Capecitabine: a review of its use in the treatment of advanced or metastatic colorectal cancer

Interactions between cardiology and oncology drugs in precision cardio-oncology

Recent advances in treatment have transformed the management of cancer. Despite these advances, cardiovascular disease remains a leading cause of death in cancer survivors. Cardio-oncology has recently evolved as a subspecialty to prevent, diagnose, and manage cardiovascular side effects of antineoplastic therapy. An emphasis on optimal management of comorbidities and close attention to drug interactions are important in cardio-oncologic care. With interdisciplinary collaboration among oncologists, cardiologists, and pharmacists, there is potential to prevent and reduce drug-related toxicities of treatments. The cytochrome P450 (CYP450) family of enzymes and the P-glycoprotein (P-g) transporter play a crucial role in drug metabolism and drug resistance. Here we discuss the role of CYP450 and P-g in drug interactions in the field of cardio-oncology, provide an overview of the cardiotoxicity of a spectrum of cancer agents, highlight the role of precision medicine, and encourage a multidisciplinary treatment approach for patients with cancer.

Glycosyl ortho-(1-phenylvinyl)benzoates versatile glycosyl donors for highly efficient synthesis of both O-glycosides and nucleosides

Both of O-glycosides and nucleosides are important biomolecules with crucial rules in numerous biological processes. Chemical synthesis is an efficient and scalable method to produce well-defined and pure carbohydrate-containing molecules for deciphering their functions and developing therapeutic agents. However, the development of glycosylation methods for efficient synthesis of both O-glycosides and nucleosides is one of the long-standing challenges in chemistry. Here, we report a highly efficient and versatile glycosylation method for efficient synthesis of both O-glycosides and nucleosides, which uses glycosyl ortho-(1-phenylvinyl)benzoates as donors. This glycosylation protocol enjoys the various features, including readily prepared and stable donors, cheap and readily available promoters, mild reaction conditions, good to excellent yields, and broad substrate scopes. In particular, the applications of the current glycosylation protocol are demonstrated by one-pot synthesis of several bioactive oligosaccharides and highly efficient synthesis of nucleosides drugs capecitabine, galocitabine and doxifluridine.

Concise total synthesis of two marine natural nucleosides: trachycladines A and B

We report the first total synthesis of trachycladines A (10 steps, 34.2% overall yield) and B (11 steps, 35.0% overall yield) by using 5-deoxy-1,2,3-tri-O-acetyl-β-D-ribofuranose as the starting material. The critical step was the SnCl₄ assisted regio- and steroselective deprotection of perbenzylated 1-O-methyl-5-deoxyribofuranose. The enzyme adenylate deaminase (EC 3.5.4.6) was successfully applied to the chemoenzymatic synthesis of trachycladines B.

A retrospective observational study on the use of capecitabine in patients with severe renal impairment (GFR <30 mL/min) and end stage renal disease on hemodialysis

Capecitabine (Xeloda) is an orally administered precursor of 5'deoxy-5-fluorouridine, which is a preferentially activated to 5-fluorouracil in tumors. It is used in the treatment of colorectal, gastric, and breast cancers. Based on a single Phase II trial, which included a total of 4 patients with severe renal impairment (GFR <30 mL/min), the manufacturer issued a 'Dear Doctor' letter contraindicating the use of capecitabine in these patients since a high rate of grade 3 and 4 adverse events were observed and because these patients tolerated shorter treatment durations.(1) We retrospectively studied 12 patients with a GFR <30 mL/min, including 2 patients with end stage renal disease on hemodialysis, who received capecitabine for mean duration of 7.1 months (1-26 months). The mean serum creatinine at the time of initiation of the drug was 2.63 mg/dL (1.8-6.4 mg/dL) and mean GFR was 20.9 mL/min (8-29 mL/min). Two patients remained on capecitabine after they progressed to end stage renal disease (ESRD) requiring hemodialysis (HD) for an additional 17 and 6 months, respectively. Most patients reported grade 1 and 2 adverse effects (AE), 2 patients reported grade 3 diarrhea and one patient died while on treatment with capecitabine. The starting dose ranged from 250 to 1000 mg/m(2), given twice daily at variable intervals. Dose modifications, with reductions of up to 50% of the starting dose, were made following reports of AEs. Serum tumor marker levels and/or follow up imaging studies were available on 9 patients. Response to capecitabine was documented in 4 patients, stable disease in 2, and disease progression in 3. We conclude that, with close monitoring of their clinical and chemical data, and with dose modification based on reported AEs, capecitabine can be safely administered to patients with severe renal impairment, including patients on hemodialysis.

