The Role of PET/CT to Detect Bone Marrow Involvement in Hodgkin Lymphoma

Hodgkin’s lymphoma (HL) comprises 12% of all lymphomas and 1% of all malignancies (1). It is possible to achieve cure with modern first line treatment modalities in about 90% of patients. However treatment fails in 10% of early stage and 30% of advanced stage disease. Cure rates are around 50% in relapsed disease, in extra-nodal disease and in patients relapsing early after treatment of advanced stage disease (2-5). Correct staging is necessary for an effective treatment plan (6,7). Bone marrow involvement (BMI) is one of the most important prognostic factors in lymphomas. BMI corresponds to stage IV disease according to the Ann Arbor staging system (8). Staging of HL is based on the Cotswold’s modification of the Ann-Arbor system (8,9) and commonly includes computerized tomography (CT) and bone marrow biopsy (9). BMI is detected in 5-14% of patients with HL (10,11). Unilateral bone marrow biopsy (BMB) performed from dorsal iliac crest is considered as standard and performed routinely during staging (12,13). However main disadvantages of BMB are its interventional nature and it allows only a limited region of bone marrow to be investigated. A previous study reported 80% false negativity of a unilateral iliac crest biopsy compared with a bilateral biopsy in patients with lymphoma (14). Imaging Objective: Bone marrow involvement (BMI) is a significant component of staging of Hodgkin’s lymphoma (HL). Unilateral bone marrow biopsy (BMB) from dorsal iliac bone is the standard method to determine BMI. Positron emission tomography/computerized tomography (PET/CT) is recommended as a complimentary technique to determine BMI and to evaluate response to treatment. The aim of this study is to determine whether PET/CT can replace BMB to detect BMI in patients with HL. Methods: A total of 159 patients diagnosed as having HL were evaluated retrospectively. One hundred and four patients who met the criteria were included in the study. BMB and PET/CT were performed on all patients during initial staging. Results: Of the 104 patients, 44 (42.3%) and 17 (16.3%) had BMI in PET/CT and BMB respectively. All patients who had BMI in BMB also had involvement in PET/CT. BMB did not detect BMI in 27 patients who had BMI in PET/CT. All 27 patients had partial or complete remission on PET/CT performed at the end of treatment. This finding was regarded as a relative indicator for BMI. PET/CT had a sensitivity and negative predictive value of 100%, specificity of 68.9% and accuracy rate of 74% to determine BMI. Conclusion: We observed that PET/CT and BMB were compatible to determine BMI in patients diagnosed with HL. Unilateral BMB may result false negative especially in cases with focal involvement. Therefore, PET/CT should be considered as a complimentary technique to determine BMI. Staging should be reevaluated in patients who have BMI in PET/CT and a negative BMB treatment should be planned accordingly.