Doxorubicin followed by sequential paclitaxel and cyclophosphamide versus concurrent paclitaxel and cyclophosphamide: 5-year results of a phase II randomized trial of adjuvant dose-dense chemotherapy for women with node-positive breast carcinoma.

PURPOSE: We conducted a randomized Phase II trial to directly compare toxicity, feasibility, and delivered dose intensities of two adjuvant dose-intensive regimens containing doxorubicin, paclitaxel, and cyclophosphamide for patients with node-positive breast carcinoma. EXPERIMENTAL DESIGN: Forty-two patients with resected breast carcinoma involving one or more ipsilateral axillary lymph nodes, were randomized to receive two different schedules of adjuvant chemotherapy using 14-day dosing intervals: either (a) three cycles of doxorubicin 80 mg/m(2) as i.v. bolus followed sequentially by three cycles of paclitaxel 200 mg/m(2) as a 24-h infusion and then by three cycles of cyclophosphamide 3.0 g/m(2) as a 1-h infusion (arm A); or (b) the same schedule of doxorubicin followed by three cycles of concurrent cyclophosphamide and paclitaxel at the same doses (arm B). All cycles were supported by granulocyte colony-stimulating factor administration. RESULTS: Forty-one patients were assessable for toxicity and feasibility; 37 (90%) completed all planned chemotherapy. There was no treatment-related mortality; however, increased toxicity was observed on arm B compared with arm A, manifested by an increase in hospitalization for toxicity, mainly neutropenic fever, and an increased incidence of transfusion of packed RBCs transfusions for anemia. The mean delivered dose intensities for paclitaxel and cyclophosphamide were significantly greater for arm A compared with arm B (P =.01 and P =.05, respectively). There is no long-term, treatment-related toxicity, and no cases of acute myelogenous leukemia or myelodysplastic syndrome have been observed. CONCLUSIONS: Dose-dense sequential single-agent chemotherapy is more feasible than doxorubicin with subsequent concurrent paclitaxel and cyclophosphamide.

Double-strand breaks and tumorigenesis.

The establishment of connections between biochemical defects and clinical disease is a major goal of modern molecular genetics. In this review, we examine the current literature that relates defects in the two major DNA double-strand-break repair pathways--homologous recombination and nonhomologous end-joining--with the development of human tumors. Although definitive proof has yet to be obtained, the current literature is highly suggestive of such a link.

Homology-directed dna repair, mitomycin-c resistance, and chromosome stability is restored with correction of a Brca1 mutation.

Chromosomal breaks occur spontaneously as a result of normal DNA metabolism and after exposure to DNA-damaging agents. A major pathway involved in chromosomal double-strand break repair is homologous recombination. In this pathway, a DNA sequence with similarity to a damaged chromosome directs the repair of the damage. The protein products of the hereditary breast cancer susceptibility genes, BRCA1 and BRCA2, interact with the Rad51 protein, a central component of homologous repair pathways. We have recently shown that this interaction is significant by demonstrating that Brca1- and BRCA2-deficient cells are defective in homology-directed chromosomal break repair. We confirm that Brca1-deficient embryonic stem (ES) cells are defective in gene targeting and homology-directed repair of an I-Sce I-induced chromosome break. The phenotypic paradigm that defines homology-directed repair mutants is extended to these Brca1-deficient cells by the demonstration of 100-fold sensitivity to the interstrand cross-linking agent mitomycin-C and spontaneous chromosome instability. Interestingly, although chromosome aberrations were evident, aneuploidy was not observed. Repair phenotypes are partially restored by expression of a Brca1 transgene, whereas correction of one mutated Brca1 allele through gene targeting fully restores mitomycin-C resistance and chromosome stability. We conclude that the inability to properly repair strand breaks by homology-directed repair gives rise to defects in chromosome maintenance that promote genetic instability and, it is likely, tumorigenesis.

Weekly trastuzumab and paclitaxel therapy for metastatic breast cancer with analysis of efficacy by HER2 immunophenotype and gene amplification.

