The role of fluorodeoxyglucose-positron emission tomography/computed tomography in differentiating between benign and malignant adrenal lesions

Our plain-English summary of The role of fluorodeoxyglucose-positron emission tomography/computed tomography in differentiating between benign and malignant adrenal lesions, by P. Ozcan Kara, T. Kara, G. Kara Gedik, et al (Nuclear Medicine Communications, 2011).

The study

• Authors: P. Ozcan Kara, T. Kara, G. Kara Gedik, F. Kara, O. Sahin, E. Ceylan Gunay, O. Sari
• Journal: Nuclear Medicine Communications
• Published: 2011;32(2):106-12
• Cited by: 39 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: This retrospective study was designed to investigate the clinical role of whole-body positron emission tomography/computed tomography (PET/CT) by using 2-[18F]fluoro-2-deoxy-D-glucose (FDG), for the evaluation of adrenal lesions and to find the best index to distinguish benign from malignant lesions in various cancer patients.

Materials And Methods: A total of 81 patients (55 male and 26 female, age range: 31-81 years, mean: 61.5) who had confirmed primary malignancies (lung cancer in 47 patients, gastrointestinal malignancies in 13 patients, malignant melanoma in one patient, renal cell cancer in three patients, mesothelioma in two patients, breast carcinoma in nine patients, cervical cancer in one patient, ovarian cancer in two patients, pheochromocytoma in one patient, unknown primary in two patients) underwent PET/CT examinations for cancer screening, staging, restaging, and detection of suspected recurrence. Of the 81 patients, 104 adrenal lesions (34 benign and 70 malignant adrenal lesions) were shown by CT. On visual analysis of PET/CT imaging, adrenal uptake was based on a three-scale grading system. For final assessment standards of references for adrenal malignant lesions was based on biopsy (n=2), interval growth, or reduction after chemotherapy. An adrenal lesion, which remained unchanged on clinical and imaging follow-up of at least 7 months (mean follow-up time 19.31 months±6.46, range 7-30 months), was decided as a benign lesion.

Results: In adrenal malignant lesions maximum standardized uptake value (SUVmax) (8.82±4.47) was higher than that of adrenal benign lesions (3.02±1.15, P<0.0001). In the differentiation of adrenal benign and malignant lesions, a CT threshold of 10 Hounsfield units corresponded to a sensitivity of 64.7%, specificity of 98.6%, and accuracy of 87.5%. An SUVmax cut-off value of 2.5 corresponded to a sensitivity of 100%, specificity of 38.2%, and accuracy of 80%. An SUVmax cut-off value of 4.2 corresponded to a sensitivity of 88.6%, specificity of 88.2%, and accuracy of 88.5%. The ratio of tumor SUVmax to liver SUVmean was 3.61±1.77 for adrenal malignant lesions whereas it was 1.20±0.38 for adrenal benign lesions (P<0.0001). T/L SUV ratio cut-off value of 1.8 corresponded to a sensitivity of 87%, specificity of 91%, and accuracy of 88.5%. T/L SUV ratio cut-off value of 1.68 corresponded to a sensitivity of 90%, specificity of 91.1%, and accuracy of 90.4%.

Conclusion: 2-[18F]fluoro-2-deoxy-D-glucose-PET/CT improves the diagnostic accuracy in the differentiation of benign from malignant adrenal lesions in various cancer patients. Combined information obtained from PET/CT (SUVmax, T/L SUV ratio, visual analysis) and unenhanced CT (size, Hounsfield units measurement) is recommended for better differentiation.

In plain English

This retrospective study from Turkey tested whether FDG-PET/CT scans can tell benign from malignant adrenal gland lesions in people already diagnosed with cancer. It did not study asbestos exposure. Two of the 81 patients had mesothelioma, and no separate results were reported for them. From 3819 scans done between January 2008 and August 2010, the authors identified 104 adrenal lesions. They judged 34 benign and 70 malignant, mostly by follow-up imaging; biopsy confirmed only 2. Malignant lesions showed higher tracer uptake: average SUVmax 8.82 ± 4.47, versus 3.02 ± 1.15 for benign lesions. A cut-off of 1.68 for the ratio of lesion uptake to liver uptake gave 90% sensitivity, 91.1% specificity and 90.4% accuracy, which the authors called the best index. The authors concluded that PET/CT improves diagnostic accuracy and recommended combining PET/CT and unenhanced CT information. They noted that the study was retrospective, had pathological confirmation in only two cases, and included patients with mixed cancer types and a high share of malignant lesions.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: retrospective diagnostic imaging study (review of past PET/CT scans)
• Who was studied: 81 patients with confirmed primary cancers (55 male, 26 female, aged 31 to 81, mean 61.5) found among 3819 PET/CT examinations from January 2008 to August 2010; authors at Turkish universities. Cancers included lung cancer (47) and mesothelioma (2).
• Exposure: No asbestos or other exposure was studied. The test evaluated was whole-body FDG-PET/CT with unenhanced CT.
• Main results:
  • The 81 patients had 104 adrenal lesions: 34 benign and 70 malignant.
  • Average SUVmax (tracer uptake) was 8.82 ± 4.47 in malignant lesions and 3.02 ± 1.15 in benign lesions (P < 0.0001).
  • The tumor-to-liver uptake ratio was 3.61 ± 1.77 for malignant lesions and 1.20 ± 0.38 for benign lesions (P < 0.0001).
  • A tumor-to-liver ratio cut-off of 1.68 gave sensitivity 90%, specificity 91.1% and accuracy 90.4%.
  • An SUVmax cut-off of 4.2 gave sensitivity 88.6%, specificity 88.2% and accuracy 88.5%.
  • An SUVmax cut-off of 2.5 gave sensitivity 100%, specificity 38.2% and accuracy 80%.
  • A CT density threshold of 10 Hounsfield units gave sensitivity 64.7%, specificity 98.6% and accuracy 87.5%.
  • Mean lesion size was 33.26 ± 22.61 mm for malignant lesions and 18.44 ± 5.07 mm for benign lesions (P < 0.0001).
  • On visual grading, no malignant lesion showed uptake lower than the liver (grade I).
  • Combining SUVmax of at least 4.2, a tumor-to-liver ratio of at least 1.68 and CT density of at least 26.5 HU gave sensitivity 98.6%, specificity 100%, positive predictive value 100%, negative predictive value 97% and accuracy 99%.
  • The authors reported the tumor-to-liver ratio threshold of 1.68 as the best index for telling benign from malignant adrenal lesions.
• The authors' conclusion: The authors concluded that FDG-PET/CT improves diagnostic accuracy in telling benign from malignant adrenal lesions in cancer patients. They recommended combining PET/CT measures (SUVmax, tumor-to-liver ratio, visual analysis) with unenhanced CT measures (size, Hounsfield units).
• Limitations the authors state:
  • The study was retrospective.
  • Most lesions were classified by clinical and imaging follow-up; pathological confirmation was available in only two cases.
  • The patients had a mix of different cancer types.
  • The proportion of malignant lesions in the study population was high.

Topics

Medical terms in this study, explained in our Lexicon: Lung Cancer, Mesothelioma, Carcinoma, Ovarian Cancer, Staging, Biopsy, Chemotherapy.

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