PET/CT in children with neurofibromatosis type 1

Objectives Neurofibromatosis type-1 (NF1) is a common neurocutaneous disorder. Two major complications in childhood NF1 are optic pathway gliomas (OPGs) and plexiform neurofibromas (PNFs). There is lack of consensus on surveillance and management of OPG and PNF in NF1. Literature is scant with the diagnostic utility of FDG positron emission tomography / computed tomography (PET/CT) in childhood NF1 with no report of its use in OPGs.

Methods A retrospective review of all PET/CT scans was performed on children with NF1 at the Children’s Hospital from Aug 2006-Dec 2008. FDG uptake in the OPG and PNF were analysed semi-quantitatively (SUVmax).

Results 18 NF1 children (10F, 8M, median age:8.5-yrs, age range: 2-14 yrs) with OPG and PNF had PET/CT scans. There were 7 OPG, 7 PNF and 4 both OPG and PNF. 19 OPGs were imaged in 11pts. Baseline SUVmax in 16/19 OPGs were < 3 in 10, ≥3-< 4 in 3 and ≥4 in 3 tumors. Following chemotherapy for OPG, SUVmax reduced to < 3 in 2/3 pts with baseline SUV>4. PET/CT diagnosed symptomatic OPGs with sensitivity of 0.63 (95% CI: 0.26-0.90) and specificity of 0.88(95%CI:0.47-0.99). 16 PNFs were imaged in 11 pts. SUVmax in 13/16 PNFs was <3 in 9, ≥3-<4 and ≥4 in 2 tumors each. The 2 PNFs with SUV>4 were confirmed as malignant peripheral nerve sheath tumors. PET/CT diagnosed malignant transformation in PNFs with a sensitivity of 1.0 (95%CI: 0.2-1.0) and a specificity of 0.82 (95%CI:0.48-0.97).

Conclusions In childhood NF1, PET/CT appears useful in surveillance of OPG, to identify those tumors that may progress and become symptomatic, to identify malignant change in PNF and to target biopsy sites in diffuse symptomatic lesions. Further prospective study is warranted.