PURPOSE: This phase II study evaluated weekly trastuzumab and paclitaxel therapy in women with HER2-normal and HER2-overexpressing metastatic breast cancer. Efficacy was correlated with immunohistochemical and fluorescent in situ hybridization (FISH) assay results. PATIENTS AND METHODS: Eligible patients had bidimensionally measurable metastatic breast cancer. Up to three prior chemotherapy regimens, including prior anthracycline and taxane therapy, were allowed. Trastuzumab 4 mg/kg and paclitaxel 90 mg/m2 were administered on week 1, with trastuzumab 2 mg/kg and paclitaxel 90 mg/m2 administered on subsequent weeks. HER2 status was evaluated using four different immunohistochemical assays and FISH. RESULTS: Patients received a median of 25 weekly infusions (range, one to 85 infusions). Median delivered paclitaxel dose-intensity was 82 mg/m2/wk (range, 52 to 90 mg/m2/wk). The intent-to-treat response rate for all 95 patients enrolled was 56.8% (95% confidence interval, 47% to 67%). A response rate of 61.4% (4.5% complete response, 56.8% partial response) was observed in 88 fully assessable patients. In patients with HER2-overexpressing tumors, overall response rates ranged from 67% to 81% compared with 41% to 46% in patients with HER2-normal expression (ranges reflect the different assay methods used to assess HER2 status). Differences in response rates between patients with HER2-overexpressing tumors and those with normal HER2 expression were statistically significant for all assay methods, with CB11 and TAB250 antibodies and FISH having the strongest significance. Therapy was generally well tolerated, although three patients had serious cardiac complications. CONCLUSION: Weekly trastuzumab and paclitaxel therapy is active in women with metastatic breast cancer. Therapy was relatively well tolerated; however, attention to cardiac function is necessary.

BRCA2 is required for homology-directed repair of chromosomal breaks.

The BRCA2 tumor suppressor has been implicated in the maintenance of chromosomal stability through a function in DNA repair. In this report, we examine human and mouse cell lines containing different BRCA2 mutations for their ability to repair chromosomal breaks by homologous recombination. Using the I-SceI endonuclease to introduce a double-strand break at a specific chromosomal locus, we find that BRCA2 mutant cell lines are recombination deficient, such that homology-directed repair is reduced 6- to >100-fold, depending on the cell line. Thus, BRCA2 is essential for efficient homology-directed repair, presumably in conjunction with the Rad51 recombinase. We propose that impaired homology-directed repair caused by BRCA2 deficiency leads to chromosomal instability and, possibly, tumorigenesis, through lack of repair or misrepair of DNA damage.

Brca1 controls homology-directed DNA repair.

Germline mutations in BRCA1 confer a high risk of breast and ovarian tumors. The role of BRCA1 in tumor suppression is not yet understood, but both transcription and repair functions have been ascribed. Evidence that BRCA1 is involved in DNA repair stems from its association with RAD51, a homolog of the yeast protein involved in the repair of DNA double-strand breaks (DSBs) by homologous recombination. We report here that Brca1-deficient mouse embryonic stem cells have impaired repair of chromosomal DSBs by homologous recombination. The relative frequencies of homologous and nonhomologous DNA integration and DSB repair were also altered. The results demonstrate a caretaker role for BRCA1 in preserving genomic integrity by promoting homologous recombination and limiting mutagenic nonhomologous repair processes.

Phase I study of escalating doses of edatrexate in combination with paclitaxel in patients with metastatic breast cancer.

