Drug interactions with the taxanes: clinical implications.

BACKGROUND: The taxanes paclitaxel and docetaxel are among the most active antitumor agents. Clinically important pharmacodynamic interactions have been reported to occur with these agents that are sequence or schedule dependent. Because the taxanes undergo hepatic oxidation via the cytochrome P450 system, pharmacokinetic interactions due to enzyme induction or inhibition can also occur. METHODS: A comprehensive literature search was conducted using Medline to identify clinically important drug-interactions with the taxanes. RESULTS: Clinically significant taxane interactions were identified for carboplatin, cisplatin, doxorubicin, docetaxel, epirubicin and anticonvulsants. Doxorubicin and epirubicin should be administered 24 h before paclitaxel, and the cumulative anthracycline dose limited to 360 mg/m(2). This will prevent the enhanced toxicities due to sequence and schedule dependent interactions between anthracyclines and paclitaxel. Conversely, paclitaxel should be administered at least 24 h before cisplatin to avoid a decrease in clearance and increase in myelosuppression. With concurrent anticonvulsant therapy, cytochrome p450 enzyme induction results in decreased paclitaxel plasma steady state concentrations, possibly requiring an increased dose of paclitaxel. A number of other drug interactions have been reported in preliminary studies for which clinical significance has yet to be established. CONCLUSION: Clinically significant drug interactions have been reported to occur when paclitaxel is administered with doxorubicin, cisplatin, or anticonvulsants (phenytoin, carbamazepine, and phenobarbital).     

The choice of adjuvant combination therapies with taxanes: rationale and issues addressed in ongoing studies

The taxanes are emerging as the most powerful compounds in breast cancer. Both compounds, paclitaxel and docetaxel, have been evaluated in the metastatic setting before proceeding with adjuvant trials. Docetaxel was shown in phase III trials to be superior, in particular, in terms of time to progression and survival, to salvage polychemotherapies after failure of prior chemotherapy including anthracyclines. Also, after failure of alkylating agents, a benefit in favor of docetaxel was reported when compared to doxorubicin, whereas paclitaxel was reported to be either as efficacious or inferior to doxorubicin, while being comparable to cyclophosphamide/methotrexate/5-fluorouracil. The role of taxanes in combination with anthracyclines in first-line therapy of advanced breast cancer is still unclear although emerging. One phase III trial showed the significant superiority of doxorubicin/docetaxel (AT) versus doxorubicin/cyclophosphamide (AC) in terms of response and time to progression. Several phase II studies with paclitaxel (over 3 hours) and anthracyclines in the metastatic setting showed high efficacy, but they also showed cardiac toxicity related to a pharmacokinetic interaction between the 2 agents. This fact led to the implementation of metastatic strategies (several phase III trials) aimed at avoiding the pharmacokinetic interaction or specifically limiting the cardiac toxicity that resulted in contradictory results. Consequently, adjuvant strategies with paclitaxel focused mostly on the sequential approach (AC followed by paclitaxel). In contrast, adjuvant strategies with docetaxel/anthracycline-based programs were implemented following both sequential and combination approaches. Results of all of these trials in the adjuvant setting are eagerly awaited in order to establish the role of taxanes in adjuvant breast cancer.     

Taxane/anthracycline combinations: setting a new standard in breast cancer?

Among the novel chemotherapeutic drugs introduced in the 1990s, the taxanes have emerged as the most powerful compounds in breast cancer. Both compounds, paclitaxel and docetaxel, have been evaluated in metastatic settings before adjuvant trials proceeded. Docetaxel was shown in several phase III trials to be superior, particularly in terms of survival, for salvaging polychemotherapies after failure of prior chemotherapy, including that with anthracyclines. A benefit of docetaxel was also reported when compared with doxorubicin after failure of alkylating agents. In phase III trials paclitaxel was reported to be as efficacious over 24 hours as doxorubicin 60 mg/m(2), while paclitaxel was significantly inferior to doxorubicin 75 mg/m(2) over 3 hours and was close to CMF in another trial. The role of taxanes in combination with anthracyclines in first-line therapy of advanced breast cancer is emerging. Following several phase II studies, a phase III trial showed the significant superiority of docetaxel/doxorubicin (AT) versus doxorubicin/cyclophosphamide (AC) in terms of response and time to progression. In several phase II studies with paclitaxel (3 hours), anthracyclines in the metastatic setting showed high efficacy but produced cardiac toxicity related to a pharmacokinetic interaction between the two agents. This finding led to the implementation of metastatic strategies (phase III trials) aimed at avoiding the pharmacokinetic interaction, while the adjuvant strategies with paclitaxel focused primarily on the sequential approach (AC followed by paclitaxel). In contrast, adjuvant strategies with docetaxel/anthracycline-based programs were implemented following both sequential and combination approaches.     

