IHP Interpretation Criteria of Interim-PET Scan Confirms Prognostic Impact In Early Stage Hodgkin Lymphoma Patients without Bulky Disease

Early stage classical Hodgkin lymphoma (cHL) is highly curable with a combination of chemotherapy and radiotherapy. Nevertheless a small proportion of patients with localized stage do not respond to therapy and progressed. We want to explore the predictive value on therapy outcome of an early evaluation of treatment response by 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) scan performed after two corses of ABVD in pts with localized Hodgkin's disease.

From 2002, 246 new localized stage cHL pts were consecutively admitted to twelve Italian hematological centers on behalf of Intergruppo Italiano Linfomi. Pts with stage I-IIA according to Ann Arbor stage, independent of presence of bulky disease, were considered for the study. FDG-PET was mandatory at baseline, after two cycles and at the end of therapy. International Harmonization Project (IHP) interpretation criteria were recommended to define PET positivity. We evaluated the progression free survival of pts starting from the time of diagnosis to relapse or progression of disease or last follow-up. No treatment variation based only on PET-2 results was allowed. All bulky-disease pts reports were centrally reviewed.

The median age was 33 years (13-78), 133 pts were female, 225 pts were stage II, bulky was reported in 76 pts, 231pts were treated with combined modality and 15 pts were treated with chemotherapy alone. The FDG-PET performed after two cycles (PET2) was positive in 32 pts (13%). Seventeen non-bulky pts were PET2 positive: 10 (59%) progressed or relapsed and 7 remained in CR. By contrast 152/153 (99%) non-bulky pts with a negative PET2 remained in CR. Thus the PPV value of a PET2 in non-bulky pts was 59% and the NPV was 99%, moreover the sensitivity and specificity of PET2 were 91% and 96%, respectively. In bulky disease pts we performed a revision of all reports according to Deauville criteria and 3 cases were converted from PET2 positive to PET2 negative. In revised bulky disease pts 15 were PET2 positive: 6 (40%) progressed or relapsed and 9 remained in CR. In this group of pts the PPV was 40%, the NPV 93% and sensitivity and specificity were 60% and 90% respectively. In univariate analysis negative FDG-PET performed after two cycles (p .0000), absence of bulky disease at diagnosis (.005) were statistically correlated with a better progression free survival. In multivariate analysis only PET2 was independently predictive of relapse/progression probability (p .000). With a median follow-up of 35 months (range 4–87), the 2-yr FFS probability for PET2 negative and for PET2 positive non-bulky patients were 98% and 29% respectively (p: .000) for patients with bulky-disease were 99% and 45% respectively (p: .002).

This multicentric study confirms that FDG-PET scan performed after two courses of conventional standard dose chemotherapy was able to predict treatment outcome in early stage non-bulky cHL. In bulky disease we suggest new interpretation criteria to define interim PET results.

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