Expression of thymidylate synthase in primary colorectal adenocarcinoma.

Thymidylate synthase (TS) is a key regulatory enzyme in the cellular pathway of de novo pyrimidine synthesis and a target enzyme for 5-fluorouracil (5-FU). Most clinical studies have shown that high levels of TS in tumors are associated with decreased sensitivity to 5-FU treatment. In this study TS expression was assessed at DNA, RNA, and protein levels. The study included 69 tumors from patients with primary colorectal adenocarcinoma. At the DNA level TS enhancer polymorphism was measured on whole blood by PCR. At the RNA level TS mRNA expression was measured on formalin-fixed paraffin-embedded tumor tissue and on fresh-frozen tumor tissue by real-time RT-PCR. Protein expression was assessed by IHC. Correlation was found between TS mRNA expression in fresh-frozen tumor tissue and formalin-fixed paraffin-embedded tissue (R=0.71). TS enhancer 3/3 had significantly higher protein levels as assessed by IHC than the TS enhancer 2/2 (P=0.02), although there was no statistically significant correlation between TS enhancer polymorphism and TS mRNA expression. An interesting observation not previously reported is that the predominant IHC reaction pattern in tumors from patients with the TS enhancer genotype 3/3 is different in tumors from patients with genotypes 2/2 and 2/3. The results indicate that clinical studies of the significance of TS with regard to 5-FU-based chemotherapy should be based on assessment of TS activity at DNA, RNA, and protein levels.     

Clinical application of 7.0 T magnetic resonance images in Gamma Knife radiosurgery for a patient with brain metastases

In the study we assessed the distortion of 7.0 T magnetic resonance (MR) images in reference to 1.5 T MR images in the radiosurgery of metastatic brain tumors. Radiosurgery with Gamma Knife Perfexion was performed for the treatment of a 54-yr-old female patient with multiple brain metastases by the co-registered images of the 7.0 T and 1.5 T magnetic resonance images (MRI). There was no significant discrepancy in the positions of anterior and posterior commissures as well as the locations of four metastatic brain tumors in the co-registered images between 7.0 T and 1.5 T MRI with better visualization of the anatomical details in 7.0 T MR images. This study demonstrates for the first time that 7.0 T MR images can be safely utilized in Perfexion Gamma Knife radiosurgery for the treatment of metastatic brain tumors. Furthermore 7.0 T MR images provide better visualization of brain tumors without image distortion in comparison to 1.5 T MR images.     

The use of thymidylate synthase inhibitors in the treatment of advanced colorectal cancer: current status

The combination of 5-fluorouracil (5-FU) and leucovorin has been the unofficial "standard" therapy for patients with colorectal cancer for over a decade. Recently, however, a number of new agents targeted against the enzyme thymidylate synthase have been synthesized and are in various stages of development. The currently available thymidylate synthase inhibitors are discussed. Enormous efforts have been made over the years to improve the efficacy of 5-FU, the most popular of these agents. Biochemical modulation by leucovorin has been the most successful so far. Continuous infusion schedules also appear to be advantageous over bolus administration. However, marked intra- and interpatient variability, combined with nonlinear elimination kinetics and erratic oral bioavailability are relative limitations to further development of 5-FU. New oral 5-FU prodrugs such as UFT, S-1, and Capecitabine may help to overcome some of these difficulties. Eniluracil, a potent inhibitor of the enzyme dihydropyrimidine dehydrogenase, may also help by overcoming potential 5-FU resistance mechanisms, in addition to increasing its bioavailability. Of the antifolate-based inhibitors, Tomudex is in the most advanced stage of development. Similar efficacy with 5-FU and a convenient schedule may suggest a role in future combination regimens. It is quite likely that even the most optimal thymidylate synthase inhibition will have limitations in terms of clinical efficacy. Novel combinations of 5-FU or its analogs with agents that have different mechanisms of action (e.g., oxaliplatin, irinotecan) could provide important new opportunities for improving the outlook of patients with colorectal cancer.     

