Abstract
ObjectiveTo quantitate and compare the dosimetric properties of three brain-sparing radiation therapy techniques for pure intracranial germinomas with dose-volume analysis of target and normal brain structures.MethodsWe identified 18 patients with central nervous system (CNS) germinoma who had achieved local control and had excellent neurocognitive outcomes. Four patients who were treated with a simultaneous integrated boost (SIB) plan of 22.5Gy to whole ventricle (WV) and 30Gy to primary were re-planned with 24Gy to WV-only and the Children’s Oncology Group (COG) protocol of 18Gy to WV with a sequential boost to 30Gy. Organ-at-risk (OAR) doses for hippocampi, temporal lobes, whole brain, whole brain minus whole ventricles planning target volume (WB-WVPTV), WVPTV, and boost volume were comparatively studied.ResultsFor patients treated with the SIB plan, an excellent neurocognitive function has previously been shown to be well preserved. Three-year event-free survival (EFS) and overall survival (OS) for this group have also previously been demonstrated (89.5% and 100%, respectively). Mean and integral OAR doses were comparable between SIB and WV-only plans but were lower for COG plans. Whole brain, whole brain minus WVPTV, and temporal lobe V20, V18, and V12, as well as hippocampi V20, V25, and V30, were comparable between SIB and WV-only plans but were lower for the COG plans.ConclusionCompared to the WV-only method, the SIB plan permits more dose to the primary site by 6 Gy without compromising neurocognitive control. While maintaining the 30Gy boost, the COG protocol reduces the WVPTV dose to 18Gy. It remains to be seen whether WV dose reduction risks reducing local control.
Highlights
Intracranial germ cell tumors represent 3%-11% of pediatric central nervous system (CNS) malignancies, of which two-thirds are pure germinomas and one-third are non-germinomatous germ cell tumors (NGGCT) and mature teratomas [1,2,3,4,5]
For patients treated with the simultaneous integrated boost (SIB) plan, an excellent neurocognitive function has previously been shown to be well preserved
Mean and integral OAR doses were comparable between SIB and whole ventricle (WV)-only plans but were lower for Children’s Oncology Group (COG) plans
Summary
Intracranial germ cell tumors represent 3%-11% of pediatric central nervous system (CNS) malignancies, of which two-thirds are pure germinomas and one-third are non-germinomatous germ cell tumors (NGGCT) and mature teratomas [1,2,3,4,5]. CSI has cure rates of greater than 90% [8], but the delivery of high CSI doses to the entire craniospinal axis is associated with significant late effects such as impaired bone growth, neurocognitive deficits, and endocrine toxicities [2]. Knowledge of these toxicities has led to a re-evaluation of treatment and a shift in the focus of research from increasing cure rates to maintaining cure rates by using chemotherapy followed by radiation therapy (RT) with lower doses [2,3]. This reduced dosing may result in decreased incidence and severity of late
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