The goal of this observational study is to assess in the cohort of CLL patients enrolled in the front-line GIMEMA LLC1114 study who discontinued ibrutinib the time to subsequent treatment. The main question it aims to answer is:

• The 12 and 24-month TTNT measured from the time of ibrutinib discontinuation due to reasons other than CLL progression, Richter syndrome, malignancy or death, or lost to the follow-up.

Participants will be observed for the duration of the study.

This is an observational, multicenter, retrospective and prospective study aimed at analyzing in the cohort of CLL patients enrolled in the front-line GIMEMA LLC1114 study the time to next treatment in patients who discontinued ibrutinib due to reasons other than CLL progression, Richter syndrome, malignancy or death, or lost to the follow-up.

Inclusion Criteria:

• Patients treated with ibrutinib included in the LLC1114 GIMEMA study who have discontinued ibrutinib after completing 78-months of treatment per protocol OR patients treated with ibrutinib included in the LLC1114 GIMEMA study who were treated for at least 12 months before discontinuing ibrutinib due to reasons other than CLL progression, Richter syndrome, malignancy or death, or lost to the follow-up and had achieved a response (CR or PR/PR-L) lasting at least 6 months before discontinuing ibrutinib
• Informed consent, if applicable.

Exclusion Criteria:

- Patients with concomitant conditions that may interfere with an appropriate assessment of the TTNT in the physician opinion.

CLL patients enrolled in the front-line GIMEMA LLC1114 study who discontinued ibrutinib due to reasons other than CLL progression, Richter syndrome, malignancy or death, or lost to the follow-up.