this study investigated the potential of single nucleotide polymorphisms as predictors of survival in two cohorts comprising 417 metastatic colorectal cancer (mCRC) patients treated with the FOLFIRI (folinic acid, 5-fluorouracil and irinotecan) regimen. The rs4806668G > t of the ribosomal protein gene RPL28 was associated with shorter progression-free survival and overall survival by 5 and 9 months (P = 0.002), with hazard ratios of 3.36 (P < 0.001) and 3.07 (P = 0.002), respectively. The rs4806668T allele was associated with an increased RPL28 expression in transverse normal colon tissues (n = 246, P = 0.007). RPL28 expression was higher in colorectal tumors compared to paired normal tissues by up to 124% (P < 0.001) in three independent datasets. Metastatic cases with highest RPL28 tumor expression had a reduced survival in two datasets (n = 88, P = 0.009 and n = 56, P = 0.009). High RPL28 was further associated with changes in immunoglobulin and extracellular matrix pathways. Repression of RPL28 reduced proliferation by 1.4-fold to 5.6-fold (P < 0.05) in colon cancer HCT116 and HT-29 cells. Our findings suggest that the ribosomal RPL28 protein may influence mCRC outcome. Metastatic colorectal cancer (mCRC) presents a 5-year relative survival just above 10% 1. There are many treatment options for these patients including irinotecan-based chemotherapy. Particularly, the FOLFIRI regimen is composed of irinotecan (CPT-11) used in combination with 5-fluorouracil (5-FU) and folinic acid alone or with targeted therapies 2. Both irinotecan and 5-FU are potent on actively replicating cancer cells. SN-38, the active metabolite of irinotecan, is an inhibitor of topoisomerase I (TOP1). It prevents DNA ligation by directly binding the TOP1-DNA complex, leading to replication arrest, double-strand breaks and cell death 3. 5-FU is a pyrimidine analog that exerts its effect by inhibiting the thymidylate synthetase and DNA synthesis. 5-FU can also be incorporated into RNA during synthesis and interferes with protein synthesis 4. The clinical response to FOLFIRI-based regimens is variable with dose-limiting toxicities occurring in a significant proportion of patients 5,6. Several markers in pharmacokinetic pathways have been linked to severe toxicities. For instance, the UGT1A1*28 polymorphism was established as a predictive marker of severe neutropenia, explained by a decreased UGT1A1