Background and Aims

Children with extremity RMS occasionally present with lymph node involvement. In-transit lymphatics may be affected at diagnosis and are also a potential site of failure. Elective radiation to in-transit lymphatics is not routinely recommended, but it was given occasionally at our institution before more conformal techniques were available; mainly in cases where radiotherapy was indicated to the primary site and proximal lymph nodes, but the distance in between was too short to arrange separate fields.

The purpose of this study was to report the incidence of in-transit failure in patients with extremity RMS and the impact of in-transit lymphatics irradiation.

Methods

This retrospective review included patients less than 18 years with extremity RMS treated at Children’s Hospital of Mexico Federico Gómez from 2000 to 2016.

Results

Thirty patients were identified, 77% had alveolar RMS; 43% presented lymph node metastases, 10% in-transit node involvement and 43% distant metastases. Twenty-six received radiotherapy, 30% with complete in-transit lymphatics irradiation. Median follow up was 17 months (range 5-124). Three patients developed in-transit failure: all with alveolar RMS, one with proximal lymph node involvement at diagnosis and one with initial in-transit node metastases; none had received irradiation to in-transit lymphatics. Of the three patients with initial in-transit node involvement, none had in-transit lymphatics irradiation and one developed in-transit failure. The percentage of in-transit failure was 0% for patients who had complete in-transit lymphatics irradiation compared to 16% for those who did not (p=0.53); in patients with initial lymph node involvement these rates were 0% and 29% (p=0.49), respectively. Progression free survival was not affected by in-transit lymphatics irradiation.

Conclusions

In-transit lymphatics represent a frequent site of failure. Complete irradiation to in-transit lymphatics may be considered in patients with alveolar RMS and initial nodal involvement.

Background and Aims

Proton therapy (PT) for primary pediatric CNS tumors can induce white matter changes (WMC) and enhancing lesions more often referred to as brain tissue radiation necrosis (RN).

Aim of this analysis was to assess the incidence and prevalence of WMC and RN, visible on MRI after pencil beam scanning PT in the Dutch national cohort of primary pediatric CNS tumors.

Methods

Between 06-2018 and 12-2019, 49 of 91 patients with a newly diagnosed CNS tumor and indication for radiotherapy (medulloblastoma, n=23; ependymoma, n=12; germ-cell tumor, n=5; glioma, n=4; other, n=5) underwent PT. Follow-up with MRI was performed at the Dutch National Center for Pediatric Oncology. Presence of new WMC and RN, defined as increased T2 signal (WMC) +/-contrast enhancement on T1 (RN), were analysed.

Kaplan-Meier and Cox proportional hazard models were used to calculate cumulative incidence and prevalence of WMC and RN, and to study potential associated factors such as gender, age, location, and dose to craniospinal axis (0GyE vs. 23.4GyE vs. ≥36GyE).

Results

Median age at PT was 9.5years (range:1.2-19.0) and median dose was 54.0GyE (range:40.0-59.4). Median follow-up time after PT was 10.7months (range:2.0-19.4).

At 3, 6, 9 and 12months, the respective cumulative incidence of WMC was 8.2%, 24.5%, 27.6%, and 27.6%, while for RN it was 4.1%, 20.5%, 23.5%, and 23.5%. Prevalence of RN at 3, 6, 9 and 12 months was 5%, 22%, 15%, 8%, respectively. In 6/12 patients, T2+/-T1-changes on MRI were associated with transient neurologic impairment.

In univariable analyses, age below <7 vs. ≥7years significantly increased the risk of RN (HR:6.1, 95% CI:1.3-28.9, P=0.02; cumulative incidence at 12months:45.0% vs. 6.9%).

Conclusions

Transient RN and WMC on MRI are frequently observed in the first year after PT with a particularly high risk in children below the age of 7 years suggesting that the developing brain is more susceptible.

Background and Aims

A proton therapy (PT) facility – Skandion clinic - opened in Uppsala in august 2015. It was stated that all children in Sweden, benefitting from PT, ought to be sent there. PT plans are prepared at six university-based radiotherapy (RT) centres and assessed by a national board. There are no additional costs for the families compared to other radiotherapy (RT) options, not even for travel and lodging.

Methods

Since 2008 all children receiving RT with any modality are registered in the Swedish Radtox registry. Inclusion is population-based, prospective and complete. Radiation oncologists from the six centres performing paediatric RT retrospectively reviewed patients who had not received PT.

Results

354 treatments were given, 252 (71%) were not PT. The reasons for choosing conventional RT were dismal prognosis in 66 patients, uncertainty due to internal movement and lack of motion-control technique at the PT centre in 63 patients, and lack of dosimetric advantage for protons in 47 patients. Infrequent reasons were lack of set up for CSI or very superficial treatment in the beginning [n=11], variations of air in the field [n=6], not robust treatment plan for other reasons (mainly metal in the field) [n=6], gamma-knife/other stereotactic treatment [n= 5], brachytherapy [n=4], TBI [n=31], acute RT start necessary [n=10], and social reasons [n=3].

Conclusions

Even though proton therapy, due to less side effects, has been advocated to be the best treatment modality for children, this might not always be the case. Sometimes conventional RT may be advantageous, despite the increased exit-dose, due to the wider penumbra of PT. Social needs and palliative situations may be more important than an optimal dose-distribution. However, technical improvement of PT by application of gating and treatment planning systems (TPS) handling dose-deposition uncertainties should make the modality available for a wider range of paediatric patients.