Automated contouring, treatment planning, and quality assurance for VMAT craniospinal irradiation (VMAT-CSI)

Purpose

Create a comprehensive automated solution for pediatric and adult VMAT-CSI including contouring, planning, and plan check to reduce planning time and improve plan quality.

Methods

Seventy-seven previously treated CSI patients (age, 2-67 years) were used for creation of an auto-contouring model to segment 25 organs at risk (OARs). The auto-contoured OARs were evaluated using the Dice Similarity Coefficient (DSC), 95% Hausdorff Distance (HD95), and a qualitative ranking by one physician and one physicist (scale: 1-acceptable, 2-minor edits, 3-major edits). The auto-planning script was developed using the Varian Eclipse Scripting API and tested with 20 patients previously treated with either low-dose VMAT-CSI (12 Gy) or high-dose VMAT-CSI (36 Gy + 18 Gy boost). Clinically relevant metrics, planning time, and blinded physician review were used to evaluate significance of differences between the auto and manual plans. Finally, the plan preparation for treatment and plan check processes were automated to improve efficiency and safety of VMAT-CSI.

Results

The auto-contours achieved an average DSC of 0.71 ± 0.15, HD95 of 4.81 ± 4.68, and reviewers' ranking of 1.22 ± 0.39, indicating close to "acceptable-as-is" contours. Compared to the manual CSI plans, the auto-plans for both dose regimens achieved statistically significant reductions in body V50% and Dmean for parotids, submandibular, and thyroid glands. The variance in the dosimetric parameters decreased for the auto-plans as compared to the manual plans indicating better plan consistency. From the blinded review, the auto-plans were marked as equivalent or superior to the manual-plans 88.3% of the time. The required time for the auto-contouring and planning was consistently between 1-2 hours compared to an estimated 5-6 hours for manual contouring and planning.

Conclusions

Reductions in contouring and planning time without sacrificing plan quality were obtained using the developed auto-planning process. The auto-planning scripts and documentation will be made freely available to other institutions and clinics.

A Pilot Study of Low-Dose Craniospinal Irradiation in Patients With Newly Diagnosed Average-Risk Medulloblastoma

Purpose

Medulloblastoma is one of the most common malignant brain tumors in children. To date, the treatment of average-risk (non-metastatic, completely resected) medulloblastoma includes craniospinal radiation therapy and adjuvant chemotherapy. Modern treatment modalities and now risk stratification of subgroups have extended the survival of these patients, exposing the long-term morbidities associated with radiation therapy. Prior to advances in molecular subgrouping, we sought to reduce the late effects of radiation in patients with average-risk medulloblastoma.

Methods

We performed a single-arm, multi-institution study, reducing the dose of craniospinal irradiation by 25% to 18 Gray (Gy) with the goal of maintaining the therapeutic efficacy as described in CCG 9892 with maintenance chemotherapy.

Results

Twenty-eight (28) patients aged 3-30 years were enrolled across three institutions between April 2001 and December 2010. Median age at enrollment was 9 years with a median follow-up time of 11.7 years. The 3-year relapse-free (RFS) and overall survival (OS) were 79% (95% confidence interval [CI] 58% to 90%) and 93% (95% CI 74% to 98%), respectively. The 5-year RFS and OS were 71% (95% CI 50% to 85%) and 86% (95% CI 66% to 94%), respectively. Toxicities were similar to those seen in other studies; there were no grade 5 toxicities.

Conclusions

Given the known neurocognitive adverse effects associated with cranial radiation therapy, studies to evaluate the feasibility of dose reduction are needed. In this study, we demonstrate that select patients with average-risk medulloblastoma may benefit from a reduced craniospinal radiation dose of 18 Gy without impacting relapse-free or overall survival.

Clinical Trial Registration

ClinicalTrials.gov identifier: NCT00031590

Treatment of common pediatric CNS malignancies with proton therapy

Radiation therapy plays an important role in the management of pediatric CNS malignancies. With the improving outcomes of these patients, the potential risk of late toxicities present with current radiation therapy techniques (i.e., 3D-CRT, IMRT, VMAT) has become apparent. Proton therapy (PRT), due to its unique physical characteristics, provides an advantage in reducing unintended dose to normal tissue structures, and the resultant acute and late side effects of this dose "bath". In this review we will highlight the current standards of care, and the benefits achieved with using PRT in treating common childhood CNS tumors.

Clinical analysis of intracranial germinoma's craniospinal irradiation using helical tomotherapy

OBJECTIVE

To evaluate the short-term clinical outcomes of intracranial germinoma patients treated with craniospinal irradiation (CSI) using helical tomotherapy (HT) system in our center.

METHODS

Twenty-three patients who were treated with CSI in our center from January 2008 to July 2012 were collected, with an average age of 20. All of the patients' CSI used the HT system. The total doses were 27-36 Gy/15-20 F (1.5-2 Gy per fraction), and total local doses were 46-60 Gy/30-50 F (5 fractions per week). All female patients for CSI were treated with left-right parallel-opposed field irradiation to protect their ovarian functions. Median follow-up time was 30.9 months (range, 5-67 months). The SPSS19.0 software was used, and the overall survival (OS) was calculated using the Kaplan-Meier method.

RESULTS

Among 17 patients with assessable tumors, 9 cases (52.9%) were CR, 7 cases (41.2%) were PR, and 1 case (5.9%) was SD. Hematological toxicity was the severest side-effect occurred in the procedure of CSI. The level 1-4 acute leukopenia were 8.7%, 30.4%, 34.8% and 21.7% and the level 1-4 acute thrombopenia were 8.7%, 30.4%, 21.7% and 8.7%, respectively.

CONCLUSIONS

For primary intracranial germinomas, HT can be used to implement CSI for simplifying radiotherapy procedures, improving radiotherapy accuracy, enhancing protection of peripheral organs at risk (ORA) and guaranteeing therapeutic effects. With the acceptable acute and long-term toxicity, CSI using HT in intracranial germinoma patients can be a safe and alternative mode.