The exploding tumour on breast magnetic resonance imaging: an infected skin comedo

A 61-year-old woman with a histologically proven invasive lobular carcinoma entered a clinical trial, which involved repeat magnetic resonance imaging (MRI). The protocol of the repeated MRI described a T4 breast cancer with involvement of the skin (Fig 1). There were only 17 days between the first and second MRI and during this short time it appeared that there had been rapid disease progression. On the initial MRI, a skin comedo could be seen in the left breast close to the tumour. The patient had squeezed the skin comedo, which had become infected. The second MRI captured the infected skin comedo, which had the appearance of an extensive breast cancer with skin involvement. The patient could be mismanaged if the clinician does not correlate the clinical findings with the radiological findings.

Combination of paclitaxel and LAG3-Ig (IMP321), a novel MHC class II agonist, as a first-line chemoimmunotherapy in patients with metastatic breast carcinoma (MBC): Interim results from the run-in phase of a placebo controlled randomized phase II

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Background: IMP321 is a recombinant soluble LAG3-Ig fusion protein that binds to MHC class II molecules and mediates antigen-presenting cell (APC) activation followed by CD8 T-cell activation. The activation of the dendritic cell network with IMP321 the day after a low dose injection of a single agent chemotherapy may lead to stronger anti-tumor CD8 T-cell responses. We report initial results of the safety run-in of a randomized, placebo-controlled phase IIb trial in patients (pts) with hormone receptor positive (HR+) MBC receiving first-line weekly paclitaxel. Methods: In the safety run-in phase 15 pts with MBC received weekly paclitaxel (80 mg/m2; D1, D8, D15) in a four week cycle in conjunction with either 6 mg (n = 6; cohort 1) or 30 mg (n = 9, cohort 2) IMP321 injections s.c. (D2 and D16) for 6 cycles. Patients without progressive disease could continue with a maintenance phase of 12 additional injections of IMP321 every 4 weeks. Blood samples for pharmacokinetics and immuno-monitoring were taken in cycle 1 and 4 just before and after IMP321 injection. Results: In total 15 pts (median age 53 years) were enrolled between Jan 2016 and Oct 2016. No dose limiting toxicities have been reported. Cytokine release syndrome grade 1 was the only serious adverse event (SAE) related to IMP321 and occurred twice in the same patient. Grade 1 and 2 injection site reactions were the most common related AEs and occurred in 14 pts (93 %). A dose-dependent increase in serum IMP321 concentration was observed among the two dose levels with a Cmaxbetween 4 and 24 hours. Increased number of circulating monocytes, dendritic cells and increased activation were observed at both dose levels of IMP321, supporting the working hypothesis. Conclusions: The 30 mg s.c. IMP321 given every two weeks in combination with weekly paclitaxel is the recommended phase 2 dose which is used in the ongoing randomized placebo controlled phase II part of the study. Clinical trial information: NCT02614833.

The smooth and bumpy road of trastuzumab administration: from intravenous (IV) in a hospital to subcutaneous (SC) at home

Trastuzumab has become standard of care in the treatment of early and metastatic HER2-positive breast cancer. Initially trastuzumab could only be administered intravenously (IV), however since a few years there is also a subcutaneous (SC) formulation. The efficacy and the safety profile of both formulations is the comparable. The administration logistics however have an impact on the patients, the health care professionals (HCPs), the hospital and the government. The preference for the patients (89%) and the HCPs (77%) is in favour of the SC formulation. The patient chair time per cycle, as defined by the time between entry and exit of infusion chair, is between 53 and 122 minutes shorter for SC administration. Also, the time actively dedicated by the HCP on preparation and administration SC, is between 17 and 50 minutes shorter per cycle. These time savings may increase the capacity of an oncological day clinic and reduce waiting lists. An additional benefit is that the use of SC formulation reduces the consumables and the waste. When the SC form was given at home instead of in the hospital the safety profile remained the same, but the satisfaction rate improved further for both the patients and the HCPs. The next and final step will be potentially to invest in teaching the patients to self-administer the medication. The home administration and the education of the patients and the HCPs will have a cost price and it will be interesting to see how the hospital financial authorities and the government will deal with this situation in the time of budgetary restrictions.

Abstract P4-22-08: A single-arm phase 2 study to assess clinical activity, efficacy and safety of enzalutamide with trastuzumab in HER2+ AR+ metastatic or locally advanced breast cancer

Background:Androgen receptor (AR) expression has been observed in up to 77% of human epidermal growth factor receptor 2–positive (HER2+) breast cancer (BC).References:1 Enzalutamide (ENZA) is a potent AR inhibitor approved for patients (pts) with metastatic castration-resistant prostate cancer. In vitro, ENZA enhances antitumor activity of trastuzumab in HER2+ AR+ cell lines and inhibits proliferation in trastuzumab-resistant HER2+ cell lines.2

Methods:Pts with metastatic or locally advanced BC that was HER2+ AR+ by local or central laboratory assessment were enrolled in a single-arm, Simon 2-stage phase 2 study (NCT02091960). Key eligibility criteria included availability of a tissue sample, presence of measurable or evaluable disease per RECIST v1.1, progression on prior trastuzumab and ≥1 prior line of anti-HER2 therapy as the most recent regimen. Brain metastases and history of seizure were exclusionary. Evaluable pts were those with centrally confirmed nuclear AR expression≥10% by immunohistochemistry who received ≥1 dose of ENZA and had ≥1 postbaseline tumor assessment. Pts received ENZA 160 mg daily and trastuzumab 6 mg/kg every 21 days until disease progression. The primary objective was clinical benefit rate at 24 weeks (CBR24), defined as complete or partial response (CR or PR) or stable disease (SD) for ≥24 weeks in evaluable pts. Additional endpoints included safety and progression-free survival (PFS). CBR24 in ≥3 of 21 evaluable pts was required to continue to stage 2 and enrollment of up to 66 evaluable pts total. This design yields a 1-sided type 1 error of 5% and 90% power when the true response is 25%.

Results:Here we present results from stage 1 (data cutoff: Mar 23, 2016), with 22 evaluable pts enrolled (pts 21 and 22 enrolled simultaneously); 18 had received ≥4 prior lines of therapy. Median duration of ENZA exposure was 144 days (range, 22-495), mean number of complete trastuzumab infusions was 6.5. CBR24 was 27.3% (95% confidence interval [CI], 10.7-50.2); 2 confirmed PR and 4 SD ≥24 weeks. Median PFS was 108 days (95% CI, 56-144). All pts experienced ≥1 adverse event (AE) any grade; 5 pts experienced AEs grade ≥3. ENZA-related AEs were reported in 16 pts (72.7%), the most common (in ≥10% of pts) were fatigue (22.7%), nausea (18.2%), diarrhea (13.6%) and arthralgia (13.6%). Serious AEs were reported in 6 pts (27.3%; 2 each of infection and back pain, 1 each of abdominal pain, nausea, vomiting, pyrexia, urinary retention and pulmonary edema). Two pts discontinued due to drug-related AEs: 1 related to both drugs, 1 related to trastuzumab. One on-study death from pulmonary edema was reported, which was not considered related to either drug.

