Positron emission tomographic imaging of head and neck lesions

Radiotherapy volume delineation using dynamic [18F]-FDG PET/CT imaging in patients with oropharyngeal cancer: a pilot study

PURPOSE

Delineation of gross tumour volume in 3D is a critical step in the radiotherapy (RT) treatment planning for oropharyngeal cancer (OPC). Static [¹⁸F]-FDG PET/CT imaging has been suggested as a method to improve the reproducibility of tumour delineation, but it suffers from low specificity. We undertook this pilot study in which dynamic features in time-activity curves (TACs) of [¹⁸F]-FDG PET/CT images were applied to help the discrimination of tumour from inflammation and adjacent normal tissue.

METHODS

Five patients with OPC underwent dynamic [¹⁸F]-FDG PET/CT imaging in treatment position. Voxel-by-voxel analysis was performed to evaluate seven dynamic features developed with the knowledge of differences in glucose metabolism in different tissue types and visual inspection of TACs. The Gaussian mixture model and K-means algorithms were used to evaluate the performance of the dynamic features in discriminating tumour voxels compared to the performance of standardized uptake values obtained from static imaging.

RESULTS

Some dynamic features showed a trend towards discrimination of different metabolic areas but lack of consistency means that clinical application is not recommended based on these results alone.

CONCLUSIONS

Impact of inflammatory tissue remains a problem for volume delineation in RT of OPC, but a simple dynamic imaging protocol proved practicable and enabled simple data analysis techniques that show promise for complementing the information in static uptake values.

18F-FDG PET/CT Imaging of Bilateral Renal Metastasis of Breast Adenoid Cystic Carcinoma

We report the case of a 65-year-old woman with a history of adenoid cystic carcinoma (ACC) of the breast. Fifteen years after mastectomy, the patient underwent a right upper lobectomy for a lung mass, and biopsy indicated ACC metastasis. Ten years after lobectomy, an F-FDG PET/CT was performed for restaging to rule out further metastases. We observed intense FDG uptake in enlarged polylobulated kidneys, which was biopsy proven as ACC metastasis.

18F-FDG PET evaluation of sinonasal papilloma

OBJECTIVE

It has been suggested that (18)F-FDG uptake determined by PET can differentiate squamous cell carcinoma from benign sinonasal papilloma. We wish to present our experience with sinonasal papillomas and PET/CT to determine if the degree of FDG uptake is indicative of benign or malignant disease.

CONCLUSION

Benign sinonasal papilloma may be associated with intense FDG uptake on PET/CT. FDG PET/CT does not appear to reliably differentiate benign from malignant sinonasal papilloma.

La TEP dans les cancers des voies aérodigestives supérieures

FDG PET is useful when cancer in the head or neck (except for tumors of the salivary glands, which cannot be characterized accurately) is diagnosed or suspected but not confirmed by biopsy. It can, for example, find evidence of suspicious lymph nodes in clinically N0 necks, detect foci suggestive of distant metastases or second cancers, and provide useful prognostic information. Because it can be very difficult to identify anatomical structures and landmarks on PET images in the head and neck region, PET/CT fusion is very helpful in this area. In early assessment of chemotherapy, the absence of a significant reduction in FDG uptake after one or two cycles predicts lack of efficacy and thus indicates the need to modify the regimen. Conversely, the disappearance of FDG foci indicates effective treatment and good prognosis but cannot rule out the persistence of any malignant tissue at the end of treatment, especially neoadjuvant. Diagnostic impact is probably greatest in monitoring for recurrence and restaging known recurrence: FDG PET should be performed - perhaps routinely - early enough that curative options are still open, but long enough after the end of treatment to avoid false positive results from inflammation. The strategy and timing of FDG PET during follow-up should be determined in more detail in the future, as should the role (if any) of fluorotyrosine (FET) PET in squamous cell carcinoma.

Intérêt de la fusion TEP/TDM dans l’exploration de l’envahissement mandibulaire des cancers de la cavité orale et de l’oropharynx

The aim of the study is to assess mandible involvement in oral cavity and oropharyngeal carcinomas.

