Craniopharyngioma in Childhood: Proton Radiotherapy and Treatment Planning With Special Attention to the Cyst Size
Presenter: Claudia Linsenmeier
Affiliation: Massachusetts General Hospital
Craniopharyngioma accounts for 5-8% of central nervous system tumors in children. It classically has a bimodal age distribution of 5-14 years and > 65 years. Endocrine deficits are common at both presentation and at the completion of treatment for this disease (90-95%). This study was performed to evaluate outcomes and specifically relate cyst size and needs of replanning treatment during proton beam therapy.
Materials and Methods
Seventeen children treated with proton beam therapy between 1/01-3/06 are included in this study. There are 5 recurrent tumors included. Surgery consisted of gross total resection (n=5), subtotal resection (n=9), or biopsy only (n=3). The mean proton dose was 52.8 Gy delivered with a median of 4 treatment fields. In defining the tumor volumes, the GTV=CTV and the PTV=CTV + 2-3 mm. Patients received CT or MRI both before and after proton radiotherapy. Eleven patients were scanned during proton therapy with a median of 2 scans.
The median time from diagnosis of craniopharyngioma to treatment with proton beam therapy was 7 months. The 5 patients with recurrences had a median disease free interval of 6 months. Cyst growth during radiation therapy was extremely common. 3/17 patients (18%) had enough cyst growth to require replanning with alteration of the proton treatment during the course of therapy. With a median follow-up of 45 months, 1 patient has died of their disease. All others are currently alive.
Cyst growth of craniopharyngioma is common during proton beam irradiation. Routine imaging during treatment is recommended with alteration of plans if significant growth occurs. Proton beam therapy is an effective treatment for craniopharyngioma.
Clinical and Scientific Implications
Many patients with craniopharyngiomas are seen after multiple attempts at surgical resection. Most of these patients have significant endocrine abnormalities both before and after treatment that require lifelong hormone therapy and medical management. Proper coverage of the target volume is critical to maintain local control. This study shows there can be significant alterations of the cyst cavity during treatment. However, because this study was done retrospectively, there was not consistency in scans during the radiation treatment. Presumably the scans were done because of changes in patient symptoms during treatment. Periodic imaging during the proton treatment is reasonable, but the specific timing of these scans is difficult to interpret based on the current study. It may be reasonable to get an MRI or CT midway through treatment to evaluate the target volume. If there are significant changes, replanning is warranted so that proper coverage of the tumor with protons occurs.