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

Impact of Volumetric Dosimetry on the Projected Cost of Radiation-Related Late Effects Screening After Childhood Cancer: A Real-World Cohort Analysis

BACKGROUND

Screening guidelines for childhood cancer survivors treated with radiation currently rely on broad anatomic irradiated regions (IR) to determine risk for late effects. However, contemporary radiotherapy techniques use volumetric dosimetry (VD) to define organ-specific exposure, which supports more specific screening recommendations that could be less costly.

PATIENTS AND METHODS

This was a cross-sectional study of 132 patients treated with irradiation at Children's Hospital Los Angeles from 2000 to 2016. For 5 key organs (cochlea, breast, heart, lung, and colon), radiation exposure was determined retrospectively using both IR and VD methods. Under each method, Children's Oncology Group Long-Term Follow-Up Guidelines were used to identify organs flagged for screening and recommended screening tests. Projected screening costs incurred under each method were computed through age 65 using insurance claims data.

RESULTS

Median age at the end of treatment was 10.6 years (range, 1.4-20.4). Brain tumor was the most common diagnosis (45%) and head/brain the most common irradiated region (61%). For all 5 organs, use of VD rather than IR resulted in fewer recommended screening tests. This led to average cumulative estimated savings of $3769 (P = .099), with significant savings in patients with CNS tumors (P = .012). Among patients with savings, average savings were $9620 per patient (P = .016) and significantly more likely for females than males (P = .027).

CONCLUSION

Use of VD to enhance precision of guideline-based screening for radiation-related late effects permits fewer recommended screening tests and generates cost-savings.

Surveillance for radiation-related late effects in childhood cancer survivors: The impact of using volumetric dosimetry

BACKGROUND

Radiation-related screening guidelines for survivors of childhood cancer currently use irradiated regions (IR) to determine risk for late effects. However, contemporary radiotherapy techniques utilize volumetric dosimetry (VD) to determine organ-specific exposures, which could inform need for late effect surveillance.

METHODS

This cross-sectional cohort study involved patients treated for cancer using computerized tomography-planned irradiation at Children's Hospital Los Angeles from 2000-2016. Organs at risk were identified using both VD and IR. Under each method, Children's Oncology Group Long-Term Follow-Up Guidelines were applied to determine radiation-related potential late effects and their correlative recommended screening practices. Patients served as their own controls. Mean number of potential late effects per patient and recommended screening practices per patient per decade of follow-up were compared using paired t-tests; comparisons were adjusted for diagnosis and gender using random effects, repeated measure linear regression.

RESULTS

In this cohort (n = 132), median age at end of treatment was 10.6 years (range, 1.4-20.4). Brain tumor was the most common diagnosis (45%) and head/brain the most common irradiated region (61%). Under IR and VD, the mean number of potential late effects flagged was 24.4 and 21.7, respectively (-11.3%, p < 0.001); concordance between the two methods was 6.1%. Under VD, the difference in mean number of recommended screening practices per patient was -7.4% in aggregate but as large as -37.0% for diagnostic imaging and procedures (p < 0.001 for both).

CONCLUSION

Use of VD rather than IR is feasible and enhances precision of guideline-based screening for radiation-related late effects in long-term childhood cancer survivors.

Trajectories of psychosocial and cognitive functioning in pediatric patients with brain tumors treated with radiation therapy

BACKGROUND

Pediatric patients with brain tumors who are treated with radiation therapy (RT) are at risk for neurocognitive and psychosocial late effects. Research to date has primarily examined these outcomes at a group level and in isolation. Advanced statistical techniques allow for person-centered analyses, as well as examination of relationships between domain-specific trajectories.

METHODS

Patients with brain tumors (craniopharyngioma, ependymoma, low-grade astrocytoma, high-grade astrocytoma) were enrolled on a phase II clinical trial of RT. Three hundred and fifty patients completed serial neurocognitive assessments as part of their treatment monitoring, including pre-RT baseline, 6 months post-RT, and then yearly for 5 years. This secondary analysis focused on outcomes of cognition (estimated IQ, parent-reported attention problems) and psychosocial effects (parent-reported socialization and social problems) post-RT.

