[Positron emission tomography (PET) in clinical oncology. Part II]

18F-FDG-PET/CT in lymphoma: two decades of experience

The use of (18)F-FDG-PET/CT has changed the management of patients with lymphoma for the last two decades. This technique improves initial staging of the disease, making a prognostic approach and appropriate treatment planning, as well as monitoring therapy response of lymphoma. However, there are still controversial issues in medical literature that impact on daily clinical practice. This comprehensive literature review summarizes the current information regarding the potential use of (18)F-FDG-PET/CT in patients with lymphoma, highlighting the main applications and the current dilemmas for the nuclear medicine physicians at the time of the evaluation of these studies, trying to standardize criteria for its assessment, particularly in restaging and therapy monitoring.

[False positive in pelvis in a PET-CT scan due to ovarian reimplantation: a case report]

We present the case of a 36-year-old premenopausal woman with a background of surgically-treated cervical neoplasm. She underwent a positron emission tomography-computed tomography (PET-CT) for evaluation of the new appearance of abnormal inguinal lymph nodes. The study showed two hypermetabolic nodules in the pelvic region suggestive of corresponding to an implant and to tumor involvement of the lymph node, respectively. After a clinical evaluation and a new PET-CT scan, it was considered that these uptake foci corresponded to physiological activity of the FDG secondary to ovarian activity in a patient with ovariopexy. This article shows the importance of having complete clinical information about the patients before evaluating the studies. We also present a review of the medical literature on the cervical neoplasm and metabolic behavior of the adnexa in relationship with the menstrual cycle of pre-menopausal women.

Fluorine-18 fluorodeoxyglucose PET in the preoperative staging of colorectal cancer

INTRODUCTION

In patients with colorectal cancer (CC), preoperative evaluation and staging should focus on techniques that might alter the preoperative or intraoperative surgical plan. Conventional imaging methods (CT, MRI) have low accuracy for identifying the depth of tumour infiltration and have limited ability to detect regional lymph node involvement. The aim of this study was to evaluate the utility of FDG-PET in the initial staging of patients with CC in comparison with conventional staging methods and to determine its impact on therapeutic management.

METHODS

One hundred and four patients with a diagnosis of CC (53 males and 51 females; mean age 66.76+/-12.36 years), selected prospectively, were studied for staging using a standard procedure (CT) and FDG-PET. When possible, the reference method was histology.

RESULTS

In 14 patients, surgery was contraindicated by FDG-PET owing to the extent of disease (only 6/14 suspected by CT). FDG-PET revealed four synchronous tumours. For N staging, both procedures showed a relatively high specificity but a low diagnostic accuracy (PET 56%, CT 60%) and sensitivity (PET 21%, CT 25%). For M assessment, diagnostic accuracy was 92% for FDG-PET and 87% for CT. FDG-PET results led to modification of the therapy approach in 50% of patients with unresectable disease. FDG-PET findings were important, revealing unknown disease in 19.2%, changing the staging in 13.46% and modifying the scope of surgery in 11.54% (with a change in the therapeutic approach in 17.85% of those patients with rectal cancer).

CONCLUSION

Compared with conventional techniques, FDG-PET appears to be useful in pre-surgical staging of CC, revealing unsuspected disease and impacting on the treatment approach.

Positron emission tomography: a false negative result in cystic encephalic mestastases from a small cell bronchial carcinoma

Lung cancer represents one of the most common malignant diseases. Many investigations are used in the staging study including, most recently, PET. We present a case of cystic cerebral metastases (with no oedema) from a small cell carcinoma which were not detected by PET.

Detección temprana con PET-FDG de tumores inesperados de colon en pacientes con otra patología tumoral conocida

Patients with known tumors can have other tumors in unexpected places, the so-called synchronic or second primary cancers. In these patients, whole-body fluorodeoxyglucose positron emission tomography (FDG-PET) to study known tumors can identify other tumors that would escape notice if only the sites of known tumors were investigated. We present 3 patients in whom whole-body FDG-PET was requested to study known tumors: 2 lung cancers and one melanoma. FDG-PET localized the known lesions and revealed hypermetabolic uptake in the abdomen in all 3 patients. Endoscopic polypectomy and pathologic analysis were performed, revealing 2 colon cancers and a tubular adenoma with a high degree of focal atypia. Whole body FDG-PET is a highly useful technique in the early diagnosis of colorectal cancer, which in turn allows complete cure of patients with this disease.

Positron-emission tomography with fluorine-18-fluoro-2-deoxy-D-glucose for gallbladder cancer diagnosis

BACKGROUND

Recent advances in hepatobiliary surgery have underscored the need for presurgical diagnosis of gallbladder cancer. Frequently, clinical presentation, biochemical analysis, and structural ultrasound or computed axial tomography images do not enable definitive differentiation of cholecystitis or cholethiasis from gallbladder cancer. The aim of this study was to evaluate the role of fludeoxy glucose-positron-emission tomography (FDG-PET) in establishing the benign or malignant nature of gallbladder lesions.

METHODS

A case series of 16 patients with clinical symptoms suggestive of biliary colic or chronic cholecystitis and with inconclusive ultrasound and/or computed axial tomography findings for presence of gallbladder cancer were studied by FDG-PET.

RESULTS

FDG-PET showed a sensitivity of 0.80, a specificity of 0.82, and positive and negative predictive values of 0.67 and 0.90, respectively. There was 1 false- negative result in 1 patient with mucinous adenocarcinoma and 2 false-positive results in 1 patient with tuberculoid granulomatous reaction and 1 patient with polypoid lesion with adenomyomatosis.

CONCLUSIONS

FDG-PET may be of utility to establish the diagnosis of gallbladder cancer in patients with nonspecific clinical and imaging findings.