Advances in the use of taxanes in the adjuvant therapy of breast cancer

Among the novel chemotherapeutic drugs introduced in the 1990s, the taxanes have emerged as the most powerful compounds in breast cancer. Paclitaxel and docetaxel have been evaluated in the metastatic setting before proceeding with adjuvant trials. The adjuvant strategies of development of both taxanes have been different, mostly as a result of pharmacokinetic differences and dose-schedule issues. As a consequence, paclitaxel was studied nearly exclusively in sequential programs such as AC (doxorubicin/cyclophosphamide) followed by paclitaxel or doxorubicin, followed by paclitaxel, followed by cyclophosphamide. In contrast, docetaxel has been investigated in sequence (AC followed by docetaxel) and in combination chemotherapy (doxorubicin/docetaxel and docetaxel/doxorubicin/cyclophosphamide). Available results of large-scale phase III trials confirm that the taxanes have the potential to change the natural history of early-stage breast cancer. It is becoming clear that sequential chemotherapy and polychemotherapy approaches with taxanes are to be considered in the treatment of patients with node-positive breast cancer. Further results are eagerly awaited to fully understand the role of taxanes and to optimize their impact on early-stage breast cancer. It is our opinion that the real pending issue is no longer whether taxanes will make a difference in the adjuvant setting (the answer is most likely yes), but the definition of their optimal strategic use for maximum patient benefit.     

Pharmacokinetic interactions of paclitaxel, docetaxel and their vehicles with doxorubicin

Background: The combination of doxorubicin (Dx) with paclitaxel or docetaxel is clinically effective but there are concerns regarding the higher incidence of cardiotoxicity of the combination compared with Dx alone. The mechanism of the increased toxicity is still unclear.Purpose: To assess whether there is a pharmacokinetic interaction between paclitaxel, docetaxel or their vehicles and Dx in mice.Materials and methods: CDF1 male mice were treated with Dx either alone (10 mg/kg i.v.) or in combination with paclitaxel (25 mg/kg) or docetaxel (25 mg/kg) or their vehicles, i.e., cremophor-ethanol-glucose (cremophor) or polysorbate80-ethanol-glucose (polysorbate). Four mice were killed 4, 8 or 24 hours after Dx in each experimental group and Dx was assayed in serum and in heart, liver, kidney and spleen by HPLC.Results: Four hours after treatment the concentrations of Dx in heart, liver and kidney were much higher in mice concomitantly treated with paclitaxel, docetaxel (dissolved in either cremophor or polysorbate) and cremophor. At subsequent times the differences were modest and only reached statistical significance in a few cases.Dx metabolites were modified by concomitant treatment with taxanes or their vehicles. In particular, the levels of Dx aglycone in liver and kidney were significantly lower in mice treated with the combination than in mice given Dx alone.Conclusions: paclitaxel, docetaxel and cremophor when given together with Dx modify its distribution and metabolism, increasing Dx levels in many tissues including the heart. This might have some bearing on the toxicity of regimens in which Dx is combined with taxanes.     

Non-haematopoietic toxicity of anthracylines is more favourable than that of taxanes: experience from Nairobi

