Intensity-Modulated Radiation Therapy With Dose Painting: A Brain-Sparing Technique for Intracranial Germ Cell Tumors
Joanna C Yang1, Stephanie A Terezakis2, Ira J Dunkel3,4
1Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York.
Background:
We sought to assess patterns of failure in pediatric patients with intracranial germ cell tumors (GCT) treated with intensity-modulated radiation therapy with dose painting (DP-IMRT).
Procedure:
Between July 2007 and October 2013, 11 patients with localized GCT-five germinomas and six nongerminoma GCT (NGGCT)-received definitive treatment with DP-IMRT. Three representative patients were selected for replanning with (i) whole ventricular irradiation (WVI) with opposed lateral beams plus IMRT to the primary tumor and (ii) sequential IMRT. These plans were compared to the patients' original DP-IMRT plans for dosimetric analyses.
Results:
Four patients with germinoma received radiation therapy alone: 45 Gy in 1.8 Gy fractions to the primary tumor and 25 Gy in 1.0 Gy fractions to whole ventricles using a dose-painting plan. One patient with germinoma received a reduced dose of 30.6 Gy to the primary tumor after neoadjuvant chemotherapy. Patients with NGGCT (n = 6) underwent multimodality treatment including chemotherapy (n = 6) and surgery (n = 3). These patients received 54 Gy to the primary tumor and 32.4-36 Gy to the whole ventricles. Dosimetric analyses showed DP-IMRT delivered decreased mean dose to whole brain, temporal lobes, hippocampi, cochleae, and optic nerves. With median follow-up of 4 years, 3-year failure-free survival was 100% for patients with germinoma and 67% for patients with NGGCT. One patient with a pineal NGGCT experienced a local recurrence within the high dose-volume while another experienced an isolated biochemical failure.
Conclusions:
DP-IMRT is dosimetrically superior to standard IMRT techniques for sparing of normal tissues. Disease control in this small series appears at least comparable to published results.
