Buccal Carcinoma: Detection of Metastases in Early Postoperative State with PET•CT Imaging

Accurate detection of metastatic disease in head and neck cancer

Prof. Tzu-Chen Yen and Prof. Chun-Ta Liao

Case study data provided by Chang Gung Memorial Hospital Linkou, Taiwan, ROC

 |  Oct 15, 2012

History
A 54-year-old man diagnosed with right buccal cancer underwent fludeoxyglucose F 18 * (18F FDG) injection PET•CT for primary staging. PET•CT study was performed on Biograph™ mCT one hour following injection of 10 mCi 18F FDG.

 

*Siemens’ PETNET Solutions is a manufacturer of fludeoxyglucose F 18 injection (18F FDG). Indication and important safety information as approved by the US Food and Drug Administration can be found at the bottom of the page for 18F FDG, adult dose 5-10 mCi, administered by intravenous injection.


Diagnosis
PET•CT study demonstrated avid 18F FDG uptake in the primary buccal tumor (SUVmax 18.5). There were also glucose avid metastatic right cervical lymph nodes (level I, SUVmax 21.3), as well as small left cervical metastatic node (level II, SUVmax 4.6) suggesting bilateral neck node metastases. No other distant metastasis was visualized. The patient subsequently underwent wide excision of primary tumor with bilateral neck dissections. Histopathological evaluation of primary tumor revealed carcinoma. Histopathology revealed three level I metastatic nodes with two demonstrating extracapsular spread. Pathological tumor margins were free. Due to the risk factors including large tumor size (N2), metastatic nodes with extracapsular spread and with very high SUVmax (21.3), patient was subjected to adjuvant concurrent chemoradiotherapy (CCRT) after radical surgery. Five weeks after surgery, he had a second 18F FDG PET•CT study. The purpose of the second scan was to understand if there was any residual/recurrent tumor in the postoperative bed or elsewhere before adjuvant CCRT. Results of the second PET•CT study demonstrated significant amount of glucose avid residual tumor in the right buccal region and right neck nodal area, determined by the physician to be either inflammatory reaction after radical surgery plus neck dissection or locoregional tumor recurrence. There were also newly visualized 18F FDG avid lung nodules in the right lung base (SUVmax 6.8) as well as a small pleural deposit in the posterior aspect of left upper lobe suggesting distant metastases. These two lung metastases were new lesions which were not visualized in the pre-operative 18F FDG PET•CT performed five weeks earlier.

Comments
Usual timing for follow up 18F FDG PET•CT in oral cavity squamous cell carcinoma (OSCC) is usually 3 to 4 months after primary definitive treatment for high-risk group (surgery plus adjuvant therapy). Inflammatory changes secondary to radiation therapy or surgical dissection are prone to complicate PET•CT interpretation. However, depending on the tumor aggressiveness (four risk factors) and the clinical condition of the patient, particularly related to immune status due to poor nutrition after operation, earlier evaluation with 18F FDG PET•CT right before adjuvant therapy may be beneficial as shown in this clinical example. 18F FDG PET•CT has shown high accuracy for delineation of the extent of primary OSCC and high sensitivity for detection of neck node metastases. However, visualization of very small nodal lesions and nodes with regional or systemic micro-metastases is problematic with 18F FDG PET•CT due to small-sized lesions and/or low level of tracer uptake in such lesions. Technological innovations available in the state-of-the-art Biograph mCT scanner including improved count rate capability due to advancements in crystal technology, improved reconstruction of PET data and time of flight acquisition have aimed to improve lesion detectability and consequently further improve the sensitivity of the PET•CT study. Follow-up studies performed 8 to 12 weeks after completion of CCRT or surgery accurately demonstrate the presence of local failure or appearance of new metastases. However, an early follow- up PET•CT study following surgery for head and neck cancers is not yet standard practice. In this patient, an early follow-up PET•CT 5 to 6 weeks after surgery involving removal of primary buccal tumor with bilateral neck node dissections showed loco-regional recurrence as well as fresh lung metastases. Such lung metastases may have developed within 5 to 6 weeks after surgery. This suggests that the poor general condition along with immuno-compromised state following surgery with low food intake, blood loss following surgery and effect of medication may cause micrometastases or residual tumor cells not removed by surgery to show a flare phenomenon and grow rapidly to produce evidence of loco-regional failure and distant metastases demonstrable on 18F FDG PET•CT very early in the course of the disease. 

 

Conclusion
Higher number of metabolically active lymph node metastases and high SUV level of the nodes in pre-therapy 18F FDG PET•CT is a strong adverse prognostic indicator in OSCC. Identification of patients with poorer prognosis helps determine who would benefit from postsurgical adjuvant therapies. Such patients may benefit with an additional high-resolution Biograph PET•CT examination in early post-operative period prior to adjuvant therapy due to possibility of early recurrence detection. However, 18F FDG PET•CT in early post-operative phase demonstrates not only possible early loco-regional recurrence, but also lung and pleural metastases suggesting hematogenous tumor spread.

 

*Fludeoxyglucose F 18 Injection
INDICATIONS AND USAGE

Fludeoxyglucose F 18 injection (18F FDG) is indicated for positron emission tomography (PET) imaging in the following setting:
Oncology: For assessment of abnormal glucose metabolism to assist in the evaluation of malignancy in patients with known or suspected abnormalities found by other testing modalities, or in patients with an existing diagnosis of cancer.
 

IMPORTANT SAFETY INFORMATION
Radiation Risks

Radiation-emitting products, including fludeoxyglucose F 18 injection, may increase the risk for cancer, especially in pediatric patients. Use the smallest dose necessary for imaging and ensure safe handling to protect the patient and health care worker.
 

Blood Glucose Abnormalities
In the oncology and neurology setting, suboptimal imaging may occur in patients with inadequately regulated blood glucose levels. In these patients, consider medical therapy and laboratory testing to assure at least two days of normoglycemia prior to fludeoxyglucose F18 injection administration.
 

Adverse Reactions
Hypersensitivity reactions with pruritus, edema and rash have been reported; have emergency resuscitation equipment and personnel immediately available.

 

Full Prescribing Information for Fludeoxyglucose F 18 Injection

 

Fludeoxyglucose F 18 injection is manufactured by Siemens' PETNET Solutions, 810 Innovation Drive, Knoxville, TN 39732

The statements by Siemens customers described herein are based on results that were achieved in the customer's unique setting. Since there is no "typical" hospital and many variables exist (e.g., hospital size, case mix, level of IT adoption) there can be no guarantee that other customers will achieve the same results.