Approach to the Patient with Unknown Primary Squamous Cell Carcinoma of the Head and Neck

Surgical Puzzle: Concurrent Comprehensive Neck Dissection Strategies Unravelling the Mystery of Carcinoma Unknown Primary when Performed with TORS Radical Tonsillectomy and Mucosal Tongue Base Wedge Biopsy in Northern Indian Cohort

The study delves into the distribution of cervical nodal metastasis among patients diagnosed with carcinoma of unknown primary who underwent definitive diagnostic surgical management in form of transoral robotic surgery assisted ipsilateral radical tonsillectomy and tongue base mucosal wedge biopsy with concurrent therapeutic open ipsilateral neck dissection. We conducted a prospective study at a tertiary care center over two-years, enrolling patients with unilateral neck swelling histopathologically confirmed as squamous cell carcinoma neck metastasis. For cases where the primary site remained undetected despite evaluation, patients underwent Transoral Robotic Surgery (TORS) assisted ipsilateral radical tonsillectomy and tongue base wedge biopsy, along with concurrent open ipsilateral neck dissection. The study examines the clinicopathological correlation of nodal metastasis in carcinoma of unknown primary and explores the concepts of Lymph node yield (LNY) and Lymph node density (LND). Clinicoradiologically, the majority of patients exhibited N2b disease (n = 10/18, 55.55%). However, histopathological examination of the neck dissection specimen revealed N3b disease in the majority (n = 5/17, 29.4%). Neck dissection was aborted for 1 patient with unresectable N3b nodal metastasis during the procedure. The most commonly affected lymph node level clinicoradiologically was level II (n = 18/18, 100%), which corresponded to level II pathologically in most cases (n = 15/18, 88.2%). Ipsilateral radical neck dissection was required in the majority of cases (n = 10/17, 58.82%). The median Lymph Node Yield (LNY) from ipsilateral neck dissection was 30.78 ± 3.52, with the highest Lymph Node Ratio (LNR) detected from level II (11.1 ± 1.56). In the context of carcinoma of unknown primary with secondary neck metastasis, exploring emerging concepts such as Lymph Node Ratio (LNR) and Lymph Node Density (LND) alongside other clinicopathological parameters is crucial. These concepts provide valuable insights into the metastatic burden and may aid in refining prognostication and treatment strategies for patients with this condition.

Head-to-head comparison of [68Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/CT for the evaluation of tonsil cancer and lymph node metastases: a single-centre retrospective study

BACKGROUND

This study aimed to compare the diagnostic value of [68 Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/CT imaging for primary lesions and metastatic lymph nodes in patients with tonsil cancer.

METHOD

Twenty-one tonsil cancer patients who underwent [68 Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/CT scans within two weeks in our centre were retrospectively enrolled. The maximum standardized uptake value (SUVmax) and tumor-to-background ratio (TBR) of the two tracers were compared by using the Mann‒Whitney U test. In addition, the sensitivity, specificity, and accuracy of the two methods for diagnosing metastatic lymph nodes were analysed.

RESULTS

In detecting primary lesions, the efficiency was higher for [68 Ga]Ga-DOTA-FAPI-04 PET/CT (20/22) than for [18F]FDG PET/CT (9/22). Although [68 Ga]Ga-DOTA-FAPI-04 uptake (SUVmax, 5.03 ± 4.06) was lower than [18F]FDG uptake (SUVmax, 7.90 ± 4.84, P = 0.006), [68 Ga]Ga-DOTA-FAPI-04 improved the distinction between the primary tumor and contralateral normal tonsillar tissue. The TBR was significantly higher for [68 Ga]Ga-DOTA-FAPI-04 PET/CT (3.19 ± 2.06) than for [18F]FDG PET/CT (1.89 ± 1.80) (p < 0.001). In lymph node analysis, SUVmax and TBR were not significantly different between [68 Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/CT (7.67 ± 5.88 vs. 8.36 ± 6.15, P = 0.498 and 5.56 ± 4.02 vs. 4.26 ± 3.16, P = 0.123, respectively). The specificity and accuracy of [68 Ga]Ga-DOTA-FAPI-04 PET/CT were higher than those of [18F]FDG PET/CT in diagnosing metastatic cervical lymph nodes (all P < 0.05).

CONCLUSION

The availability of [68 Ga]Ga-DOTA-FAPI-04 complements the diagnostic results of [18F]FDG by improving the detection rate of primary lesions and the diagnostic accuracy of cervical metastatic lymph nodes in tonsil cancer compared to [18F]FDG.

The Role of Trans Oral Robotic Surgery in the Carcinoma of Unknown Primary: A New Evidence in the Horizon?

