The diagnosis of cancer can be a major trigger for new sleep problems, especially insomnia, in people who did not have sleep issues before. Insomnia may appear early in the care pathway and can continue over time, often interacting with other physical or emotional symptoms. The main goal of this preliminary study is to describe how insomnia develops during the first months after a cancer diagnosis in patients who had no sleep problems at the time of diagnosis. This will be done through regular follow-up over time. A secondary aim is to identify the factors that may contribute to the onset or persistence of insomnia, such as the cancer treatments patients receive, as well as any medical or non-medical therapies used to manage sleep difficulties. The study will also look at whether patients who develop sleep problems are referred to psychologists trained in specific therapies for insomnia, and how well they follow and adhere to these treatments.