Identifying and distinguishing treatment effects and complications from malignancy at FDG PET/CT.

Fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is increasingly used in the initial staging, evaluation of treatment response, and surveillance of many malignancies. Uptake of FDG is substantially increased in most malignancies, compared with its uptake in normal tissues, and the finding of FDG avidity often leads to cancer detection earlier than abnormalities can be seen at anatomic imaging. However, FDG is not a cancer-specific agent, and FDG avidity can be seen in many benign processes. It can be particularly challenging to discriminate malignancy from benign FDG-avid changes caused by surgery and procedures, radiation therapy, and chemotherapy. FDG-avid abnormalities caused by surgery and procedures include inflammation at sites of incision or dissection, inflammation from vascular compromise or surgical retraction, surgical transposition of structures with physiologic FDG avidity (such as ovaries or testes), and pleurodesis inflammation. Radiation therapy may induce FDG-avid pneumonitis, esophagitis, or hepatitis, as well as osteoradionecrosis or fractures. FDG-avid chemotherapy complications include pneumonitis, osteonecrosis, enterocolitis, and pancreatitis. Use of granulocyte colony stimulating factor for treatment of bone marrow suppression after chemotherapy induces temporary increases of FDG avidity in the bone marrow and spleen. Familiarity with common and unusual iatrogenic causes of FDG avidity that can confound interpretation of FDG PET/CT results will improve the accuracy of distinguishing treatment effects and complications from residual or recurrent malignancy at FDG PET/CT examinations

False-positive FDG PET/CT due to liver parenchymal injury caused by a surgical retractor.

A 70-year-old man underwent partial gastrectomy with pathology demonstrating gastric follicular lymphoma. After surgery, a staging FDG PET/CT study demonstrated an FDG-avid low-attenuation band in the liver. Corresponding MRI demonstrated a high T2 signal abnormality. This was believed to represent liver parenchymal injury due to liver retraction during surgery. The patient was managed conservatively. MRI at 1 month of follow-up demonstrated resolution of the T2 signal abnormality. FDG PET/CT at 6 months of follow-up demonstrated resolution of FDG uptake. Tissue injury from surgical retraction can produce FDG-avid lesions that need to be distinguished from malignancy on PET/CT

Ipilimumab-induced colitis on FDG PET/CT.

A 52-year-old woman with metastatic melanoma was treated with ipilimumab. After 2 cycles of treatment, she developed watery diarrhea, sweats, and chills. An FDG PET/CT study demonstrated new FDG-avid (maximum standardized uptake value 15.6) diffuse colonic wall thickening, suggestive of ipilimumab-induced colitis. The patient was treated with systemic steroids, with subsequent resolution of her symptoms. Based on the response to steroids, the diagnosis of ipilimumab-induced enterocolitis was made. Ipilimumab may cause several immune-mediated toxicities, the most common of which is enterocolitis. Physicians interpreting FDG PET/CT examinations of patients treated with ipilimumab should be aware of these FDG-avid immune-mediated toxicities

Treadmill exercise inducing mild to moderate ischemia has no significant effect on skeletal muscle or cardiac 18F-FDG uptake and image quality on subsequent whole-body PET scan.

We report the effects of treadmill exercise on (18)F-FDG uptake in skeletal muscles and image quality of torso PET and compare stress myocardial perfusion imaging patterns with myocardial (18)F-FDG uptake. There were 3 groups of patients: 48 patients underwent PET within 8 h after a treadmill test (Ex 8), 45 patients within 48 h after a treadmill test (Ex 48), and 34 patients without prior exercise. Mean workload (8.4 ± 2.3 [Ex 8] vs. 8.9 ± 2.6 metabolic equivalents [Ex 48]) was similar in both exercise groups. Muscle uptake was assessed by standardized uptake value. Myocardial uptake patterns were compared visually. Minor differences between patient groups were noted only for maximum standardized uptake value in quadriceps muscles. There was no correlation between perfusion defects and myocardial (18)F-FDG uptake patterns. Thus, treadmill exercise does not affect muscle (18)F-FDG uptake or image quality on subsequent PET. Cardiac (18)F-FDG uptake on torso PET scans is unrelated to myocardial perfusion status

Single photon emission computed tomography SPECT-CT improves sentinel node detection and localization in cervical and uterine malignancy.