Conclusion:Stage 1 met its primary objective. No new safety signals were identified, and the safety profile in this study was similar to that in men with prostate cancer and women with other BC subtypes treated with ENZA. These results are encouraging for a heavily pretreated population with advanced HER2+ AR+ BC. Enrollment in stage 2 continues with the combination of ENZA and trastuzumab.

1. Micello D et al. Virchows Arch. 2010;457:467-476.

2. Richer J. Presented at AACR Advances in Breast Cancer, San Diego, CA, 2013.

Citation Format: Krop I, Cortes J, Miller K, Huizing MT, Provencher L, Gianni L, Chan S, Trudeau M, Steinberg J, Sugg J, Liosatos M, Paton VE, Peterson A, Wardley A. A single-arm phase 2 study to assess clinical activity, efficacy and safety of enzalutamide with trastuzumab in HER2+ AR+ metastatic or locally advanced breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-22-08.

18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) as early imaging biomarker of axillary sentinel lymph node (SLN) status in locally advanced node-positive breast cancer (NPBC) patients (pts) receiving neoadjuvant chemotherapy (NACT)

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Background: Use of FDG-PET in the early evaluation of NACT for NPBC is currently under investigation. The aim of this study is to assess FDG-PET in NPBC pts receiving NACT in order to identify a subset of pts that can be spared axillary lymph node dissection (ALND) in case of response. Methods: All pts (period 2009-2011) had [cT2 (≥3cm)-T4, pN1-3], and no prior BC treatment. All pts received 8 cycles (cy) of NACT +/- trastuzumab. FDG-PET was performed at baseline and after 2 cy. After NACT, mastectomy with SLN and ALND was peformed. As primary endpoint, the change in maximum standardized uptake value (SUVmax) in the primary tumor (PT) and ALNs was compared with pathological response (Jonckheere-Terpstra test). Logistic regression was used to determine the predictive value of a 50% reduction in SUVmax on pathological response and SLN status. Results: Forty-one pts were evaluable for the primary endpoint and 31 pts had successful SN procedures. The median age was 49.8 years (range 27-75). Overall, 9.8% (4/41; 95% CI 2.7 – 23.1) of pts had progressive disease (PD), 7.3% (3/41 ; 95% CI 1.5 – 19.9 ) stable disease (SD), 53.7% (22/41; 95% CI 37.4 – 69.3) partial response (PR), and 21.9% (9/41; 95% CI 10.6 – 37.6) a complete pathological response (pCR). A linear trend existed between pCR and higher decreases in SUVmax of the PT site (p=0.008), but not with lymph node SUVmax (p=0.294). The odds of achieving a pCR, increased significantly when SUVmax of the PT decreased with >50% (OR 10.7; 95% CI 1.2 - 98.0; p=0.03), but not lymph node SUVmax (OR 4.75; 95% CI 0.82 - 27.5; p=0.08). Achieving a true negative SLN status was more likely with >50% reductions in PT SUVmax (OR 41.2; 95% CI 4.0 - 421.9; p= 0.002). A reduction of >50% in nodal SUVmax was not predictive of negative SLN status (OR 3.33; 95% CI 0.66 - 16.8; p=0.1). Conclusions: Early changes in PT metabolism imaged with FDG-PET after only 2 cy of NACT is a promising biomarker in the management of the axilla in NPBC. Molecular imaging of PT biology and to a lesser extent of axillary lymph nodes using FDG-PET warrants further study.

Open label phase I/II study of Wilms' tumor gene 1 (WT1) mRNA-transfected autologous dendritic cell vaccination in patients with solid tumors

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Background: Active specific immunotherapy, aimed at stimulating tumor-specific immunity, is widely under investigation to determine its place in cancer treatment. Methods: We are conducting an open label phase I/II clinical trial to evaluate the feasibility, toxicity and immunogenicity of intradermal vaccination with keyhole limpet hemocyanin (KLH)-exposed WT1 mRNA-transfected autologous monocyte-derived dendritic cells (DC). Recruitment has finished, but vaccination and follow-up continue. Vaccination consists of biweekly intradermal injection of 10 million DC in the medial region of the arm close to the axilla. Clinical evaluation with PET, CAT or MRI is done before start of the vaccination and repeated every 8 weeks. After 4 vaccinations patients undergo a delayed-type hypersensitivity (DTH) skin test to evaluate immunological responses. Results: 18 patients (8 breast cancer and 3 astrocytoma patients, 1 melanoma, 1 mesothelioma, 1 ovarian, 1 colon, 1 esophageal, 1 renal cell and 1 peritoneal cancer patient) were included in this trial from May, 2010 until January, 2012 to whom we administered a total of 175 vaccines. The median number of vaccines produced per patient was 15 (range 5-34). Median follow-up from start of the vaccination is 26 weeks (range 2-83). All evaluable patients exhibited local symptoms such as itching and/or redness at the sites of injection after the second vaccination and onward (n=17) and displayed positive DTH skin reactions (induration ≥2 mm) to the vaccine and its components (n=15). Systemic side effects were limited to 2 patients who each experienced a single episode of flu-like symptoms within 24 hours after vaccination. Thus far, 3 patients died of disease progression, while 7 others had progressive disease and 6 had stable disease at the most recent evaluation compared to before vaccination according to RECIST 1.1. Of the latter group 4 patients received another form of therapy at some point during vaccination. Conclusions: Based on these results our WT1 mRNA-transfected DC vaccination appears to be feasible and safe for patients with solid tumors. Furthermore, our vaccine is capable of inducing immune responses in these patients.

Desmoplastic small round cell tumor (DSRCT) arising in the ovary: report of a case diagnosed at an early stage and review of the literature

BACKGROUND

Desmoplastic small round cell tumor (DSRCT) is a rare sarcoma tumor affecting mainly young adult males. It rarely has an ovarian involvement.

CASE

A 29-year-old woman presented to her gynecologist for amenorrhoea. The laboratory results demonstrated a menopausal status and the ultrasound revealed a large mass of the right ovary. The right ovary was completely removed by laparoscopy. Pathology, cytology and immunochemistry revealed a DSRCT. In January 2009 a left salpingo-oophorectomy and a right salpingectomy were performed via laparoscopy. After 35 months from diagnosis there was no clinical evidence of disease recurrence.

