Abstract
Purpose
Cutaneous squamous cell carcinoma (cSCC) behaves aggressively in patients with chronic lymphocytic leukemia (CLL). Lymphadenopathy due to CLL can obscure the clinical and radiological assessment of nodal involvement by cSCC. This study aimed to evaluate whether functional imaging with positron emission tomography (PET)/computed tomography (CT) may clarify the clinical picture.
Methods
Five consecutive patients with cSCC and CLL who had a PET/CT scan for the purposes of cSCC staging between July 2000 and July 2010 were analyzed. PET/CT findings were compared to histopathology from subsequent neck dissection.
Results
PET/CT can distinguish nodal cSCC from leukemic infiltration with high specificity, allowing prompt appropriate management of nodal disease.
Conclusions
PET/CT is a promising modality for nodal staging in patients with cSCC and CLL, with the potential to improve outcomes in this poor prognosis group. Larger confirmatory studies are needed.
1
Introduction
Positron emission tomography (PET) is a widely used imaging modality in oncology, with an established role in the management of mucosal head and neck cancers . Hybrid imaging combining PET with computed tomography (CT) improves anatomical localization and accuracy compared with PET alone , and combined PET/CT scanners are now standard. The major strength of PET/CT lies in its ability to provide functional rather than purely structural information.
Cutaneous squamous cell carcinoma (cSCC) is a very common malignancy, associated with relatively low recurrence rates and seldom mortality in immunocompetent individuals. Patients with chronic lymphocytic leukemia (CLL) are immunosuppressed due to the disease and its treatment. Cutaneous SCC is more common and behaves more aggressively in patients with CLL . The pre-test probability of nodal involvement by cSCC is therefore greater in this population.
The presence of nodal metastases is a major determinant of prognosis in patients with cSCC, and nodal burden (number/size of nodes) correlates with outcome . Patients with CLL frequently have lymphadenopathy due to leukemic infiltration, obscuring the clinical assessment of nodal status in patients with cSCC. The aim of this case series is to highlight the potential role of PET/CT in the nodal staging of cSCC in patients with CLL.
2
Materials and methods
The hospital records of consecutive patients with cSCC and CLL who had a PET/CT scan for the purposes of cSCC staging between July 2000 and July 2010 were retrospectively analyzed. All patients had cSCC of the head and neck region. Data collection was approved by the institutional ethics committee.
2.1
Fluorodeoxyglucose (FDG)-PET/CT scanning
All PET/CT studies were acquired on a PET/CT scanner (Discovery V690 or STE, GE Medical Systems, Milwaukee, WI, USA). Patients were fasted for a minimum of four hours prior to scanning and generally in excess of 6 h. Blood glucose levels were less than 10 mmol/L at the time of FDG administration. A dose of 285–370 MBq was administered intravenously via a cannula based on patient weight. A non-contrast CT scan was acquired in helical mode at 140 kVp, 80 mA and reconstructed at a slice thickness of 3.27 mm. The FDG-PET scan encompassed the same axial extent as the CT scan, from the vertex to the proximal thighs, representing 4–6 bed positions depending on the size of the patient, with the patient’s arms by the sides to minimize reconstruction artefacts in the head and neck region. Each bed position had an acquisition time of 5-min and was acquired in 2-D or 3-D mode depending on the patient’s weight. The images were reconstructed using iterative reconstruction using the order-subset estimate maximization (OSEM) algorithm.
2.2
FDG-PET scan interpretation
PET, CT and PET/CT fused images were reviewed on a dedicated workstation (multimodality workstation using True-D software, Siemens). The FDG-PET/CT scan was interpreted using qualitative criteria. The FDG-PET/CT was reported as negative or positive for malignancy. Negative was defined as no FDG uptake beyond normal physiological activity or low grade activity commonly seen in CLL, and positive as FDG uptake beyond normal physiological activity or above what is perceived as acceptable low grade activity commonly seen in CLL nodes, with the pattern of uptake suggestive of malignancy such as squamous cell carcinoma. The PET images were subsequently reviewed and semi-quantitative analysis of all PET-positive lesions was performed using maximum standardized uptake value (SUVmax).
All patients had a subsequent neck dissection within 8 weeks of the PET/CT scan. PET/CT findings were compared with surgical pathology. Confidence intervals were calculated using an online statistical software package ( http://statpages.org/ctab2x2.html ).
2
Materials and methods
The hospital records of consecutive patients with cSCC and CLL who had a PET/CT scan for the purposes of cSCC staging between July 2000 and July 2010 were retrospectively analyzed. All patients had cSCC of the head and neck region. Data collection was approved by the institutional ethics committee.
2.1
Fluorodeoxyglucose (FDG)-PET/CT scanning
All PET/CT studies were acquired on a PET/CT scanner (Discovery V690 or STE, GE Medical Systems, Milwaukee, WI, USA). Patients were fasted for a minimum of four hours prior to scanning and generally in excess of 6 h. Blood glucose levels were less than 10 mmol/L at the time of FDG administration. A dose of 285–370 MBq was administered intravenously via a cannula based on patient weight. A non-contrast CT scan was acquired in helical mode at 140 kVp, 80 mA and reconstructed at a slice thickness of 3.27 mm. The FDG-PET scan encompassed the same axial extent as the CT scan, from the vertex to the proximal thighs, representing 4–6 bed positions depending on the size of the patient, with the patient’s arms by the sides to minimize reconstruction artefacts in the head and neck region. Each bed position had an acquisition time of 5-min and was acquired in 2-D or 3-D mode depending on the patient’s weight. The images were reconstructed using iterative reconstruction using the order-subset estimate maximization (OSEM) algorithm.
2.2
FDG-PET scan interpretation
PET, CT and PET/CT fused images were reviewed on a dedicated workstation (multimodality workstation using True-D software, Siemens). The FDG-PET/CT scan was interpreted using qualitative criteria. The FDG-PET/CT was reported as negative or positive for malignancy. Negative was defined as no FDG uptake beyond normal physiological activity or low grade activity commonly seen in CLL, and positive as FDG uptake beyond normal physiological activity or above what is perceived as acceptable low grade activity commonly seen in CLL nodes, with the pattern of uptake suggestive of malignancy such as squamous cell carcinoma. The PET images were subsequently reviewed and semi-quantitative analysis of all PET-positive lesions was performed using maximum standardized uptake value (SUVmax).
All patients had a subsequent neck dissection within 8 weeks of the PET/CT scan. PET/CT findings were compared with surgical pathology. Confidence intervals were calculated using an online statistical software package ( http://statpages.org/ctab2x2.html ).
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