The isolation and clinical use of anthracyclines and taxanes were major breakthroughs in cancer chemotherapy. Their use has lead to cures and palliation of patients with diverse cancer types, notably breast cancer, malignant lymphomas, ovarian cancer and acute leukaemia. More recently there have been efforts to exclude anthracyclines from early breast cancer protocols because of toxicity and also hypothesized lack of efficacy in non-Her2/Neu amplified, and by the extrapolation of non-topoisomerase II-?? co-amplified tumours. We studied the records of 212 patients treated in three private oncology facilities in Nairobi with anthracycline-or taxane-containing protocols. In total, 225 treatment protocols were analysed since some patients were treated with more than one protocol. Breast carcinoma accounted for 61.8% of the cases, followed by non-Hodgkin??s lymphomas, which accounted for 16.5%. Doxorubicin was used in 58.2% of the protocols, paclitaxel in 7.6% and docetaxel in 11.1%. Clinical cardiac toxicity was recorded in 4.6% of the protocols containing doxorubicin, none with paclitaxel and 12% with docetaxel. Neurotoxicity was recorded in 2 (1.5%) of the protocols with doxorubicin, 5 (29.4%) with paclitaxel and 4 (16%) with docetaxel. Fluid retention was not experienced with doxorubicin, but in 1 (5.9%) with paclitaxel and in 5 (20%) with docetaxel. Toxicity was not recorded in 93.9% of protocols with doxorubicin, 64.7% with paclitaxel and 52% with docetaxel. These differences were highly significant (P < 0.001). We conclude that non-haematopoietic toxicity of anthracyclines is more favourable than that of taxanes.     

Oral co-administration of elacridar and ritonavir enhances plasma levels of oral paclitaxel and docetaxel without affecting relative brain accumulation

Background:

The intestinal uptake of the taxanes paclitaxel and docetaxel is seriously hampered by drug efflux through P-glycoprotein (P-gp) and drug metabolism via cytochrome P450 (CYP) 3A. The resulting low oral bioavailability can be boosted by co-administration of P-gp or CYP3A4 inhibitors.

Methods:

Paclitaxel or docetaxel (10 mg/kg) was administered to CYP3A4-humanised mice after administration of the P-gp inhibitor elacridar (25 mg kg⁻¹) and the CYP3A inhibitor ritonavir (12.5 mg kg⁻¹). Plasma and brain concentrations of the taxanes were measured.

Results:

Oral co-administration of the taxanes with elacridar increased plasma concentrations of paclitaxel (10.7-fold, P<0.001) and docetaxel (four-fold, P<0.001). Co-administration with ritonavir resulted in 2.5-fold (paclitaxel, P<0.001) and 7.3-fold (docetaxel, P<0.001) increases in plasma concentrations. Co-administration with both inhibitors simultaneously resulted in further increased plasma concentrations of paclitaxel (31.9-fold, P<0.001) and docetaxel (37.4-fold, P<0.001). Although boosting of orally applied taxanes with elacridar and ritonavir potentially increases brain accumulation of taxanes, we found that only brain concentrations, but not brain-to-plasma ratios, were increased after co-administration with both inhibitors.

Conclusions:

The oral availability of taxanes can be enhanced by co-administration with oral elacridar and ritonavir, without increasing the brain penetration of the taxanes.     

Preclinical pharmacology of the taxanes: implications of the differences

Taxanes are one of the most powerful classes of compounds among all chemotherapeutic drugs. Only 30 years separate the isolation of the first taxane from the results of direct clinical comparisons in metastatic breast, ovarian, and lung cancer between the two taxanes available in routine clinical practice. These results suggest a more favorable benefit-to-risk ratio for docetaxel compared to paclitaxel when these drugs are used as single agents or in combination with other chemotherapeutic agents in an every-3-week dosing regimen. Pharmacological data support the difference between the taxanes, likely explaining the clinical results. Considering the molecular pharmacology of the two drugs, docetaxel appears to bind to beta-tubulin with greater affinity and has a wider cell cycle activity than paclitaxel. Docetaxel also appears to have direct antitumoral activity via an apoptotic effect mediated by bcl-2 phosphorylation. In addition, docetaxel has a longer retention time in tumor cells than paclitaxel because of greater uptake and slower efflux. Pharmacokinetics and pharmacodynamics of the taxanes show both agents to be extensively metabolized in the liver, and paclitaxel has a nonlinear pharmacokinetic behavior while docetaxel has linear pharmacokinetics. These differences explain the more simple treatment schedule and favorable results for docetaxel as a single agent and in combination therapy. Last, but not least, there is a pharmacokinetic interaction between paclitaxel and the anthracyclines, an active class of compounds commonly used in the treatment of breast cancer. This pharmacokinetic interaction is associated with greater cardio- and myelotoxicities, which are sequence dependent. These pharmacological data likely explain the different clinical development strategies for the two molecules as well as the different clinical results from individual trials and direct comparisons.     