5-Fluorouracil–lipid conjugate: Potential candidate for drug delivery through encapsulation in hydrophobic polyester-based nanoparticles

The encapsulation of 5-fluorouracil (5-FU) in hydrophobic polymeric materials is made feasible by a lipid-based prodrug approach. A lipid–5-FU conjugate of 5-FU with palmitic acid was synthesized in two-step process. A synthesized dipalmitoyl derivative (5-FUDIPAL) was characterized using Fourier transform infrared spectroscopy and ¹H-nuclear magnetic resonance. The 5-FUDIPAL was encapsulated in polyester-based polymers by the double emulsion–solvent evaporation method. The nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy and dynamic light scattering. The thermal stability was assessed by differential scanning calorimetry data. In vitro release kinetics measurements of the drug from nanoparticles showed the controlled release pattern over a period of time. Cytotoxicity measurements by MTT assay confirmed that dipalmitoyl derivative in nano formulation successfully inhibited the cell growth. Thus the combined physical and biological evaluation of the different polyester-based nanoparticle containing the modified drug showed a facile approach to delivering 5-FU to the tumour site with enhanced efficacy.     

Multimodal assessment of early tumor response to chemotherapy: comparison between diffusion-weighted MRI, 1H-MR spectroscopy of choline and USPIO particles targeted at cell death

The aim of this study was to determine the value of different magnetic resonance (MR) protocols to assess early tumor response to chemotherapy. We used a murine tumor model (TLT) presenting different degrees of response to three different cytotoxic agents. As shown in survival curves, cyclophosphamide (CP) was the most efficient drug followed by 5-fluorouracil (5-FU), whereas the etoposide treatment had little impact on TLT tumors. Three different MR protocols were used at 9.4 Tesla 24 h post-treatment: diffusion-weighted (DW)-MRI, choline measurement by (1) H MRS, and contrast-enhanced MRI using ultrasmall iron oxide nanoparticles (USPIO) targeted at phosphatidylserine. Accumulation of contrast agent in apoptotic tumors was monitored by T(2) -weighted images and quantified by EPR spectroscopy. Necrosis and apoptosis were assessed by histology. Large variations were observed in the measurement of choline peak areas and could not be directly correlated to tumor response. Although the targeted USPIO particles were able to significantly differentiate between the efficiency of each cytotoxic agent and best correlated with survival endpoint, they present the main disadvantage of non-specific tumor accumulation, which could be problematic when transferring the method to the clinic. DW-MRI presents a better compromise by combining longitudinal studies with a high dynamic range; however, DW-MRI was unable to show any significant effect for 5-FU. This study illustrates the need for multimodal imaging in assessing tumor response to treatment to compensate for individual limitations.     

Developments with targeted enzymes in cancer therapy.

Cancer therapy based on the delivery of enzymes to tumour sites has advanced in several directions since antibody-directed enzyme/prodrug therapy was first described. It has been shown that methoxypolyethylene glycol (MPEG) can be used to deliver enzyme to a variety of solid tumours. MPEG-enzyme conjugates show reduced immunogenicity and may allow repeated treatment with enzymes of bacterial origin. Enzyme delivery to tumours by polymers can be used to convert a low toxicity prodrug to a potent cytotoxic agent. An example of such a prodrug is CB1954, which can be activated by a human enzyme in the presence of a cosubstrate. Tumour-located enzymes can also be used in conjunction with a combination of antimetabolites and rescue agents. The rescue agent protects normal tissue but is degraded at cancer sites by the enzyme, thus deprotecting the tumour and allowing prolonged antimetabolite action.     

Per os administration of 5-fluorocytosine is effective in the regression of CD-expressing liver metastases in rats

The bacterial cytosine deaminase (CD) gene, associated to the 5-fluorocytosine (5-FC) prodrug, is one of the more widely used suicide systems in gene therapy. Introduction of the CD gene within a tumor induces, after 5-FC treatment of the animal, a local production of 5-fluorouracil (5-FU) resulting in intratumor chemotherapy. Destruction of the gene-modified tumor is then followed by the triggering of an anti-tumor immune reaction resulting in the regression of distant wild-type metastasis. In pre-clinical studies, 5-FC is generally administered by daily intraperitoneal injections. However, when used as an anti-fungal in humans, either IV or oral administration is used. In this study, we compared oral and intraperitoneal 5-FC administration in rats bearing a wild-type and a cytosine deaminase-expressing liver tumors. The results indicate that per os 5-FC administration is as efficient as intraperitoneal for the induction of CD-expressing tumor regression and the triggering of a distant bystander effect, acting on wild-type liver tumor and extra-hepatic metastasis.     