RESULTS

Latent growth curve modeling indicated that estimated IQ and socialization were best served by quadratic models, while attention and social problems were best served by linear models. Growth mixture modeling indicated 3-class models were the best fit for IQ and socialization, and 2-class models for attention and social problems. Baseline IQ and socialization scores were associated, but there was no association over time. Young age at diagnosis and pre-RT treatments (surgery, chemotherapy) were associated with class membership.

CONCLUSIONS

Person-centered statistical analyses provide rich information regarding the variability in neurocognitive and psychosocial functioning following RT for pediatric brain tumor. While many patients do well over time, a subset are exhibiting significant cognitive and/or psychosocial deficits. Class membership was associated with some medical factors (eg, pre-radiation surgery/chemotherapy, age at diagnosis, shunted hydrocephalus).

Leptomeningeal malignancy of childhood: sharing learning between childhood leukaemia and brain tumour trials

Leptomeningeal malignancy complicates childhood cancers, including leukaemias, brain tumours, and solid tumours. In leukaemia, such malignancy is thought to invade leptomeninges via the vascular route. In brain tumours, dissemination from the primary tumour, before or after surgery, via CSF pathways is assumed; however, evidence exists to support the vascular route of dissemination. Success in treating leptomeningeal malignancy represents a rate-limiting step to cure, which has been successfully overcome in leukaemia with intensified systemic therapy combined with intra-CSF therapy, which replaced cranial radiotherapy for many patients. This de-escalated CNS-directed therapy is still associated with some neurotoxicity. The balanced benefit justifies exploration of ways to further de-escalate CNS-directed therapy. For primary brain tumours, standard therapy is craniospinal radiotherapy, but attendant risk of acute and delayed brain injury and endocrine deficiencies compounds post-radiation impairment of spinal growth. Alternative ways of treating leptomeninges by intensifying drug therapy delivered to CSF are being investigated-preliminary evidence suggests improved outcomes. This Review seeks to describe methods of intra-CSF drug delivery and drugs in use, and consider how the technique could be modified and additional drugs might be selected for this route of administration.

How do patient characteristics and anatomical features correlate to accuracy of organ dose reconstruction for Wilms' tumor radiation treatment plans when using a surrogate patient's CT scan?

In retrospective radiation treatment (RT) dosimetry, a surrogate anatomy is often used for patients without 3D CT. To gain insight in what the crucial aspects in a surrogate anatomy are to enable accurate dose reconstruction, we investigated the relation of patient characteristics and internal anatomical features with deviations in reconstructed organ dose using surrogate patient's CT scans. Abdominal CT scans of 35 childhood cancer patients (age: 2.1-5.6 yr; 17 boys, 18 girls) undergoing RT during 2004-2016 were included. Based on whether an intact right or left kidney is present in the CT scan, two groups were formed each containing 24 patients. From each group, four CTs associated with Wilms' tumor RT plans with an anterior-posterior-posterior-anterior field setup were selected as references. For each reference, a 2D digitally reconstructed radiograph was computed from the reference CT to simulate a 2D radiographic image and dose reconstruction was performed on the other CTs in the respective group. Deviations in organ mean dose (DE_mean) of the reconstructions versus the references were calculated, as were deviations in patient characteristics (i.e. age, height, weight) and in anatomical features including organ volume, location (in 3D), and spatial overlaps. Per reference, the Pearson's correlation coefficient between deviations in DE_mean and patient characteristics/features were studied. Deviation in organ locations and DE_mean for the liver, spleen, and right kidney were moderately correlated (R² > 0.5) for 8/8, 5/8, and 3/4 reference plans, respectively. Deviations in organ volume or spatial overlap and DE_mean for the right and left kidney were weakly correlated (0.3 < R² < 0.5) in 4/4 and 1/4 reference plans. No correlations (R² < 0.3) were found between deviations in age or height and DE_mean. Therefore, the performance of organ dose reconstruction using surrogate patients' CT scans is primarily related to deviation in organ location, followed by volume and spatial overlap. Further, results were plan dependent.

Are age and gender suitable matching criteria in organ dose reconstruction using surrogate childhood cancer patients' CT scans?

