en Cancer Cancer Original Article Original Article Background: Survival of Colorectal cancer (CRC) patients is considerably stage-dependent therefore, early diagnosis is a pivotal factor in decreasing mortality and morbidity associated with this cancer. GM-CSF and IL-7 are reported to increase in different cancers and we aim to investigate the pre-treatment serum levels of GM-CSF and IL-7 in Iranian patients with colorectal cancer. Methods: 127 patients (68 males and 59 females) before receiving chemotherapy or radiotherapy entered to this study. A control group of 50 healthy age/sex matched individuals (27 males and 23 females) were included in the study. Serum levels of GM-CSF and IL-7 were measured using commercial enzyme linked immunosorbent assays. Results: A significantly higher level of GM-CSF was found in the sera of patients with colorectal cancer compared with healthy age/sex matched controls (p=0.013). However, there was no significant difference between the levels of IL-7 in sera of patients and controls. We observed a significant elevation in the level of GM-CSF in poorly differentiated tumors (p=0.024). Also a significant correlation between lymphatic invasion and the level of GM-CSF in sera of CRC patients was detected (p=0.01). We found an increase in the level of IL-7 in the three patients in the moderate stages of the tumor concomitant with a decrease in the level of GM-CSF. Conclusion: Increase in the level of GM-CSF is accompanied by CRC progression in Iranian patients, while there may be a potential therapeutic effect of IL-7 in this disease. Colorectal cancer, Serum, GM-CSF, IL-7 26 34 http://ijmcmed.org/browse.php?a_code=A-10-150-1&slc_lang=en&sid=1 Mehdi Taghipour Fard Ardekani mehditfa@yahoo.co.in 10031947532846003532 10031947532846003532 No Shiraz Institute for Cancer Research, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran. Mahyar Malekzadeh malekzadem@sums.ac.ir 10031947532846003533 10031947532846003533 No Shiraz Institute for Cancer Research, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran. Mohammad Vahid Hosseini ghaderia@sums.ac.ir 10031947532846003534 10031947532846003534 No Department of Immunology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran. Elahe Bordbar ihhbordbar@yahoo.com 10031947532846003535 10031947532846003535 No Shiraz Institute for Cancer Research, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran. Zahra Mojtahei mojtahediz@sums.ac.ir 10031947532846003536 10031947532846003536 No Shiraz Institute for Cancer Research, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran. Mehrnoosh Doroudchi mdoroud@sums.ac.ir 10031947532846003537 10031947532846003537 Yes Shiraz Institute for Cancer Research, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran. Abbas Ghaderi ghaderia@sums.ac.ir 10031947532846003538 10031947532846003538 No Shiraz Institute for Cancer Research, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.