CONCLUSION

DSRCT is a rare ovarian tumor in adolescence with a general poor outcome. Every ovarian mass regardless of age should be approached with caution.

Safety and pharmacology of paclitaxel in patients with impaired liver function: a population pharmacokinetic-pharmacodynamic study

AIMS

To assess quantitatively the safety and pharmacology of paclitaxel in patients with moderate to severe hepatic impairment.

METHODS

Solid tumour patients were enrolled into five liver function cohorts as defined by liver transaminase and total bilirubin concentrations. Paclitaxel was administered as a 3-h intravenous infusion at doses ranging from 110 to 175 mg m(-2), depending on liver impairment. Covariate and semimechanistic pharmacokinetic-pharmacodynamic (PK-PD) population modelling was used to describe the impact of liver impairment on the pharmacology and safety of paclitaxel.

RESULTS

Thirty-five patients were included in the study, and PK data were assessed for 59 treatment courses. Most patients had advanced breast cancer (n = 22). Objective responses to paclitaxel were seen in four patients (11%). Patients in higher categories of liver impairment had a significantly lower paclitaxel elimination capacity (R2 = -0.38, P = 0.05), and total bilirubin was a significant covariate to predict decreased elimination capacity with population modelling (P = 0.002). Total bilirubin was also a significant predictor of increased haematological toxicity within the integrated population PK-PD model (P < 10(-4)). Data simulations were used to calculate safe initial paclitaxel doses, which were lower than the administered doses for liver impairment cohorts III-V.

CONCLUSIONS

Total bilirubin is a good predictor of paclitaxel elimination capacity and of individual susceptibility to paclitaxel-related myelosuppression in cancer patients with moderate to severe liver impairment. The proposed, adapted paclitaxel doses need validation in prospective trials.

Phase II feasibility study of concurrent radiotherapy and gemcitabine in chemonaive patients with squamous cell carcinoma of the head and neck: long-term follow up data

BACKGROUND

Radiotherapy (RT) with concurrent chemotherapy is the current standard of care for patients with unresectable locally advanced squamous cell carcinoma of the head and neck (SCCHN). Gemcitabine (GEM) is a potent radiosensitizer and in addition has activity as an anticancer agent in SCCHN.

PATIENTS AND METHODS

Twenty-six patients with locally far advanced SCCHN were enrolled in a chemoradiation feasibility study between November 1998 and September 2003. Use was made of conventionally fractionated RT and GEM 100 mg/m(2), which was given within 2 h prior to radiotherapy on a weekly basis starting on day 1 of RT. Response was assessed according to WHO criteria, toxicity according to NCI-CTC version 2.

RESULTS

The patients received a median of 7 (2-8) weekly cycles of gemcitabine and a median cumulative RT dose of 70 Gy (66-84.75). Hematologic toxicity was mild, but non-hematologic toxicity was severe: grade 3-4 stomatitis occurred in 85% of patients, dermatitis in 69%, pharyngitis/esophagitis in 81% and 80% of the patients needed a feeding tube during treatment. All 22 evaluable patients responded (50% complete, 50% partial). Median follow up of the surviving patients is 46 months. Median disease-free and overall survival is 13 months and 19 months, respectively; 27% of the patients are alive without evidence of recurrence beyond 3 years.

CONCLUSIONS

Conventionally fractionated RT in combination with GEM 100 mg/m(2) weekly is feasible and highly active in the treatment of locally advanced SCCHN. In particular, long-term local control rate is promising. Acute mucosal toxicities are significant but manageable. Long-term toxicity interferes with normal food intake.

Bisphosphonates and osteonecrosis of the jaw: cause and effect or a post hoc fallacy?

BACKGROUND

An increasing amount of reports are being published suggesting a relationship between the use of bisphosphonates (BPs) and the development of osteonecrosis of the jaw (ONJ). We reviewed the currently available evidence and explore the potential mechanisms of action based on the known effects of the concerned BP.

DESIGN

The MEDLine, Current Contents and Science Citation Index Expanded databases were queried and the results augmented by analyzing cited references and recent congress proceedings.

RESULTS

22 papers were included detailing 225 patients, all based on retrospective chart review without control groups. The prevalence of ONJ was estimated at 1.5%. The involved BPs were pamidronate, zoledronic acid, alendronate and risedronate, all potent nitrogen-containing agents. The most common symptom was pain (81.7%), although 12.2% of cases were asymptomatic. In 69.3% of patients ONJ was preceded by a dental extraction. At the time of diagnosis, 74.5% of patients were receiving chemotherapy and in 38.2% of cases corticosteroids were administered. Although various conservative and surgical treatment modalities were reported, residual sites of ONJ persisted in 72.5% of cases.

CONCLUSION

Although not enough evidence is available to prove a causal link, it seems that under specific circumstances local defenses can become overwhelmed resulting in ONJ.

Cremophor EL pharmacokinetics in a phase I study of paclitaxel (Taxol) and carboplatin in non-small cell lung cancer patients

The purpose of our study was to investigate the pharmacokinetics of Cremophor EL following administration of escalating doses of Taxol (paclitaxel dissolved in Cremophor EL/ethanol) to non-small cell lung cancer (NSCLC) patients. Patients with NSCLC stage IIIb or IV without prior chemotherapy treatment were eligible for treatment with paclitaxel and carboplatin in a dose-finding phase I study. The starting dose of paclitaxel was 100 mg/m2 and doses were escalated with steps of 25 mg/m2, which is equal to a starting dose of Cremophor EL of 8.3 ml/m2 with dose increments of 2.1 ml/m2. Carboplatin dosages were 300, 350 or 400 mg/m2. Pharmacokinetic sampling was performed during the first and the second course, and the samples were analyzed using a validated high-performance liquid chromatographic assay. A total of 39 patients were included in this pharmacokinetic part of the study. The doses of paclitaxel were escalated up to 250 mg/m2 (20.8 ml/m2 Cremophor EL). Pharmacokinetic analyses revealed a low elimination-rate of Cremophor EL (CI=37.8-134 ml/h/m2; t 1/2=34.4-61.5 h) and a volume of distribution similar to the volume of the central blood compartment (Vss=4.96-7.85 l). In addition, a dose-independent clearance of Cremophor EL was found indicating linear kinetics. Dose adjustment using the body surface area, however, resulted in a non-linear increase in systemic exposure. The use of body surface area in calculations of Cremophor EL should therefore be re-evaluated.