Additive and supra-additive cytotoxicity of cisplatin-taxane combinations in ovarian carcinoma cell lines

The purpose of this study was to compare the growth-inhibitory effect of cisplatin–paclitaxel with that obtained with a cisplatin–docetaxel combination and to assess the type of interaction. Concomitant use of taxanes and cisplatin was studied in seven human ovarian carcinoma cell lines, using the 96-well plate clonogenic assay. Chemosensitivity was expressed in terms of IC₅₀ values, the drug concentration causing 50% inhibition of clonogenic survival. The type of interaction was studied using the area under the survival curve ratios (AUC ratios) obtained by numerical integration. Comparison of the AUC ratio and the surviving fraction (SF) value after taxane alone was made using Student''s t-test. The influence of the drug concentration was tested by one-way analysis of variance (Anova). A supra-additive or additive effect was seen when seven ovarian carcinoma cell lines were exposed to paclitaxel or docetaxel concomitantly with cisplatin. A supra-additive effect was found in four cell lines (UT-OC-3, UT-OC-4, UT-OC-5 and SK-OV-3) after simultaneous use of cisplatin with all docetaxel concentrations tested, and in two cell lines (UT-OC-4 and SK-OV-3) when cisplatin was used concomitantly with paclitaxel. A more pronounced supra-additive effect was seen with the combination of cisplatin and docetaxel. The degree of supra-additivity was dose dependent, with increasing synergy after a higher taxane dose. The data obtained in this study suggest that a supra-additive or additive effect can be achieved in ovarian carcinoma with the concomitant use of cisplatin and a taxane. © 1999 Cancer Research Campaign     

Ongoing US cooperative group trials using taxanes in the adjuvant setting

The use of systemic adjuvant therapy in women with early-stage breast cancer has been demonstrated to have a profound impact on survival. The role of paclitaxel and docetaxel in the adjuvant setting has attracted a great deal of attention. Both of these agents are highly active in patients with advanced breast cancer. In addition, they can be utilized in combination with anthracyclines, which have been shown to provide a slightly better outcome in patients with early-stage breast cancer compared to non-anthracycline-containing regimens. Randomized trials have demonstrated a potential role for paclitaxel in adjuvant chemotherapy. In the Cancer and Leukemia Group B 9344 trial, which explored the use of doxorubicin and cyclophosphamide with or without paclitaxel, the initial analysis demonstrated a 22% reduction in the relative risk of relapse and a 26% reduction in the relative risk of death in the paclitaxel group. However, a clear role for the use of paclitaxel in adjuvant therapy remains to be defined. The Breast Cancer International Research Group trial 001 compared the combination of docetaxel/doxorubicin/cyclophosphamide to 5-fluorouracil/doxorubicin/cyclophosphamide. This trial demonstrated a promising reduction in the relative risk of recurrence of 32% for the docetaxel/doxorubicin/cyclophosphamide group. Ongoing trials will help to further define the role of taxanes in the adjuvant setting for patients with operable breast cancer.     

Weekly paclitaxel combined with pegylated liposomal doxorubicin (CaelyxTM) given every 4 weeks: dose-finding and pharmacokinetic study in patients with advanced solid tumors.

BACKGROUND: We aimed to define the maximum tolerated dose (MTD) and characterize the toxicity of the combination of pegylated liposomal doxorubicin (PLD; Caelyx trade mark ) and weekly paclitaxel (wPTX), and to investigate pharmacokinetics of PLD in this combination. METHODS: A phase I study was performed with an initial dose of 50 mg/m(2) wPTX and 30 mg/m(2) PLD. The paclitaxel dose was escalated in increments of 10 mg/m(2) and PLD in increments of 5 mg/m(2) until the MTD was reached. The pharmacokinetics of PLD were studied at the highest achieved dose levels. RESULTS: Forty-four cancer patients were enrolled. The MTD was 30/90 and 35/80 mg/m(2) for PLD/wPTX. Dose-limiting toxicities included treatment delay for neutropenia grade 3, febrile neutropenia, palmar-plantar erythrodysesthesia and deep venous thrombosis. Toxicity below the MTD was mild: skin toxicity grade 1-2 developed at high cumulative doses and vascular thrombotic events occurred in two patients with predisposing factors. No cardiotoxicity or clinically relevant peripheral neuropathy was seen. Nausea/vomiting and alopecia were negligible. Three complete responses and nine partial responses were documented among 34 evaluable cases. PLD plasma concentrations were evaluated in seven patients treated at subMTD. Paclitaxel produced a median 53.5% increase of PLD area under the concentration curve (range 4.4%-219%). CONCLUSIONS: The combination of PLD/wPTX constitutes an active chemotherapy regimen with mild toxicity that merits investigation in phase II at 30/80 or 35/70 mg/m(2). Patients should be monitored for a potentially increased risk of thromboembolic events.     

