The observational study, as defined by the National Cancer Institute, involves research conducted among cancer patients and healthy populations without any intervention or alteration in the status of the participants. This type of study focuses on observing and analyzing existing conditions and behaviors without introducing new treatments or interventions.The observational study, as defined by the National Cancer Institute, involves research conducted among cancer patients and healthy populations without any intervention or alteration in the status of the participants. This type of study focuses on observing and analyzing existing conditions and behaviors without introducing new treatments or interventions.