Hypothyroidism after craniospinal irradiation with proton or photon therapy in patients with medulloblastoma

Proton PBS Planning Techniques, Robustness Evaluation, and OAR Sparing for the Whole-Brain Part of Craniospinal Axis Irradiation

Proton therapy is a promising modality for craniospinal irradiation (CSI), offering dosimetric advantages over conventional treatments. While significant attention has been paid to spine fields, for the brain fields, only dose reduction to the lens of the eye has been reported. Hence, the objective of this study is to assess the potential gains and feasibility of adopting different treatment planning techniques for the entire brain within the CSI target. To this end, eight previously treated CSI patients underwent retrospective replanning using various techniques: (1) intensity modulated proton therapy (IMPT) optimization, (2) the modification/addition of field directions, and (3) the pre-optimization removal of superficially placed spots. The target coverage robustness was evaluated and dose comparisons for lenses, cochleae, and scalp were conducted, considering potential biological dose increases. The target coverage robustness was maintained across all plans, with minor reductions when superficial spot removal was utilized. Single- and multifield optimization showed comparable target coverage robustness and organ-at-risk sparing. A significant scalp sparing was achieved in adults but only limited in pediatric cases. Superficial spot removal contributed to scalp V30 Gy reduction at the expense of lower coverage robustness in specific cases. Lens sparing benefits from multiple field directions, while cochlear sparing remains impractical. Based on the results, all investigated plan types are deemed clinically adoptable.

Proton versus photon radiation therapy: A clinical review

While proton radiation therapy offers substantially better dose distribution characteristics than photon radiation therapy in certain clinical applications, data demonstrating a quantifiable clinical advantage is still needed for many treatment sites. Unfortunately, the number of patients treated with proton radiation therapy is still comparatively small, in some part due to the lack of evidence of clear benefits over lower-cost photon-based treatments. This review is designed to present the comparative clinical outcomes between proton and photon therapies, and to provide an overview of the current state of knowledge regarding the effectiveness of proton radiation therapy.

Endocrinopathy After Treatment for Medulloblastoma: Results From the SJMB03 Trial of Risk-Adapted Radiation Therapy

PURPOSE

The objective of this study was to estimate the cumulative incidence of endocrinopathy in pediatric patients treated for medulloblastoma with surgery, risk-adapted photon craniospinal irradiation, and dose-intensive chemotherapy.

METHODS AND MATERIALS

Children and adolescents (n = 156) treated between 2003 and 2013 were evaluated for evidence of endocrinopathy. Clinical information and mean radiation dose to hypothalamus and thyroid were calculated and used to estimate cumulative incidence of growth hormone deficiency, hypothyroidism, adrenal insufficiency, hypogonadism, and precocious puberty.

RESULTS

The 5-year cumulative incidences were estimated for growth hormone deficiency, 68.9% (60.9%, 75.6%); hypothyroidism, 48.4% (95% confidence interval (CI), 40.2%-56.1%); adrenal insufficiency, 13.0% (95% CI, 8.3%-18.9%); hypogonadism, 33.9% (95% CI, 25.2%-42.7%); and precocious puberty, 2.0% (95% CI, 0.6%-5.4%). Growth hormone deficiency was associated with increased hypothalamus dose (hazard ratio [HR], 1.035; 95% CI, 1.010-1.061; P = .0055) in average-risk patients and cerebrospinal fluid shunt (HR, 2.532; 95% CI, 1.325-4.838; P = .0049) in high-risk patients. In average-risk patients, hypothyroidism was associated with younger age (HR, 0.902; 95% CI, 0.842-0.973; P = .0070), hypothalamus dose (HR, 1.039; 95% CI, 1.004-1.075; P = .0273), and thyroid dose (HR, 1.070; 95% CI, 1.008-1.136; P = .0263). In high-risk patients, hypothyroidism was associated with increased hypothalamus dose (HR, 1.068; 95% CI, 0.995-1.147; P = .0671) and thyroid dose (HR, 1.050; 95% CI, 1.000-1.104; P = .0515). Adrenal insufficiency was associated with increased hypothalamus dose (HR, 1.112; 95% CI, 1.058-1.170; P < .0001). Growth hormone deficiency incidence was higher when comparing patients treated with cerebrospinal fluid shunt versus those not having a shunt/extraventricular drain placed during initial surgery (HR, 1.712; 95% CI, 1.109-2.643).