Differential expression of uridine phosphorylase in tumors contributes to an improved fluoropyrimidine therapeutic activity

Abrogation of uridine phosphorylase (UPase) leads to abnormalities in pyrimidine metabolism and host protection against 5-fluorouracil (5-FU) toxicity. We elucidated the effects on the metabolism and antitumor efficacy of 5-FU and capecitabine (N(4)-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) in our UPase knockout (UPase(-/-)) model. Treatment with 5-FU (85 mg/kg) or capecitabine (1,000 mg/kg) five days a week for four weeks caused severe toxicity and structural damage to the intestines of wild-type (WT) mice, but not in UPase(-/-) animals. Capecitabine treatment resulted in a 70% decrease in blood cell counts of WT animals, with only a marginal effect in UPase(-/-) mice. UPase expressing colon 38 tumors implanted in UPase(-/-) mice revealed an improved therapeutic efficacy when treated with 5-FU and capecitabine because of the higher maximum tolerated dose for fluoropyrimidines achievable in UPase(-/-) mice. (19)F-MRS evaluation of capecitabine metabolism in tumors revealed similar activation of the prodrug in UPase(-/-) mice compared with WT. In WT mice, approximately 60% of capecitabine was transformed over three hours into its active metabolites, whereas 80% was transformed in tumors implanted in UPase(-/-) mice. In UPase(-/-) mice, prolonged retention of 5'dFUR allowed a proportional increase in tumor tissue. The similar presence of fluorinated catabolic species confirms that dihydropyrimidine dehydrogenase activity was not altered in UPase(-/-) mice. Overall, these results indicate the importance of UPase in the activation of fluoropyrimidines, the effect of uridine in protecting normal tissues, and the role for tumor-specific modulation of the phosphorolytic activity in 5-FU or capecitabine-based chemotherapy.

Retinal vein thrombosis in a patient with metastatic colon cancer receiving XELOX chemotherapy combined with bevacizumab pre-hepatic resection

Retinal vein thrombosis is a common vascular occlusive disorder of the retina responsible for varying degrees of vision impairment. It is an adverse effect rarely associated with cancer and its treatment. We report the case of a patient with metastatic colon cancer who developed central retinal vein thrombosis (CRVT) in the right eye following two cycles of chemotherapy with capecitabine and oxaliplatin (XELOX) plus bevacizumab given prior to hepatic resection. Despite cessation of chemotherapy, vision has not improved. The etiology of the CRVT in this case is not clear due to risk factors for venous thrombotic events including colonic malignancy and previous major surgery. However, the proximity of chemotherapy administration to the initial development of symptoms suggests the possibility of a medication-related cause, with bevacizumab and capecitabine the most likely suspects.

Advances in the pharmacological treatment of gastro-oesophageal cancer

Despite a sharp decline in the incidence of gastric cancer during the second half of the 20th century, this malignancy remains the second leading cause of cancer mortality in the world. The incidence and mortality rate of gastric cancer increase with age; at present, the median ages at diagnosis are 67 years for men and 72 years for women in the US. This article reviews and discusses current medical treatment options for both the general population and elderly gastric cancer patients. Management of localized gastric cancer has changed significantly over recent years. Adjuvant chemoradiation is not generally recommended outside the US. After decades of trials of adjuvant chemotherapy with inconclusive results, a significant survival benefit for perioperative combination chemotherapy - as compared with surgery alone - in patients with resectable or locally advanced gastro-oesophageal cancer was recently demonstrated in the UK MAGIC trial. A further large, randomized trial from Japan demonstrated a significant survival benefit for adjuvant chemotherapy with S-1 after D2 resection for gastric cancer. However, both trials are applicable only to the population in which the trials were conducted. Specific data on elderly patients are missing. For patients with metastatic disease, oral fluoropyrimidines, such as capecitabine, have been developed. In Asian patients, treatment with the oral fluoropyrimidine S-1 is safe and effective. Docetaxel, oxaliplatin and irinotecan have demonstrated activity against gastric cancer in appropriately designed, randomized, phase III trials and have increased the available treatment options significantly. In addition, according to preliminary data, trastuzumab in combination with chemotherapy has significantly improved activity when compared to chemotherapy alone in patients with human epidermal receptor (HER)-2-positive gastric and gastro-oesophageal cancers. Thus, therapeutic decisions in patients with advanced gastric cancer may be adapted to the molecular subtype and co-morbidities of the individual patient. Data from retrospective analyses suggest that oxaliplatin seems to be better tolerated than cisplatin in elderly patients.