Motivated by the observation of preclinical synergy, a Phase I dose escalation study of edatrexate in combination with a 3-h paclitaxel infusion was performed in patients with advanced breast cancer to determine the maximum tolerated dose (MTD) of edatrexate and the toxicities associated with this combination and to report preliminary observations of efficacy with this novel combination. Thirty-six patients were enrolled in this Phase I trial. Thirty-five eligible patients were treated every 21 days in cohorts of at least three patients and were assessable for toxicity. One patient was ineligible due to hyperbilirubinemia. Stepwise dose escalations of edatrexate were administered until grade >3 nonhematological dose-limiting toxicities were reported. The initial dose level of edatrexate was 180 mg/m2; subsequent cohorts were treated with escalating doses of edatrexate (210, 240, 270, 300, 350, and 400 mg/m2). Edatrexate was administered by i.v. infusion over 1 h. Paclitaxel was administered 24 h later at a fixed dose of 175 mg/m2 as a 3-h infusion with standard dexamethasone, diphenhydramine, and cimetidine premedication. The MTD of edatrexate was reached at the 350 mg/m2 level in this study. Grade 3 diarrhea was seen in one patient at the 300 and 400 mg/m2 dose levels, requiring dose reductions. Two patients experienced grade 4 stomatitis at the 400 mg/m2 dose level and also required dose reduction, establishing the MTD as 350 mg/m2. Grade 3 nausea and vomiting were noted in two of three patients at the highest dose level. Of 35 patients, 4 patients reported grade 3 myalgias and 1 patient reported grade 3 neurosensory complaints, which were seen mostly at the 350 and 400 mg/m2 dose levels; however, 1 patient reported grade 3 myalgias at 180 mg/m2. No cumulative neurotoxicity was observed, and no patient experienced an allergic reaction to paclitaxel. In 23 patients with bidimensionally measurable disease, there were four complete (17%) and seven partial responses, with an overall response rate of 48% (95% confidence interval, 27-69%). All of the responses were seen in patients who had not received prior chemotherapy for stage IV disease. The median duration of response was not assessable because many responding patients went on to receive high-dose chemotherapy treatment with stem cell support. The combination of edatrexate and paclitaxel for treatment of metastatic breast cancer is a feasible and safe regimen. The MTD of edatrexate was 350 mg/m2 when combined with a 3-h infusion of paclitaxel (175 mg/m2) given 24 h later. Activity was noted even among patients who had relapsed shortly after receiving methotrexate- and/or doxorubicin-containing adjuvant regimens. Additional studies evaluating the sequences and dosing schema for this combination are warranted to improve the response proportion and define the duration of the response.

Double-strand break repair by interchromosomal recombination: suppression of chromosomal translocations.

To directly determine whether recombinational repair of double-strand breaks (DSBs) can occur between heterologous chromosomes and lead to chromosomal rearrangements in mammalian cells, we employed an ES cell system to analyze recombination between repeats on heterologous chromosomes. We found that recombination is induced at least 1000-fold following the introduction of a DSB in one repeat. Most (98%) recombinants repaired the DSB by gene conversion in which a small amount of sequence information was transferred from the unbroken chromosome onto the broken chromosome. The remaining recombinants transferred a larger amount of information, but still no chromosomal aberrations were apparent. Thus, mammalian cells are capable of searching genome-wide for sequences that are suitable for DSB repair. The lack of crossover events that would have led to translocations supports a model in which recombination is coupled to replication.

Dose-dense therapy with weekly 1-hour paclitaxel infusions in the treatment of metastatic breast cancer.

PURPOSE: To evaluate the efficacy and toxicity of paclitaxel administered as a 1-hour infusion on weekly basis, without interruption, to patients with metastatic breast cancer who had received prior therapy. PATIENTS AND METHODS: Thirty patients with metastatic breast cancer received sustained weekly paclitaxel therapy at an initial dose of 100 mg/m2 until disease progression. Prior therapy included adjuvant only (n=17), metastatic only (n=7), or both (n=6). Eighteen patients had received prior anthracycline therapy, 12 of whom had demonstrated progression of disease within 12 months of it. All patients were assessable for efficacy; 29 patients were assessable for toxicity. Pharmacokinetic studies of paclitaxel were also performed. RESULTS: A total of 469 weekly paclitaxel infusions were administered to 30 patients (median, 14 infusions/patient). The median delivered dose-intensity was 91 mg/m2/wk (range, 80 to 108). The overall response rate was 53% (95% confidence interval [CI], 34% to 72%), with 10% complete responses (CRs) and 43% partial responses (PRs). Median response duration was 7.5 months (range, 2 to 11+). Responses were observed in nine of 18 (50%) patients with prior anthracycline therapy, including six of 12 (50%) with disease progression on anthracycline within 1 year (three of four within 6 months). Therapy was well tolerated and remarkable for a lack of overall and cumulative myelosuppression. Grade 3/4 neutropenia occurred in four patients; febrile neutropenia was not observed. Peripheral neuropathy prohibited dose escalation above 100 mg/m2, and grade 3 neuropathy was observed in two of 21 patients at < or = 100 mg/m2. CONCLUSION: Weekly paclitaxel therapy is active and well tolerated in patients with metastatic breast cancer. Weekly therapy should be considered as a current clinical option for these patients and should be incorporated into future comparative clinical trials.

