Extramedullary gastric relapse of acute lymphoblastic leukemia following allogeneic stem cell transplant: staging with F-18 FDG PET/CT

Applications of 18F-Fluorodesoxyglucose PET Imaging in Leukemia

The main finding that 18F-FDG PET imaging can reveal in patients with leukemias is the presence of bone marrow (BM) infiltration in both acute or chronic forms. This ability can influence and guide the use of BM biopsy but also assess to therapy response. Additionally 18F-FDG PET imaging has been reported as particularly useful for the diagnosis of leukemias in patients with non specific symptoms. In the case of acute leukemias it revealed also a role for the evaluation of extramedullary forms while in the case of chronic forms a role for the assessment of Richter transformation has been reported.

PET/CT in leukemia: utility and future directions

2-Deoxy-2-[ 18 F]fluoro- d -glucose PET/computed tomography ([ 18 F]FDG PET/CT) has proven to be a sensitive method for the detection and evaluation of hematologic malignancies, especially lymphoma. The increasing incidence and mortality rates of leukemia have raised significant concerns. Through the utilization of whole-body imaging, [ 18 F]FDG PET/CT provides a thorough assessment of the entire bone marrow, complementing the limited insights provided by biopsy samples. In this regard, [ 18 F]FDG PET/CT has the ability to assess diverse types of leukemia The utilization of [ 18 F]FDG PET/CT has been found to be effective in evaluating leukemia spread beyond the bone marrow, tracking disease relapse, identifying Richter's transformation, and assessing the inflammatory activity associated with acute graft versus host disease. However, its role in various clinical scenarios in leukemia remains unacknowledged. Despite their less common use, some novel PET/CT radiotracers are being researched for potential use in specific scenarios in leukemia patients. Therefore, the objectives of this review are to provide a thorough assessment of the current applications of [ 18 F]FDG PET/CT in the staging and monitoring of leukemia patients, as well as the potential for an expanding role of PET/CT in leukemia patients.

Applications of PET in Diagnosis and Prognosis of Leukemia

As a malignant hematopoietic stem cell disease, leukemia remains life-threatening due to its increasing incidence rate and mortality rate. Therefore, its early diagnosis and treatment play a very important role. In the present work, we systematically reviewed the current applications and future directions of positron emission tomography (PET) in patients with leukemia, especially ¹⁸F-FDG PET/CT. As a useful imaging approach, PET significantly contributes to the diagnosis and treatment of different types of leukemia, especially in the evaluation of extramedullary infiltration, monitoring of leukemia relapse, detection of Richter’s transformation (RT), and assessment of the inflammatory activity associated with acute graft versus host disease. Future investigations should be focused on the potential of PET/CT in the prediction of clinical outcomes in patients with leukemia and the utility of novel radiotracers.

Extramedullary Gastric Relapse at the Time of Bone Marrow Relapse of Acute Lymphoblastic Leukemia after Allogeneic Bone Marrow Transplantation

Extramedullary relapse (EMR) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is relatively rare. The most commonly reported sites in acute lymphoblastic leukemia (ALL) patients after allo-HSCT are soft tissue and the central nervous system, and the gastrointestinal system is an uncommon site. We herein report a unique case with massive hematemesis resulting from gastrointestinal relapse of ALL after allo-HSCT. Upper gastrointestinal endoscopy showed bleeding from a 1.5-cm submucosal tumorous lesion with central ulceration on the anterior wall of the stomach. At the same time, computed tomography revealed extramedullary relapse at the breast and bilateral adrenal glands.

Usefulness and pitfalls of F-18-FDG PET/CT for diagnosing extramedullary acute leukemia

PURPOSE

It is very important to identify whether there is extramedullary involvement in acute leukemia (AL), especially in those with recurrent disease. This retrospective study aimed to assess the role of (18)F-FDG PET/CT for diagnosing extramedullary AL.

MATERIALS AND METHODS

PET/CT examinations were performed in 9 patients with newly diagnosed AL, and 70 patients suspected to have recurrent AL. All the patients were diagnosed with AL by bone marrow biopsy. The diagnosis of extramedullary lesions was established according to the combination of pathology, physical examination, and imaging techniques including magnetic resonance imaging (MRI) and PET/CT, and/or cerebrospinal fluid (CSF) cytologic testing, and clinical follow-up.

RESULTS

Of the 79 patients, including 34 acute lymphocytic leukemia (ALL) and 45 acute myeloid leukemia (AML) cases, 30 patients were diagnosed with extramedullary AL. (18)F-FDG PET/CT demonstrated (18)F-FDG positive lesions in the extramedullary regions in 42 patients. Among them, 28 patients were diagnosed to have extramedullary AL and the other 14 were diagnosed with non-hematological malignancies (false positive disease). The sensitivity, specificity, and accuracy of (18)F-FDG PET/CT in diagnosing extramedullary involvement of AL were 93.3% (28/30), 71.4% (35/49), and 79.7%, respectively. The (18)F-FDG uptake of lesions was not significantly different between extramedullary AL and false positive cases (SUVmax: 6.66 ± 2.65 vs. 5.85 ± 1.88, t=1.275, P=0.206). The FDG uptake of extramedullary AL between ALL and AML were also not significantly different (SUVmax: 7.01 ± 2.82 vs. 6.10 ± 2.29, t=1.332, P=0.188). The predominant locations of extramedullary AL were the spleen, soft tissue, lymph nodes, central nerve system, liver, testis, and kidney. A total of 48.2% (27/56) of extramedullary AL lesions presented as diffuse FDG uptake compared with 6.25% (1/16) in the false positive lesions (χ(2)=9.221, P=0.002).

CONCLUSION

(18)F-FDG PET/CT is a sensitive, but not specific imaging modality for diagnosing extramedullary AL. Diffuse (18)F-FDG uptake in extramedullary lesions may indicate leukemia involvement.

Increased bone marrow uptake of 18F-FDG in leukemia patients: preliminary findings

The aim of this retrospective study was to evaluate the characteristics of increased bone marrow uptake of 18F-FDG in patients with leukemia who underwent whole-body 18F-FDG PET/CT. The 18F-FDG PET/CT images of 9 patients with histologically proven leukemia were reviewed. The accumulation of 18F-FDG in the bone marrow was evaluated, and was compared with histological subtype, clinical course, and hematological findings. Nine patients (4 males, 5 females; age range, 5-58 years) had increased bone marrow uptake of 18F-FDG, including 6 patients with acute lymphoblastic leukemia, 1 with acute myeloid leukemia, 1 with chronic myeloid leukemia, and 1 with mature B cell neoplasm. Bone marrow uptake was generally diffuse but focal or inhomogeneous uptake was common, especially in the upper and lower extremities. Patients with increased bone marrow uptake of 18F-FDG commonly complained of fever and bone pain. No correlations between 18F-FDG uptake and peripheral blood findings were observed. Patients with leukemia may have increased bone marrow uptake of 18F-FDG on PET/CT, possibly reflecting leukemic cell activity. Leukemia can be included in the differential diagnosis when increased bone marrow uptake of 18F-FDG is observed.