If you think fasting for 3 days is to difficult, intermittent fasting is another option where you eat normally for 5 days and then eat 600cal for 2 days/week. Preliminary evidence shows that this approach harnesses the beneficial effects of fasting without the extended restrictive periods. I recommend that you see a a health care practitioner before you try fasting since there are some cases it may not be right for you and could be harmful. If you have cancer, then you should have a consult with a ND that has experience in this field.
Watch this video for a great overview
Longo and Fontana. Calorie restriction and cancer prevention: metabolic and molecular mechanisms Trends Pharmacol Sci. 2010 February ; 31(2): 89–98. doi:10.1016/j.tips.2009.11.004