The TYMS-TSER polymorphism is associated with toxicity of low-dose capecitabine in patients with advanced gastrointestinal cancer

Concomitant Administration of Capecitabine and Folate Supplements: Need to Encourage Medication Reconciliation

Hand-Foot syndrome (HFS) and diarrhoea are dose-limiting Adverse Drug Reactions (ADRs) of capecitabine-based chemotherapy. Four polymorphisms in the dihydropyrimidine dehydrogenase (DPYD) gene, encoding the DPD enzyme responsible for the metabolism of fluoropyrimidines, such as capecitabine, are strongly associated with severe ADRs, and their screening should be performed before starting treatment. Moreover, capecitabine-related toxicity may worsen due to drug-drug and drug-supplement interactions. Here we investigated factors responsible for severe HFS and diarrhoea presented by two patients, non-carriers of the recommended DPYD single nucleotide polymorphisms (SNPs) but carriers of other genetic variants suggested to increase the risk of capecitabine-related ADRs. Through careful therapy recognition, we demonstrated that, unbeknownst to the oncologists, the patients were taking folic acid during the treatment with capecitabine at a dosage higher than 2000 mg/m2, which is the maximum tolerated dose when folate is administered. To resolve the ADRs, the therapy had to be drastically changed. In one case, dose reduction of capecitabine and discontinuation of lipid-lowering agents were carried out. In the other case, discontinuation of capecitabine and folic acid and capecitabine re-administration were performed after a month. Genetic and environmental factors should be considered good predictors of severe capecitabine-related toxicity. Medication reconciliation should be encouraged to avoid the harmful consequences of inappropriate treatments.

Gender-dependent association of TYMS-TSER polymorphism with 5-fluorouracil or capecitabine-based chemotherapy toxicity

Aim: TYMS gene encodes for TS enzyme involved in 5-fluorouracil (5-FU) and capecitabine (CAP) metabolism. This study assessed the association of TYMS-TSER and 3RG>C polymorphisms with 5-FU/CAP adverse event (AE) incidence. Materials & methods: TYMS-TSER and 3RG>C polymorphisms were analyzed by use of PCR/PCR-RFLP in 313 5-FU/CAP-treated cancer patients. Results: Female TYMS-TSER 2R carriers were at increased risk for 5-FU/CAP AEs (odds ratio: 2.195; p = 0.032). 2R/2R genotype was the only factor that increased risk for delayed drug administration or therapy discontinuation (odds ratio: 5.049; p = 0.016). No other associations were found. Conclusion: TYMS-TSER 3R/2R polymorphism was associated with incidence of AEs in female cancer patients. This gender-driven association potentially implicates the ER that, in female patients, potentially regulates TS expression.

5-Fluorouracil degradation rate as a predictive biomarker of toxicity in breast cancer patients treated with capecitabine

Capecitabine is an oral prodrug of 5-fluorouracil with a relevant role in the treatment of breast cancer. Severe and unexpected toxicities related to capecitabine are not rare, and the identification of biomarkers is challenging. We evaluate the relationship between dihydropyrimidine dehydrogenase, thymidylate synthase enhancer region and methylenetetrahydrofolate reductase polymorphisms, 5-fluorouracil degradation rate and the onset of G3–4 toxicities in breast cancer patients. Genetic polymorphisms and the 5-fluorouracil degradation rate of breast cancer patients treated with capecitabine were retrospectively studied. Genetic markers and the 5-fluorouracil degradation rate were correlated with the reported toxicities. Thirty-seven patients with a median age of 58 years old treated with capecitabine for stages II–IV breast cancer were included in this study. Overall, 34 (91.9%) patients suffered from at least an episode of any grade toxicity while nine patients had G3–4 toxicity. Homozygous methylenetetrahydrofolate reductase 677TT was found to be significantly related to haematological toxicity (OR = 6.5 [95% IC 1.1–37.5], P = 0.04). Three patients had a degradation rate less than 0.86 ng/mL/106 cells/min and three patients greater than 2.1 ng/mL/106 cells/min. At a univariate logistic regression analysis, an altered value of 5-fluorouracil degradation rate (values < 0.86 or >2.10 ng/mL/106 cells/min) increased the risk of G3–4 adverse events (OR = 10.40 [95% IC: 1.48–7.99], P = 0.02). A multivariate logistic regression analysis, adjusted for age, comorbidity and CAPE-regimen, confirmed the role of 5-fluorouracil degradation rate as a predictor of G3–4 toxicity occurrence (OR = 10.9 [95% IC 1.2–96.2], P = 0.03). The pre-treatment evaluation of 5-fluorouracil degradation rate allows to identify breast cancer patients at high risk for severe 5-FU toxicity.