Enzyme histochemical study on bone tumors

A total of 19 cases with bone tumors, including six osteosarcomas. three giant cell tumors of bone, one malignant fibrous histiocytoma, four nonossifying fibromas, four chondromas and one chondrosarcoma, were examined as to enzyme histochemistry; the enzymes consisted of alkaline phosphatase (ALPase), acid phosphatase (ACPase), nonspecific esterase (NSE), adenosine triphosphatase (ATPase), 5'-nucleotidase (5'-Nucl) and beta-glucuronidase (beta-Gl). Osteosarcoma was strongly positive for ALPase followed by 5'-Nucl. Giant cell tumor, malignant fibrous histiocytoma and nonossifying fibroma showed enzyme histochemistry similar to each other: multinucleated giant cells and round cells in these tumors were strongly positive for ACPase, NSE, ATPase and 5'-Nucl simulating osteoclasts and histiocytes, whereas spindle cells were positive for ATPase and 5'-Nucl in their cytoplasm and weakly positive for ACPase. Chondroma and chondrosarcoma were focally positive for ACPase and NSE; the ACPase was sensitive to tartaric acid treatment. These observations showed that ALPase activity is very characteristic to osteosarcoma, and is useful for its diagnosis. From enzyme histochemistry, giant cell tumor, malignant fibrous histiocytoma and nonossifying fibroma can be regarded as a histiocyte-derived tumor of bone in contrast to osteosarcoma and cartilaginous tumors.     

在大剂量5-氟尿嘧啶治愈荷瘤小鼠过程中外周血细胞的变化与肿瘤消退之间的相关性分析

目的:观察在单一剂量5-氟尿嘧啶(5-FU)治愈荷瘤小鼠过程中外周血细胞数量的变化与肿瘤结节缩小之间的关系,为进一步研究化疗治愈肿瘤的作用机制奠定基础.方法:利用单一剂量5-FU治愈荷瘤野生型C57BL/6小鼠模型,荷瘤小鼠腹腔内分别注入25、75、135 mg/kg的5-FU,等量生理盐水对照,确定5-FU治愈肿瘤的量效关系.然后,再取6只荷瘤小鼠,分别在75 mg/kg 5-FU治疗前3 d、治疗后第1、4、7、11、15、28天内眦静脉取血,进行血常规检测,分析外周血白细胞、血红蛋白和血小板的变化与荷瘤小鼠肿瘤结节缩小之间的相关性.结果:75、135 mg/kg的5-FU均可使荷瘤小鼠的肿瘤结节在治疗后1周内逐渐缩小、直至消退,因此5-FU治愈荷瘤小鼠的最低有效量为75 mg/kg.75 mg/kg 5-FU治疗后第1天外周血白细胞降为(5.0±1.1)×109/L,并持续到化疗后第4天,与治疗前(9.5±1.58)×109/L比较差异有统计学意义(P<0.01);5-FU治疗后第7 ～15天外周血白细胞的数量升至化疗前水平,随后逐渐下降,在治疗后第28天降至(5.9±1.96)×109/L,低于化疗前水平(P<0.01).Hb含量在5-FU治疗后第1天也出现降低,由化疗前的(133±7) g/L降为(112±9) g/L,差异有统计学意义(P<0.01),随后Hb含量持续在低水平,治疗后15 d 逐渐恢复至化疗前水平.75 mg/kg的5-FU对荷瘤小鼠血小板的抑制作用不明显,反而在治疗后第1、11天出现2次血小板一过性增高(P<0.01).结论:75 mg/kg 5-FU可引起外周血白细胞数和血红蛋白浓度的降低,但对血小板的抑制作用不明显.5-FU发挥抗肿瘤作用使荷瘤小鼠的肿瘤结节缩小与化疗后外周血白细胞和Hb的降低无关,而与化疗后第1天血小板计数的增加有关.     

