Table 4 Post-treatment imaging of oral cavity cancer beyond the first 3–6-month baseline imaging study. Overview of included studies evaluating the results obtained with routine imaging surveillance compared to symptom-directed imaging and/or clinical finding-directed imaging

Imaging surveillance (at least once) after 3–6 months appears to be beneficial (in terms of lesion detection)

 Fukumoto 2021 [52]

CT/PET-CT

• Retrospective study including 324 patients

• It is desirable to perform PET/CT within 3–6 months and at 1 year after surgery and to consider CECT as an option in between PET/CT

 Liu 2021 [53]

CT/MRI

• Retrospective study including 741 patients

• 19.7% of recurrences were found during routine imaging only

• In late-stage and elderly patients, frequent head and neck CT/MRI scan was associated with a better prognosis

 Ravanelli 2021 [54]

PET-CT

• Retrospective observational study including 87 patients

• Performing imaging studies every 6 months for 2 years changed the diagnostic/therapeutic strategy in about one-fifth of patients

 Chi 2020 [55]

(?)

• Retrospective study including 83 patients

• 29.4% of recurrences were detected by serial imaging alone in asymptomatic patients; most of them (92.3%) occurred within the first 2 years

 Lin 2017 [56]

PET-CT

• Retrospective study including 111 patients

• Scheduled periodic PET/CT surveillance is a valuable tool for early detection of recurrent lesion(s) in asymptomatic OSCC patients who bear risk factors for disease recurrence

 Peisker 2017 [57]

RX/CT

• Retrospective study including 228 patients

• The results of this study suggest an intensified imaging follow-up within the first 2 years after surgery

 Rivelli 2011 [58]

CT

• Retrospective study including 294 patients

• Routine CT for follow-up is indicated for detecting lymph node metastases as well as local recurrence

Imaging surveillance after 3–6 months appears to have no or only limited benefit

 Al-Shwaiheen 2014 [59]

MRI

• Retrospective study including 62 patients

• Routine MRI after 6 months may be unnecessary in patients without concurrent suspicious symptoms or exam findings

Imaging surveillance after 3-6 m is of uncertain benefit/other

 Krabbe 2009 [60]

PET-CT

• Prospective study including 48 patients

• PET is a suitable routine posttreatment surveillance tool and detects malignancy before clinical suggestion by the regular follow-up arises

• The best timing of a systematic PET scan is between 3 and 6 months after treatment