This study will examine DNA from Gastrointestinal Tract of cancer patients treated with oxaliplatin to look for a variation (mutation) of the ABCG2 gene that may lead to drug-induced peripheral neuropathy in certain patients.

The DNA will be extracted from patients' blood samples and are analyzed for the ABCG2 single nucleotide polymorphism (G34A - rs2231137 and A/A -rs3114018 genotypes) and correlated with peripheral neuropathy grades.

Pharmacogenetic analysis/genotyping :

Genotyping is conducted via High Resolution Melting (HRM) TECHNIQUE, To confirm the genotyping results, the Polymerase chain reaction (PCR) product of the samples will be examine via direct sequencing using 3500 Genetic analyzer from ThermoFisher (applied biosystem) at two ABCG2 loci using the following PCR primers:

1-ABCG2 G34A - rs2231137

Forward :

5'-TGC AAT CTC ATT TAT CTG GAC TA-'3

Reverse :

5'-AAT GCC TTC AGG TCA TTG GA-'3

-Annealing temp :57 -Product size : 163

2- ABCG2 A/A - rs3114018

Forward :

5'- TGATGTTCCTTCAGCCACTG-'3

Reverse :

5'-TTGTGGAAACCTCACAAAAGTG-'3

- Annealing temp : 59 - Product size : 124

Inclusion Criteria:

• Gastrointestinal Tract Cancer patients treated with Oxaliplatin-containing chemotherapy
• Measurable disease
• Age of 18 years to 80 years

Exclusion Criteria:

• Pregnant women
• History of allergic reactions attributed to compounds of similar chemical or biologic composition to Oxaliplatin.
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
• Neurologic disease or patients with disease impairing the neurologic function affecting

Patients with Gastrointestinal tract (GIT) Cancer