CONCLUSIONS

Incidence and time to onset of clinically significant endocrinopathy after photon craniospinal irradiation for pediatric medulloblastoma is influenced by radiation dose to target organs and patient age at time of treatment. Advanced radiation therapy methods and dose-reduction strategies are needed to reduce the incidence of endocrinopathy.

Management of childhood cancer survivors at risk for thyroid function abnormalities: A Delphi study

BACKGROUND

Thyroid function abnormalities can occur after treatment for childhood cancer. Evidence for the management of thyroid dysfunction among asymptomatic childhood cancer survivors (CCS) is lacking. We used a Delphi consensus methodology to expand guidelines for screening asymptomatic CCS at risk for thyroid dysfunction and explore recommendations for the clinical management of abnormal results.

PROCEDURE

A Delphi panel of 40 expert physicians representing oncology, endocrinology, and primary care participated in three rounds of anonymous, iterative questionnaires formatted as clinical scenarios. Consensus is defined as ≥ 90% of panelists agree with recommendation and disagreement as < 70% agree.

RESULTS

Panelists reached consensus that CCS treated with radiation including neck, total body, whole brain, brain including the hypothalamic-pituitary axis (HPA), and therapeutic meta-iodobenzylguanidine (MIBG) should have annual, lifelong screening using serum thyroid-stimulating hormone (TSH) and free T4 starting within one year off-treatment (98%). Panelists disagreed on continuing to screen CCS for thyroid dysfunction after immunotherapy associated with acute thyroid injury (31%-50%). There was also disagreement on indications for brain (17%-43%) or thyroid (50%-65%) imaging, laboratory tests to assess the HPA (29%-75%), and TSH threshold to initiate treatment of subclinical hypothyroidism. Lack of evidence was the most frequent rationale panelists offered for not recommending additional testing or medications. Panelists' recommendations did not vary by geography, specialty, or survivorship clinical experience.

CONCLUSIONS

Consensus was reached on most recommendations for screening and management of cancer treatment-related thyroid dysfunction. Screening after completion of thyroid-toxic immunotherapy, indications for imaging, and treatment of subclinical hypothyroidism are areas of disagreement for further investigation.

Medulloblastoma in the Modern Era: Review of Contemporary Trials, Molecular Advances, and Updates in Management

Critical discoveries over the past two decades have transformed our understanding of medulloblastoma from a single entity into a clinically and biologically heterogeneous disease composed of at least four molecularly distinct subgroups with prognostically and therapeutically relevant genomic signatures. Contemporary clinical trials also have provided valuable insight guiding appropriate treatment strategies. Despite therapeutic and biological advances, medulloblastoma patients across the age spectrum experience tumor- and treatment-related morbidity and mortality. Using an updated risk stratification approach integrating both clinical and molecular features, ongoing research seeks to (1) cautiously reduce therapy and mitigate toxicity in low-average risk patients, and (2) thoughtfully intensify treatment with incorporation of novel, biologically guided agents for patients with high-risk disease. Herein, we review important historical and contemporary studies, discuss management updates, and summarize current knowledge of the biological landscape across unique pediatric, infant, young adult, and relapsed medulloblastoma populations.

Post-treatment Neuroendocrine Outcomes Among Pediatric Brain Tumor Patients: Is there a difference between proton and photon therapy?

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Endocrinopathies were common among pediatric brain tumor survivors.

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Proton craniospinal irradiation had a lower risk of hypothyroidism.

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Non-medulloblastoma patients were less likely to develop endocrinopathies.

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Non-medulloblastoma patients were less likely to need hormone replacement therapy.

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Sex hormone deficiency was not observed in the proton cohort.

Purpose

Pediatric brain tumor patients are vulnerable to radiotherapy (RT) sequelae including endocrinopathies. We compared post-RT neuroendocrine outcomes between pediatric brain tumor patients receiving photons (XRT) versus protons (PRT).

