Ribomustin in the Second Line Therapy of Relapsed or Refractory Indolent B-cell Non-Hodgkin's Lymphoma

Inclusion Criteria: * Doctor's decision to prescribe Ribomustin and rituximab combined therapy for the treatment of relapsed or refractory indolent B-cell Non-Hodgkin's Lymphoma (iNHL) * Informed Consent Form for personal data handling signed by the program participant, authorized by the Independent Ethics Committee * Eastern Cooperative Oncology Group (ECOG) status \< 2. * Confirmed relapse or disease progression of B-cell CD20+ Non-Hodgkin's Lymphoma (lymphocytic, lymphocytoplasmocytic, follicular, marginal zone) after minimum one line of iNHL treatment * Patients with relapsed or refractory indolent B-cell Non-Hodgkin's Lymphoma with current or planned Ribomustin and rituximab combined therapy with following rituximab maintenance therapy Exclusion Criteria: * Indolent Non-Hodgkin's Lymphoma transformation * Lymphoma with central nervous system (CNS) involvement * Presence of second malignant tumor. * Currently participating in any clinical trial, and/or has taken an investigational drug within 28 days prior to enrollment. * Contraindications for Ribomustin usage in accordance with product label * Contradictions for rituximab usage in accordance with product label