化疗治愈荷瘤小鼠模型的建立及氟尿嘧啶抑瘤作用的免疫机制

目的:建立荷瘤野生型C57BL/6小鼠及C57BL/6裸鼠模型,探讨5-氟尿嘧啶(5-FU)抑瘤作用的免疫机制。方法:给正常野生型C57BL/6小鼠皮下接种小鼠淋巴瘤EL4细胞,建立荷EL4肿瘤的小鼠模型。接种瘤细胞后12d,荷瘤小鼠腹腔单次注射不同剂量的5-FU,找出5-FU可发挥最大的抑瘤作用、并能致使荷瘤小鼠肿瘤消退不再复发的最小使用剂量。遗传背景相同的野生型C57BL/6小鼠及C57BL/6裸鼠同时皮下接种小鼠淋巴瘤EL4细胞,建立两种荷瘤小鼠模型。接种瘤细胞后12d,两种荷瘤小鼠腹腔内同时注射可使野生型C57BL/6荷瘤小鼠肿瘤消退不再复发5-FU的最低剂量,以正常野生型C57BL/6小鼠为对照,观察5-FU对T淋巴细胞缺陷裸鼠的抑瘤作用。结果:以75mg/kg5-FU治疗1周后,两种荷瘤小鼠的肿瘤以相同的速率缩小直至消失。但在5-FU治疗2周后,T淋巴细胞缺陷的C57BL/6裸鼠肿瘤复发,而免疫功能正常的野生型C57BL/6小鼠肿瘤治愈。结论:单一剂量的5-FU对荷淋巴瘤EL4小鼠具有明显的近期治疗效果,5-FU抑瘤作用的发挥不需要T细胞参与;但5-FU抗肿瘤作用的远期疗效与机体T淋巴细胞功能密切相关。     

Immunohistochemical expression of thymidylate synthase as predictor of response to capecitabine in patients with advanced colorectal adenocarcinoma

Capecitabine is an oral prodrug to 5-fluorouracil (5-FU). The primary target of 5-FU is thymidylate synthase (TS). A mainstay of colorectal adenocarcinoma chemotherapy is inhibition of TS, which may be one of many determinant factors when predicting the outcome of chemotherapies based on fluoropyrimidine treatment. This retrospective study included 39 patients with advanced colorectal adenocarcinoma treated with capecitabine. Response was assessed by measuring the amount of tumour in the course of treatment. TS expression was evaluated by scoring the immunohistochemical (IHC) reaction and assessing the predominant IHC reaction pattern. This study showed significant correlation between the predominant IHC reaction pattern and response, but no correlation between IHC score and response. The predominant IHC reaction pattern may be a useful parameter in prediction of clinical outcome in patients treated with capecitabine.     

Synthesis and preliminary biological assessments of a new class of amphiphilic telomers bearing 5-fluorouracil moieties

The synthesis and biological studies of cotelomers derived from tris(hydroxymethyl)acrylamidomethane (THAM) and bearing 5-FU moieties are reported. These macromolecular carriers were obtained by radical cotelomerization of THAM and an N-1-acyloxymethyl derivative of 5-FU. Different telomers were prepared in order to specify the influence of the prodrug on the efficiency of the therapeutic agent. An evaluation of their cytotoxic activity was performed in vitro on a melanoma cell line B16 using the colony-forming method. It appears from these biological assays that, while the monomeric substrates are less active than free 5-FU, the multiplication of active ligands obtained by telomerization involves a sharp enhancement of the antitumoral activity.     

Biochemical modulation of 5-fluorouracil with a streptococcal preparation, OK-432, against murine colon-26 carcinoma

Conventional therapy for colorectal carcinoma using 5-fluorouracil (5-FU) has shown limited antitumor action. The purpose of our study was to investigate synergistic antitumor effects of the streptococcal preparation of OK-432 and 5-FU, and to elucidate the mechanisms of interaction between the 2 agents in mice. Biochemical modulation of OK-432 and 5-FU were determined in vivo against colon-26 carcinoma. The concentration of 5-FU and its metabolites, and the activity of thymidylate synthase and thymidine kinase, respectively, were measured using cytosolic extracts of the tumors. Combination treatment with OK-432 produced a significant increase in intratumor 5-FU and 5-FU in RNA (F-RNA) concentrations, increased the thymidylate synthetase inhibition rate, and decreased thymidine kinase activity, as compared with the results observed in the control mice. These additive antitumor effects are obtained by use of the 2 agents; the mechanism of action is considered to be the suppression of both the de novo and the salvage pathway for DNA synthesis, along with the suppression of RNA synthesis.     

Preparation of anti-orotate phosphoribosyltransferase antibody and its application to immunochemical detection in human tumor cells

Orotate phosphoribosyltransferase (OPRT) is a key enzyme in the anabolism of 5-fluorouracil (5-FU), and its expression in tumors is thought to increase the efficacy of 5-FU against the tumor. To detect the OPRT protein by immunoblot and/or immunohistochemical methods, we prepared highly specific antibody to the peptides contained in the human OPRT amino acid sequence. The anti-OPRT polyclonal antibodies, obtained by immunizing rabbits with the OPRT peptides, had a high specificity for the OPRT protein in human tumor xenografts when it was analyzed by immunoblotting, and furthermore, there was a positive correlation between OPRT activity and protein content in 12 human tumors (R2 = 0.632). These results suggest that immunohistochemical detection of tumoral OPRT protein expression with our anti-OPRT antibodies may provide a useful method for predicting the clinical response to 5-FU-based chemotherapy.     

