LAUSR

Stage I–II follicular lymphoma (FL) is commonly treated with curative-intent radiotherapy (RT) with a 10-year freedom from progression of approximately 50%. Relapses may be detected clinically with investigations arranged for patient signs/symptoms or radiologically by active surveillance imaging (SI). There is uncertainty regarding the clinical benefit of earlier detection of relapse by SI. The purpose of this study was to evaluate whether the detection of recurrent FL through active SI impacts overall survival (OS) in limited-stage FL. Patients with biopsy-confirmed grade 1–3A, stage IA–IIA, non-bulky FL, who were treated at BC Cancer with curative-intent RT alone between January 2000 and December 2015 were retrospectively reviewed. FL patients were routinely staged with a bone marrow biopsy and computed tomography (CT) imaging, but not positron emission tomography scans. Involved-site RT alone was delivered with a minimum dose of 20 Gy. Following RT, utilization and frequency of SI was at the discretion of the most responsible physician. This study received ethics approval through the BC Cancer/University of British Columbia Research Ethics Board. Method of relapse detection was categorized into clinical detection (i.e. investigations arranged for patient symptoms, abnormal physical examination, or laboratory abnormalities) or SI detection (i.e. radiologic investigations in asymptomatic patients). Imaging investigations following completion of RT were analyzed until date of first relapse or date of last followup in patients without relapse. The indication for imaging was classified as SI or clinical suspicion. SI was categorized as true negative if there was no radiologic, clinical, or pathologic evidence of relapse in the imaged site for at least 30 days. To adjust for multiple observations per patient when analyzing positive predictive value (PPV) and specificity, we calculated 95% confidence intervals (CIs) via the means of the bootstrap method with 10 000 bootstrap samples, where each bootstrap sample is created such that each sample has either all or none of a given patient’s records. Between January 2000 and December 2015, 330 patients with limited-stage FL were treated with curative-intent RT alone. Baseline characteristics are summarized in Table I. Of all imaging investigations in the follow-up period (n = 1150), 830 (72 2%) were arranged for SI and 320 (27 8%) were arranged for clinical suspicion. Imaging modalities and corresponding diagnostic yields are outlined in Table SI. Table I. Patient, tumour, and radiotherapy characteristics.