Pharmacology and therapeutic efficacy of capecitabine: focus on breast and colorectal cancer

Capecitabine (N -pentyloxycarbonyl-5-deoxy-5-fluorocytidine), an oral prodrug of 5-fluorouracil, has provided compelling efficacy data for the treatment of metastatic breast cancer and stage III or IV colorectal cancer, both as monotherapy and in combination regimens. The preferential conversion of capecitabine to 5-fluorouracil in neoplastic tissues renders this fluoropyrimidine particularly appealing for clinical use. The enzyme thymidine phosphorylase, which mediates the final step of the capecitabine activation pathway, is expressed in higher concentration in neoplastic than in healthy tissues. This makes capecitabine more tumor specific than other chemotherapeutic agents. Accordingly, capecitabine is generally well tolerated. In particular, the incidence of myelosuppression and alopecia is low, and the most common side effects, hand-foot syndrome and diarrhea, are usually manageable. Given its good toxicity profile, capecitabine was assessed in combination with several chemotherapeutic or biologic agents. In addition, the observation that thymidine phosphorylase is upregulated after treatment with other anticancer drugs, namely taxanes, provided a rationale for the prominent antitumor activity recently observed for the combination of capecitabine with these agents. This review provides an evidence-based update of clinical trials investigating the role of capecitabine in the treatment of breast and colorectal cancer, with special emphasis on pharmacological and safety issues that form the basis of currently used schedules.

A phase II study of capecitabine and cisplatin (XP) as first-line chemotherapy in patients with advanced esophageal squamous cell carcinoma

PURPOSE

The combination of 5-fluorouracil (5-FU) and cisplatin (FP) remains the mostly used regimen for metastatic esophageal squamous carcinoma. This phase II study assessed the efficacy and safety of capecitabine/cisplatin (XP) as a first-line chemotherapy in a homogenous cohort of patients with metastatic or recurrent esophageal squamous cell carcinoma.

MATERIALS AND METHODS

Patients received 60 mg/m(2) of cisplatin intravenously (IV) on day 1 and capecitabine 1,250 mg/m(2)/dose orally twice a day on days 1-14. Treatment cycles were repeated every 3 weeks until the documented disease progression, unacceptable toxicity, or patient's refusal. Immunohistochemical studies against thymidylate synthase (TS) and thymidine phosphorylase (TP) were performed to seek predictive markers for treatment response.

RESULTS

Between December 2003 and March 2006, 45 patients entered the study. All patients had histologically proven squamous cell carcinoma of the esophagus. The overall response rate (ORR) was 57.8% (95% CI, 43.3-72.2) with 0 CR and 26 PRs. The median duration of response in responders was 4.6 months (1.0-15.6 months). With a median follow-up duration of 25.7 months (10.8-42.6 months), the median time to progression was 4.7 months (95% CI, 2.5-7.0) and the median survival time was 11.2 months (95% CI, 8.5-13.9). Common grade 3 or 4 non-hematological adverse events were anorexia (18/191, 9.4%), fatigue (9/191, 4.7%), constipation (6/191, 3.1%), hand-foot syndrome (6/191, 3.1%) and diarrhea (4/191, 2.1%). The most common grade 3 or 4 hematological adverse events were neutropenia (33/191, 17.3%), followed by leucopenia (11/191, 5.8%), anemia (2/191, 1.0%) and thrombocytopenia (1/191, 0.5%). There was no treatment-related death. Neither TS nor TP showed predictive value for treatment response.

