To ascertain the safety and efficacy of Istodax® in actual clinical settings in patients with relapsed or refractory peripheral T-cell lymphoma (PTCL) who receive Istodax.

1. Planned registration period 4 years
2. Planned surveillance period 5 years and 6 months

Inclusion Criteria:

- Patients who have been diagnosed with relapsed or refractory PTCL who receive Istodax for the first time.

Exclusion Criteria:

N/A

Since the number of patients with PTCL was 48 and 131 in the Japanese and overseas clinical studies, respectively, the number of subjects to be surveyed was established at 130 to allow comparison of results between this survey and Japanese clinical study, or between this survey and overseas clinical study.

Among events that were established as the key survey items of this survey, QT interval prolonged had the lowest incidence (3.8%) in the overseas/Japanese clinical studies of Istodax in patients with PTCL. When 130 subjects are collected, it would be possible to collect at least 1 case of an event that occurs at the frequency of 2.3% with a reliability of 95%. Thus, assuming that adverse events occur under the actual use conditions at similar frequencies as in clinical studies, it would be possible to obtain at least 1 case of all events that have been established as the key survey items.