Atrial fibrillation is a common complication of both cancer and anticancer drugs but the consequences of such events remain poorly known and are not adressed in both phase III oncological trials and cardiological guidelines. The objective of this study is to create a prospective multicenter international registry of adult patients with an active cancer and experiencing atrial fibrillation to study major cardiovascular events occurrence during a 1 year follow-up.

Inclusion Criteria:

• adult patients
• outpatients or hospitalized patients
• with a confirmed cancer (other than basal-cell or squamous-cell carcinoma of the skin, primary brain tumor, known intracerebral metastases, or acute leukemia) and an active cancer (defined as cancer that had been diagnosed within the past 6 months or recurrent locally advanced or metastatic cancer, for which anticancer treatment was being given at the time of enrollment or during 6 months before enrollment)
• at least 1 episode of atrial fibrillation (new onset AF occuring after cancer diagnosis or history of paroxysmal of persistant AF prior to cancer diagnosis and an AF recurrence after cancer diagnosis)
• in sinus rhythm at the time of cancer diagnosis

Exclusion Criteria:

• patient with palliative cares or other conditions resulting in short term death (death expected in the month following atrial fibrillation occurrence)
• history of long-standing persistant or permanent AF prior to cancer diagnosis

Patients with a cancer will defined as patients with confirmed cancer other than basal-cell or squamous-cell carcinoma of the skin, primary brain tumor, known intracerebral metastases, or acute leukemia.

Active cancer will be defined as cancer that had been diagnosed within the past 6 months or recurrent locally advanced or metastatic cancer, and an anticancer treatment given at the time of enrollment or during 6 months before enrollment (according to Agnelli et al. NEJM 2020).

AF patients will be both patients with incident AF (first AF episode diagnosed after cancer diagnosis) and those with prevalent AF (AF recurrence occurring after cancer diagnosis and a first AF episode prior to cancer diagnosis)