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J Thorac Cardiovasc Surg 2007;133:1385-1386
© 2007 The American Association for Thoracic Surgery
Brief Communication |
University of Minnesota Department of Surgery, Section of Thoracic and Foregut Surgery, Minneapolis, Minn.
Received for publication December 4, 2006; accepted for publication January 5, 2007. * Address for reprints: Michael A. Maddaus, MD, Professor and Program Director, University of Minnesota Department of Surgery, MMC 207, 420 Delaware St SE, Minneapolis, MN 55455. (Email: madda001{at}umn.edu).
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After patients have undergone adjuvant treatment for gynecologic malignancies, newly positive mediastinal lymph nodes (LNs) on integrated 18-fluorodeoxyglucose (FDG) positron emission tomography (PET) and computed tomography (CT) images may suggest recurrent metastatic disease. We present the cases of 2 patients who underwent cytoreductive abdominal surgery and adjuvant chemoradiation for gynecologic malignancies whose subsequent follow-up surveillance FDG-PET/CT scan results revealed PET-positive mediastinal LNs. Neither patient had any previous thoracic disease, and prior FDG-PET results were negative.
Patient 1
A 57-year-old woman with stage IIIc endometrioid uterine adenocarcinoma underwent total abdominal hysterectomy, bilateral salpingo-oophorectomy, pelvic LN dissection, cytologic washings, and omentectomy. Final pathology demonstrated tumor invasion into the myometrium, positive estrogen and progesterone receptors on the tumor, and metastasis to 2 of 31 resected pelvic LNs. Three cycles of systemic chemotherapy (docetaxel and carboplatin), whole pelvic radiotherapy and brachytherapy, and 3 additional cycles of chemotherapy (docetaxel and carboplatin) were given. An integrated FDG-PET/CT scan obtained 6 months after completing adjuvant treatment revealed newly positive perihilar and subcarinal LN, raising concerns of metastatic disease (Figure 1). Her carbohydrate antigen (CA)-125 level was 13 mg/dL (normal range, 0-30 mg/dL). Diagnostic mediastinoscopy (stations 3, 4R, and 7) was performed; the LN biopsy results demonstrated necrotic granulomas negative for fungi, mycobacteria, and malignancy. A repeat FDG-PET/CT scan 6 months later demonstrated resolution of all abnormal metabolic activity (Figure 1, C). Follow-up CA-125 levels have remained normal. Two years after the initial operation, she is alive without evidence of recurrent disease.
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Because of the fusion images of newer integrated PET/CT machines, CT and PET scans are increasingly used to screen for recurrent disease in patients with cancer, individually, serially, or concomitantly. When FDG-PET is used for preoperative staging, false-positive results can occur. In Cerfolio and colleagues’ study1
of 400 patients with non–small cell lung cancer (NSCLC), the false-positive rate was as high as 76% for preoperative N2 disease. They found that PET-positive LNs at station 4R, 4L, and 7 were most likely to be false-positives (as in our 2 patients). When FDG-PET scans are used as a postoperative surveillance tool in patients with NSCLC, false-positives can also occur, but at a much lower rate. According to another study, FDG-PET scans, when used for recurrence surveillance at a median of 19 months after primary therapy in patients with NSCLC, had a sensitivity of 93% and a specificity of 89%, with only 2.7% false-positives (2/73).2
In 2 studies of gynecologic malignancies (uterine and cervical carcinomas), FDG-PET scans used for surveillance after treatment had a sensitivity of 90% to 96% and a specificity of 70% to 78%.3,4 The false-positive rate ranged from 10.7% to 65% for thoracic LN lesions. The true mediastinal or hilar LN recurrence rate was 26.5% to 46.2%. However, the false-positive rate for hilar and mediastinal LNs was as high as 73.5%.4 Neither of these gynecologic studies routinely used serial FDG-PET examinations.
To our knowledge, no other specific cases have been reported of delayed metabolic activation of mediastinal LNs causing false-positive images after treatment for gynecologic malignancies. Possible explanations for false-positive LNs include infection, benign inflammatory processes, and residual inflammation from local treatment effects.3-5 In our 2 patients, the mediastinal LNs were negative for fungi, bacteria, and malignancy, none of which were manifest in the radiation field after adjuvant therapy.
New FGD-PET–positive mediastinal LNs manifesting after treatment of gynecologic malignancies raise concerns for metastatic disease. Although false-positives can occur, tissue biopsies must be obtained to definitively exclude metastatic disease.
Acknowledgments
The authors thank Mary Knatterud, PhD, for her editorial assistance.
References
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