Suicide gene therapy mediated by the Herpes Simplex virus thymidine kinase gene/Ganciclovir system: fifteen years of application

Gene-directed enzyme prodrug therapy (GDEPT) is a two step therapeutic approach for cancer gene therapy. In the first step, the transgene is delivered into the tumor and expressed. In the second step a prodrug is administered and is selectively activated by the expressed enzyme. The first GDEPT system described was the thymidine kinase gene of the Herpes Simplex virus (HSVtk) in combination with the prodrug Ganciclovir (GCV). A large number of experiments have been performed with this system, in different types of tumors and initial studies in animal models were very promising. This encouraged investigators to move into clinical trials although poor results have been obtained so far. A large effort has been made with numerous different strategies to enhance HSVtk/GCV efficacy in cellular and in vivo models and very strong cytotoxic effects have been obtained. The present review describes the current state of preclinical research and summarizes the results of the clinical trials undertaken.     

A novel antimetabolite, TAS-102 retains its effect on FU-related resistant cancer cells

TAS-102 is a new oral anti-tumor drug preparation, composed of a 1:0.5 mixture (on a molar basis) of alpha,alpha,alpha-tri-fluorothymidine (FTD) and thymidine phosphorylase inhibitor (TPI). TAS-102 is currently undergoing clinical trials, and has been demonstrated to have at least 2 mechanisms; inhibition of thymidylate synthase (TS) and incorporation into DNA. 5-FU is widely used in the treatment of solid tumor, but the inherent or acquired resistance of certain tumors to 5-FU therapy is a major clinical problem. In the present study, we investigated FTD in vitro and in vivo comparing with 5-FU and using FU-resistant cells. There was no relationship between FTD and 5-FU growth inhibition effect in vitro. A different sensitivity pattern was observed by the log-mean graph. We next investigated the anti-tumor activity of TAS-102 in a FU-resistant xenograft model. Comparative efficacy was observed between FU-resistant cell and its parent cell. We also studied the influence of TAS-102 on liver metastasis in a mouse model of human colorectal cancer, because liver metastasis of colorectal cancer is associated with patient survival. Human cancer DNA was detected by PCR, and TAS-102 markedly inhibited the number of liver metastasis. A novel angiogenic factor, platelet-derived endothelial cell growth factor (PD-ECGF), was shown to be identical to a previously characterized intracellular enzyme, thymidine phosphorylase, TAS-102 can be expected to have not only anti-tumor cytocidal effects but also antiangiogenesis activity and may inhibit liver metastasis. Our findings suggested that TAS-102 is a promising candidate for clinical use and can be expected to decrease minimal residual disease.     

Diamine oxidase as a marker of intestinal mucosal injury and the effect of soluble dietary fiber on gastrointestinal tract toxicity after intravenous 5-fluorouracil treatment in rats

The level of plasma diamine oxidase (DAO) activity is associated with the maturation and integrity of small intestinal mucosa. This study in rats investigated whether a decreased level of plasma DAO could reflect the severity of mucosal injury due to intravenous 5-fluorouracil (5-FU) treatment. The beneficial effect of soluble dietary fiber (SDF) on preventing diarrhea after 5-FU treatment was also examined. To induce diarrhea, 5-FU (50 mg/kg/day for four days) was administered via the tail vein with or without SDF supplementation. After 5-FU treatment, the majority of rats developed moderate to severe diarrhea, and levels of plasma DAO activity significantly decreased compared to those of control group (P < 0.05). Scanning electron microscopy revealed disarrangement of the small intestinal villi. Contrarily, the rats supplemented with SDF had diarrhea less frequently (50.0 vs. 91.7 %, P = 0.025) on day five, and DAO activity levels were significantly higher than in those rats administered 5-FU alone (8.25 ± 5.34 vs. 5.50 ± 4.32, P = 0.023). In conclusion, plasma DAO activity decreases in response to severe intestinal mucosal injury after 5-FU treatment, and SDF supplementation might be a practical and useful treatment for reducing the intestinal toxicity of 5-FU.     

