The outcome of watchful waiting in patients with previously treated follicular lymphoma.

Watchful waiting (WW) is one of the standard approaches for newly diagnosed follicular lymphoma (FL) patients with low-tumor burden. However, the impact of WW in FL patients at the first progression, remains unclear. We reviewed 206 FL patients who experienced the first progression after responding to the initial treatment at our institution between 1998 and 2017. Patients were classified into either the WW cohort (132 patients) or the immediate treatment cohort (74 patients). Overall, the median follow-up from the first progression was 79.8 months (range, 2.1-227.0 months). In the WW cohort, the estimated median time to next treatment (TNT) was 19.7 months (95% confidence interval [CI], 13.4-30.2), and 76.5% (95% CI, 68.0-84.1) of the patients subsequently underwent the second-line treatment at 5 years. There was a significant difference in the median time to treatment failure in the WW cohort (72.8 months; 95% CI, 64.6-94.0) compared to the immediate treatment cohort (23.3 months; 95% CI, 13.4-38.8) (HR, 2.13; 95% CI, 1.48-3.06), whereas overall survival and the cumulative incidence of histological transformation were not significantly different between two cohorts. In a multivariate analysis, rituximab refractory status, progression of disease within 24 months from the induction of first-line therapy, and a high Follicular Lymphoma International Prognostic Index score at diagnosis were significantly associated with shorter TNT. Interestingly, 15 patients (11%) of the WW cohort experienced spontaneous tumor regression during WW, and their TNT (median, 82.1 months, 95% CI, 11.7-NA) was longer than that of the remaining patients in the WW cohort (median, 16.5 months, 95% CI, 13.0-25.4), with a significant difference (p = 0.01). The results of the present study suggested that WW could be a safe and reasonable option even at the first progression for the selected FL patients, without a negative impact on clinical outcomes.