Page 97 - Read Online

Sell et al. Mini-invasive Surg 2024;8:3 https://dx.doi.org/10.20517/2574-1225.2023.105 Page 5 of 10

[37]
hypermetabolism . However, it is characteristically not specific for cancerous cells because immature
18
granulation tissue, macrophages and fibroblasts all avidly uptake FDG, particularly following
radiotherapy [38,39] . As a result, PET/CT is very reassuring when negative with a high NPV, but has poor
[21]
specificity, particularly in the context of sinonasal malignancy . Studies have demonstrated that specificity
falls to ~40% and PPV to ~50% for sinonasal malignancies, most likely due to the nonspecific radiotracer
update in the inflammatory environment in the posttreatment sinonasal cavity [27,39] . Many centers that care
for patients with sinonasal malignancy will perform FDG-PET between one and four times per year, but
18
this must be balanced with costs and reduced quality of life for patients as a result of false positives [40,41] .

Generally, for head and neck cancer patients, practice guidelines recommend a three-month PET/CT
following completion of primary treatment [22,42-44] . A retrospective study of PET/CT in surveillance of
sinonasal malignancy between 2000 and 2015 demonstrated that compared to head and neck cancers
overall, sinonasal tumors have a prolonged hypermetabolic period . The team found that the specificity
[17]
and PPV of PET/CT were improved when performed at baseline and then at least six months posttreatment,
consistent with previous findings . The prolonged period of hypermetabolism in the posttreatment
[45]
sinonasal skull base may warrant reevaluation of the general recommendation that patients with head and
neck cancer have a PET/CT completed by 10-12 weeks following primary treatment [17,45] . Although the
optimal timing of surveillance PET/CT may remain unclear, the lack of pathologic FDG uptake on the first
PET/CT following treatment was associated with improved overall survival (OS) for patients with
SNSCC . However, increasing the total number or frequency of scans during the first year has not been
[46]
associated with reduced time to recurrence. Overall, at least one surveillance PET/CT should be performed
for patients with sinonasal malignancy, although the optimal timing for PET/CT is still under
investigation [47,48] .

18 FDG-PET/CT can play a particularly important role in the surveillance of patients with some subtypes of
rare sinonasal malignancies. For patients with high-grade SNEC, recurrence can present locoregionally or
distantly metastasis, perhaps warranting closer surveillance of these patients with FDG-PET/CT [49,50] . There
18
are no definitive recommendations regarding the use of Gadolinium-DOTATATE PET/CT for SNEC, but a
few reports have evaluated its utility for diagnosing low-grade SNEC where no radiotracer uptake was found
[51]
on FDG PET/CT . There have also been evaluations on the use of Gadolinium-DOTATATE PET/CT for
the evaluation and surveillance of olfactory neuroblastomas, given that 99% of these tumors are positive for
SSTR2 expression . Additionally, SNUC is an aggressive disease with a partial neuroendocrine profile that
[52]
confers a poor prognosis, and Gadolinium-DOTATATE PET/CT may be able to assist in the close
surveillance of these patients. However, the use of Gadolinium-DOTATATE PET/CT for the surveillance of
SNUC remains under investigation . SNUCs are often locally recurrent and frequently metastasize,
[48]
resulting in significant morbidity and mortality. Mucosal melanoma has a high recurrence rate with a
tendency for distant failure (38%-57%) and demonstrates high FDG avidity, making PET/CT particularly
useful [19,53,54] . FDG PET/CT is also recommended in patients with NUT carcinoma, given the particularly
high risk for metastatic disease. PET/CT should be performed for optimal detection of metastases in
patients with extranodal Nk/T-cell lymphoma . Involvement of the bone marrow is rare, but aspiration
[55]
and biopsy can be considered for evaluation, particularly given that PET/CT may also have the ability to
detect bone marrow disease [56,57] . For patients with olfactory neuroblastoma, PET/CT is often not indicated
except when symptomatic distant metastatic disease or pathology shows high-grade features. Somatostatin
receptor-based methods can also be utilized because these tumors frequently express somatostatin
receptors [58,59] .