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Youngil Koh, MD
Photo by Larry Young

LA JOLLA, CA—Fluorodeoxyglucose positron emission tomography (FDG PET) cannot replace bone marrow (BM) biopsy in T-cell lymphomas, according to a speaker at the 10th Annual T-cell Lymphoma Forum.

Researchers found that FDG PET results did not exactly correlate with BM biopsy results relating to tumor involvement in patients with T-cell lymphomas.

However, results from FDG PET were found to be an independent prognostic factor for progression-free survival (PFS) and overall survival (OS).

Youngil Koh, MD, of Seoul National University Hospital in Seoul, South Korea, presented this research in a poster and oral presentation at this year’s T-cell Lymphoma Forum.

He and his colleagues set out to investigate the clinical value of FDG PET for evaluating BM tumor involvement and prognosis in T-cell lymphoma patients.

The team analyzed 109 patients who underwent staging with FDG PET and BM biopsy. Most patients had extranodal natural killer/T-cell lymphoma, nasal type (NKTCL, n=46), or angioimmunoblastic T-cell lymphoma (AITL, n=41).

Patients also had peripheral T-cell lymphoma not otherwise specified (n=12), anaplastic large-cell lymphoma (n=4), enteropathy-associated T-cell lymphoma (n=4), and subcutaneous panniculitis-like T-cell lymphoma (n=2).

Most patients (87.2%) received chemotherapy as first-line treatment. Fifty percent were CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisolone) or CHOP-like regimens, 48.1% were IMEP (ifosphamide, methotrexate, etoposide, and prednisolone) or IMEP-like regimens, and 1.9% were “other” regimens.

Other first-line treatments included radiotherapy followed by chemotherapy (10.1%), excision (0.9%), and no treatment (1.8%).

The patients’ median OS was 60.03 months, and the median PFS was 15.7 months.

BM involvement

The researchers analyzed PET BM uptake both visually and quantitatively using the marrow-to-liver ratio (MLR), and they compared these results to BM biopsy results.

According to BM biopsy, 35.8% of patients had tumor involvement.

By visual analysis, the sensitivity of PET for diagnosing positive BM biopsy was 58.5%, and the specificity was 77.9%. By MLR, the sensitivity was 64.1%, and the specificity was 72.9%.

The diagnostic performance of PET for BM involvement was not different across the lymphoma subtypes, Dr Koh said.

Prognosis

“Although FDG PET did not correlate very well with bone marrow biopsy, it had prognostic value, especially MLR,” Dr Koh noted. “And most importantly, in bone marrow biopsy-negative patients, it [MLR] had prognostic value.”

MLR was a significant prognostic factor for PFS (P=0.005) and OS (P<0.001). The same was true for BM biopsy (P=0.009 for PFS and P<0.001 for OS), while visual PET analysis was a significant prognostic factor for OS (P=0.015) but not PFS (P=0.476).

In patients negative by BM biopsy, MLR was a significant prognostic factor for PFS (P=0.001) and OS (P=0.005).

Dr Koh and his colleagues also analyzed the prognostic value of PET and BM biopsy specifically in patients with NKTCL and AITL.

In AITL patients, BM biopsy was a significant prognostic factor for OS (P=0.002) but not PFS (P=0.246). Visual PET analysis was not significant for PFS (P=0.910) or OS (P=0.581), and neither was MLR (P=0.053 for PFS and P=0.156 for OS).

In patients with NKTCL, BM biopsy was a significant prognostic factor for PFS (P=0.008) and OS (P<0.001). Visual PET analysis was not significant for PFS (P=0.469) or OS (P=0.092). And MLR was significant for PFS (P=0.004) and OS (P=0.012).

“Bone marrow findings of FDG PET are an independent prognostic factor in these tumors,” Dr Koh said, “suggesting the biologic relevance of FDG PET findings for aggressiveness or covert bone marrow involvement of tumor cells.”


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