Irinotecan-based systemic therapy is shown to have promising results in metastatic or unresectable colorectal cancer. However, this therapy has two major disadvantages, including an unpredictable individual treatment response and late-onset systemic and gastrointestinal toxicity. To target these problems, biomarkers are needed which could be used to predict treatment response and toxicity before start of the treatment. The molecular profile of the tumor (consensus molecular subtypes (CMS)), the UGT1A1 genotype and the gut microbiota-derived enzyme β-glucuronidase are promising candidates in this context. Recent research demonstrated that irinotecan-based systemic therapy increased both progression free survival (PFS) and optimal survival (OS) predominantly in patients with CMS4 cancers, as well as in preclinical models representing this subtype. For the other CMS subtypes (CMS1-3), irinotecan-based systemic therapy was shown to be significantly less efficient. For the UGT1A1 genotypes, decreased activity of the UGT1A1 enzyme (converting the toxic metabolite SN-38 into the inactive SN-38G) will increase the concentration of toxic SN-38, resulting in systemic toxicity. Lastly, the importance of studying bacterial β-glucuronidase (β-GUS) activity in CRC patients during treatment with irinotecan can be derived from recent animal studies, and indirect human evidence. Previous research has shown that high bacterial β-GUS activity (converting the inactive SN-38G into the toxic SN-38) might be a possible indicator for irinotecan-induced late-onset gastrointestinal toxicity due to SN-38 accumulation. Therefore, the OPTIMA study was developed to combine prediction of tumor sensitivity towards irinotecan (by CMS classification), UGT1A1 expression for irinotecan dose determination, and β-GUS for risk assessment for late-onset gastrointestinal toxicity. The aim of the study is to investigate whether the molecular profile of the tumor (e.g. based on CMS), the UGT1A1 genotype and β-GUS activity can act as a predictor for therapy efficiency, late-onset systemic and gastrointestinal toxicity, as well as OS and quality of life (QoL).
Irinotecan-based systemic therapy is a treatment option for metastatic or unresectable colorectal cancer. However, this therapy has two major disadvantages, namely, an unpredictable response to the treatment and severe side effects, for instance diarrhea or a low white blood cell count (neutropenia). Therefore, the OPTIMA study was developed to find out if biomarkers, such as the molecular profile of the tumor, the UGT1A1 genotype and activity of the bacterial enzyme β-glucuronidase, can predict response and side effects during irinotecan treatment. By looking at these biomarkers, treatments could be more personalized, resulting into enhanced therapy efficiency, increased optimal survival and a better quality of life.