Disease Control After Reduced Volume Conformal and Intensity Modulated Radiation Therapy for Childhood Craniopharyngioma

Abstract

PURPOSE To estimate the rate of disease control after conformal radiation therapy using reduced clinical target volume (CTV) margins and determine factors that predict for tumor progression. METHODS AND MATERIALS Eighty-eight children (median age 8.5 years, range 3.2–17.6 years) received conformal or intensity-modulated radiation therapy between 1998 and 2009. This included those prospectively treated from 1998 to 2003 using a 10 mm CTV, defined as the margin surrounding the solid and cystic tumor targeted to receive the prescription dose of 54 Gy. The CTV margin was subsequently reduced after 2003 yielding two groups of patients: those treated with a CTV margin greater than 5 mm (n=26) and those treated with a CTV margin less than or equal to 5 mm (n=62). Disease progression was estimated on the basis of additional variables including sex, race, extent of resection, tumor interventions, target volume margins, and the frequency of weekly surveillance MR imaging during radiation therapy. The median follow-up was 5 years. RESULTS There was no difference comparing progression-free survival based on CTV margin (>5mm vs. ≤ 5mm) at 5 years, 88.1 + 6.3% vs. 96.2 + 4.4% (P=0.6386). There was no difference based on the planning target volume (PTV) margin (or combined CTV+PTV). The PTV was systematically reduced from 5 to 3mm during the time period of the study. Factors predictive of superior progression-free survival included Caucasian race (P=0.0175), absent CSF shunting requirement (P=0.0066), and the number of surveillance imaging studies during treatment (P=0.0216). Patients whose treatment protocol included a higher number of weekly surveillance MR imaging evaluations had a lower rate of tumor progression. CONCLUSIONS These results suggest that targeted volume reductions for radiation therapy using smaller margins are feasible and safe but require careful monitoring. We are currently investigating the differences in outcome based on host factors to explain the results.

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

“…As radiation becomes more conformal and the use of particle therapy (e.g., PBT) becomes more prevalent, monitoring and accounting for cyst changes during treatment are essential to avoid underdosing target structures or overdosing critical structures. 17-23 Furthermore, cystic components of craniopharyngiomas can also change after RT is completed. However, both the incidence and implications of such changes are unclear and complicate the evaluation of treatment response.…”

Surgical Approaches

“…In a phase II trial of conformal radiation therapy in pediatric craniopharyngioma, nearly half the patients demonstrated cystic enlargement during therapy; 13 of 28 patients required cyst aspiration at least once during treatment and in three the tumor change was significant enough to require revision of the treatment plan (Merchant et al, 2006). In another study evaluating tumor control after conformal and intensity-modulated radiation therapy using a reduced planning volume, cyst enlargement requiring a change in treatment plan occurred in 22 of 88 cases (Merchant et al, 2013). A change in the solid component was not observed in any patient.…”

Pediatric Radiation

“…Experience with 3D conformal radiation is also excellent with most modern series, suggesting disease control rates between 80e100% (Stripp et al, 2004;Jalali et al, 2005;Merchant et al, 2006;Kiehna and Merchant, 2010). Although less data on outcomes for IMRT are available, published studies also report favorable outcomes (Merchant et al, 2013). Data for proton therapy are even more scarce, but Winkfield et al reported 100% local control for 24 patients at a median follow-up of 40.5 months (Winkfield et al, 2009).…”