¹⁸F-FDG PET Response of Skeletal (Bone Marrow and Bone) Involvement After Induction Chemotherapy in Pediatric Hodgkin Lymphoma: Are Specific Response Criteria Required?

Abstract

To determine whether the current F-FDG PET response criterion for skeletal involvement in Hodgkin lymphoma (HL) is suitable, we performed a systematic evaluation of the different types of skeletal involvement and their response on PET after 2 cycles of chemotherapy (PET-2). A secondary objective was to observe the influence of the initial uptake intensity (measured as qPET) and initial metabolic tumor volume (MTV) of skeletal lesions on the PET-2 response. The initial PET scans of 1,068 pediatric HL patients from the EuroNet-PHL-C1 trial were evaluated for skeletal involvement by central review. Three types of skeletal lesions were distinguished: PET-only lesions (those detected on PET only), bone marrow (BM) lesions (as confirmed by MRI or BM biopsy), and bone lesions. qPET and MTV were calculated for each skeletal lesion. All PET-2 scans were assessed for residual tumor activity. The rates of complete metabolic response for skeletal and nodal involvement on PET-2 were compared. Of the 1,068 patients, 139 (13%) showed skeletal involvement (44 PET-only, 32 BM, and 63 bone). Of the 139 patients with skeletal involvement, 101 (73%) became PET-2-negative in the skeleton and 94 (68%) became PET-2-negative in the lymph nodes. The highest number of PET-2-negative scans in the skeleton was 42 (95%) in the 44 PET-only patients, followed by 22 skeletal lesions (69%) in the 32 BM patients and 37 (59%) in the 63 bone patients. Lesions that became PET-2-negative showed a lower initial median qPET (2.74) and MTV (2 cm) than lesions that remained PET-2-positive (3.84 and 7 cm, respectively). In this study with pediatric HL patients, the complete response rate for skeletal involvement on PET-2 was similar to that for nodal involvement. Bone flare seemed to be irrelevant. Overall, the current skeletal PET response criterion-comparison with the local skeletal background-is well suited. The initial qPET and MTV of skeletal lesions were predictive of the PET-2 result. Higher values for both parameters were associated with a worse PET-2 response.

Polyostotic Fibrous Dysplasia Mimicking Bone Involvement in Hodgkin Lymphoma: A Pediatric Case and Literature Review

“…Bone lesions in HL could extend to the cortex. Since PET/CT is usually positive independently of the cortical nature of the lesion, other imaging techniques may be helpful: lesions limited to the bone marrow are detected by MRI but not by CT and scintigraphy; cortical involvement is visible on CT and on scintigraphy but not on MRI [4]. There have been attempts to define PET/CT standardized parameters to improve the distinction between a benign and malignant lesion tracer uptake.…”

“…Hodgkin lymphoma (HL), a malignant lymphoproliferative disorder that usually affects young adults, represents 6% of childhood cancers with the highest incidence among adolescents. Bone involvement in HL is rare at onset, occurring only in 1–4% of the cases, and does not seem to be an independent adverse prognostic factor [1-4]. The differential diagnosis between bone localization of HL and other benign and malignant skeletal diseases (acute and chronic osteomyelitis, primitive and secondary tumors, Paget disease, and fibrous dysplasia) may be difficult, especially in case of single lesions [5].…”