2091

Stereotactic cysto-ventricular catheters in craniopharyngiomas: an effective minimally invasive method to improve visual impairment and achieve long-term cyst volume reduction

Craniopharyngiomas are typically located in the sellar region and frequently contain space-occupying cysts. They usually cause visual impairment and endocrine disorders. Due to the high potential morbidity associated with radical resection, several less invasive surgical approaches have been developed. This study investigated stereotactic-guided implantation of cysto-ventricular catheters (CVC) as a new method to reduce and control cystic components. Twelve patients with cystic craniopharyngiomas were treated with CVC in our hospital between 04/2013 and 05/2017. The clinical and radiological data were retrospectively analysed to evaluate safety aspects as well as ophthalmological and endocrine symptoms. The long-term development of tumour and cyst volumes was assessed by volumetry. The median age of our patients was 69.0 years and the median follow-up period was 41.0 months. Volumetric analyses demonstrated a mean reduction of cyst volume of 64.2% after CVC implantation. At last follow-up assessment, there was a mean reduction of cyst volume of 92.0% and total tumour volume of 85.8% after completion of radiotherapy. Visual acuity improved in 90% of affected patients, and visual field defects improved in 70% of affected patients. No patient showed ophthalmological deterioration after surgery, and endocrine disorders remained stable. Stereotactic implantation of CVC proved to be a safe minimally invasive method for the long-term reduction of cystic components with improved ophthalmological symptoms. The consequential decrease of total tumour volumes optimised conditions for adjuvant radiotherapy. Given the low surgical morbidity and the effective drainage of tumour cysts, this technique should be considered for the treatment of selected cystic craniopharyngiomas.

Radiotherapy Advances in Pediatric Neuro-Oncology

Radiation therapy (RT) represents an integral component in the treatment of many pediatric brain tumors. Multiple advances have emerged within pediatric radiation oncology that aim to optimize the therapeutic ratio—improving disease control while limiting RT-related toxicity. These include innovations in treatment planning with magnetic resonance imaging (MRI) simulation, as well as increasingly sophisticated radiation delivery techniques. Advanced RT techniques, including photon-based RT such as intensity-modulated RT (IMRT) and volumetric-modulated arc therapy (VMAT), as well as particle beam therapy and stereotactic RT, have afforded an array of options to dramatically reduce radiation exposure of uninvolved normal tissues while treating target volumes. Along with advances in image guidance of radiation treatments, novel RT approaches are being implemented in ongoing and future prospective clinical trials. As the era of molecular risk stratification unfolds, personalization of radiation dose, target, and technique holds the promise to meaningfully improve outcomes for pediatric neuro-oncology patients.

A quantitative analysis of craniopharyngioma cyst expansion during and after radiation therapy and surgical implications

OBJECTIVE

When complete resection of craniopharyngioma is not achievable or the sequelae are prohibitive, limited surgery and radiation therapy have demonstrated excellent local disease control while minimizing treatment-related sequelae. When residual tissue exists, there is a propensity for further cyst development and expansion during and after radiation therapy. This can result in obstructive hydrocephalus, visual changes, and/or clinical decline. The authors present a quantitative analysis of cyst expansion during and after radiotherapy and examine how it affected subsequent management.

METHODS

The authors performed an institutional review board–approved retrospective study of patients with histologically confirmed craniopharyngioma treated between 2000 and 2015 with surgery and intensity-modulated radiation therapy (IMRT) at a single institution. Volumetric measurements of cyst contours were generated by radiation oncology treatment planning software postoperatively, during IMRT, and up to 12 months after IMRT. Patient, tumor, and treatment–related variables were collected until the last known follow-up and were analyzed.

RESULTS

Twenty-seven patients underwent surgery and IMRT. The median total radiation dose was 54 Gy. Of the 27 patients, 11 patients (40.7%) demonstrated cyst expansions within 1 year of IMRT. Of note, all tumors with cyst expansion were radiographically Puget Grade 2. Maximal cyst expansion peaked at 4.27 months following radiation therapy, with a median volume growth of 4.1 cm3 (mean 9.61 cm3) above the postoperative cyst volume. Eight patients experienced spontaneous cyst regression without therapeutic intervention. Three patients experienced MRI-confirmed cyst enlargement during IMRT, all of whom required adaptive planning to ensure adequate coverage of the entire tumor volume. Two of these 3 patients required ventriculoperitoneal shunt placement and additional intervention. One underwent additional resection, and the other had placement of an intracystic catheter for aspiration and delivery of intracystic interferon within 12 months of completing IMRT. All 3 patients now have stable disease.

CONCLUSIONS

Craniopharyngioma cyst expansion occurred in approximately 40% of the patients during or after radiotherapy. In the majority of patients, cyst expansion was a self-limiting process and did not confer a worse outcome. During radiotherapy, cyst expansion may be apparent on image-guided radiation therapy. Adaptive IMRT planning may be required to ensure that the intended IMRT dose covers the entire tumor and cyst volume. The sequelae of cyst expansion include progressive hydrocephalus, which may be treated with a shunt. For patients with solitary cyst expansion, cyst aspiration and/or intracystic interferon may result in disease control.

