Background: PET/CT-ascertained bone marrow involvement (BMI) is the most frequent reason for Hodgkin Lymphoma (HL) upstaging by baseline PET/CT (PET-0). However, shared rules for BMI detection in PET/CT still lack. This study analyzed the diagnostic and prognostic value of BM FDG uptake pattern in PET-0. Patients and methods: 186 early unfavorable and advanced stage HL patients (pts), enrolled in two International studies on the role of interim PET (PET-2) in HL, were analyzed. Treatment (Tx) was ABVD x 6 cycles (advanced) or x 4 cycles plus IF radiation (early unfavorable). No Tx adaptation on PET-2 was allowed. Two reviewers blinded to Tx outcome independently reviewed PET-0; discordant results were jointly discussed. Focal BM lesions (fPET+) were defined as focally increased FDG-uptake > liver uptake (with or without CT abnormalities), visible in ≥ 2 slices of fused images. Diffusely increased FDG-uptake was defined as a diffuse uptake > liver (dPET+). No uptake (nPET+) was defined as absent or faint (< liver) diffuse uptake. Results: After a median follow-up of 33.8 (16.6 – 109.4) months, 40 pts (21.5%) progressed or relapsed, and 9 (4.9%) died. The 3-Y OS and PFS was 98.0% and 83.8%, respectively. In 33/40 (82.5%) pts with a fPET+ all the PET-0 focal lesions had disappeared in PET-2. Half of pts (90/186: 48.4%) had a nPET+. dPET+, recorded in 56 (30.1%) pts, correlated with younger age, low hemoglobin, leukocytosis, low albumin and diffuse FDG spleen uptake. Notably, dPET+ had an identical 3-Y PFS to nPET+ pts: 83.2% and 81.6%, respectively (p=0.732). Out of 40 (21.5%) fPET+ pts, 11 had unifocal and 29 multifocal (≥ 2) lesions, with a 3-y PFS of 70.1% and 67.0%, respectively. Multifocal fPET+ pts had a worse PFS compared to dPET+ p. (p=0.05). BM biopsy (BMB) was positive in 6/40 (15%) of fPET+ and 0/56 (0%) of dPET+ pts. In univariate analyses, bulky disease (HR 2.4, p=0.008), IPS (HR 3.4, p=0.0001), and PET-2 (HR 11.0, p<0.0001) were significantly associated with PFS, but only PET-2 was still significant in multivariate analysis (p<0.0001). The kappa-value for inter-observer agreement was 0.83 for focal and 0.78 for diffuse uptake. Conclusions: The study confirms that (1) FDG-PET scan is a reliable tool for BMI assessment in HL; (2) only focal FDG uptake in PET-0 has an adverse prognostic value and should be considered to represent BMI; (3) BMI could be detected with high accuracy and inter-observed agreement in routine HL staging with PET/CT.
This abstract has been presented as Abstract Talk in “PET – Where Are We?”
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