CONCLUSION

The XP regimen demonstrated a promising antitumor activity in metastatic esophageal squamous cell carcinoma, which may potentially replace the FP regimen.

Capecitabine: in advanced gastric or oesophagogastric cancer

The oral fluoropyrimidine capecitabine is metabolised preferentially in tumour tissue to the cytotoxic moiety fluorouracil. In a well designed phase III trial in patients with advanced gastric cancer, capecitabine plus cisplatin was noninferior to fluorouracil plus cisplatin in terms of progression-free survival (hazard ratio [HR] 0.81 [95% CI 0.63, 1.04]). In another similarly designed phase III trial in patients with oesophagogastric cancer (REAL 2), pooled capecitabine-based regimens were noninferior to pooled fluorouracil-based regimens in terms of overall survival (HR 0.86 [95% CI 0.80, 0.99]). These data are supported by randomised and noncomparative phase II trials in treatment-naive or pretreated patients with advanced gastric cancer or oesophagogastric cancer receiving capecitabine either as monotherapy or in combination with other antitumour agents. Given the nature of chemotherapy, capecitabine-based regimens were generally well tolerated, with the nature of treatment-related adverse events occurring with capecitabine-based regimens being similar to those of fluorouracil-based regimens.

Pharmacogenetics of folate-related drug targets in cancer treatment

Folate metabolism is the target of two major drug groups: folate antagonists (for example, methotrexate) and thymidylate synthase inhibitors (for example, 5-fluorouracil). These agents are used in the treatment of cancer, as well as for other conditions, such as rheumatoid arthritis. High-dose cancer treatment protocols can induce a state of acute folate depletion which may lead to significant treatment-related toxicity. Polymorphisms in folate-metabolizing enzymes may modify the therapeutic effectiveness and toxicity of these drugs. This review briefly summarizes the drugs targeting the folate pathway and describes common polymorphisms in folate-metabolizing enzymes and transport proteins. Pharmacogenetic studies investigating folate-related drug targets in the treatment of colorectal cancers and hematologic malignancies will subsequently be discussed. Findings to date illustrate a potential for targeting therapy based on patients' genotypes, in order to improve outcomes and reduce toxicity. However, larger, well-designed studies are needed to confirm these early findings.

Phase I and Pharmacokinetic Study of Weekly Docetaxel, Cisplatin, and Daily Capecitabine in Patients with Advanced Solid Tumors

Purpose: Docetaxel, cisplatin, and capecitabine are three active chemotherapeutic agents with different mechanisms of action. This phase I study investigated the feasibility and pharmacokinetics of this combination given on a weekly schedule.

Experimental Design: Docetaxel and cisplatin were given i.v. over 30 minutes on days 1 and 8 and capecitabine was given orally bid on days 1 to 14 (every 21 days). Escalation occurred in cohorts of three patients until the maximum tolerated dose was defined. Pharmacokinetics studies of docetaxel and total and ultrafiltrate platinum after cisplatin administration were done on cycle 1 (with capecitabine) and cycle 2 (without capecitabine).

Results: Twenty-five patients were enrolled. Two of six patients at dose level 5 had a dose-limiting infection and diarrhea. One of six evaluable patients at dose level 4 (27 mg/m2 docetaxel, 27 mg/m2 cisplatin, 825 mg/m2 capecitabine) had a dose-limiting hypomagnesemia. Pharmacokinetics of docetaxel were similar on cycles 1 and 2. Area under the plasma concentrations versus time curves of total platinum was significantly greater in cycle 2 compared with cycle 1 (P = 0.001). There was no difference in the disposition of docetaxel on cycles 1 and 2.

Conclusions: The recommended docetaxel, cisplatin, and capecitabine dose for phase II studies is 27/27/825 mg/m2. The alteration in total and ultrafiltrate platinum disposition on cycle 2 compared with cycle 1 may be inherent to sequential cisplatin administration; however, prior treatment with capecitabine cannot be ruled out as a factor.