PURPOSE

The purpose of this work was to assess the feasibility of using surrogate CT scans of matched patients for organ dose reconstructions for childhood cancer (CC) survivors, treated in the past with only 2D imaging data available instead of 3D CT data, and in particular using the current literature standard of matching patients based on similarity in age and gender.

METHODS

Thirty-one recently treated CC patients with abdominal CT scans were divided into six age- and gender-matched groups. From each group, two radiotherapy plans for Wilms' tumor were selected as reference plans and applied to the age- and gender-matched patients' CTs in the respective group. Two reconstruction strategies were investigated: S1) without field adjustments; S2) with manual field adjustments according to anatomical information, using a visual check in digitally reconstructed radiographs. To assess the level of agreement between the reconstructed and the reference dose distributions, we computed (using a collapsed cone algorithm) and compared the absolute deviation in mean and maximum dose normalized by the prescribed dose (i.e., normalized errors |NE_mean | and |NE_2cc |) in eight organs at risk (OARs): heart, lungs, liver, spleen, kidneys, and spinal cord. Furthermore, we assessed the quality of a reconstruction case by varying acceptance thresholds for |NE_mean | and |NE_2cc |. A reconstruction case was accepted (i.e., considered to pass) if the errors in all OARs are smaller than the threshold. The pass fraction for a given threshold was then defined as the percentage of reconstruction cases that were classified as a pass. Furthermore, we consider the impact of allowing to use a different CT scan for each OAR.

RESULTS

Slightly smaller reconstruction errors were achieved with S2 in multiple OARs than with S1 (P < 0.05). Among OARs, the best reconstruction was found for the spinal cord (average |NE_mean | and |NE_2cc | ≤ 4%). The largest average |NE_mean | was found in the spleen (18%). The largest average |NE_2cc | was found in the left lung (26%). Less than 30% of the reconstruction cases (i.e., pass fraction) meet the criteria that |NE_mean | < 20% and |NE_2cc | < 20% in all OARs when using age and gender matching and a single CT to do reconstructions. Allowing other matchings and combining reconstructions for OARs from multiple patients, the pass fraction increases substantially to more than 60%.

CONCLUSIONS

To conclude, reconstructions with small deviations can be obtained by using CC patients' CT scans, making the general approach promising. However, using age and gender as the only matching criteria to select a CT scan for the reconstruction is not sufficient to guarantee sufficiently low reconstruction errors. It is therefore suggested to include more features (e.g., height, features extracted from 2D radiographs) than only age and gender for dose reconstruction for CC survivors treated in the pre-3D radiotherapy planning era and to consider ways to combine multiple reconstructions focused on different OARs.

Patterns of relapse for children with localized intracranial ependymoma

We examined patterns of relapse and prognostic factors in children with intracranial ependymoma. Records of 82 children diagnosed with localized intracranial ependymoma were reviewed. 52% first presented to our institution after relapse. Median age at initial diagnosis was 4 years (range 0-18 years). Gender was 55% male. Initial tumor location was infratentorial in 71% and supratentorial in 29%. Histology was WHO Grade II in 32% and Grade III in 68%. As part of definitive management, 99% had surgery, 70% received RT (26% 2D/3D-conformal RT[CRT], 22% intensity-modulated RT [IMRT], 22% proton), and 37% received chemotherapy. Median follow-up was 4.6 years (range 0.2-32.9). Overall, 74% of patients relapsed (50% local, 17% distant, 7% local + distant) at a median 1.5 (range 0.1-17.5) years. Five-year OS and FFS for patients presenting prior to relapse are 70% (95% confidence interval [CI], 50-83%) and 48% (95% CI 30-64%), respectively. On log-rank, superior overall survival (OS) was demonstrated for gross total resection (p = 0.03). Superior failure-free survival (FFS) was demonstrated for age < 5 years (p = 0.04). No difference in OS or FFS was found between 2D/3D-CRT versus IMRT/proton (p > 0.05). On multivariate analysis, age ≤ 5 was independently associated with a lower risk of death and failure versus older patients (p < 0.05). Contrary to previous reports, young age may not be a poor prognostic factor in patients who can tolerate intensive treatment. Future studies examining patients stratified by clinical and molecular attributes are warranted.