Combination of taxanes and anthracyclines in first-line chemotherapy of metastatic breast cancer: an interim report

Anthracyclines and taxanes are among the most effective agents in the treatment of advanced breast cancer, refractory or non-responsive to endocrine manipulation. Several recently published phase III studies have addressed the role of these compounds in combination compared with established chemotherapy regimens. This report considering a total of 4244 patients evaluates the data of those trials with respect to the efficacy and toxicity of the treatment regimens. Currently, evidence is growing that especially patients with symptomatic visceral tumour spread may benefit from the combined application of anthracyclines and taxanes. Adequately dosed polychemotherapy appears to be more successful than monotherapy, and, at present, the combination of anthracyclines (doxorubicin, epirubicin) and taxanes (docetaxel (Doc), paclitaxel (Pac)) might lead to a promising approach to improve the course of the metastatic disease.     

Taxanes Synergize with the Bispecific Antibody MDXH447 to Enhance Antibody-Dependent Cell-Mediated Cytotoxicity

Abstract

The interaction between antibody based therapy and cytotoxic chemotherapy is complex. To explore these interactions we investigated, in vitro, the effects of IC₂₀ growth inhibitory concentrations of taxanes on bispecific antibody-mediated tumor cell cytotoxicity. MDXH447 is a bispecific antibody with specificity for the high affinity IgG receptor (CD64) and the type I epidermal growth factor receptor type (EGF-R). A431 cells, an epidermoid carcinoma cell line that over expresses EGF-R, were exposed to a range of IC20 growth inhibitory concentrations of paclitaxel or docetaxel. Interferon gamma activated monocytes were armed with MDXH447 and a standard chromium release antibody-dependent cell-mediated cytotoxicity (ADCC) assay was performed. Using the Chou and Talalay median effect analysis, we found that MDXH447-mediated ADCC was enhanced when A431 target cells were pretreated with paclitaxel or docetaxel. Median effect analysis of these interactions supported a synergistic interaction (CI < 1). Pretreatment of A431 cells with taxanes did not increase EGF-R expression compared to untreated controls. A431 epidermoid carcinoma cells pretreated with IC20 growth inhibitory concentrations of taxanes enhanced interferon gamma activated monocyte mediated ADCC killing through MDXH447.     

Weekly administration of docetaxel and paclitaxel in metastatic or advanced breast cancer

The taxanes docetaxel (Taxotere; Aventis Pharmaceuticals Inc., Bridgewater, NJ, http://www.aventispharma-us.com) and paclitaxel (Taxol; Bristol-Myers Squibb, Princeton, NJ, http://www.bms.com) have significant clinical activity in metastatic breast cancer. A number of clinical trials have evaluated the tolerability and efficacy of weekly taxane administration to optimize the benefit-to-risk ratio in metastatic breast cancer. Single-agent studies with docetaxel and paclitaxel in metastatic breast cancer show clinically significant antitumor activity even in advanced, heavily pretreated, resistant, and/or refractory disease. This activity is also evident with taxane-based combination regimens. Severe hematologic and nonhematologic toxicities are infrequent, with other toxicities noted based on the dose and weekly regimen selected. Weekly docetaxel and paclitaxel regimens represent valuable therapeutic options for women with metastatic breast cancer and have entered evaluation as part of adjuvant therapy for this disease.     

