Being diagnosed with a life-threatening illness is a very stressful event. During the treatment, many factors will trigger stress responses, such as fear of treatment not being effective, awaiting biopsy results, doctor visits, wondering about the recurrence of cancer, and many others. This may lead you to having recurrent feelings of shock, fear, helplessness, prolonged sadness, and other overwhelming symptoms. Seeking help in moments of struggle is a starting point to improve a situation.
Check out this website for more information
https://www.cancer.gov/about-cancer/coping/survivorship/new-normal/ptsd-pdq