PET/CT in children with neurofibromatosis type 1

  • Dr Mahendranath Moharir, The Children's Hospital at Westmead, Australia
  • Dr Kevin London, The Children's Hospital at Westmead, Australia
  • Prof Robert Howman-Giles, The Children's Hospital at Westmead, Australia
  • Prof Kathryn North, The Children's Hospital at Westmead, Australia

    • Background: Neurofibromatosis type-1 (NF1) is a common neurocutaneous disorder. Two major complications in childhood NF1 are optic pathway gliomas (OPGs) and plexiform neurofibromas (PNFs). Literature is scant with diagnostic utility of FDG 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 from Aug2007-Dec2008. FDG uptake in the OPG and PNF were analysed semi-quantitatively (SUVmax).

    Results: 18NF1 children (10F, 8M, median age:8.5-yrs, 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 proven malignant peripheral nerve sheath tumors. PET/CT diagnosed malignant transformation in PNFs with a sensitivity of 1.0 (95%CI:0.20-1.0) 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 tumors that may progress and become symptomatic, to identify malignant change in PNF and target biopsy sites in diffuse symptomatic lesions. Further prospective study is warranted.