Abstract P117

Frequency and indicators of primary refractoriness in low-risk non-bulky early-stage Hodgkin’s lymphoma patients and negative interim PET – report from the RAFTING trial

Introduction: The RAFTING trial is a phase 2, multicenter, international prospective study investigating risk-adapted treatment strategy in non-bulky early-stage Hodgkin’s lymphoma (eHL) pts. Around 10% of the pts from low-risk (LR) group in the RAFTING trial showed inadequate end-of-chemotherapy (EOC) response (non-CR), that fulfill the definition of primary refractoriness (PrR). Research financed by the Medical Research Agency, Poland, Project number 2019/ABM/01/00060.

Methods: Pts from low-risk group in the RAFTING trial were defined by low (<84 ml) baseline metabolic tumor volume (MTV) and negative interim PET after 2 ABVD cycles. Within the LR group the pts without any risk factors according to modified EORTC (mEORTC) criteria (largest nodal mass (LNM) 5-10 cm, Age>50 yo, ESR>50mm/h, ≥4 nodal areas (NA)) (group 1a) were treated with 2 ABVD cycles only whereas pts with at least 1 risk factor (group 1b) – with 4 ABVD cycles. Additional PET was performed after the end of the 4 ABVD cycle in group 1b or in case of relapse suspicion 3 months in group 1a. Pts with CR or non-CR in the EOC-PET were compared by demographic and clinical characteristics (age, gender, age> 50 yo, LNM, ESR>50mm/h, ≥4 NA, >2 risk factors according to mEORTC, combination of LNM and ≥4 NA, total lesion glycolysis (TLG) and MTV measurement).

Results: Up to May 2024 all 128 enrolled pts (56 males and 72 females) with a mean age of 38 (18-69) years from the LR group completed CT. In 15 cases (11%), primary refractoriness was observed at the EOC PET. Complete information on risk factors was available for 90% of pts at the data cut-off. Patients’ characteristics are presented in the table 1. The most common risk factors among pts with primary refractoriness were LNM (9 pts, 64%), ≥4 NA (6 pts, 43%); and more than 1 risk factor had 5 pts, (36%). In the univariate analysis, the only risk factor that significantly increased the risk of refractoriness (p=0.048) was the number of “NA”. A trend was also observed for the presence of LNM (p=0.087). Similar results were shown in logistic regression model: the presence of ≥4 NA was the most important risk factor with OR 14.9 (p=0.012), followed by LNM with OR 6.9 (p=0.07).

Conclusion: The frequency of primary refractoriness to CT in the low-risk (low TMTV and negative iPET) eHL pts enrolled in the RAFTING TRIAL is 11%. The most important risk factor of primary refractoriness is the number of NA, followed by LNM.