Hand-foot syndrome in patients treated with capecitabine-containing combination chemotherapy

Clinical characteristics and risk factors of hand-foot syndrome were investigated in patients who received capecitabine-containing chemotherapy. Toxicity data were analyzed from 179 patients in 4 prospective clinical trials testing docetaxel/capecitabine/cisplatin in stomach cancer, capecitabine/cisplatin in biliary or stomach cancer, and vinorelbine/capecitabine in breast cancer. Hand-foot syndrome was reported in 116/179 (64.8%) of patients, with grade 3 hand-foot syndrome in 8/179 (4.5%). Hand-foot syndrome first developed within the first 3 chemotherapy cycles in 100/116 (86.2%) patients, with the median onset for all 3 treatment regimens occurring during cycle 2. Because severe reactions were rare, hand-foot syndrome was not a major factor influencing treatment schedule. Risk factor analyses showed that combined use of docetaxel and preceding chemotherapy-related stomatitis were significant risk factors for the development of hand-foot syndrome. Our results suggest that a combined treatment agent and a patient's susceptibility to chemotherapy-related toxicity may increase the risk of capecitabine-induced hand-foot syndrome.

Oral capecitabine plus subcutaneous interferon alpha in advanced squamous cell carcinoma of the skin

PURPOSE

Squamous cell carcinoma of the skin (SSC) is a UV-damage-related skin tumor. The first-line treatment is surgery, which has a high cure rate. In advanced cases, however, the established treatment is often not curative and shows a high rate of side effects. Improved treatment modalities are necessary.

METHODS

Oral capecitabine plus subcutaneous interferon alpha were used in a prospective case series in advanced SSC of the skin at an academic teaching hospital for dermatology. Four patients with advanced SCC were included. Capecitabine 950 mgm(-2) body surface on days 1 to 14 was combined with interferon alpha 3x3 mioU s.c. three times a week. The chemotherapy was repeated on day 22. Clinical response, histology, monitoring of side effects and health performance status were assessed.

RESULTS

Four patients (two females and two males) with advanced SCC were included (age range: 19 to 75 years). Complete remission (CR) was obtained in two and partial response (PR) in two. The final outcome was CR in two and progressive disease in one. One patient died of an unknown cause. Side effects were mild. Adjuvant treatment was unnecessary. Health performance status was not affected by the treatment.

CONCLUSIONS

The treatment protocol with a combination of capecitabine and interferon alpha seems to be effective and well tolerated in patients with advanced SCC. Controlled trials are necessary to prove the benefit we observed in this case series.

Synthesis of [18F]Xeloda as a novel potential PET radiotracer for imaging enzymes in cancers

Xeloda (Capecitabine), a prodrug of antitumor agent 5-fluorouracil, is the first and only oral fluoropyrimidine to be approved for use as second-line therapy in metastatic breast cancer, colorectal cancer, and other solid malignancies. Fluorine-18 labeled Xeloda may serve as a novel radiotracer for positron emission tomography (PET) to image enzymes such as thymidine phosphorylase and uridine phosphorylase in cancers. The precursor 2',3'-di-O-acetyl-5'-deoxy-5-nitro-N(4)-(pentyloxycarbonyl)cytidine (11) was synthesized from D-ribose and cytosine in 8 steps with approximately 18% overall chemical yield. The reference standard 5'-deoxy-5-fluoro-N(4)-(pentyloxycarbonyl)cytidine (Xeloda; 1) was synthesized from D-ribose and 5-fluorocytosine in eight steps with approximately 28% overall chemical yield. The target radiotracer 5'-deoxy-5-[(18)F]fluoro-N(4)-(pentyloxycarbonyl)cytidine ([(18)F]Xeloda; [(18)F]1) was prepared by nucleophilic substitution of the nitro-precursor with K(18)F/Kryptofix 2.2.2 followed by a quick deprotection reaction and purification with the HPLC method in 20-30% radiochemical yields.