Methods

Using a prospectively maintained single-institution database, we analyzed 112 pediatric primary brain tumor patients (80 XRT, 32 PRT) from 1996 to 2019. Patient/treatment characteristics and endocrinopathy diagnoses (growth hormone deficiency [GHD], sex hormone deficiency [SHD], hypothyroidism, and requirement of hormone replacement [HRT]) were obtained via chart review. Univariable/multivariable logistic regression identified neuroendocrine outcome predictors. Time-adjusted propensity score models accounted for treatment type. Craniospinal irradiation (CSI) patients were evaluated as a sub-cohort.

Results

Median follow-up was 6.3 and 4.4 years for XRT and PRT patients respectively. Medulloblastoma was the most common histology (38%). Half of patients (44% in XRT, 60% in PRT) received CSI. Common endocrinopathies were GHD (26% XRT, 38% PRT) and hypothyroidism (29% XRT, 19% PRT). CSI cohort PRT patients had lower odds of hypothyroidism (OR 0.16, 95% CI[0.02–0.87], p = 0.045) on multivariable regression and propensity score analyses. There were no significant differences in endocrinopathies in the overall cohort and in the odds of GHD or HRT within the CSI cohort. SHD developed in 17.1% of the XRT CSI group but did not occur in the PRT CSI group.

Conclusion

Endocrinopathies were common among pediatric brain tumor survivors. Among CSI patients, PRT was associated with lower risk of hypothyroidism, and potentially associated with lower incidence of SHD. Future studies should involve collaborative registries to explore the survivorship benefits of PRT.

The Alliance AMBUSH Trial: Rationale and Design

Simple Summary

Medulloblastoma, the most common embryonal tumor in children, can also arise in older patients. Clinical studies in children with medulloblastoma have increased our understanding of molecular pathways and improved treatment strategies. We now know that medulloblastoma has at least four subtypes and each maybe best suited to specific therapies. The sonic hedgehog (SHH) pathway is altered in a significant proportion of older patients with medulloblastoma. The Alliance for Clinical Trials in Oncology cooperative group is developing the AMBUSH trial: Comprehensive Management of Adolescent and Young Adult (AYA) and Adult Patients with Medulloblastoma or Pineal Embryonal Tumors With A Randomized Placebo Controlled Phase II Focusing on Sonic Hedgehog Pathway Inhibition in SHH Subgroup Patients (Adult & Adolescent MedulloBlastoma Using Sonic Hedgehog Trial). The trial gives treatment directions for all patients and randomizes patients with average risk SHH-activated medulloblastoma to maintenance sonidegib, a hedgehog signaling pathway inhibitor, or placebo. This trial will establish a baseline for future trial comparison and investigate the benefit of a novel targeted agent.

Abstract

Unlike medulloblastoma (MB) in children, robust prospective trials have not taken place for older patients due to the low incidence of MB in adults and adolescent and young adults (AYA). Current MB treatment paradigms for older patients have been extrapolated from the pediatric experience even though questions exist about the applicability of these approaches. Clinical and molecular classification of MB now provides better prognostication and is being incorporated in pediatric therapeutic trials. It has been established that genomic alterations leading to activation of the sonic hedgehog (SHH) pathway occur in approximately 60% of MB in patients over the age of 16 years. Within this cohort, protein patched homolog (PTCH) and smoothened (SMO) mutations are commonly found. Among patients whose tumors harbor the SHH molecular signature, it is estimated that over 80% of patients could respond to SHH pathway inhibitors. Given the advances in the understanding of molecular subgroups and the lack of robust clinical data for adult/AYA MB, the Alliance for Clinical Trial in Oncology group developed the AMBUSH trial: Comprehensive Management of AYA and Adult Patients with Medulloblastoma or Pineal Embryonal Tumors with a Randomized Placebo Controlled Phase II Focusing on Sonic Hedgehog Pathway Inhibition in SHH Subgroup Patients (Adult & Adolescent MedulloBlastoma Using Sonic Hedgehog Trial). This trial will enroll patients 18 years of age or older with MB (any molecular subgroup and risk stratification) or pineal embryonal tumor. Patients will be assigned to one of three cohorts: (1) average risk non-SHH-MB, (2) average risk SHH-MB, and (3) high risk MB or pineal embryonal tumors. All patients will receive protocol-directed comprehensive treatment with radiation therapy and chemotherapy. Patients with SHH-MB in cohort 1 will be randomized to a smoothened inhibitor or placebo as maintenance therapy for one year.

