Pain is one of the most prevalent symptoms during and after cancer. Pain can be the consequence of several situations (disease progression, surgery, and anticancer drugs). However, pain can frequently be associated with a substance use disorder (alcohol, tobacco, drugs, and illicit products such as cannabis). The relationship between substance use and pain is known to be complex and interdependent, i.e. pain can reinforce substance use and substance use can promote pain. However, few data in the literature are available on the use of psychoactive substances in relation to pain in the context of cancer (cancer patients and cancer survivors). Moreover, the scientific literature agrees on the fact that these elements are little studied and underestimated in the clinic.

The investigators hypothesize that, in cancer patients or cancer survivors, the prevalence of the use of psychoactive substances would be higher in the presence of pain, and would be associated with its intensity and its impact on the quality Health-Related Living (HRQoL).

The main objective of this study will be to compare, in an adult population of patients suffering from cancer or having had cancer, the prevalence of the consumption of psychoactive substances in painful patients compared to non-painful patients.

Patients will answer to an online questionnaire thanks to associations of cancer patients and social networks, in order to explore their substance use and pain status.

Inclusion Criteria:

- Adult patient, male or female, declaring himself as suffering or having suffered from cancer and recruited as such via appropriate communication systems (patient associations, etc.)

Exclusion Criteria:

• Difficulty to understand French language
• Residence outside France (will be verified by the information from the department at the start of the questionnaire)
• Patient close relative
• Protected adults

Cancer patients and cancer survivors recruited thanks to associations of cancer patients and social networks