Pharmacokinetics and metabolism of docetaxel administered as a 1-h intravenous infusion

Docetaxel, a taxane antitumor agent, was administered to 24 patients by a 1-h intravenous infusion at a dose level of 100 mg/m(2) with pharmacokinetic monitoring. The plasma concentration-versus-time data were fitted with a three-compartment model. The mean area under the curve (AUC) for docetaxel was 3.1 +/- 0.9 h. mg/l and the clearance was 34.8 +/- 9.3 l/h per m(2). There was considerable interpatient pharmacokinetic variability. In 33% of the patient population, metabolites were detected in plasma samples collected 5-30 min after the end of the infusion. The cyclized oxazolidinedione metabolite M4 was most frequently present and was detected in 8 out of 24 patients with maximal concentrations between 0.022 and 0.23 mg/l. Logistic regression analysis was performed to predict M4 docetaxel metabolism. In the final model, alanine aminotransferase and alkaline phosphatase levels were the strongest predictors. No relationship was found between M4 metabolism and percentage decrease in neutrophil count in this study. Three patients with high M4 concentrations in plasma during course 1 suffered from most pronounced fluid retention (grade 2-3) after two to five courses.

A limited-sampling model for the pharmacokinetics of carboplatin administered in combination with paclitaxel

PURPOSE

Carboplatin doses are often determined by using modified Calvert formulas. It has been observed that the area under the concentration versus time curve (AUC) for free carboplatin is lower than expected when modified formulas are used for carboplatin/paclitaxel chemotherapy combination regimens. By using limited-sampling models, the carboplatin AUC actually reached can easily be verified, and the dose adjusted accordingly.

METHODS

In this report, we describe the development and validation of a limited-sampling model for carboplatin from 77 pharmacokinetic curves, when carboplatin is used in combination with paclitaxel.

RESULTS

The following single-point model was selected as optimal: AUC carboplatin (min mg(-1) ml(-1)) = 418. c(2.5 h)(mg/ml) + 0.43 (min mg(-1) ml(-1)), where c(2.5 h) is the concentration (mg/ml) of carboplatin 2.5 h after the start of a 30-min infusion. This model proved to be unbiased (mean prediction error = 3.4 +/- 1.6%) and precise (root mean square error = 10.1 +/- 1.5%).

CONCLUSIONS

The proposed model can be very useful for ongoing and future carboplatin/paclitaxel studies aimed to optimise and individualize treatment.

Cremophor EL causes (pseudo-) non-linear pharmacokinetics of paclitaxel in patients

The non-linear plasma pharmacokinetics of paclitaxel in patients has been well established, however, the exact underlying mechanism remains to be elucidated. We have previously shown that the non-linear plasma pharmacokinetics of paclitaxel in mice results from Cremophor EL. To investigate whether Cremophor EL also plays a role in the non-linear pharmacokinetics of paclitaxel in patients, we have established its pharmacokinetics in patients receiving paclitaxel by 3-, 24- or 96-h intravenous infusion. The pharmacokinetics of Cremophor EL itself was non-linear as the clearance (Cl) in the 3-h schedules was significantly lower than when using the longer 24- or 96-h infusions (Cl175-3 h = 42.8+/-24.9 ml h(-1) m(-2); CI175-24 h = 79.7+/-24.3; P = 0.035 and Cl135-3 h = 44.1+/-21.8 ml h(-1) m(-1); Cl140-96 h = 211.8+/-32.0; P < 0.001). Consequently, the maximum plasma levels were much higher (0.62%) in the 3-h infusions than when using longer infusion durations. By using an in vitro equilibrium assay and determination in plasma ultrafiltrate we have established that the fraction of unbound paclitaxel in plasma is inversely related with the Cremophor EL level. Despite its relatively low molecular weight, no Cremophor EL was found in the ultrafiltrate fraction. Our results strongly suggest that entrapment of paclitaxel in plasma by Cremophor EL, probably by inclusion in micelles, is the cause of the apparent nonlinear plasma pharmacokinetics of paclitaxel. This mechanism of a (pseudo-)non-linearity contrasts previous postulations about saturable distribution and elimination kinetics and means that we must re-evaluate previous assumptions on pharmacokinetics-pharmacodynamics relationships.

A single 24-hour plasma sample does not predict the carboplatin AUC from carboplatin-paclitaxel combinations or from a high-dose carboplatin-thiotepa-cyclophosphamide regimen

PURPOSE

It has been observed that the area under the free carboplatin concentration in plasma ultrafiltrate versus time curve (AUC) is related to toxicity and tumour response. For this reason, it can be important to measure the carboplatin AUC and subsequently adjust the dose to achieve a predefined target AUC. The use of limited sampling strategies enables relatively simple measurement and calculation of actual carboplatin AUCs.

METHODS

We studied the performance of a limited sampling model, based on a single 24-h sample (the Ghazal-Aswad model). in 52 patients who received carboplatin in two different chemotherapy regimens (a carboplatin-paclitaxel combination and a high-dose carboplatin-thiotepa-cyclophosphamide combination).

RESULTS

The measured mean AUC in our population was 4.1 min x mg/ml (median 3.9, range 1.9 6.3, SD 1.0 min x mg/ml). With the limited sampling model, the predicted mean AUC was 4.4 min x mg/ml (median 4.2, range 2.4-8.4, SD 1.2 min x mg/ml). Statistical analysis revealed that the model was slightly biased (MPE%, 6.5%), but imprecise (RMSE%, 20.6%) in our study population.

CONCLUSION

Although easy and attractive to use, the Ghazal-Aswad formula is not precise enough to predict the carboplatin AUC, and needs to be evaluated prospectively in other patient populations.

Pharmacologic study of 3-hour 135 mg M-2 paclitaxel in platinum pretreated patients with advanced ovarian cancer

Paclitaxel (Taxol(R)) is an active agent in platinum-refractory ovarian cancer. Since the available pharmacokinetic data of 135 mg m-2 paclitaxel administered by 3-h infusion are scarce and fragmented, we now describe a comprehensive pharmacologic study in a group of 13 patients who were pretreated with platinum for advanced ovarian cancer. The mean paclitaxel AUC was 10.3+/-2.4 h micromol l-1 (range 6.8-13.9 h micromol l-1). Quantification of the two major paclitaxel metabolites, 6alpha-hydroxypaclitaxel and 3'-p-hydroxypaclitaxel yielded AUCs of 0.44+/-0.30 h micromol l-1 and 0.31+/-0.20 h micromol l-1, respectively. The AUC of 3'-p-hydroxypaclitaxel was significantly different from that of patients with an altered hepatic function. The administration of 135 mg m-2 single-paclitaxel was safe, and the toxicities observed at higher doses in earlier studies were absent in this study. This is important, because the schedule and paclitaxel dose of 135 mg m-2 given by a 3-h infusion is expected to be used more frequently in combination with other cytotoxic agents with the aim of improving efficacy.