Single-agent capecitabine in patients with metastatic colorectal cancer refractory to 5-fluorouracil/leucovorin chemotherapy

OBJECTIVE

The effectiveness of capecitabine, an oral fluoropyrimidine carbamate, is well documented in previously untreated metastatic colorectal cancer patients (overall response rate: 25%). However, its efficacy in patients with metastatic colorectal cancer refractory to 5-fluorouracil/leucovorin (5-FU/LV) has not been determined. This study was performed to evaluate the efficacy and to identify the side-effects of capecitabine in patients with metastatic colorectal cancer showing progression despite 5-FU/LV-based combination chemotherapy.

METHODS

Fifty-one metastatic colorectal cancer patients who showed progressive disease in 5-FU/LV-containing regimens (median: two regimes) were treated with capecitabine 1,250 mg/m(2) twice daily (days 1-14 repeated every 3 weeks).

RESULTS

Only one partial response was observed (response rate: 2%). Twenty-seven patients (53%) showed stable disease after two cycles. The median time to disease progression of either a partial response or stable disease was 3.4 months. Hand-foot syndrome was the main toxicity of capecitabine and occurred in 35% of cases (grade 3 or 4 in 6%). The median number of cycles administered was two and the relative dose intensity of capecitabine was 80%.

CONCLUSION

The response rate to capecitabine was low in metastatic colorectal cancers that were refractory to 5-FU/LV-containing chemotherapy. However, disease stabilization was seen in a significant number of patients.

The evolving role of oxaliplatin in the management of colorectal cancer

The introduction of oxaliplatin into the chemotherapy of advanced colorectal cancer has substantially increased the frequency and magnitude of clinical response compared with that achieved using 5-FU/leucovorin, and has extended progression-free and overall survival. Research is now in progress on several fronts to determine how oxaliplatin-based therapy can be optimized. A phase III multicentre trial recently compared the efficacy and safety of the FUFOX regimen, based on high dose infusional 5-FU/leucovorin and 50 mg/m2 oxaliplatin given weekly for 4 weeks in a 5-week cycle (n = 123) with the Mayo clinic 5-FU/leucovorin regimen (n = 129) in the first-line therapy of metastatic disease. The response rate with the FUFOX regimen was 48.3%, more than twice that in the Mayo regimen (22.6%; P < 0.0001) and median survival was 20.4 months, despite the fact that the FUFOX regimen had lower toxicity. The value of high dose oxaliplatin and 5-FU/leucovorin has also been demonstrated in the FOLFOX series of studies, where patients who received more than 85 mg/m2 oxaliplatin per 2-week cycle had double the response rate of patients receiving less than 85 mg/m2. In the FOLFOX7 regimen based on a simplified high dose bolus/infusional regimen of 5-FU/leucovorin (sLV5FU2) plus 130 mg/m2 oxaliplatin, a response rate of over 40% has been achieved in second line therapy. Studies have also compared first-line therapy based on oxaliplatin with irinotecan-based first-line therapy. A large trial coordinated by the North Central Cancer Treatment Group (NCCTG) recently compared the IFL regimen, which is currently the standard irinotecan-based first-line treatment for advanced colorectal cancer in the United States, with oxaliplatin-based treatment using the FOLFOX4 regimen. Compared with irinotecan-based chemotherapy, oxaliplatin was associated with a 30% increase in overall survival (19.5 months vs. 15.0 months; P = 0.0001), a higher response rate (45% vs. 31%, P = 0.002) and lower toxicity. Further studies are investigating how therapy can be optimized over multiple lines. In a phase III two-line study comparing first-line therapy with FOLFOX6 and second line therapy with irinotecan-based therapy (FOLFIRI) (n = 109) with the reverse sequence (n = 111), progression-free and overall survival were comparable whichever regimen was used first, although patient numbers were smaller than in the NCCTG study and less able to detect treatment differences. FOLFOX6 was also more effective than FOLFIRI in second-line therapy. Currently, studies based on FOLFOX7, novel FOLFIRI regimens and sLV5FU2 are in progress to determine how disease control can be sustained in the long-term, and the development of drug resistance delayed, in multiline therapeutic management. In parallel with these studies, two large phase III trials are now investigating the role of oxaliplatin in the adjuvant treatment of nonmetastatic colorectal cancer. The first of these studies, MOSAIC, has already shown a very encouraging 23% decrease in the risk of relapse at 3 years (P = 0.002) with FOLFOX4 compared to LV5FU2.