Taxanes in elderly breast cancer patients

Breast cancer in elderly patients (70+) is a major health problem that will only increase in the future. Besides adequate local treatment and hormone therapy, there can be an indication for chemotherapy in this patient group. Due to concerns of excessive toxicity, there is often a defeatist attitude towards chemotherapy in elderly patients. As taxanes are considered to be the most effective drugs in breast cancer, and as the weekly regimens seem at least as effective as the 3-weekly regimens but with less toxicity, these weekly regimens are very attractive for elderly breast cancer patients. Many different doses have been used for the weekly taxane regimens in phase II trials. Although large comparative studies are lacking, pharmacological studies are suggestive for a decreased clearance of both paclitaxel and docetaxel in elderly patients compared to non-elderly patients. It seems therefore safe to use the lower range of proposed doses of the weekly regimens until further data provide stronger evidence for optimal dosing in elderly patients. A dose of paclitaxel 80 mg/m(2)/week and docetaxel 36 mg/m(2)/week seems tolerable for elderly patients without excessive toxicity and with impressive response rates. The dose limiting toxicity for 3-weekly taxanes, severe neutropaenia, is generally very limited in weekly regimens, also in the elderly or frail patients. However, neuropathy (paclitaxel) or fatigue and fluid retention (docetaxel) can be troublesome, and eventually require dose modifications. In general however, weekly taxanes are a reasonable option for older patients with metastatic breast cancer.     

The farnesyl protein transferase inhibitor SCH66336 synergizes with taxanes in vitro and enhances their antitumor activity in vivo

Purpose: SCH66336 is an orally active, farnesyl protein transferase inhibitor. SCH66336 inhibits ras farnesylation in tumor cells and suppresses tumor growth in human xenograft and transgenic mouse cancer models in vivo. The taxanes, paclitaxel (Taxol) and docetaxel (Taxotere) block cell mitosis by enhancing polymerization of tubulin monomers into stabilized microtubule bundles, resulting in apoptosis. We hypothesized that anticancer combination therapy with SCH66336 and taxanes would be more efficacious than single drug therapy. Methods: We tested the efficacy of SCH66336 and taxanes when used in combination against tumor cell proliferation in vitro, against NCI-H460 human lung tumor xenografts in nude mice, and against mammary tumors in wap-ras transgenic mice. Results: SCH66336 synergized with paclitaxel in 10 out of 11 tumor cells lines originating from breast, colon, lung, ovary, prostate, and pancreas. SCH66336 also synergized with docetaxel in four out of five cell lines tested. In the NCI-H460 lung cancer xenograft model, oral SCH66336 (20 mg/kg twice daily for 14 days) and intraperitoneal paclitaxel (5 mg/kg once daily for 4 days) caused a tumor growth inhibition of 56% by day 7 and 65% by day 14 compared to paclitaxel alone. Male transgenic mice of the wap-ras/F substrain [FVB/N-TgN(WapHRAS)69LlnYSJL] spontaneously develop mammary tumors at 6–9 weeks of age which have been previously shown to be resistant to paclitaxel. Paclitaxel resistance was confirmed in the present study, while SCH66336 inhibited growth of these tumors. Most importantly, SCH66336 was able to sensitize wap-ras/F mammary tumors to paclitaxel chemotherapy. Conclusion: Clinical investigation of combination therapy using SCH66336 and taxanes in cancer patients is warranted. Further, SCH66336 may be useful for sensitizing paclitaxel-resistant tumors to taxane treatment. Received: 30 November 1999 / Accepted: 10 May 2000     

Safety and Activity of the Combination of Pegylated Liposomal Doxorubicin and Weekly Docetaxel in Advanced Breast Cancer

BACKGROUND: The present study was designed with the aim of evaluating the tolerability and activity of pegylated liposomial doxorubicin (PLD) in combination with weekly docetaxel as first line treatment of advanced breast cancer. PATIENTS AND METHODS: Fifty-seven patients entered the study. PLD was administered at escalating doses starting from 30 mg/m2, on day 1; docetaxel was administered at the fixed dose of 35 mg/m2 on days 2 and 9. A cycle of therapy consisted of 21 days. RESULTS: The MTD was achieved at the dose of 40 mg/m2 of PLD, being febrile neutropenia and palmar-plantar-erythrodisesthesia (PPE) the dose-limiting toxicities (DLTs), so that the fixed dose of PLD for the Phase II study was 35 mg/m2. Forty-two consecutive patients received treatment at the established dose for a total of 194 cycles: among these, three patients were withdrawn for severe allergic reaction at the first administration of PLD. Hematological toxicity was moderate, the most common grade 1-3 non-hematological toxicities were stomatitis and PPE, occurring in 20 (47.5%) and 16 (38%) patients, respectively. No cardiac toxicity was recorded. According to the intent to treat analysis a major objective response was observed in 59.5% of patients (95% CI, 43.3-74.4%), with a median time to progression of 9 months and an estimated overall survival at 18 months of 62%. CONCLUSION: The combination of PLD and weekly docetaxel is an effective first-line therapy for patients with advanced breast cancer. PPE and mucositis are the most relevant side effects of such a combination.     