OBJECTIVES: Planar lymphoscintigraphy (LSG) is frequently performed for the assessment of the sentinel lymph nodes (SLN) in gynecologic malignancies. Planar imaging helps to localize hot nodes but lacks accuracy of the anatomic location of those nodes. In this study, we compared SPECT-CT to planar LSG in endometrial and cervical cancer to assess its ability to localize SLN. METHODS: We conducted a prospective nonrandomized study of SLN mapping in women with endometrial and cervical cancer. Forty patients with endometrial cancer and 10 with cervical cancer underwent pre-operative LSG with 1 or 4 mCi of (99m)Tc sulfur colloid administered as injections into the cervix. All patients were scanned immediately with planar LSG obtained in the anterior and lateral views. SPECT-CT imaging was obtained following the planar imaging. RESULTS: Planar LSG alone localized SLN in 30/40 (75%) endometrial cancer patients while SPECT-CT localized SLN in all 40 patients (100%). In the 10 cases where SLN was not identified with planar imaging, SPECT-CT localized nodes in the external iliac, internal iliac, common iliac and obturator groups. In cervical cancer, planar LSG alone localized sentinel lymph nodes in 8/10 patients (80%) as compared to SPECT-CT, which localized nodes in all 10 patients (100%). SPECT-CT imaging was especially useful in delineating external iliac versus internal iliac or obturator nodes, and the parametrial nodal uptake. CONCLUSIONS: SPECT-CT appears to improve sentinel lymph node detection and anatomic localization as compared to planar imaging in cervical and uterine cancer

Evaluation of romidepsin for clinical activity and radioactive iodine reuptake in radioactive iodine-refractory thyroid carcinoma.

BACKGROUND: Historically, systemic therapy for radioactive iodine (RAI)-refractory thyroid cancer has been understudied. Available drugs have modest efficacy. Romidepsin is a histone deacetylase inhibitor with potent antitumor effects both in vitro and in vivo. In thyroid cancer cell lines, romidepsin increases expression of both thyroglobulin and the sodium iodide symporter messenger RNAs, suggesting the possibility of improved iodine concentrating ability of RAI-resistant tumors. METHODS: This was a single-institution Simon 2-stage phase II clinical study. Eligible patients had progressive, RAI-refractory, recurrent/metastatic, nonmedullary, nonanaplastic thyroid cancer. Response Evaluation Criteria in Solid Tumors (RECIST) 1.0 measurable disease and adequate organ/marrow function were required. Romidepsin 13 mg/m² was administered intravenously on days 1, 8, and 15, in cycles of 28 days. The primary endpoint was the response rate by RECIST; change in RAI avidity was a secondary endpoint. The study closed after the first stage due to the lack of response. RESULTS: Twenty patients were enrolled: female, 50%; median age, 64 years; histology, 8 papillary/1 follicular/11 Hürthle. Grade 4-5 adverse events (AEs) possibly related to the drug: grade 5, 1 sudden death; grade 4, 1 pulmonary embolus. Twelve of 20 subjects had a reported adverse event. No RECIST major responses have been seen. Response per protocol: stable disease, 13; disease progression, 7. Restoration of RAI avidity was documented in two patients. Median overall survival and time on study was 33.2 (1-71+) and 1.7 (0.46-12) months, respectively. CONCLUSIONS: We observed preliminary signs of in vivo reversal of RAI resistance after treatment with romidepsin. However, no major responses were observed and accrual was poor after the grade 5 AE