New oxaliplatin-based combinations in the treatment of colorectal cancer

The synergism between oxaliplatin and 5-fluorouracil (5FU)/leucovorin in the treatment of colorectal cancer raises the prospect of further clinically effective combinations. Phase I/II trials of capecitabine, an oral fluoropyrimidine, plus oxaliplatin have established this combination (XELOX) as an effective treatment for advanced disease, with response rates of over 50% in first line therapy. Phase III studies of XELOX are now in progress, while further studies are investigating the combined use of oxaliplatin and a second oral fluoropyrimidine, UFT, after positive phase I/II results. Studies of combined oxaliplatin and irinotecan treatment have reported response rates varying from 25% to 60% in second-line therapy of treatment resistant metastatic disease, and 42% in first line therapy. The optimum dosing combination of these two agents has yet to be determined however, and in many patients it is likely that greater overall survival will be achieved by using them in successive lines rather than in combination. Clinical studies have also demonstrated clinically significant response rates when oxaliplatin is combined with other agents including raltitrexed and mitomycin C. Alongside these novel chemotherapeutic combinations, a range of biological therapies is now being investigated in combination with oxaliplatin in advanced colorectal cancer. Cetuximab (C225) is a monoclonal antibody that inhibits signalling through the epidermal growth factor receptor (EGFR), a pathway that has been associated with a variety of pathological process in cancer including dysregulated growth, differentiation, angiogenesis, cell motility and cell adhesion. Studies of second-line therapy combining oxaliplatin and cetuximab in advanced disease and in patients with unresectable liver-only metastases are in progress in the United States. A phase I/II study is also investigating the combined use of oxaliplatin and ZD1839 ('Iressa'), a small molecule inhibitor of the EGFR specific tyrosine kinase activating the same pathways. Anti-angiogenesis agents are also being studied intensely. A key angiogenic pathway in the stimulation of tumour growth is the vascular endothelial growth factor (VEGF) pathway, inhibited by the monoclonal antibody bevacizumab. Phase II first line and phase III second line studies of oxaliplatin in combination with bevacizumab are now in progress. Oxaliplatin is being investigated in combination with a number of other classes of biological agent, including the proteasome inhibitor PS-341. The sudden appearance of a wide range of chemotherapeutic and biological agents with activity against colorectal cancer presents many challenges to the current system of clinical trials, given the large number of permutations requiring prospective testing. However, by building upon the encouraging results achieved using oxaliplatin plus 5FU/leucovorin, the introduction of new agents will eventually translate into significantly improved clinical outcomes.

Capecitabine: a review of its pharmacology and therapeutic efficacy in the management of advanced breast cancer

Capecitabine is an orally administered prodrug of fluorouracil which is indicated in the US and Europe, in combination with docetaxel, for the treatment of patients with metastatic breast cancer failing anthracycline therapy, and as monotherapy for metastatic breast cancer resistant to paclitaxel and anthracycline therapy (US) or failing intensive chemotherapy (Europe). Capecitabine is also approved for use in metastatic colorectal cancer. Capecitabine is metabolically activated preferentially at the tumour site, and shows antineoplastic activity and synergy with other cytotoxic agents including cyclophosphamide or docetaxel in animal models. Bioavailability after oral administration is close to 100%. In patients with pretreated advanced breast cancer, capecitabine is effective as monotherapy and also in combination with other agents. Combination therapy with capecitabine 1,250 mg/m(2) twice daily for 2 weeks of every 3-week cycle plus intravenous docetaxel 75 mg/m(2) on day one of each cycle was superior to intravenous monotherapy with docetaxel 100 mg/m(2) on day one of each cycle. Capecitabine plus docetaxel significantly reduced the risks of disease progression and death by 35% (p = 0.0001) and 23% (p < 0.05), respectively, and significantly increased median survival (p < 0.05) and objective response rates (p < 0.01). Efficacy has also been demonstrated with capecitabine monotherapy and combination therapy in previously untreated patients in preliminary trials. The most common adverse effects occurring in patients receiving capecitabine monotherapy include lymphopenia, anaemia, diarrhoea, hand-and-foot syndrome, nausea, fatigue, hyperbilirubinaemia, dermatitis and vomiting (all >25% incidence). While gastrointestinal events and hand-and-foot syndrome occurred more often with capecitabine than with paclitaxel or a regimen of cyclophosphamide, methotrexate and fluorouracil (CMF), neutropenic fever, arthralgia, pyrexia and myalgia were more common with paclitaxel, and nausea, stomatitis, alopecia and asthenia were more common with CMF. The incidence of adverse effects and hospitalisation was similar in patients receiving capecitabine plus docetaxel and those receiving docetaxel monotherapy. In conclusion, capecitabine, an oral prodrug of fluorouracil which is activated preferentially at the tumour site, is an effective and convenient addition to the intravenous polychemotherapeutic treatment of advanced breast cancer in pretreated patients, and also has potential as a component of first-line combination regimens. Combined capecitabine plus docetaxel therapy resulted in similar rates of treatment-related adverse effects and hospitalisation to those seen with docetaxel monotherapy. Capecitabine is also effective as monotherapy in pretreated patients and phase II data for capecitabine as first-line monotherapy are also promising. While gastrointestinal effects and hand-and-foot syndrome occur often with capecitabine, the tolerability profile was comparatively favourable for other adverse effects (notably, neutropenia and alopecia).

