Investigating chemopotentiation by low-dose fractionated radiation therapy for disseminated intra-abdominal gastric cancer.

242 Background: Treatment options are rather limited for gastrointestinal cancer patients whose disease has disseminated into the intra-abdominal cavity. There is currently no modality that has been shown to prolong survival of this patient sub-population. Here, we designed pre-clinical studies to evaluate the potential application of chemopotentiation by Low Dose Fractionated Radiation Therapy (LDFRT) for disseminated gastric cancer and evaluate the role of a likely biomarker, the Dual Oxidase 2 (DUOX2) enzyme. Methods: Nude mice were injected orthotopically with human gastric cancer cells expressing endogenous or lower levels of DUOX2 and randomly assigned to four treatment groups: 1; vehicle alone, 2; chemotherapy consisting of a modified regimen of docetaxel, cisplatin and 5’-fluorouracil (mDCF) for three consecutive days, 3; Low Dose- Whole Abdomen Radiation Therapy (LD-WART) (5 fractions of 15 cGy in three days), 4; mDCF and LD-WART. Blood was harvested at day 14 and 45 and cancer progression was evaluated by fluorescence imaging (Xenogen). Results: The combined regimen was well tolerated in all animals and led to DUOX2 upregulation, increased serum protein oxidation and reduced cancer progression in the DUOX2 positive tumors. Tumors expressing lower DUOX2 levels were more sensitive to chemotherapy but no additional benefit was obtained with LD-WART. The potential clinical significance of these findings is exemplified by a tumor microarray demonstrating that only about 46% of human gastric tumors expressed DUOX2. The molecular mechanisms underlying DUOX2 effects in response to the combined regimen include NF-kB upregulation and VEGF down regulation. Moreover, the combined regimen of mDCF and LDFRT was also effective on a Cancer Stem Cell (CSC)-Like subpopulation of mouse gastric cancer cells. Conclusions: Taken together these data suggest that DUOX2 could be used as a potential biomarker for patient stratification for chemopotentiation by LD-WART for positive tumors while chemotherapy alone would be more effective for DUOX2 negative tumors. The absence of added toxicity suggests that these cycles could be repeated.