Influence of Cremophor EL on the quantification of paclitaxel in plasma using high-performance liquid chromatography with solid-phase extraction as sample pretreatment

For the quantitative determination of paclitaxel in human plasma reversed-phase high-performance liquid chromatographic (HPLC) methods with solid-phase extraction (SPE) as sample pretreatment procedure are frequently used. Recovery problems arose during the quantification of paclitaxel in plasma samples of patients. The major problems were a large batch-to-batch difference in performance of the SPE columns and the effects of the pharmaceutical vehicle Cremophor EL on the performance of the SPE. Cremophor EL concentrations exceeding 1.0% (v/v) had a great impact on the absolute recovery of paclitaxel from human plasma with the SPE procedure. The recoveries decreased approximately 10 to 40% depending on the quality of the batch SPE columns. The problems are avoided by using 2'-methylpaclitaxel as the internal standard. This study points out the importance of including the effects of a pharmaceutical vehicle, like Cremophor EL, in the validation programme of a bioanalytical assay and the use of an internal standard in HPLC paclitaxel assays preceded by SPE as sample pretreatment procedure.

Hepatic metabolism of paclitaxel and its impact in patients with altered hepatic function

Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) has been demonstrated to be an active anticancer agent, including in platinum-refractory ovarian cancer. The pharmacokinetics of paclitaxel have been extensively described. It displays nonlinear pharmacokinetics in humans, especially when administered in shorter infusion times and at higher doses. Several relationships have been established between pharmacokinetics and pharmacodynamics. In both animal and human studies, hepatic metabolism and biliary excretion have been identified as the main elimination pathways of paclitaxel. It thus can be expected that hepatic dysfunction will have a major impact on the pharmacokinetics of paclitaxel and its main metabolite 6alpha-hydroxypaclitaxel and, thus, on pharmacodynamic outcome (toxicities and responses). Because patients with an altered hepatic function were excluded from most phase I and II studies conducted thus far, little is known about the pharmacokinetics and pharmacodynamics in this group of patients. This report summarizes paclitaxel's metabolism and clinical observations concerning its pharmacokinetics and pharmacodynamics in patients with altered hepatic function. It has been shown that hepatic impairment has a great influence on the systemic exposure of paclitaxel and metabolites with pharmacodynamic consequences. A decrease of biliary elimination is probably the major mechanistic effect that influences paclitaxel metabolism and elimination. Specific dosing guidelines in the treatment of patients with altered hepatic function are required.

Phase I and pharmacologic study of the combination paclitaxel and carboplatin as first-line chemotherapy in stage III and IV ovarian cancer

PURPOSE

To determine the maximum-tolerated dose for the combination paclitaxel and carboplatin administered every 4 weeks and to gain more insight into the pharmacokinetics and pharmacodynamics of this combination in previously untreated ovarian cancer patients.

PATIENTS AND METHODS

Thirty-five chemotherapy-naive patients with suboptimally debulked stage III (tumor masses > 3 cm) and stage IV ovarian cancer were entered onto this phase I trial in which paclitaxel was administered as a 3-hour intravenous (IV) infusion at dosages of 125 to 225 mg/m2 immediately followed by carboplatin over 30 minutes at dosages of 300 to 600 mg/m2. A total of six courses was planned, followed by a second-look laparoscopy/laparotomy. Patients with a response and/or minimal residual disease at second-look laparoscopy received three additional courses. Twenty-six patients participated in the pharmacokinetic part of the study.

RESULTS

The most important hematologic toxicity encountered was neutropenia. Neutropenia was more pronounced for the higher dose levels (DLs) and was cumulative. Thrombocytopenia was mild in the first eight DLs, but increased during the treatment courses. Nonhematologic toxicities consisted mainly of vomiting, neuropathy, fatigue, rash, pruritus, myalgia, and arthralgia. Dose-limiting toxicities (DLTs) in this trial were neutropenic fever, thrombocytopenia that required platelet transfusions, and cumulative neuropathy. Of 33 patients assessable for response, 26 major responders (78%, 20 complete response [CR] and six partial response [PR]) were documented. The maximal concentration (Cmax) of paclitaxel and the area under the concentration-time curve (AUC) were not different from the historical data for paclitaxel as a single agent. Retrospective analysis using a modified Calvert formula showed that the measured carboplatin AUCs in plasma ultrafiltrate (pUF) were 30% +/- 3.4% less than the calculated carboplatin AUC. Neutropenia was more pronounced than could be expected on the basis of the historical times above a threshold concentration greater than 0.1 mumol/L (T > or = 0.1 mumol/L) or 0.05 mumol/L (T > or = 0.05 mumol/L), and thrombocytopenia was less than could be expected from historical sigmoidal Emax models.

CONCLUSION

The combination of paclitaxel 200 mg/ m2 and carboplatin 550 mg/m2 every 4 weeks is a well-tolerated treatment modality. The paclitaxel-carboplatin combination is highly active in stage III (bulky) and stage IV ovarian cancer. No indications for a pharmacokinetic drug-drug interaction between carboplatin and paclitaxel were found.

Clinical pharmacology of carboplatin administered in combination with paclitaxel

The clinical pharmacology of carboplatin (C) administered with paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) (P) was investigated in two phase I studies undertaken in 83 previously untreated patients with either non-small cell lung cancer or ovarian cancer. Carboplatin was administered over 30 minutes and paclitaxel over 3 hours. Both agents were given every 4 weeks. Non-small cell lung cancer patients were randomized to two administration sequences, either carboplatin followed by paclitaxel (C-->P) or the reverse (P-->C). Each patient received the alternate sequence during the second and subsequent courses. Ovarian cancer patients uniformly received paclitaxel before carboplatin. Platinum concentrations in plasma ultrafiltrate were measured via flameless atomic absorption spectrometry, and 122 concentration-time curves were obtained. For non-small cell lung cancer patients, the mean area under the concentration-time curve (AUC) per 300 mg/m2 carboplatin was 3.52 mg/mL x min (range, 1.94 to 5.83) for the sequence C-->P and 3.62 mg/mL x min (range, 1.91 to 5.01) for the sequence P-->C. No sequence-dependent effect was observed (P > .5). For ovarian cancer patients, the mean AUC per 300 mg/m2 carboplatin was 3.83 mg/mL x min (range, 2.72 to 6.10), showing no difference when compared with data derived from non-small cell lung cancer patients (P = .13). In addition, the carboplatin AUC was not influenced by increasing paclitaxel doses from 100 to 250 mg/m2. Neutropenia was the principal toxicity, and anemia was frequent. However, there was a striking lack of thrombocytopenia. Modeling of the relationship between the carboplatin AUC and the decrease in platelets revealed a 50% decrease in platelets at a carboplatin AUC (AUC50) of 6.3 mg/mL x min. This contrasts with historical data documenting a carboplatin AUC50 of 4.0 mg/mL x min. Our findings suggest that there is a considerable interaction of both drugs at the cellular level, with at least an additive effect of carboplatin on the main hematologic toxicity of paclitaxel (ie, neutropenia). There is also a protective effect exerted by paclitaxel on carboplatin-related toxicity (ie, thrombocytopenia). The clear protective effect of paclitaxel in this combination suggests that it is possible to reduce the dose interval to 3 weeks. Studies are in progress to test this hypothesis and to investigate the underlying pharmacologic interactions.

