year overall survival were 99.1% and 96.1%, respectively, and 5-and 10-year event-free survival (EFS) were 92.7% and 89.4%. Factors contributing to 10-year EFS were: early CR (P = .02), absence of B symptoms (P = .01), lymphocyte predominant histologic subtype (P = .04), and less than three initial sites of disease (P = .02). Organ toxicity has been limited to correctable hypothyroidism in 42% of irradiated patients, and one case of cardiac dysfunction. Seventeen healthy babies have been born to 106 survivors. There have been two malignant tumors: one thyroid cancer within the radiation therapy field and one Ewing's sarcoma outside the radiation therapy field.

CONCLUSION

Risk-adapted, combined-modality therapy using VAMP chemotherapy with radiation is effective and well tolerated. Pediatric patients with low-risk Hodgkin's disease can be cured with therapy without an alkylating agent, bleomycin, etoposide, or high-dose, extended-field radiotherapy. Thus, these children are expected to retain normal fertility, organ function, and be at low risk of a second malignant tumor.

A model for quantitative changes in the magnetic resonance parameters of muscle in children after therapeutic irradiation

PURPOSE/OBJECTIVE

This study aimed to develop objective models of radiation effects on musculature in children with soft tissue sarcoma using treatment dosimetry and clinical and quantitative magnetic resonance imaging (MRI) parameters that may be used to guide treatment planning or predict side effects.

METHODS

In the initial 13 patients undergoing external beam radiation therapy (RT) on a Phase II study of conformal or intensity-modulated RT for the treatment of soft tissue sarcoma approved by an Institutional Review Board, we evaluated quantitative MRI changes in the musculature to assess radiation-related treatment effects. Patients with soft tissue sarcoma, including Ewing's sarcoma, had quantitative T1, T2 and dynamic enhanced MRI (DEMRI) performed before, during (Week 4) and after RT (Week 12). Regions of interest were selected in consistent locations within and outside the high-dose regions (on ipsilateral and contralateral sides when available). Mean RT dose, T1, T2 and DEMRI parameters were calculated and modeled using a mixed random coefficient dose model.

RESULTS

The mean doses to the high- and low-dose regions were 56.4 Gy (41.8-75.3 Gy) and 13.0 Gy (0.1-37.5 Gy), respectively. Compared with tissues distant from the tumor bed, maximal enhancement was significantly increased in tissues adjacent to the tumor/tumor bed prior to RT (60.6 vs. 44.2, P=.045) and remained elevated after 12 weeks. T1 was significantly elevated in tissues adjacent to the tumor bed prior to RT (942.4 vs. 759.0, P=.0078). The slope of longitudinal change in T1 was greater for tissues that received low-dose irradiation than those that received high-dose irradiation (P=.0488). The effect of dose on the slope of T2 was different (P=.0333) when younger and older patients are compared.

CONCLUSIONS

Acute affects of irradiation in muscle are quantifiable via MRI. These models provide evidence that quantifiable MRI parameters may be correlated with patient parameters of radiation dose and clinical factors including patient age. Long-term follow-up will be required to determine if acute changes correlate with clinically significant late effects.

The Effect of Radiation Therapy on Normal Tissue Function

As more patients are treated for their primary malignancy with cure or increased disease-free intervals, injury to normal tissues will become more detectable and an important endpoint for study. Future protocols will probably be modified based on toxicity endpoints. In Hodgkin's disease, current protocols use response-based treatment strategies to limit therapy. The objective is to provide the same level of tumor control and follow normal tissue endpoints for outcome analysis. DVH analysis has improved the ability to analyze endpoint data for normal tissues. These image-guided platforms will provide the infrastructure needed to continue efforts in improving the delivery of radiation therapy.

The effects of external beam irradiation on the growth of flat bones in children: modeling a dose-volume effect

PURPOSE

To model the effects of external beam irradiation on the developing flat bones of pediatric patients undergoing radiation therapy (RT) for tumors involving the musculoskeletal system.

METHODS AND MATERIALS

Patients with image-guided RT plans including areas adjacent to facial or pelvic flat bones underwent retrospective contouring of nontumor involved flat bones ipsilateral and contralateral to the treatment side. Radiation dose-volume information and bone volume data (initial and the most recent follow-up) were analyzed in 15 paired flat bones from 10 patients (ages 1.0-17.0 years). The models to predict bone growth after completion of RT (v(post)) were based on initial bone volume (v(pre)), the patient's age, time to follow-up (t), and the dose-volume parameter (v(Int35+)).

RESULTS

We developed a dose effects model as follows: Log (v(post) / v(pre)) = beta(time)t + beta(age group)t + beta(dose)t v(Int35). The dose-volume parameter v(Int35) predicted significantly for alterations in growth in younger patients, but not for older patients. The predictability of the fitted model for relative change in bone growth improved in the younger age group with the addition of the dose-volume term v(Int35) (correlation coefficient of r = 0.5510 to r = 0.6760 with the addition v(Int35)).

CONCLUSIONS

Our model accurately predicted flat bone growth and is notable for the inclusion of radiation dose-volume information, which is now available in the image-guided RT era. Further refinement of this model in a prospective patient population is underway.

Special issues in pediatric Hodgkin's disease

Childhood Hodgkin's disease (HD) is not a biologically unique disease; it differs from adult HD primarily in the relative incidence of disease histology. Preadolescent children are more likely to have Mixed Cellularity and nodular lymphocyte predominant HD. Adolescent and young adult HD is indistinguishable, with a predominance of nodular sclerosing (NS) HD. Nonetheless, treatment paradigms have diverged over the years as pediatric oncologists responded first to developmental issues in the young child, and later to the long-term treatment consequences in all young survivors. The latter concerns are of equal relevance to the young adult with HD. The increasing convergence of treatment approaches in the past decade is therefore most appropriate. Reproductive potential, risk of secondary malignancy and cardiopulmonary consequences of therapy have driven the pediatric treatment paradigm of care. Chemotherapy with low dose, limited field radiation is standard, with low-stage patients often treated by chemotherapy alone. Algorithms tailor therapy to response. The prognostic importance of very early chemotherapy response rather than end-of-chemotherapy response has led the Children's Oncology Group to use early response (after 6 wk) to titrate individual therapy and dense regimens to maximize the early response rates. Although the dose dense regimens of adult groups are similar, the pediatric algorithms emphasize using the enhanced efficacy to limit cumulative therapy. This review intends to address the special issues of childhood HD, with the intent of further encouraging understanding that will foster convergence of pediatric and adult treatment paradigms.