Hypopharyngeal post-treatment PET/RM examination showing an increase of

Hypopharyngeal SCC originates
most frequently in the pyriform sinus, followed by the posterior pharyngeal
wall, and the postcricoid area;14 its incidence is estimated to be
0.78 cases per 100000 individuals in the United States each year.15
Tumours are traditionally graded into well-, moderately-, and poorly
differentiated SCC. The overall 5-year survival rate is 62.5% and TNM is the
most significant predictor of survival.16 In our case series, the two patients with hypopharynx carcinoma showed a
partial response after concurrent CHT/RT. In both cases there was a concordant
increase of ADC (mean,
minimum and maximum) values and a reduction of  iAUC and Kep post-treatment values; however, while in patient 2 a reduction of Ktrans and
Ve values was also observed, patient 1 showed a paradoxal increase of such
parameters; this difference could be explained by the different tumor grade (G3
in patient 1 and G2 in patient 2) or could be an early sign of a different
prognosis even if, at present, both patients show the same stable outcome.

Squamous cell carcinoma of the oropharynx is
increasing in incidence, related to an increase in incidence in human
papillomavirus (HPV) infections among middle aged men, and sexual behavior is a
risk factor.17 HPV+ oropharyngeal squamous cell carcinoma represents
a distinct subset of head and neck cancers with different epidemiological,
clinical and molecular features that are associated to better prognosis as
compared to HPV- cancers. Tumour size and nodal status are the most significant
prognostic factors. Histological grade correlates poorly with patient outcome.16
In our study, patient 3 with a HPV- retromolar trigone carcinoma, treated with
concurrent CHT/RT, was classified as SD. In this patient, who also underwent
drainage of a large intratumoral abscess, the solid tumor was considered stable
at post-treatment PET/RM examination showing an increase of ADC (mean,
minimum and maximum) values and of all perfusion post-treatment values except
for Ve; the increase of perfusion parameters, despite the stable disease, could
be considered predictive of the progression disease observed during the
clinical and instrumental follow-up, as often occurs in HPV- tumors.

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Nasopharyngeal carcinoma is a rare malignancy, it is
endemic in a few well defined populations and the fourth most common new
malignancy in Hong Kong.18 It is near constantly associated with
EBV, irrespective of ethnic background, indicating a probable oncogenic role of
the virus in the genesis of this tumour. Positive serology against Epstein-Barr
virus (EBV) is found in close to 100% of patients with non-keratinizing nasopharyngeal
carcinoma. The mainstay of treatment is radiation therapy; the average 5-year
survival steadily increased until 75% in patient without distant metastasis.
The presenting stage is the most important prognostic factor. Younger age and
female gender are associated with better prognosis. In our case series, both patients 4 and 5 with
nasopharynx carcinoma a complete response was observed with no detectable tumor
lesions on PET/MR post-treatment examinations. Interestingly, these two
patients showed the lowest ADC and iAUC pre-treatment mean values; this is in
accordance with the current literature in which is reported that low
pre-treatment ADC values are associated to a good response to therapy.4
In addition, the finding of low iAUC pre-treatment values in these two patients
could support the hypothesis of a reduced aggressiveness of hypovascular
tumors. In a previous study
by King et al, who analyzed the role of DCE MRI for pre-treatment prediction and
assessment of response to CHT and or RT in 49 patients with head and neck
carcinoma, site control residual masses showed significantly lower Kep and iAUC
compares with site failure residual masses.19 Moreover, site control
residual masses showed a decrease in the iAUC while the site failure residual
masses showed an increase in iAUC. Even if at present the data for
pre-treatment DCE-MRI seems to be insufficient to allow translation to clinical
practice, some perfusion parameters i.e. iAUC and Kep may be reliable in assessing
the response to treatment in patients with HNSCC.

In conclusion, multiparametric evaluation with
contrast-enhanced simultaneous PET/MRI could be a useful tool to assess the
response to CHT and/or RT in patients with HNSCC. Future studies in a larger
cohort of patients are necessary to confirm our results and to identify possible
metabolic and/or functional biomarkers that could be predictive of patient’s
response to therapy.