Clinical utility of interim CT scans in patients receiving bendamustine and rituximab for first line treatment of follicular lymphoma.

Abstract

e19565 Background: Interim imaging with computed tomography scanning (CT) has been performed during most clinical trials of chemoimmunotherapy in patients with follicular lymphoma (FL) receiving first line systemic therapy. Based on this, interim imaging is commonly performed, but there is little evidence of its utility in clinical practice. Methods: The objective of this study was to retrospectively review outcomes of interim CTs (iCT) in adult patients with biopsy proven FL (grade 1-3a, 3b excluded) who received first line therapy with bendamustine and rituximab (BR) at Princess Margaret Cancer Centre from January 1 2013- December 31 2018. Baseline patient characteristics at diagnosis and treatment were retrieved from a prospectively populated database, and results of interim, end of treatment and end of maintenance therapy (if applicable) imaging were assessed. Disease response was assessed using Lugano response criteria as partial response (PR), complete response (CR), stable disease (SD) or progressive disease (PD). Descriptive statistics and Kaplan Meier Survival functions with a log rank test were used to analyze the data. The study was approved by the Princess Margaret Research Ethics Board. Results: A total of 108 patients were identified: mean age at diagnosis 61 years (IQR 52.4-69.5), 83% with stage III/IV disease, 27.8% bulky ( > 10cm) and median FLIPI score 2. Median follow up was 55.9 months (6.6-100.1 months). Of them, 101 patients (93.5%) had interim imaging done between cycle 2 and cycle 5 , most commonly CT scan (n = 98, 97.0%). The majority of iCTs showed a PR (n = 81, 80.1%), with a minority showing a CR (n = 11, 10.9%) and SD (n = 2, 1.9%). Seven patients had PD noted on iCT. Four patients had a second malignancy identified on biopsy of lesions found on iCT (thymoma, poorly differentiated carcinoma, lung adenocarcinoma and spindle cell tumour), 2 of whom were symptomatic at the time of iCT. Three patients had biopsy proven transformation to diffuse large B cell lymphoma (DLBCL); 2 were symptomatic at the time of iCT and only 1 had asymptomatic PD. The 3 year progression free survival (PFS) for all patients was 87.55%. Patients with a PR on iCT had similar 3 year PFS compared to those with CR (87.25% vs 90.00%, p = .52) as well as overall survival (94.80% vs 88.89%, p = .88). Conclusions: In this cohort, iCT was not useful for identifying patients with asymptomatic early progression of FL during treatment with BR. The majority of patients receiving systemic treatment for FL have at least a PR to BR on iCT, which is not associated with inferior PFS or OS compared to those with CR. Patients with symptomatic or asymptomatic PD during treatment warrant biopsy to identify histologic transformation or other malignancies. The rate of second cancers identified on iCT will be further explored in a cohort of FL patients treated with R-CVP and R-CHOP.