PK/PD Investigation of Calciumfolinat in Blood, Tumor and Adjacent Mucosa in Patient With Colon Cancer

Cytotoxic treatment of patients with colorectal cancer (CRC) includes most various different drugs but 5-fluorouracil (5-FU) is the cornerstone in most regimens. Leucovorin (LV) is frequently used as a part of a standard treatment regime for advanced CRC in combination with 5-FU. In numerous randomized clinical trials the addition of LV to 5-FU has been shown to significantly improve the antitumor activity and to prolong the survival of patients receiving adjuvant chemotherapy or treatment for advanced disease as to compared to treatment with 5-FU as single drug therapy. In most European countries 5-FU is given as an infusion during 46 hours in combination with a two hour infusion of LV. This regime is called the deGramont schedule. In the Nordic countries, 5-FU and LV are often given as bolus injections according to the regime called Nordic FLV. Leucovorin is a prodrug which has to be metabolized to methylenetetrahydrofolate (mTHF) in order to increase inhibition of the target enzyme thymidylate synthase (TS). Due to the low concentrations of the reduced folate forms intracellular there is a lack of knowledge of the pharmacodynamics of LV when used as an infusion. When the 5-FU/LV used today was introduced it was technically not possible to measure the different metabolites of the reduced folates in blood and tissue. In the literature there is only one published reference measuring the blood concentration after a two hour infusion of LV. However, it has recently been possible to separate and quantitate the different folates using sensitive Liquid Chromatography/Masspectrometry (LC/MS) methods. Furthermore it has been stated that differences in enzyme activity for genes involved in the transport and metabolism of folates may be responsible for the large inter individual differences in folate tissue concentrations. This study is designed to gain an understanding of how a single intravenous infusion of LV affects the folate concentration in blood, tumor and adjacent mucosa tissue. By using the LC/MS method which was recently developed and it is now possible to quantitate the different metabolites of LV in small tissue samples as well as in blood. It is further now possible to measure by quantitative Polymerase Chain Reaction techniques (PCR) the most important genes involved in the folate transport and metabolism ((SHMT1), SerineHydroxyMethylTransferase1 and (ABCC3) ATP-binding cassette, sub-family C, (CFTR/MRP), member 3)).