Sequential treatment with betulinic acid followed by 5-fluorouracil shows synergistic cytotoxic activity in ovarian cancer cells

Betulinic acid selectively inhibits the growth of ovarian carcinoma cell lines without affecting the normal cells. In the present study, the effect of 5-fluorouracil (5-FU) and betulinic acid (BA) combination on ovarian carcinoma cells was studied. The results demonstrated that ovarian carcinoma cells on concurrent or 5-FU followed by BA treatment show increased Sub-G1 cell population, increased rate of cell apoptosis and morphological changes in mitochondrial membrane. In OVCAR 432 cells treatment with sequential combination of 5-FU and BA increased the Sub-G1 cell population to 51.3% and growth inhibition rate of > 72%. However, exposure to BA before 5-FU treatment caused a decrease in rate of inhibition to < 35%. Treatment with combination of 5 μM of 5-FU and 1 μM of BA for 48 h, led to an induction of apoptosis in 79.7% and induced morphological changes in OVCAR 432 cells. The Western blot results showed high concentration of cytochrome c in the cell cytosol after 24 h of 5-FU and BA combination treatment. Treatment of BA-responsive RMS-13 cells with 5-FU and BA combination resulted in inhibition of GLI1, GLI2, PTCH1, and IGF2 genes. In addition, we found a significant reduction in hedgehog activity of RMS-13 cells after 5-FU and BA combination treatment by means of a hedgehog-responsive reporter assay. Therefore, 5-FU and BA combination can be a promising regimen for the treatment of ovarian carcinoma.     

Effects of bolus injection of 5-fluorouracil on steady-state plasma concentrations of 5-fluorouracil in Japanese patients with advanced colorectal cancer

Objectives: The irinotecan (CPT-11) + 5-fluorouracil (5-FU)/leucovorin (LV) + UFT/LV chemotherapy, in which repetitive oral administration of UFT/LV replaces the infusion of 5-FU/LV in the FOLFIRI regimen, has been proposed previously. In this study, five of 10 patients were injected with a bolus of 5-FU and the other were not injected with it in order to examine the effect of omitting it in terms of pharmacokinetics of 5-FU.Methods: The treatment consisted of the intravenous infusions of CPT-11 at 100 mg/m² and l-LV at 15 mg/m², and the injection of a bolus of 5-FU at 500 mg/m² on day 1, and the repetitive oral administration of UFT/LV (300 mg/m²/day as tegafur + 75 mg/day of LV) on days 1-5. A total of 13 measurements of the plasma concentrations of uracil, 5-FU and tegafur were made per patient within 48 hr after the start of chemotherapy and the value of area under the concentration-time curve (AUC_0-48) was evaluated. The plasma concentration was also determined at 2 weeks to assess long-term exposure to 5-FU.Results: The plasma concentrations of 5-FU at 24 hr after the start of treatment were 27.4 ng/mL and 9.4 ng/mL in the patients with and without the bolus injection, respectively. At 48 hr, they were 31.3 ng/mL and 10.4 ng/mL with the AUC_0-48 values of 22.16 mg*h/L and 0.65 mg*h/L, respectively. The 5-FU was detected in the plasma at 226 hr after the last administration of UFT/LV for the patients with the bolus injection, but not for those without.Conclusion: A bolus of 5-FU on day 1 provided long-term exposure to 5-FU.     

Prevention of oral mucositis due to 5-fluorouracil treatment with oral cryotherapy

INTRODUCTION: One of the most common and important side effects of 5-fluorouracil (5-FU) is mucositis with ulcerations in the oral cavity. We investigated the effects of local cryotherapy on mucositis incidence administrated durng 5-FU treatment. METHODS: In a total of 99 courses, 5-FU and folinic acid combination chemotherapy was given to 40 patients. In our study, we considered every course as a single case, and cryotherapy was given to the same patient in one course but not given in the next. RESULTS: While mucositis developed in 6.7% of the courses given with cryotherapy, this ratio was 38.9% in courses given without cryotherapy. In the logistic regression analysis, development of mucositis had been found to correlate only with cryotherapy. Odds ratio (OR) = 11.5; in the 95% confidence interval (CI) = 3.2 - 41.9; (p = 0.001). DISCUSSION: Results of initial studies evaluating the effects of cryotherapy in preventing mucositis due to 5-FU based chemotherapy regimens were promising. We concluded that oral cooling prevents 5-FU induced mucositis. This effective prophylactic treatment should be used in patients who are at increased risk for developing 5-FU induced mucositis.