PS1263 CONSOLIDATION THERAPY USING 90Y‐IBRITUMOMAB TIUXETAN AFTER BENDAMUSTINE AND RITUXIMAB IN PATIENTS WITH RELAPSED FOLLICULAR LYMPHOMA; A MULTICENTER, PHASE II STUDY (BRIZ2012)

Background: The role of consolidation therapy with 90 Y‐ibritumomab tiuxetan ( 90 YIT) for patients with follicular lymphoma (FL) after receiving second or third line immunochemotherapy has not been established. Aims: Thus, we conducted a multicenter phase II trial evaluating the efficacy and toxicities of bendamustine and rituximab (BR) followed by 90 YIT for patients with relapsed FL. Methods: This study included patients who had biopsy‐proven, relapsed FL (Grade 1/2 or 3a); one or two prior therapies; age of 20–74 years; ECOG performance status of 0–2; measurable lesion(s); no severe organ dysfunction; 3 months or longer life expectancy; and written informed consent. BR consisted of rituximab (375 mg/m 2 , day 1) and bendamustine (90 mg/m 2 , day 2 and 3), and repeated every 4 weeks up to 4–6 cycles. As the consolidation therapy, 14.8 MBq/kg of 90 YIT was administered to patients who achieved complete response (CR) or partial response after BR therapy. The primary endpoint was 2‐year progression‐free survival (PFS) after the consolidation with 90 YIT. The secondary endpoints were response rates after BR therapy, response rates after consolidation with 90 YIT, 2‐year overall survival (OS) rate after the consolidation with 90 YIT, and toxicities. Results: A total of 30 patients were registered between 2013 and 2015. Of these patients, 6 were excluded from the study because of pathological diagnoses other than FL in the central review (n = 3), unmet criteria (n = 2), and the other advanced cancer found (n = 1), respectively. Thus, 24 patients with a median 60 years of age (range 47–74 years) and a median of 6.7 years (range 1.6–14.8 years) of duration from the initial diagnosis were evaluated. Among them, R‐CHOP based chemotherapy was the most common initial treatment (92%). The FLIPI2 score at the time of registration was high in 3, intermediate in 7, and low in 14 patients, respectively. After re‐induction treatment with BR, 22 patients (92%) ultimately received consolidation with 90 YIT, resulting in an overall response rate of 95% and a CR rate of 91%, respectively. Within the 2‐year observation period, 10 patients relapsed and 3 of them had a histological transformation to diffuse large B‐cell lymphoma. Severe non‐hematological toxicities were rare and no treatment‐related mortality was observed. Within the observation period, one patient died of disease progression. Second primary malignancies were not observed. Consequently, the 2‐year PFS and OS rates after the consolidation were 58%, and 94%, respectively. Summary/Conclusion: Consolidation therapy with 90 YIT after BR re‐induction therapy was feasible in patients with relapsed FL. Clinical efficacy was comparable, but the long‐term effect should be further investigated. Trial protocol number: UMIN8793, release date: 03. September 2012