Transient enlargement of craniopharyngioma after radiation therapy: pattern of magnetic resonance imaging response following radiation

Clinical experience suggests that craniopharyngiomas may temporarily increase in size after radiation therapy (RT). The study goal is to determine the incidence and natural history of this response in a cohort of patients managed at Children's Healthcare of Atlanta (CHOA) or Emory Healthcare (EHC). Between 08/1998 and 06/2009, 41 children and young adults were diagnosed with craniopharyngioma at CHOA and/or EHC. Of these, 21 received external-beam radiation and were included in our analysis. Serial magnetic resonance imaging (MRI) studies were evaluated volumetrically to assess response to RT. Median age at diagnosis was 8.2 years (range 3.2-23.5 years). Median radiation dose was 54.0 Gy using standard fractionation (1.8-2.0 Gy/day). With median follow-up of 41.3 months (range 7.2-121.8 months), actuarial local control and overall survival rates at 5 years were 78.7 % and 100 %, respectively. Of subjects, 52.4 % of subjects (11 of 21) were noted on serial MRI evaluation to have tumor enlargement (mostly cystic component) after radiation before eventual shrinkage without further intervention. For tumors that expanded, the median volume increase was 33.9 % (range 15.6-224.4 %). Median time to maximal tumor/cyst expansion was 1.5 months (range 1.0-5.0 months). Finally, nearly all patients (20 of 21) showed a measurable objective response to therapy by MRI regardless of ultimate disease control. Median time to maximal response post-radiation, as defined by MRI, was 9.5 months (range 3.5-39.9 months). In summary, RT is effective for managing craniopharyngioma. However, despite good ultimate responses, approximately 50 % of the patients show tumor/cyst expansion on MRI over the first few months post-radiation. Caution should be taken not to subject these patients to "salvage surgery" or cyst aspiration during this early time unless there are other overriding surgical indications. Understanding the natural history of this phenomenon could potentially help guide the management of these craniopharyngioma patients.

On the benefits and risks of proton therapy in pediatric craniopharyngioma

PURPOSE

Craniopharyngioma is a pediatric brain tumor whose volume is prone to change during radiation therapy. We compared photon- and proton-based irradiation methods to determine the effect of tumor volume change on target coverage and normal tissue irradiation in these patients.

METHODS AND MATERIALS

For this retrospective study, we acquired imaging and treatment-planning data from 14 children with craniopharyngioma (mean age, 5.1 years) irradiated with photons (54 Gy) and monitored by weekly magnetic resonance imaging (MRI) examinations during radiation therapy. Photon intensity-modulated radiation therapy (IMRT), double-scatter proton (DSP) therapy, and intensity-modulated proton therapy (IMPT) plans were created for each patient based on his or her pre-irradiation MRI. Target volumes were contoured on each weekly MRI scan for adaptive modeling. The measured differences in conformity index (CI) and normal tissue doses, including functional sub-volumes of the brain, were compared across the planning methods, as was target coverage based on changes in target volumes during treatment.

RESULTS

CI and normal tissue dose values of IMPT plans were significantly better than those of the IMRT and DSP plans (p < 0.01). Although IMRT plans had a higher CI and lower optic nerve doses (p < 0.01) than did DSP plans, DSP plans had lower cochlear, optic chiasm, brain, and scanned body doses (p < 0.01). The mean planning target volume (PTV) at baseline was 54.8 cm(3), and the mean increase in PTV was 11.3% over the course of treatment. The dose to 95% of the PTV was correlated with a change in the PTV; the R(2) values for all models, 0.73 (IMRT), 0.38 (DSP), and 0.62 (IMPT), were significant (p < 0.01).

CONCLUSIONS

Compared with photon IMRT, proton therapy has the potential to significantly reduce whole-brain and -body irradiation in pediatric patients with craniopharyngioma. IMPT is the most conformal method and spares the most normal tissue; however, it is highly sensitive to target volume changes, whereas the DSP method is not.

Dosimetric effect of target expansion and setup uncertainty during radiation therapy in pediatric craniopharyngioma

PURPOSE

Investigate the effect of tumor change and setup uncertainties on target coverage for pediatric craniopharyngioma during RT.

METHODS AND MATERIALS

Fifteen pediatric patients with craniopharyngioma (mean 5.1 years) were included in this study. MRI was performed before and a median of six times during RT to monitor changes in the tumor volume. IMRT plans were created and compared to the CRT plan used for treatment. The role of adaptive therapy based on GTV changes was investigated. Dosimetric effects of interfraction and intrafraction motion were examined.

RESULTS

The mean of the maximal change in the GTV was 28.5% [-20.7% to 82.0%]. For the standard margin IMRT plans, the mean D(95) of the base plan on the base target was 53.6 Gy [53.1-54.1]. The mean D(95) of the base plans on the adaptive targets was 52.1 Gy [47.9-54.1]. The D(95) for the adaptive plan on the adaptive target was 53.8 Gy [53.4-54.3]. A linear regression equation of y=-0.12x , r(2)=0.70, was found for the percent change in D(95) of the PTV (y) vs. the percent change in the GTV (x). Inter and intrafraction motion did not affect the target coverage for standard and reduced margin plans.

CONCLUSIONS

The GTV of pediatric craniopharyngioma patients change size during therapy and adaptive planning is critical for conformal plans; therefore early and regular surveillance imaging is required.