18F FDG*-PET•CT-based RT Planning & Follow-up in a Case of Carcinoma of the Tongue Base

Annika Loft Jakobsen, MD, Department of Nuclear Medicine, Rigshospitalet, Copenhagen, Denmark |  2013-12-01

History

A 44-year-old female patient presented with swelling on the left side of her neck, which was suggestive of an enlarged lymph node on clinical examination. The neck node was surgically removed and biopsy revealed metastases from squamous cell carcinoma. All clinical investigations including nasopharyngeal endoscopies were negative. In order to detect the primary tumor, the patient underwent Fludeoxyglucose F 18 (18F FDG) PET•CT.

  

 

*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

 An 18F FDG PET•CT scan was performed using a BiographTM mCT, which is capable of high-resolution PET acquisition. High matrix reconstructions enabled by Hi-Rez acquisition and high count rate capability with ultraHD•PET on Biograph mCT enables excellent visualization of small metastatic lesions with high lesion contrast and low partial volume effect. The PET•CT study revealed a hypermetabolic primary tumor in the left side of the base of tongue. Radiation planning was performed using the PET•CT data. SUVmax threshold- based tumor regions of interest (ROI) were contoured (Figure 2A) and exported to a radiation-treament-planning system. The dose plan as shown (Figure 2B) delivered a high dose level to the primary tumor and the location of the initial lymph node.

1. 18F FDG PET•CT axial section through the base of tongue shows a hypermetabolic primary tumor in the base of the tongue toward the left side. Note the free margins of the adjacent epiglottis. No clearly defined hypermetabolic lymph nodal metastases is delineated.

Examination Protocol

Scanner          Biograph mCT 128

Scan dose      10 mCi (370 NBq) 18F FDG

San Delay      1 hour post injection

Parameters     Whole body: 2 min/bed, Neck: single bed 5 min

Acquisition     400x400 matrix ultraHD•PET reconstruction

CT                  130 kV, 70 eff mAs

 

Comments

The patient underwent radiation therapy according to the PET•CTbased dose escalation plan. A second PET•CT performed 3 months after the completion of radiotherapy showed no sign of residual or recurrent tumor.

 

This clinical example demonstrates the sensitivity of 18F FDG PET/CT for detection of primary tumor in patients presenting with malignant cervical nodal metastases from unknown primary. In a study of 38 consecutive patients with neck node metastases from unknown primary, Wartski et al1 found 18F FDG PET/CT positive in 68% of patients (26/38), which helped guide biopsies. PET/CT impacted treatment in 23 out of 38 patients (60%) including modification of radiation planning and surgery and in some cases cancellation of futile surgery.

 

A recent meta-analysis2 involving 7 studies (246 patients) of the accuracy of 18F FDG PET and PET/CT in neck node metastases with unknown primary showed a sensitivity of 97%, but with a specificity of 68%.

 

PET/CT-based radiation therapy planning for oropharyngeal tumors has been widely adopted. High-matrix-resolution of PET acquisition along with improved lesion contrast provided by time-of-flight PET and point spread function (PSF) reconstruction have le to sharper delineation of tumor margins, as evident in this clinical example using Biograph mCT. Biograph mCT also incorporates a wide bore that supports radiation therapy planning with breast board and other immobilization devices. Dose escalation strategies based on PET uptake intensity have shown the potential for improving dose delivery to the target, while reducing toxicity to surrounding tissue and critical structures. Moreover, PET/ CT-based metabolic imaging can be used as an effective follow-up tool after chemoradiation therapy. In a recent publication Chan et al3, 77 patients with HPV-positive oropharyngeal squamous cell carcinoma underwent a follow-up 18F FDG PET/CT approximately 90 days after chemoradiation therapy. 18F FDG PET/CT with SUVmax threshold of 2 showed 100% negative predictive value compared to NPV of 85% shown by CT. Neck dissection was avoided in all patients negative on follow-up 18F FDG PET/CT with no regional failures after 6 months following PET/CT. In the present study, a follow-up 18F FDG PET/CT was performed 3 months after completion of chemoradiation therapy and showed complete response of the primary tumor and no evidence of neck nodal metastases. The prognostic value of such findings is extremely positive. As demonstrated in this clinical example, 18F FDG PET/CT is an integral part of staging, therapy planning and follow up of oropharyngeal cancer. A recent meta-analysis2 involving 7 studies (246 patients) of the accuracy of 18F FDG PET and PET/CT in neck node metastases with unknown primary showed a sensitivity of 97%, but with a specificity of 68%. PET/CT-based radiation therapy planning for oropharyngeal tumors has been widely adopted. High-matrix-resolution of PET acquisition along with improved lesion contrast provided by time-of-flight PET and point spread function (PSF) reconstruction have led to sharper delineation of tumor margins, as evident in this clinical example using Biograph mCT. Biograph mCT also incorporates a wide bore that supports radiation therapy planning with breast board and other immobilization devices. Dose escalation strategies based on PET uptake intensity have shown the potential for improving dose delivery to the target, while reducing toxicity to surrounding tissue and critical structures. Moreover, PET/CT-based metabolic imaging can be used as an effective follow-up tool after chemoradiation therapy. In a recent publication Chan et al3, 77 patients with HPV-positive oropharyngeal squamous cell carcinoma underwent a follow-up 18F FDG PET/CT approximately 90 days after chemoradiation therapy. 18F FDG PET/CT with SUVmax threshold of 2 showed 100% negative predictive value compared to NPV of 85% shown by CT. Neck dissection was avoided in all patients negative on follow-up 18F FDG PET/CT with no regional failures after 6 months following PET/CT.

 

In the present study, a follow-up 18F FDG PET/CT was performed 3 months after completion of chemoradiation therapy and showed complete response of the primary tumor and no evidence of neck nodal metastases. The prognostic value of such findings is extremely positive. As demonstrated in this clinical example, 18F FDG PET/CT is an integral part of staging, therapy planning and follow up of oropharyngeal cancer.

 

 

*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

**Based on competitive information available at time of publication. Data on file.

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.
 

References:

1. Nucl Med Commun. 2007 May;28(5):365-71

2. Zhu et al Surg Oncol. 2013 Jul 10

3. Arch Otolaryngol Head Neck Surg. 2012 November 1; 138(11): 1040-1046