Fluorouracil for allergic reactions to capecitabine

OBJECTIVE

To report the safe use of fluorouracil in a patient with breast cancer who had allergic reactions to capecitabine.

CASE SUMMARY

A 42-year-old African American woman with metastatic breast cancer developed progressive disease. Capecitabine 1500 mg taken by mouth twice daily was prescribed as the salvage chemotherapy. She developed a generalized rash and itching, sore throat, and dizziness approximately 4 hours after the first dose of capecitabine. These reactions recurred immediately after the second dose. Capecitabine was discontinued and the allergic reactions resolved after the woman took diphenhydramine for 1 week. In view of limited therapeutic options for her progressive disease, a trial of fluorouracil 300 mg/m(2)/d continuous intravenous infusion over 5 days was initiated without any premedications. She did not experience any reactions. The dose of fluorouracil in the second cycle was increased to 400 mg/m(2)/d continuous infusion over 5 days.

DISCUSSION

Capecitabine is not intrinsically cytotoxic, but is converted to fluorouracil in tumor tissues via a 3-step enzymatic pathway. Capecitabine reaches peak blood concentrations in about 1.5 hours, with peak fluorouracil concentrations occurring at 2 hours. The elimination half-life of both drugs is 0.5-0.7 hours. The patient tolerated the rechallenge with fluorouracil without complications. Objective causality assessment revealed that the adverse event was probably drug induced. It was postulated that the allergic reaction was most likely caused by capecitabine or the intermediate metabolites based on the immediate reappearance of symptoms from the rechallenge, pharmacokinetic data, and well-tolerance of fluorouracil.

CONCLUSIONS

The use of fluorouracil treatment with careful monitoring can be considered in a patient with mild allergic reactions to capecitabine.

Pharmacogenetics and folate metabolism -- a promising direction

Folate metabolism is the target of two major drug groups: folate antagonists (e.g., methotrexate) and thymidylate synthase inhibitors (for example, 5-fluorouracil). These agents are widely used in cancer chemotherapy, as treatment for rheumatoid arthritis, and for other conditions. The administration of these drugs in cancer chemotherapy can induce a state of acute folate depletion with sometimes life-threatening toxic sequelae. Recent studies suggest that polymorphisms in folate-metabolizing enzymes may modify the therapeutic effectiveness and toxicity of drugs targeting folate metabolism. This review briefly summarizes major drugs targeting the folate pathway and describes common polymorphisms in folate-metabolizing enzymes and transport proteins. Pharmacogenetic studies investigating the relevance of these polymorphisms with respect to patients' response to antifolate chemotherapeutic agents are discussed. Investigating genetic variability in folate metabolism in the framework of pharmacogenetics is a promising field. Findings to date illustrate the potential for targeting therapy based on patients' genotypes with improved outcomes and reduced toxicity.