This study is to explore risk factors for poor progression-free survival (PFS) and overall survival (OS) in ENKTL, and establish a prognostic model for ENKTL patients treated with non-anthracycline based treatment.

This is a retrospective cohort study using anonymized information from patients with ENKTL. The following criteria are required: (1) Patients diagnosed with ENKTL, nasal type between January 1, 1995 and December 31, 2014; (2) Patients treated with non-anthracycline based therapy as an initial treatment. The pathology of initial diagnosis was reviewed by designated pathologists.

Inclusion Criteria:

• Patients diagnosed with ENKTL, nasal type
• Patients diagnosed between January 1, 1995 and December 31, 2014
• Patients treated with nonanthracycline-based therapy as the initial treatment after diagnosis
• Nonanthracycline-based therapy includes the following treatments:
• Radiotherapy including concurrent chemoradiation
• Chemotherapy not including anthracycline such as doxorubicin (e.g. SMILE, VIPD) The type of salvage treatment will not be a criterion for exclusion. Thus, patients who had received various kinds of salvage treatment including anthracycline-containing regimens can be included. Patients who had undergone autologous or allogeneic stem cell transplantation can also be included in the analysis if they satisfy the above-mentioned inclusion criteria.

Exclusion Criteria:

• Patients who had received anthracycline-based therapy, such as CHOP or CHOP-like regimens, as the initial treatment.
• Patients who do not have pathology slides available for central review.

1. Patients diagnosed with ENKTL, nasal type between January 1, 1995 and December 31, 2014;
2. Patients treated with non-anthracycline based therapy as an initial treatment.