The detection of the primary site in Carcinoma of Unknown Primary (CUP) is a challenging task which can significantly alter the course of management and also prognosis. Various modalities have been assessed with varying sensitivity and specificity. Imaging and cytological diagnosis have formed a key part of the diagnostic algorithm of CUP. Trans Oral Robotic Surgery offers the advantage of being both diagnostic as well as therapeutic with promising sensitivity and specificity and can form an integral part in the management of CUP. A prospective study was carried out at a tertiary care centre over a period of one year. Patients with unilateral neck swelling which was histopathologically proven squamous cell carcinoma neck metastasis were included in the study. They were evaluated with endoscopy and radiology according to the standard algorithm. When these failed to detect the primary, the patients underwent ipsilateral radical tonsillectomy and tongue base mucosal wedge biopsy via TORS. Post-operative histopathological examination was done on the resected specimens to detect the primary site. Transoral Robotic Surgery was able to localise primary in 50% of the patients enrolled in the study. Out of the primary site identified by TORS; 55.56% were located in the tonsil and 44.4% in the tongue base. TORS can offer promising detection rates of the occult primary in CUP and should form an integral part of the diagnostic algorithm.

The Added Value of 68Ga-FAPI-04 PET/CT in Patients with Head and Neck Cancer of Unknown Primary with 18F-FDG Negative Findings

¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) plays an important role in locating of primary tumor for patients with head and neck cancer of unknown primary (HNCUP). Nevertheless, it can be challenging to locate the primary malignancy in ¹⁸F-FDG-PET/CT scan in some cases. As ⁶⁸Ga-radiolabeled fibroblast activation protein inhibitor (FAPI) PET/CT has promising results in detecting different tumor entities, our study aimed to evaluate the performance of ⁶⁸Ga-FAPI-PET/CT for detecting the primary tumor in HNCUP patients with negative ¹⁸F-FDG findings. Methods: A total of eighteen patients (16 males and 2 females; median age, 55 years; range, 24-72 years) with negative ¹⁸F-FDG findings were enrolled in this study. All patients underwent ¹⁸F-FDG and ⁶⁸Ga-FAPI-PET/CT within one week. Biopsy and histopathological examinations were done in the sites with positive ⁶⁸Ga-FAPI-PET/CT findings. Results: ⁶⁸Ga-FAPI-PET/CT detected the primary tumor in 7 out of 18 patients (38.89%). Among the 7 patients, in respect of the primary tumor sites, 1 was in nasopharynx, 2 were in palatine tonsil, 2 were in submandibular gland, and 2 were in hypopharynx. The primary tumors showed moderate to intensive uptake of FAPI (mean SUV_max, 8.79; range, 2.60-16.50) and excellent tumor-to-contralateral normal tissue ratio (mean SUV_max ratio, 4.50; range, 2.17-8.21). In lesion-based analysis, a total of 65 lymph nodes and 17 bone metastatic lesions were identified. The mean SUV_max of lymph node metastases were 9.05 ± 5.29 for FDG and 9.08 ± 4.69 for FAPI (P = 0.975); as for bone metastases, the mean SUV_max were 8.11 ± 3.00 for FDG and 6.96 ± 5.87 for FAPI, respectively (P = 0.478). The mean tumor-to-background ratio (TBR) values of lymph node and bone metastases were 10.65 ± 6.59 vs. 12.80 ± 8.11 (P = 0.100) and 9.08 ± 3.35 vs. 9.14 ± 8.40 (P = 0.976), respectively. Conclusion: We presented first evidence of diagnostic role of ⁶⁸Ga-FAPI-PET/CT in HNCUP, and our study demonstrated that ⁶⁸Ga-FAPI-PET/CT had the potential to improve the detection rate of primary tumor in HNCUP patients with negative FDG findings. Moreover, ⁶⁸Ga-FAPI had similar performance in assessing metastases with ¹⁸F-FDG.

Diagnostic performance of 18F-FDG PET/CT for the detection of occult primary tumors in squamous cell carcinoma of unknown primary in the head and neck: a single-center retrospective study

OBJECTIVE

To investigate the diagnostic performance of 18F-FDG PET/computed tomography (CT) for the detection of occult primary tumors in patients with squamous cell carcinoma of unknown primary (SCCUP) in the head and neck.

PATIENTS

From March 2016 to January 2020, 37 patients diagnosed as SCCUP before PET/CT were retrospectively reviewed. The diagnosis of SCCUP was made when an overt primary tumor location could not be found for histologically proven squamous cell cervical lymphadenopathy after a complete diagnostic workup which includes full medical history, physical examinations, flexible rhinolaryngoscopy and CT or MRI. The PET/CT images were visually assessed by two nuclear medicine radiologists. Histopathological investigations after the PET scan served as the reference standard.

RESULTS

The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of PET/CT for SCCUP were 71.4, 43.8, 62.5, 53.9 and 59.5%, respectively. PET/CT allowed identification of previously undetected lesions in 40.5% of the SCCUP patients. A total of 24 PET/CT scans indicated a positive result. Among them, nine were categorized into false-positive because of negative results from subsequent targeted and random biopsies. There were 13 PET/CT scans with a negative result, six of which, however, were revealed to have a primary site by subsequent random biopsies.

CONCLUSION

18F-FDG PET/CT was shown to be useful in detecting a primary tumor for SCCUP, but had limitations in terms of both false-positive cases and false-negative cases. Therefore, histopathological investigations such as targeted and random biopsy should be viewed as necessary practice irrespective of PET/CT results.