This retrospective study was proposed by the investigators to analyze treatment status and outcome in patients with early relapsed follicular lymphoma. In patients with follicular lymphoma who experienced disease progression within 24 months after initiation of treatment, the second-line therapy, stem cell transplantation, tumor response, progression free survival, and overall survival will be analyzed.

Follicular lymphoma is the second most common non-Hodgkin's lymphoma in Western countries, but it is relatively less frequent in Asia. As a result, the prognosis and treatment status in Korean patients with follicular lymphoma have been rarely studied.

With the recent addition of monoclonal antibodies targeting CD20 into existing cytotoxic chemotherapy, the overall life expectancy of patients with follicular lymphoma has improved a lot. However, nearly 20% of these patients experience early worsening of disease within the first 24 months of treatment, followed by poor prognosis. Since patients with early relapse within 24 months usually experience worsening of disease during treatment with rituximab combined with chemotherapy or during rituximab maintenance therapy, optimal treatment for such patients is unknown, but remission induction therapy followed by stem cell transplantation, bendamustine combined with obinutuzumab, PI3K inhibitors, and lenalidomide are possible options. However, most of these drugs are limited for use in Korea, and there is little information with regard to treatment guidelines for patients with early relapsed follicular lymphoma or their treatment outcome in Korea.

This retrospective study was proposed by the investigators to analyze treatment status and outcome in patients with early relapsed follicular lymphoma. This study will provide basic data for follicular lymphoma study in Korea and for future clinical trial design.

Inclusion Criteria:

1. Patients histologically diagnosed with follicular lymphoma (ICD-10 C82.0 to C82.9)

2. Radiologically confirmed disease progression within 24 months from the start date of an induction chemotherapy

3. All of the following should be available for retrospective analysis.

   • Pathologic findings report
   • Medical records containing age, sex, date of diagnosis, clinical symptoms, laboratory findings, treatment methods, progression, survival, death, etc.

Exclusion Criteria:

1. Known histologic transformation to aggressive lymphoma
2. Follicular lymphoma grade 3B
3. Patients whose pathologic findings report and appropriate medical records are not available

The analysis will involve patients diagnosed with follicular lymphoma who received induction chemotherapy and then experienced a worsening of disease within 24 months from the start date of the treatment.