Paclitaxel and docetaxel enhance the metabolism of doxorubicin to toxic species in human myocardium.

Doxorubicin cardiotoxicity is a multifactorial process in which the alcohol metabolite doxorubicinol mediates the transition from reversible to irreversible damage. We investigated whether the tubulin-active taxane paclitaxel increases conversion of doxorubicin to doxorubicinol, thus explaining the high incidence of congestive heart failure when doxorubicin is used with paclitaxel. Specimens of human myocardium from patients undergoing bypass surgery were processed to obtain cytosolic fractions in which doxorubicin was converted to doxorubicinol by NADPH-dependent aldo/keto or carbonyl reductases. In this model, clinically relevant concentrations of paclitaxel (1-2.5 microM) increased doxorubicinol formation by mechanisms consistent with allosteric modulation of the reductases. Stimulation was observed over a broad range of basal enzymatic activity, and was accompanied by a similar pattern of enhanced formation of doxorubicinol aglycone, a metabolite potentially involved in the reversible phase of cardiotoxicity. The closely related analogue docetaxel had effects similar to paclitaxel, but increased doxorubicinol formation over a narrower range of enzymatic activity. The unrelated tubulin-active alkaloid vinorelbine had no effect. These results demonstrate that taxanes have a unique potential for enhancing doxorubicin metabolism to toxic species in human myocardium. The effects on doxorubicinol formation provide clues to explain the clinical pattern of doxorubicin-paclitaxel cardiotoxicity and also caution against the potential toxicity of combining docetaxel with high cumulative doses of doxorubicin.     

Taxanes for breast cancer: an evidence-based review of randomized phase II and phase III trials

The taxanes paclitaxel and docetaxel have an important role in the treatment of breast cancer, and numerous randomized trials have evaluated their efficacy for this indication. A systematic, evidence-based review was performed, which included all randomized, controlled trials evaluating taxanes for the treatment of early-or advanced-stage breast cancer that were identified in CANCERLIT and MEDLINE searches. The primary objectives of this review were to determine the dose and schedule for each taxane that was associated with the most favorable therapeutic index, and to determine whether (and under what circumstances) the taxanes improved survival. The search revealed 18 randomized phase II (n = 1) or phase III (n = 17) trials. For metastatic breast cancer, the dose and schedule associated with the most favorable therapeutic index for paclitaxel was 175 mg/m2 given as a 3-hour infusion every 3 weeks, and docetaxel was 60-100 mg/m2 given as a 1-hour infusion every 3 weeks. Survival was improved under the following circumstances: (1) when 4 cycles of paclitaxel (175 mg/m2 every 3 weeks) was given following 4 cycles of conventional doxorubicin-cyclophosphamide for axillary node-positive operable breast cancer, (2) when trastuzumab was added to paclitaxel as first-line therapy for metastatic breast cancer that overexpressed HER2/neu, and (3) when docetaxel was given as second-line therapy for anthracycline-resistant disease. Although a survival benefit was found for taxanes as a component of first-line therapy in two of six trials, the interpretation of both positive trials was confounded by a lack of crossover to taxane therapy in those who were initially randomized to receive standard therapy. The taxanes improve survival in patients with early-stage breast cancer and selected patients with metastatic breast cancer. Further research is necessary in order to identify the efficacy of docetaxel relative to paclitaxel, the optimal dose of docetaxel, the role of weekly taxane therapy, the role of trastuzumab plus taxanes in early-stage disease, and whether taxanes are more effective when given concomitantly or sequentially in patients with early-stage disease.