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

Abstract

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.

Proton Beam Therapy Versus Conformal Photon Radiation Therapy for Childhood Craniopharyngioma: Multi-institutional Analysis of Outcomes, Cyst Dynamics, and Toxicity

“…However, both the incidence and implications of such changes are unclear and complicate the evaluation of treatment response. 24,25 Significant expansion of cysts after treatment may compress critical structures, necessitating additional invasive procedures. Transient asymptomatic enlargement, however, may reflect only a response to treatment, as has been noted for other high- and low-grade tumors.…”

Linear Accelerator-Based Fractionated Radiotherapy

“…One point of caution, however, is that it has been found by a recently published study that up to 52.4% of patients may develop some transient tumor enlargement (usually of the cystic component) on serial MRI evaluation after the completion of radiation (Shi et al, 2012). The median time to tumor or cyst expansion in this investigation was reported to be 1.5 months.…”

“…Thereafter, the tumor or cyst would begin to contract and a median time to maximal response post-radiation was found to be approximately 9.5 months. Given the transient nature of this tumor enlargement, the authors advised against a rapid, reactionary salvage surgery during the early period post-radiation (Shi et al, 2012).…”

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

“…[3][4][5]10,14,16 Cyst enlargement caused recurrent hydrocephalus in 2 patients whose ventriculomegaly originally resolved following surgery, requiring treatment with a VP shunt. However, we demonstrate that the majority of cyst changes are self-limiting, in concordance with the literature.…”

“…2,5,9,14,16 Previously, it was thought that any cyst enlargement was a sign of recurrence and thus required surgical intervention. However, cyst enlargement seen during or after radiotherapy is often followed by regression without the need for additional therapeutic intervention.…”