Thymidylate synthase gene variants as predictors of clinical response and toxicity to fluoropyrimidine-based chemotherapy for colorectal cancer

BACKGROUND

Fluoropyrimidines form the chemotherapy backbone of advanced and metastatic colorectal cancer (CRC). These drugs are frequently associated with toxicity events that result in dose adjustments and even suspension of the treatment. The thymidylate synthase (TYMS) gene is a potential marker of response and toxicity to fluoropyirimidines as this enzyme is the molecular target of these drugs. Our aim was to assess the association between variants of TYMS with response and toxicity to fluoropyrimidines in patients with CRC in independent retrospective and prospective studies.

METHODS

Variants namely rs45445694, rs183205964, rs2853542 and rs151264360 of TYMS were genotyped in 105 CRC patients and were evaluated to define their association with clinical response and toxicity to fluoropyrimidines. Additionally, the relationship between genotypes and tumor gene expression was analyzed by quantitative polymerase chain reaction.

RESULTS

The 2R/2R (rs45445694) was associated with clinical response (p=0.05, odds ratio (OR)=3.45) and severe toxicity (p=0.0014, OR=5.21, from pooled data). Expression analysis in tumor tissues suggested a correlation between the 2R/2R genotype and low TYMS expression.

CONCLUSIONS

The allele 2R (rs45445694) predicts severe toxicity and objective response in advanced CRC patients. In addition, the alleles G(rs2853542) and 6bp-(rs151264360) are independent predictors of response failure to chemotherapy. This is the first study made on a Latin American population that points out TYMS gene variants have predictive values for response and toxicity in patients with CRC treated with fluoropyrimidine-based chemotherapy.

Potential role of metronomic chemotherapy in the treatment of esophageal and gastroesophageal cancer

Patients with esophagogastric cancer have poor prognoses in spite of the best available therapies. Patients are debilitated and may not tolerate, or may progress, on standard cytotoxic chemotherapy regimens. Metronomic chemotherapy is an attractive treatment option due to its very low reported toxicity, modest efficacy, low cost and ease of administration. Capecitabine is the most common drug used in metronomic scheduling; other drugs include cyclophosphamide and paclitaxel. Dosing of capecitabine can range from 1000 mg orally daily for 4 weeks on and 1 week off to a continuous dosing schedule of 1500 mg orally daily. Reported toxicities, including neutropenia, mucositis and hand-foot syndrome, occur in <10% of patients. As there is a lack of well-conducted, randomized clinical trials evaluating the role of metronomic chemotherapy in esophagogastric cancer, it cannot be recommended as the standard of care; however, it can be considered to be a therapeutic option, especially in elderly patients with relapsed disease for whom other therapeutic options are limited.

Tackling pancreatic cancer with metronomic chemotherapy

Pancreatic tumours, the majority of which arise from the exocrine pancreas, have recently shown an increasing incidence in western countries. Over the past few years more and more new selective molecules directed against specific cellular targets have become available for cancer therapy, leading to significant improvements. However, despite such advances in therapy, prognosis of pancreatic cancer remains disappointing. Metronomic chemotherapy (MCT), which consists in the administration of continuous, low-dose anticancer drugs, has demonstrated the ability to suppress tumour growth. Thus, it may provide an additional therapeutic opportunity for counteracting the progression of the tumour. Here we discuss evidence arising from preclinical and clinical studies regarding the use of MCT in pancreatic cancer. Good results have generally been achieved in preclinical studies, particularly when MCT was combined with standard dose chemotherapy or antinflammatory, antiangiogenic and immunostimolatory agents. The few available clinical experiences, which mainly refer to retrospective data, have reported good tolerability though mild activity of metronomic schedules. Further studies are therefore awaited to confirm both preclinical findings and the preliminary clinical data.