OBJECTIVE

To evaluate interest of fusion of Positron Emission Tomography (PET) with Computed Tomography scan (CT scan).

METHOD

Eight patients were included in this prospective study. Each patient underwent PET and CT scan of the head and neck before surgery including tumorectomy and mandibulectomy. We compared results of PET- CT fusion with histologic examinations.

RESULTS

Oral cavity (6), oropharyngeal (2) carcinoma: Mandibular invasion was suspected by PET-CT in 3 cases, but was confirmed in histological examination in only 2 cases. In 5 cases, PET-CT did not find mandibular invasion; this was confirmed in histological examination in all cases. Sensibility of PET-CT fusion was 100%, specificity was 83%. Positive predictive value was 66% and negative predictive value was 100%.

DISCUSSION

PET-CT fusion provided maximal sensitivity. Specificity was better than for MRI but less than CT-scan. There were no false negatives and the false positive rate was 33%.

CONCLUSION

PET-CT fusion is interesting to predict mandible involvement. Further studies are necessary to confirm these preliminary results.

Positron emission tomographic imaging of acoustic neuromas

Positron emission tomography (PET) examination with both [11C]methyl-l-methionine (Met) and [18F]fluoro-2-deoxyglucose (FDG) was performed in the same patients with acoustic neuroma wherever possible in order to compare the usefulness of the two methods. The study included six patients who visited the Osaka City University Hospitals, between April 1994 and October 1998, for complaints associated with acoustic neuroma. All patients were examined by magnetic resonance imaging (MRI) and Met-PET. Four patients were examined by FDG-PET. The tumor's region of highest accumulation was selected as the region of interest; the tumor/normal ratio (T/N ratio) was defined as the ratio of radioisotope counts for tumor and normal gray matter. All tumors in this series were detected by MRI. In the Met-PET images, four tumors were easily identified, with a high T/N ratio. However, two tumors could not be identified using Met-PET. On FDG-PET, no cases could be identified. The T/N ratio for the four patients with positive Met-PET findings averaged 1.694 +/- 0.266. PET, especially Met-PET, is a powerful means of examination providing functional information on tumors in acoustic neuroma. Met-PET may therefore be useful for acoustic neuroma, which is known to proliferate slowly, as for malignant tumors, in evaluating the proliferating potential of a tumor, in determining patients in whom to perform radiological treatment and in monitoring post-treatment progress.

Evaluation of recurrent squamous cell carcinoma of the head and neck with FDG positron emission tomography

PURPOSE

This study compared the effectiveness of fluorodeoxyglucose (FDG) positron emission tomography (PET) with computed tomography (CT), magnetic resonance imaging (MRI), or both for the assessment of recurrent squamous cell carcinoma of the head and neck. The value of quantifying the standardized uptake values (SUV) to distinguish recurrent neoplasm from inflammatory lesions and normal structures was also evaluated.

METHODS

Forty-three patients with head and neck cancer were examined with F-18 FDG PET at least 4 months after their last course of radiation therapy (mean, 11 months). The SUVs were measured in visually identified regions of abnormally increased activity and were compared with the values in normal mucosa, the base of the tongue, and the hard palate to determine if an optimal cutoff value exists for diagnosing recurrence of malignant lesions. The final diagnosis of recurrence was made based on biopsy or at least 6 months' clinical follow-up.

RESULTS

FDG PET correctly detected recurrence in 20 of 22 patients who had 45 discrete lesions located in the field of the upper aerodigestive tract. Two false-negative and three false-positive results were identified. The accuracy of FDG PET was 88% (38 of 43 patients), compared with 66% (25 of 38 patients) for CT, MRI, or both. Although there was a significant difference of SUVs (P = 0.0036) between the recurrent lesions and normal structures, the optimal cutoff values were difficult to define.

CONCLUSIONS

Visual analysis of FDG PET is significantly more accurate in the diagnosis of recurrent squamous cell cancer of the head and neck than are CT or MRI. However, single SUV quantification does not significantly enhance efficacy.