Hodgkin lymphoma: a negative interim‐PET cannot circumvent the need for end‐of‐treatment‐PET evaluation

We examined the outcome of a cohort of patients with Hodgkin lymphoma (HL) in order to assess if fluorodeoxyglucose (FDG) positron emission tomography–computed tomography (PET/CT) at the end of treatment (end‐PET) can be omitted when the interim PET (int‐PET) is negative. Seventy‐six ABVD(adriamycin, bleomycin, vinblastine, dacarbazine)‐treated patients were retrospectively included. No change in treatment was made on the basis of int‐PET results. Suspicious foci on end‐PET received biopsy confirmation whenever possible. Median follow‐up was 58·9 months. Uptake on int‐PET higher than liver (scores 4–5) was rated positive according to the Lugano classification, while a positive end‐PET corresponded to scores 3, 4 and 5. Fifteen patients had treatment failure. Sensitivity, specificity, positive predictive value (PPV), negative predictive value and accuracy of int‐PET were 46·7%, 85·2%, 43·8%, 86·7% and 77·6%, respectively. For end‐PET the figures were: 80%, 93·4%, 75%, 95% and 90·8%. Eight patients with negative int‐PET had treatment failure; six of them were identified as non‐responders with end‐PET. The 5‐year progression‐free survival (PFS) was 87% for patients with negative int‐PET versus 56% with positive int‐PET. The 5‐year PFS was 96% with negative end‐PET versus 23% with positive end‐PET. The prognostic information from int‐PET as regards PFS (log‐rank test P = 0·0048) was lower than that provided by end‐PET (P < 0·0001). Int‐PET predicted only half of the failures. When used in clinical routine, a negative int‐PET study cannot obviate the need for end‐PET examination.