Dose-Effect of Proton and Photon Craniospinal Irradiation on Vertebral Growth in Pediatric Patients with Medulloblastoma

PURPOSE/OBJECTIVE(S)

Craniospinal irradiation (CSI) directly damages vertebral growth plates causing skeletal dysplasia leading to reduced height in pediatric long-term survivors. The objective of this study is to quantify the adjusted effect of CSI on standing and sitting height by radiation dose and modality in children.

MATERIALS/METHODS

Two hundred sixty-five patients (M/F 169/96) were treated at a single institution on a clinical and molecular risk-directed trial for medulloblastoma (NCT01878617) using proton or photon therapy. Three CSI dose regimens were evaluated: 15 Gy (n = 31), 23.4 Gy (n = 103), ≥36 Gy (n = 131). Vertebral body dose was limited to 18-20 CGE for 23.4 Gy or 36 Gy proton therapy. All patients received post-CSI protocol-specified chemotherapy. Non-parametric tests were applied for baseline patient comparison. Changes in growth over time were calculated using random coefficients models using patient-specific intercepts and slopes. Dose-effects were modeled for ages 5, 10, and 18 years.

RESULTS

Age at CSI and race were similar between the three dose levels. Females most often received 23.4 Gy and males ≥36 Gy (p = 0.001). Higher CSI doses were associated with photon therapy (p<0.001). Median follow-up was 3 years (range 0.1-7.1). Annual growth rate was significantly different between 15 Gy (3.66 cm/year) and the higher dose levels of 23.4 Gy (2.81 cm/year, p = 0.0389) and ≥36 Gy (2.46 cm/year, p = 0.0032). Lower annual growth rate in females (vs. males, p = 0.0331) was observed in models for those aged 5 (-0.17 cm/year), 10 (-0.35 cm/year), and 18 years (-0.62 cm/year). In multivariate analysis, modelled annual growth rate was dose-dependent at ages 5 and 10 years. The differences were, respectively, 1.68 cm/year between 15 and 23.4 Gy (p = 0.0005) and 0.98 cm/year between 23.4 and ≥36 Gy (p = 0.0002), and 1.13 cm/year between 15 and 23.4 Gy (p = 0.0002) and 0.68 cm/year between 23.4 and ≥36 Gy (p = 0.0003). Radiation modality did not impact standing height over time significantly. Annual sitting height growth was 2.34, 1.67 and 1.1 cm/year for the three dose levels (p<0.0001-0.001). In the multivariate model, a 5-year-old receiving 15 or 23.4 Gy had similar annual sitting height growth, but not when 23.4 Gy was compared to ≥36 Gy (0.83 cm/year, p<0.0001). In a separate model for a patient aged 10 years, there was a difference comparing all CSI regimens (0.81 cm/year, p<0.0001, 15 vs 23.4 Gy; 0.54 cm/year, p = 0.0002, 23.4 vs ≥36 Gy). Sitting height growth was affected by CSI dose at age 18 years, with a difference of 2.2 cm/year between 15 vs 23.4 Gy (p = 0.0013), and no difference between 23.4 and ≥36 Gy.

CONCLUSION

Annual growth rates show a dose-response relationship, independent of treatment modality. A dose-response in sitting height growth rate is seen at any age, while the annual standing height growth rate was only affected by CSI dose in 5- and 10-year-olds. While all CSI doses had a significant impact on the annual standing height, sitting height growth rates approximated normal values for those treated with a low CSI dose.

Phase I study of vandetanib (ZD6474) administered during and after irradiation (RT) in children with diffuse intrinsic pontine glioma (DIPG)

10020

Background: Children with DIPG have a dismal prognosis despite use of RT, which is the mainstay of therapy. All chemotherapy regimens used so far demonstrated no benefit. EGFR and VEGFR pathways are considered important in tumorigenesis of DIPG. Methods: We conducted a traditional phase I study combining oral vandetanib (VEGFR-2 and EGFR inhibitor) during and after local RT in children with DIPG. Five dosage levels were tested (50, 65, 85, 110, and 145mg/m2 per day). Vandetanib and RT started on the same day. The first 6 weeks of therapy constituted the dose-limiting toxicity (DLT)-evaluation period. Correlative studies consisted of pharmacokinetic analysis (PK), pharmacodynamic studies in blood, and standard and investigational imaging (before and 1, 3, and 6 weeks after start of therapy). Results: Twenty-one patients were enrolled on study (50 [n = 3], 65 [n = 3], 85 [n = 3], 110 [n = 6], and 145mg/m2 [n = 6]). Two patients experienced DLT consisting of rash/mucositis (level 4) and diarrhea (level 5). The maximum-tolerated dose (MTD) of vandetanib was not reached. Other significant toxicities included lymphopenia grade 3/4 (n = 10), grade 3 neutropenia and hypophosphatemia (one each), grade 2 proteinuria (n = 2), grade 2 hypertension (n = 4), and mild QTc prolongation (n = 7) .Once the phase I component was completed, two extra patients were enrolled at dosage level 5; one of them developed grade 4 seizure secondary to posterior reversible encephalopathy syndrome. PK (n = 21) showed similar drug clearance and volume of distribution compared to adults. However, drug exposure at steady state normalized by dose seemed higher in children. Increased tumor perfusion during the first 6 weeks of therapy was observed in the first 12 patients analyzed. Conclusions: Although MTD was not reached, we recommend administration of vandetanib at a dose of 110mg/m2 per day during and after local RT in children. Further combination studies of vandetanib in children with DIPG are planned.

No significant financial relationships to disclose.

M1 medulloblastoma should be considered high risk at any age

2016

Background: Metastatic (M) stage is an important prognostic marker in medulloblastoma. With current therapy including higher-dose craniospinal irradiation and dose intensive chemotherapy, older children with metastatic medulloblastoma have had improved survival. Some investigators have suggested that older children with M1 medulloblastoma be treated as average-risk patients. Additionally, the prognostic value of M1 disease in very young children has not been documented. Methods: We retrospectively reviewed the records of all newly diagnosed medulloblastoma patients treated at St. Jude Children’s Research Hospital from 1984 to 2006. Treatment generally included resection and chemotherapy. Older children received post-operative craniospinal and tumor bed irradiation; radiotherapy for younger children depended on treatment era and physician/family preference. We compared event-free and overall survival for patients with M1 disease to that of patients with M0 and M2/M3 disease for both age groups using the Kaplan-Meier method. Results: 286 patients were included. 56 were <3 years old at diagnosis and 230 were =3 years old. Event-free (EFS) and overall survival (OS) by age and M-stage are reported below. Within the younger group, a significant difference in 5-year EFS was detected among M-stage groups (p<0.002 by Mantel-Haenszel test); 5-year EFS for M0 (n=33), M1 (n=5), and M2/M3 (n=18) patients was 67%, 20%, and 22%, respectively. The difference in 5-year EFS by M-stage was also significant for older patients (p<0.0001); 5-year EFS for 154 M0, 13 M1, and 63 M2/M3 patients was 82%, 59%, and 42%, respectively. Results were similar for OS; differences in OS were significant for older (p<0.0001), but not younger (p=0.21) children. Conclusions: Children <3 years old with M1 medulloblastoma fared poorly in our small series. Survival for older children with M1 disease treated with higher-dose CSI was better than that of M2/M3 patients, but still less than optimal; our findings do not support reduction in therapy for either cohort.

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No significant financial relationships to disclose.