The cancer incidence increase in elderly patients determines the actuality of this study, because oncological illnesses are often accompanied by mental disturbances. This article considers clinical psychological risk factors of the posttraumatic stress disorder (PTSD) onset in prostate and rectal cancer elderly patients after surgical treatment. The study results showed that lack of social support, deficit of the successful stress coping experience in the past, maladaptive internal disease model, and destructive personality profile proved to be statistically significant risk factors and consequently psychotherapeutic interventions targets in PTSD treatment and prevention. Consideration of the elderly oncology patient clinical, psychological and social characteristics allows to elaborate effective personalized strategies of the complex medical-psychological care in geriatric medicine.