Short-term fasting (48 hours) was shown to be effective in protecting normal cells and mice but not
cancer cells against high dose
chemotherapy, termed Differential Stress Resistance (DSR), but the feasibility and effect of fasting in
cancer patients undergoing
chemotherapy is unknown. Here we describe 10 cases in which patients diagnosed with a variety of
malignancies had voluntarily fasted prior to (48-140 hours) and/or following (5-56 hours)
chemotherapy. None of these patients, who received an average of 4 cycles of various
chemotherapy drugs in combination with fasting, reported significant side effects caused by the fasting itself other than hunger and
lightheadedness.
Chemotherapy associated toxicity was graded according to the Common Terminology Criteria for Adverse Events (CTCAE) of the National Cancer Institute (NCI). The six patients who underwent
chemotherapy with or without fasting reported a reduction in
fatigue, weakness, and gastrointestinal side effects while fasting. In those patients whose
cancer progression could be assessed, fasting did not prevent the
chemotherapy-induced reduction of
tumor volume or
tumor markers. Although the 10 cases presented here suggest that fasting in combination with
chemotherapy is feasible, safe, and has the potential to ameliorate side effects caused by
chemotherapies, they are not meant to establish practice guidelines for patients undergoing
chemotherapy. Only controlled-randomized clinical trials will determine the effect of fasting on clinical outcomes including quality of life and therapeutic index.