Pharmacokinetics of paclitaxel and carboplatin in a dose-escalating and dose-sequencing study in patients with non-small-cell lung cancer. The European Cancer Centre

PURPOSE

To investigate the pharmacokinetics and pharmacodynamics of paclitaxel (P) and carboplatin (C) in a sequence-finding and dose-escalating study in untreated non-small-cell lung cancer (NSCLC) patients.

PATIENTS AND METHODS

Fifty-five chemotherapy-naive patients with NSCLC were entered onto the pharmacokinetic part of a large phase I trial in which P was administered as a 3-hour infusion at dosages of 100 to 250 mg/m2, and C over 30 minutes at dosages of 300 to 400 mg/m2. Patients were randomized for the sequence of administration, first C followed by P or vice versa. Each patient received the alternate sequence during the second and subsequent courses.

RESULTS

The most important hematologic toxicity encountered-was neutropenia. Hematologic toxicity was not dependent on the sequence in which P and C were administered, but there was cumulative neutropenia. Nonhematologic toxicities consisted mainly of vomiting, myalgia, and arthralgia. No sequence-dependent pharmacokinetic interactions for the P area under the concentration-time curve (P-AUC), maximal plasma concentration (P-Cmax), or time above a threshold concentration of 0.1 mumol/L (P-T > or = 0.1 mumol/L) were observed. However, there was a significant difference for the metabolite 6 alpha-hydroxypaclitaxel AUC (6OHP-AUC). Higher 6OHP-AUCs were observed when C was administered before P. The mean plasma ultrafiltrate AUC of C (CpUF-AUC) at the dosage of 300 mg/m2 for the sequence C-->P was 3.52 mg/mL.min (range, 1.94 to 5.83) and 3.62 mg/mL.min for the sequence P-->C (range, 1.91 to 5.01), which is not significantly different (P = .55). Of 45 assessable patients, there were five major responders (three complete responders and two partial responders). Four of five responses occurred at dosages above dose level 4 (P 175 mg/m2 + C 300 mg/m2). The median survival duration was best correlated with the P dose (4.8 months for doses < 175 mg/m2 v 7.9 months for doses > or = 175 mg/m2, P = .07; P-T > or = 0.1 mumol/L, 4.8 months for < 15 hours v 8.2 months for > or = 15 hours, P = .06).

CONCLUSION

There was no pharmacokinetic-sequence interaction between C and P in this study. A clear dose-response relation with respect to response rate and survival was observed. The pharmacokinetic parameter P-T > or = 0.1 mumol/L was related to improved survival in this study.

Determination of polyoxyethyleneglycerol triricinoleate 35 (Cremophor EL) in plasma by pre-column derivatization and reversed-phase high-performance liquid chromatography

A sensitive and selective reversed-phase high-performance liquid chromatographic (HPLC) method for the determination of polyoxyethyleneglycerol triricinoleate 35 (Cremophor EL; CrEL), which requires only microvolumes (20 microliters) of plasma, has been developed and validated. The procedure is based on saponification of CrEL in alcoholic KOH, followed by extraction of the released fatty acid ricinoleic acid with chloroform and derivatization with 1-naphthylamine. Margaric acid was used as the internal standard. The products are separated using an HPLC system consisting of an analytical column packed with Spherisorb ODS-1 material and a mobile phase of methanol-acetonitrile-10 mM potassium phosphate buffer pH 7.0 (72:13:15, v/v). Detection was executed by UV absorption at 280 nm. The lower limit of quantitation and the lower limit of detection in plasma are 0.01 and 0.005% (v/v) of CrEL, respectively. The percentage deviation and precision of the procedure, over the validated concentration range of 0.01 to 1.0% (v/v) of CrEL in plasma, are < or = 8.0% and < or = 6.6%, respectively. Compared to the previously described bioassay, the presented HPLC method possesses superior sensitivity and reliability. Preliminary pharmacokinetic studies of CrEL in mice and patients receiving paclitaxel formulated in CrEL have demonstrated the applicability of the presented assay.

Isolation, purification and biological activity of major docetaxel metabolites from human feces

We have developed a procedure suited for the isolation of metabolites of docetaxel (Taxotere) from human feces. The compounds were extracted from the feces with diethyl ether and further purified by (semipreparative) HPLC. Four metabolic products were obtained in submilligram quantities. Analytical HPLC with photodiode array detection showed that the purity of each compound was higher than 98%. There structures have been characterized by UV absorption and FAB/MS. All four compounds were oxidation products of the tert-butyl group attached to the C13-side chain, and corresponded to structures identified previously. The purified products were used for evaluating their cytotoxic activities against a human ovarian cancer (A2780) and a rat colon cancer (CC531) cell line, and their myelosuppressive effects in a hematopoietic progenitor toxicity assay. Although distinctions in biological activities between the compounds were evident, all metabolites showed a marked reduction in both cytotoxic and myelotoxic properties.

Quantification of paclitaxel metabolites in human plasma by high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic (HPLC) method has been validated for the quantitative determination of the three major paclitaxel metabolites (6 alpha-hydroxypaclitaxel, 3'-p-hydroxypaclitaxel, 6 alpha,3'-p-dihydroxypaclitaxel) in human plasma. The HPLC system consists of an APEX-octyl analytical column and acetonitrile-methanol-0.02 M ammonium acetate buffer pH 5 (AMW; 4:1:5, v/v/v) as the mobile phase. Detection is performed by UV absorbance measurement at 227 nm. The sample pretreatment of the plasma samples involves solid-phase extraction (SPE) on Cyano Bond Elut columns. The concentrations of the metabolic products could be determined by using the paclitaxel standard curve with a correction factor of 1.14 for 6 alpha,3'-p-dihydroxypaclitaxel. The recoveries of paclitaxel and the metabolites 6 alpha,3'-p-dihydroxypaclitaxel, 3'-p-hydroxypaclitaxel and 6 alpha-hydroxypaclitaxel in human plasma were 89, 78, 91 and 89%, respectively. The accuracy of the assay for the determination of paclitaxel and its metabolites varied between 95 and 97%, at a 50 ng/ml analyte concentration. The lower limit of quantitation was 10 ng/ml for both the parent drug and its metabolites.

