Fasting Reduces Intestinal Radiotoxicity, Enabling Dose-Escalated Radiation Therapy for Pancreatic Cancer

Int J Radiat Oncol Biol Phys. 2019 Nov 1;105(3):537-547. doi: 10.1016/j.ijrobp.2019.06.2533. Epub 2019 Jul 2.

Abstract

Purpose: Chemotherapy combined with radiation therapy is the most commonly used approach for treating locally advanced pancreatic cancer. The use of curative doses of radiation in this disease setting is constrained because of the close proximity of the head of the pancreas to the duodenum. The purpose of this study was to determine whether fasting protects the duodenum from high-dose radiation, thereby enabling dose escalation for efficient killing of pancreatic tumor cells.

Methods and materials: C57BL/6J mice were either fed or fasted for 24 hours and then exposed to total abdominal radiation at 11.5 Gy. Food intake, body weight, overall health, and survival were monitored. Small intestines were harvested at various time points after radiation, and villi length, crypt depth, and number of crypts per millimeter of intestine were determined. Immunohistochemistry was performed to assess apoptosis and double-strand DNA breaks, and microcolony assays were performed to determine intestinal stem cell regeneration capacity. A syngeneic KPC model of pancreatic cancer was used to determine the effects of fasting on the radiation responses of both pancreatic cancer and host intestinal tissues.

Results: We demonstrated that a 24-hour fast in mice improved intestinal stem cell regeneration, as revealed by microcolony assay, and improved host survival of lethal doses of total abdominal irradiation compared with fed controls. Fasting also improved survival of mice with orthotopic pancreatic tumors subjected to lethal abdominal radiation compared with controls with free access to food. Furthermore, fasting did not affect tumor cell killing by radiation therapy and enhanced γ-H2AX staining after radiation therapy, suggesting an additional mild radiosensitizing effect.

Conclusions: These results establish proof of concept for fasting as a dose-escalation strategy, enabling ablative radiation in the treatment of unresectable pancreatic cancer.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abdomen / radiation effects
  • Animals
  • Apoptosis
  • Cell Line, Tumor
  • DNA Breaks, Double-Stranded
  • Duodenum / radiation effects*
  • Fasting*
  • Female
  • Histones / metabolism
  • Intestine, Small / cytology
  • Intestine, Small / radiation effects
  • Male
  • Maximum Tolerated Dose
  • Mice
  • Mice, Inbred C57BL
  • Organ Sparing Treatments*
  • Organs at Risk / radiation effects
  • Pancreatic Neoplasms / mortality
  • Pancreatic Neoplasms / radiotherapy*
  • Proof of Concept Study
  • Radiation Injuries / mortality
  • Radiation Injuries / prevention & control
  • Radiation Tolerance*
  • Radiotherapy Dosage
  • Random Allocation
  • Regeneration
  • Stem Cells / physiology
  • Stem Cells / radiation effects*
  • Time Factors
  • Tumor Stem Cell Assay / methods

Substances

  • Histones
  • gamma-H2AX protein, mouse