Background: To date, Hodgkin's lymphoma (HL) patients have achieved long-term survival of more than 80%. Unfortunately, longer follow-up has shown serious adverse effects of the treatments used. For this reason, therapeutic strategies are becoming more tailored to the individual patient s prognosis. Pre-treatment risk factors for early-stage and advanced-stage HL are well known indicators of prognosis. Recently, early interim (18)F-FDG PET has been shown as a strong and independent predictor of progression-free survival in HL. Our aim was to assess response to therapy by repeating (18)F-FDG-PET/CT after four and six chemotherapy cycles.
Material and methods: We evaluated 21 consecutive patients affected by (HL) and presenting for assessment over a period of three years. All patients underwent initial staging with (18)F-FDG-PET/CT along with standard staging procedures. We tailored an individual treatment plan dependent on pre-treatment risk factors and initial (18)F-FDG-PET/CT. With the aim of the best definition of response to treatment, we repeated (18)F-FDG-PET/CT after two (FDG-PET 2), four (FDG-PET 4) and six (FDG-PET 6) chemotherapy cycles. Chemotherapy was typically given for four cycles in early disease stages and was prolonged to six to eight cycles in advanced disease stages, depending on PET findings.
Results: Our results showed a strong negative predictive value in detecting responders in early stage HL and a positive predictive value in advanced-stage patients. Clinical stage, extra-nodal sites and the positivity of the (18)F-FDG-PET/CT performed during chemotherapy were also noted as strong determinants of response to treatment. Moreover, in our series the (18)F-FDG-PET/CT data obtained after only two chemotherapy cycles (FDG-PET 2) were the same of those obtained after FDG-PET 4 and FDG-PET 6 controls.
Conclusion: The preliminary data of the present study confirm those of previous published studies about the negative predictive value of (18)F-FDG-PET/CT performed after four and six chemotherapy cycles, which contributed to the decision to stop treatment and to avoid radiotherapy in HL patients. Nonetheless, our preliminary data seems to suggest that only the (18)F-FDG-PET/CT performed after two cycles of chemotherapy (FDG-PET 2) is able to provide the same prognostic information of the FDG-PET 4 and FDG-PET 6 earlier.