Intermittent continuous infusion of ifosfamide and 5-fluorouracil in patients with advanced adenocarcinoma of the pancreas

BACKGROUND

In advanced adenocarcinoma of the pancreas treatment with 5-fluorouracil (5-FU) or ifosfamide results in response rates of approximately 20%. Continuous infusion of these drugs is on many grounds theoretically attractive and may therefore offer advantages over bolus or short-term infusion.

PATIENTS AND METHODS

Sixteen patients with advanced adenocarcinoma of the pancreas with progressive measurable disease and no previous chemotherapy entered the study. After implantation of a subcutaneous infusion chamber patients were treated on days 1-12 with ifosfamide (1.0 g/m2/day) and 5-FU (300 mg/m2/day) as a continuous intravenous infusion using a portable infusion pump. Mesna (1.0 g/m2/day) was added as uroprotective agent from day 1-14. Courses were repeated every 4 weeks.

RESULTS

Fifteen of the 16 patients were evaluable for response. One partial response was observed (response rate 7% [95% CI: 0%-32%]). Toxicity occurred in 64% of the courses. Dose limiting toxic effects were grade 3 nausea/vomiting (WHO) in 3 patients, grade 2 mucositis in 1 patient and grade 4 leukopenia in 1 patient.

CONCLUSION

Intermittent continuous infusion with ifosfamide, mesna and 5-FU is feasible on an outpatient basis. Although continuous infusion of ifosfamide may have a more favorable toxicity profile, the combination of 5-FU and ifosfamide in this schedule is no more effective than bolus or short-term infusion.

Pharmacokinetics of paclitaxel and three major metabolites in patients with advanced breast carcinoma refractory to anthracycline therapy treated with a 3-hour paclitaxel infusion: a European Cancer Centre (ECC) trial

BACKGROUND

Hepatic metabolism and biliary clearance play pivotal roles in the disposition of the anticancer drug paclitaxel. 6-alpha-hydroxypaclitaxel, 3'-p-hydroxypaclitaxel and 6-alpha,3'-p-dihydroxypaclitaxel were the major metabolic products of paclitaxel found in human bile. Recently, these metabolic products were detected in human plasma. The pharmacokinetics of paclitaxel and its metabolites were investigated in anthracycline-resistant breast cancer patients treated with high-dose paclitaxel and granulocyte colony-stimulating factor (G-CSF) support.

PATIENTS AND METHODS

Nine patients were entered into this study in which paclitaxel was administered at the relatively high dose of 250 mg/m2 during a 3-hour infusion. G-CSF was administered daily subcutaneously (s.c.)on days 2 to 19 following chemotherapy. Analysis of paclitaxel and metabolite concentrations was performed by a new highly sensitive reversed-phase high performance liquid chromatographic (HPLC) assay.

RESULTS

The dose-limiting toxicity in this study was cumulative neurotoxicity. One patient had a partial response and 2 patients had mixed responses of their skin metastases. Relatively low peak plasma concentration (Cmax), with mean values of 6.91 micromol/L (range 3.08 to 8.98) and area under the plasma concentration time curve (AUC), with mean values of 27.04 micromol/L.h (range 14.88 to 40.57), were observed. The total body clearance was 16.99 L/h (range, 10.25 to 27.39). The pharmacokinetic parameter for the prediction of leuko-neutropenia, the duration of the plasma concentration above the threshold of 0.1 micromol/L.h (T > or = 0.1 microM), was 19.72 h (range 10.54 to 26.31). The three major metabolites detected in human plasma were identified as 6-alpha-hydroxypaclitaxel, 3'-p-hydroxypaclitaxel and 6-alpha,3'-p-dihydroxypaclitaxel. Cmax and AUC values of these metabolites are reported.

CONCLUSIONS

The three main metabolic products of paclitaxel in human plasma are 6-alpha-hydroxypaclitaxel, 3'-p-hydroxypaclitaxel and the dihydroxymetabolite 6-alpha,3'-p-dihydroxypaclitaxel. Two patients with liver function disturbances showed a tendency to higher paclitaxel and 6-alpha-hydroxypaclitaxel AUC levels, with more pronounced neuropathy.

Photodynamic therapy in AIDS-related cutaneous Kaposi's sarcoma

For evaluating the role of photodynamic therapy (PDT) in the local treatment of acquired immune deficiency syndrome (AIDS)-related cutaneous Kaposi's sarcoma (KS), nine treatments were performed in eight human immunodeficiency virus-positive homosexual men. The patients received 2 mg Photofrin/kg and either 120 J/cm2 (n = 5) or 70 J/cm2 (n = 4) laser light (630 nm). A total of 83 lesions were evaluable for response with a follow-up of 3-8 months. The overall response rates by patient for all treated lesions were 50-100% (120 J/cm2) and 83.3-90.3% (70 J/cm2), with a median duration of 3 months (range, 2-6 months). Tumors located at the head had higher response rates than those at the trunk or extremities (p = 0.005 and p - 0.015 respectively). The size of the KS showed a negative relationship with the probability of complete response (p = 0.047). Local and general side effects occurred, including pain, blisters, temperature increase, muscle stiffness, and severe edema. The cosmetic result was unsatisfactory because of a high prevalence of scars and long-lasting hyperpigmentation. Although the response rates of PDT are high, light dose of 70-120 J/cm2 cannot be recommended in the treatment of cutaneous KS in combination with 2 mg/kg Photofrin because of severe side effects and unsatisfactory cosmetic result.

High-dose paclitaxel with granulocyte colony-stimulating factor in patients with advanced breast cancer refractory to anthracycline therapy: a European Cancer Center trial

Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) is a novel cytostatic agent that has shown interesting antitumor activity in patients with advanced breast cancer. Depending on variable patient characteristics and amount and type of prior therapy, as well as the applied dose and schedule of paclitaxel, response rates have varied from 13% to 62%. However, optimal dose and schedule are still unknown. We studied a high-dose (250 to 300 mg/m2) 3-hour paclitaxel infusion schedule in a poor prognostic group of breast cancer patients who progressed or relapsed while taking anthracyclines. This regimen was given every 3 weeks. Twenty-one of the 36 patients studied had increased liver enzymes and 18 had documented liver metastases. The objective response rate was only 6%, but response rate by disease site indicated that soft tissue lesions responded in 30% of cases. For a better comparison with other reported data a uniform definition of "anthracycline refractory" is needed. Neuropathy, which was found to be dose limiting, and arthralgia/myalgia syndrome were the most frequently occurring toxicities. Both severe myelosuppression (and infections) and severe diarrhea and mucositis were reported more frequently in patients with liver dysfunction. As higher peak levels, increased areas under the concentration time curves, and longer times during which plasma concentrations were above the threshold level of 0.1 mumol/L were found in patients with elevated liver enzymes, a correlation with the observed toxicities is assumed. Further pharmacodynamic studies in such patients receiving a 3-hour infusion seem warranted.