Reduced-volume radiotherapy for patients with localized intracranial nongerminoma germ cell tumors

Craniospinal irradiation is standard radiotherapy (RT) for localized intracranial nongerminoma germ cell tumors (NGGCT). Given its toxicity, there is interest in using smaller fields. We examined outcomes of NGGCT patients receiving reduced-volume RT at a single institution. Records of 16 patients who received reduced-volume RT as part of definitive treatment between 1996 and 2016 were reviewed. Median age at presentation was 10.8 years (range 4.6-41.0 years). Ten patients had pineal tumors and 6 had suprasellar tumors. All received chemotherapy and 9 patients received second-look surgery thereafter. RT volume was tumor-only to a median of 54 Gy (range 50.4-54 Gy) in 3 patients and whole-ventricle irradiation to a median of 30.6 Gy (range 30.6-36 Gy) with a boost to 54 Gy in 13 patients. Median follow-up was 4.1 years (range 1.9-19.3 years). Three patients recurred locally at a median 9.9 months (range 9.6-10.6 months) after diagnosis, and one of these developed leptomeningeal relapse after 30 months. One patient expired from disease 2.6 years post-diagnosis and another due to stroke 19.3 years post-diagnosis. Fourteen patients are alive with no evidence of disease. Kaplan-Meier estimates of the 4-year overall survival and failure-free survival are 92% (95% confidence interval [CI], 57-99%) and 81% (95% CI 53-94%), respectively. Excellent disease control was observed in these patients with no initial relapses outside of these RT fields. The results of ACNS1123 may better delineate patterns of failure and identify subgroups likely to benefit from this approach.

A chemical screen for medulloblastoma identifies quercetin as a putative radiosensitizer

Treatment of medulloblastoma in children fails in approximately 30% of patients, and is often accompanied by severe late sequelae. Therefore, more effective drugs are needed that spare normal tissue and diminish long-term side effects. Since radiotherapy plays a pivotal role in the treatment of medulloblastoma, we set out to identify novel drugs that could potentiate the effect of ionizing radiation.Thereto, a small molecule library, consisting of 960 chemical compounds, was screened for its ability to sensitize towards irradiation. This small molecule screen identified the flavonoid quercetin as a novel radiosensitizer for the medulloblastoma cell lines DAOY, D283-med, and, to a lesser extent, D458-med at low micromolar concentrations and irradiation doses used in fractionated radiation schemes. Quercetin did not affect the proliferation of neural precursor cells or normal human fibroblasts. Importantly, in vivo experiments confirmed the radiosensitizing properties of quercetin. Administration of this flavonoid at the time of irradiation significantly prolonged survival in orthotopically xenografted mice. Together, these findings indicate that quercetin is a potent radiosensitizer for medulloblastoma cells that may be a promising lead for the treatment of medulloblastoma in patients.

Proton therapy for the treatment of children with CNS malignancies

Proton therapy is a novel technique for treating pediatric malignancies. As a tool to reduce normal-tissue dose, it has the potential to decrease late toxicity. Although proton therapy has been used for over five decades, most pediatric dosimetry studies and clinical series have been published over the last 10 years. The purpose of this article is to review the physical, radiobiological and economic rationales for proton therapy in pediatric CNS malignancies, and provide an overview of the current challenges and future direction of research and utilization of this approach.

Proton beam therapy: a fad or a new standard of care

PURPOSE OF REVIEW

Newer methods and advances in radiation therapy promise to reduce the risk of complications in children who require irradiation. They have secured the role of radiation therapy in the treatment of a variety of pediatric central nervous system and solid tumors and for young patients enrolled on clinical trials.

RECENT FINDINGS

Proton therapy is the latest advancement in radiation therapy. Its availability is increasing as new centers are built throughout the United States. Pediatric specialists should understand that proton therapy is in its pioneering stage of development and that advantages have not been quantitatively demonstrated. Proton therapy clearly reduces collateral radiation dose to normal tissue when compared with photon (X-ray)-based methods of irradiation and has the potential to selectively and safely escalate dose to high-risk tumors; however, research results are lacking in both of these areas, leading to some confusion among pediatric specialists with regard to indications and the need to refer patients for this limited resource and expensive form of radiation therapy.

SUMMARY

This review highlights a number of issues surrounding proton therapy in children and supports the use of proton therapy in clinical trials.