Influence of an intratumoral cyst on drug distribution by convection-enhanced delivery: case report.

Convection-enhanced delivery (CED) uses positive pressure to induce convective flow of molecules and maximize drug distribution. Concerns have been raised about the effect of cystic structures on uniform drug distribution with CED. The authors describe the case of a patient with a diffuse intrinsic pontine glioma (DIPG) with a large cyst and examine its effect on drug distribution after CED with a radiolabeled antibody. The patient was treated according to protocol with CED of 124I-8H9 to the pons for nonprogressive DIPG after radiation therapy as part of a Phase I trial (clinical trial registration no. NCT01502917, clinicaltrials.gov). Care was taken to avoid the cystic cavity in the planned catheter track and target point. Co-infusion with Gd-DTPA was performed to assess drug distribution. Infusate distribution was examined by MRI immediately following infusion and analyzed using iPlan Flow software. Analysis of postinfusion MR images demonstrated convective distribution around the catheter tip and an elongated configuration of drug distribution, consistent with the superoinferior corticospinal fiber orientation in the brainstem. This indicates that the catheter was functioning and a pressure gradient was established. No infusate entry into the cystic region could be identified on T2-weighted FLAIR or T1-weighted images. The effects of ependymal and pial surfaces on drug delivery using CED in brainstem tumors remain controversial. Drug distribution is a critical component of effective application of CED to neurosurgical lesions. This case suggests that cyst cavities may not always behave as fluid "sinks" for drug distribution. The authors observed that infusate was not lost into the cyst cavity, suggesting that lesions with cystic components can be treated by CED without significant alterations to target and infusion planning.