Isolation, purification, and biological activity of mono- and dihydroxylated paclitaxel metabolites from human feces

Three metabolites of the cytotoxic drug paclitaxel (Taxol) were isolated and purified from the feces of cancer patients receiving the agent as an intravenous infusion. The procedures involved sample homogenization in water followed by liquid-liquid extraction with diethyl ether and high-performance liquid chromatography (HPLC). Approximately 1-3.5 mg of each metabolite was obtained from 100 g of feces. As judged from the chromatographic traces of analytical HPLC with ultraviolet (UV) detection at 227 nm, the purity of each compound was > 97%. On-line photodiode-array detection demonstrated that the UV spectrum of the isolated compounds closely resembles that of the parent drug. Mass spectrometry provided evidence that these metabolites are mono- and dihydroxy-substituted derivatives, namely, 6 alpha-hydroxypaclitaxel, 3'-p-hydroxypaclitaxel, and 6 alpha, 3'-p-dihydroxypaclitaxel. The two 6 alpha-hydroxy-substituted metabolites were shown to have lost their cytotoxicity in in vitro clonogenic assays using the A2780 human ovarian carcinoma and the CC531 rat colon-carcinoma tumor cell lines. In addition, the metabolites showed reduced myelotoxic effects as compared with paclitaxel in an in vitro hemopoietic progenitor toxicity assay. Our procedure for the isolation and purification of paclitaxel metabolites in milligram quantities should be useful for testing the biological activities of these compounds and for the preparation of calibration standards essential for pharmacokinetics studies.

High-performance liquid chromatographic procedures for the quantitative determination of paclitaxel (Taxol) in human urine

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed and validated for the quantitative determination of paclitaxel in human urine. A comparison is made between solid-phase extraction (SPE) and liquid-liquid extraction (LLE) as sample pretreatment. The HPLC system consists of an APEX octyl analytical column and acetonitrile-methanol-0.2 microM ammonium acetate buffer pH 5 (4:1:5, v/v) as the mobile phase. Detection is performed by UV absorbance measurement at 227 nm. The SPE procedure involves extraction on Cyano Bond Elut columns. n-Butylchloride is the organic extraction fluid used for the LLE. The recoveries of paclitaxel in human urine are 79 and 75% for SPE and LLE, respectively. The accuracy for the LLE and SPE sample pretreatment procedures is 100.4 and 104.9%, respectively, at a 5 micrograms/ml drug concentration. The lower limit of quantitation is 0.01 microgram/ml for SPE and 0.25 microgram/ml for LLE. Stability data of paclitaxel in human urine are also presented.

Taxanes: a new class of antitumor agents

Taxanes belong to a new group of antineoplastic agents with a novel mechanism of action for a cytotoxic drug. They promote microtubule assembly and stabilize the microtubules. Paclitaxel, the first agent in this group to become available, was isolated from the Pacific yew, Taxus brevifolia, in 1971. In preclinical and clinical studies, paclitaxel and its semisynthetic analog docetaxel exhibit significant antitumor activity. This review deals with the physicochemical properties, pharmacology, and results of preclinical and clinical trials of the taxanes.

Bioanalysis, pharmacokinetics, and pharmacodynamics of the novel anticancer drug paclitaxel (Taxol)

Several high-performance liquid chromatographic assays have been reported for the analysis of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) in biologic matrices. The recently developed method of using solid-phase extraction as a sample pretreatment is preferred, as it is the most sensitive assay and is also capable of detecting metabolites in the plasma of treated patients. The pharmacokinetics of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ), administered in different doses and schedules, has been studied using this method. After cessation of the infusion, a three-phasic decay of plasma concentrations has been found. There are indications for nonlinear pharmacokinetics when paclitaxel is administered as a short infusion and at higher doses. Different metabolic products of paclitaxel have been detected in the plasma of treated patients. Three hydroxylated metabolites have been identified so far. Pharmacokinetics have been related with pharmacodynamics. Neuropathy, mucositis, and leukopenia correlate with pharmacokinetic parameters such as area under the plasma concentration time curve and steady-state paclitaxel levels. The hematologic toxicity of paclitaxel also has been modelled with a sigmoidal maximum effect equation with the time spent above the biologically active threshold concentration of 0.1 mumol/L as a pharmacokinetic parameters.

Pharmacokinetics of paclitaxel and metabolites in a randomized comparative study in platinum-pretreated ovarian cancer patients

PURPOSE

To investigate the pharmacokinetics and pharmacodynamics of paclitaxel in a randomized comparative study with four different treatment arms in patients with platinum-pretreated ovarian carcinoma.

PATIENTS AND METHODS

Eighteen patients were entered onto this study in which paclitaxel was administered at a high dose of 175 mg/m2 versus a low dose of 135 mg/m2 on a 3- or 24-hour infusion schedule. A solid-phase extraction technique for sample pretreatment followed by a reverse-phase high-performance liquid chromatographic (HPLC) assay was used for analysis of plasma.

RESULTS

Grade 3 neutropenia occurred in all four treatment arms. However, it was more severe on the 24-hour infusion schedule. Paclitaxel concentrations as low as 0.012 mumol/L were measured with the HPLC assay. With this low quantitation threshold, we found the plasma disappearance of paclitaxel to be triphasic, with half-lives t1/2(alpha), t1/2(beta), and t1/2(gamma) mean values for the different treatment arms of 0.19 hours (range, 0.01 to 0.4), 1.9 hours (range, 0.5 to 2.8), and 20.7 hours (range, 4 to 65), respectively. Eleven possible metabolites were found, of which three were identified as taxanes by on-line HPLC-photodiode array (PDA) detection. Investigation of pharmacodynamics shows no clear relationship between the pharmacokinetic parameters area under the plasma concentration time curve (AUC), area under the plasma concentration moment curve (AUMC), maximal plasma concentration (Cmax), clearance, and toxicity. However, a relationship was found between the duration of plasma concentrations above a threshold of 0.1 mumol/L with absolute neutrophil count (ANC) and white blood cell count (WBC).

CONCLUSION

Paclitaxel is metabolized, and putative metabolic products can be found in plasma of patients treated with the drug. Our results indicate that myelosuppression can be predicted by the measurement of the duration of plasma concentrations above the threshold of 0.1 mumol/L.