Comparison of hypothyroidism, growth hormone deficiency, and adrenal insufficiency following proton and photon radiotherapy in children with medulloblastoma

BACKGROUND

Endocrine deficiencies are common following Craniospinal irradiation (CSI) in children with brain tumors, but empirical data comparing outcomes following proton (PRT) and photon radiation therapy (XRT) are limited.

METHODS

This retrospective chart review compared the incidence of hypothyroidism, Growth hormone deficiency (GHD), and Adrenal insufficiency (AI) in patients with medulloblastoma treated with XRT and PRT between 1997 and 2016. All patients received CSI and had routine endocrine screening labs to evaluate for thyroid dysfunction, GHD, and AI. We used proportional hazards regression to calculate hazard ratios (HR) and 95% confidence intervals (CI) comparing the development of hypothyroidism, AI, and GHD between radiation modalities, adjusting for age at diagnosis, sex, race/ethnicity, and CSI dose.

RESULTS

We identified 118 patients with medulloblastoma who were followed for a median of 5.6 years from the end of radiotherapy. Thirty-five (31%) patients developed hypothyroidism, 71 (66%) GHD, and 20 (18%) AI. Compared to PRT, XRT was associated with a higher incidence of primary hypothyroidism (28% vs. 6%; HR = 4.61, 95% CI 1.2-17.7, p = 0.03). Central hypothyroidism, GHD, and AI incidence rates were similar between the groups.

CONCLUSIONS

Primary hypothyroidism occurs less often after PRT CSI, compared to XRT CSI. This suggests that the thyroid and pituitary glands receive less radiation after spine and posterior fossa boost RT, respectively, using PRT.

Overview and recent advances in the targeting of medulloblastoma cancer stem cells

Introduction: Medulloblastoma, an embryonal small round blue cell tumor primarily arising in the posterior fossa, is the most common malignancy of the central nervous system in children and requires intensive multi-modality therapy for cure. Overall 5-year survival is approximately 75% in children with primary disease, but outcomes for relapsed disease are very poor. Recent advances have identified molecular subgroups with excellent prognosis, with 5-year overall survival rates >90%, and subgroups with very poor prognosis with overall survival rates <50%. Molecular subtyping has allowed for more sophisticated risk stratification of patients, but new treatments for the highest risk patients have not yet improved outcomes. Targeting cancer stem cells may improve outcomes, and several candidate targets and novel drugs are under investigation.Areas covered: We discuss medulloblastoma epidemiology, biology, treatment modalities, risk stratification, and molecular subgroup analysis, links between subgroup and developmental biology, cancer stem cell biology in medulloblastoma including previously described cancer stem cell markers and proposed targeted treatments in the current literature.Expert opinion: The understanding of cancer stem cells in medulloblastoma will advance therapies targeting the most treatment-resistant cells within the tumor and therefore reduce the incidence of treatment refractory and relapsed disease.

Proton beam therapy for children and adolescents and young adults (AYAs): JASTRO and JSPHO Guidelines

Children and adolescents and young adults (AYAs) with cancer are often treated with a multidisciplinary approach. This includes use of radiotherapy, which is important for local control, but may also cause adverse events in the long term, including second cancer. The risks for limited growth and development, endocrine dysfunction, reduced fertility and second cancer in children and AYAs are reduced by proton beam therapy (PBT), which has a dose distribution that decreases irradiation of normal organs while still targeting the tumor. To define the outcomes and characteristics of PBT in cancer treatment in pediatric and AYA patients, this document was developed by the Japanese Society for Radiation Oncology (JASTRO) and the Japanese Society of Pediatric Hematology/Oncology (JSPHO).