Dose-dense therapy with paclitaxel via weekly 1-hour infusion: preliminary experience in the treatment of metastatic breast cancer.

In an ongoing effort to establish the most appropriate dose and administration schedule for paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ), the feasibility and safety of weekly 1-hour infusions were evaluated in 16 women with metastatic breast cancer previously treated with at least one chemotherapy regimen. Paclitaxel was administered on an outpatient basis at a starting dose of 100 mg/m2/wk for 4 consecutive weeks, with 4-week cycles continued until disease progression or the onset of intolerable toxicity. With 215 weekly infusions administered so far (median, 13 per patient), no episodes of febrile neutropenia have occurred, and no hematopoietic growth factors have been used. Plans for dose escalation were abandoned after grade 3 sensorimotor neuropathy developed in five of nine patients treated at paclitaxel 110 to 120 mg/m2. With dose escalation eliminated, further severe neurotoxicities were rare, but some degree of cumulative peripheral neuropathy was noted in all but three patients. No acute hypersensitivity reactions were noted. To date, six of 15 evaluable patients have achieved a major response to therapy, with one complete response and five partial responses. Four other patients had a minor response to therapy, one patient had an early death due to autopsy-proven extensive pulmonary microvascular carcinomatosis, and five patients have stable disease. Although the potential neurotoxicity of this regimen merits attention, the overall profile of a high therapeutic index, manageable toxicity, and convenient administration schedule makes this an attractive treatment alternative for patients with metastatic breast cancer.

Loss of heterozygosity induced by a chromosomal double-strand break.

The repair of chromosomal double-strand breaks (DSBs) is necessary for genomic integrity in all organisms. Genetic consequences of misrepair include chromosomal loss, deletion, and duplication resulting in loss of heterozygosity (LOH), a common finding in human solid tumors. Although work with radiation-sensitive cell lines suggests that mammalian cells primarily rejoin DSBs by nonhomologous mechanisms, alternative mechanisms that are implicated in chromosomal LOH, such as allelic recombination, may also occur. We have examined chromosomal DSB repair between homologs in a gene targeted mammalian cell line at the retinoblastoma (Rb) locus. We have found that allelic recombinational repair occurs in mammalian cells and is increased at least two orders of magnitude by the induction of a chromosomal DSB. One consequence of allelic recombination is LOH at the Rb locus. Some of the repair events also resulted in other types of genetic instability, including deletions and duplications. We speculate that mammalian cells may have developed efficient nonhomologous DSB repair processes to bypass allelic recombination and the potential for reduction to homozygosity.

A model for testing recombinogenic sequences in the mouse germline.

Homologous recombination is a conserved process of genetic exchange generated by homologous pairing of nucleotides. Species diversity and gene evolution are dependent on the outcomes of recombination during germ cell development, yet systems to study mammalian germline recombination, especially those with applications to human genetics, are not well developed. We report on a transgenic mouse system designed to study recombination within test sequences in the male germline utilizing an intron-interrupted lacZ reporter gene. beta-galactosidase positive sperm are detected and quantitated by flow cytometry using fluorogenic substrates. Examination of recombination within a 1.7 kb repeat of test sequences derived from the human glycophorin breakpoint cluster region detects approximately 0.04-0.09% fluorescent sperm. Confirmation that these sperm result from recombination in the germline comes from histochemical staining of testicular cells, examination of spliced mRNA, and PCR analysis of sorted sperm populations. The system is readily adaptable to studies of other sequences reported to have elevated levels of recombination, including those implicated in human genetic disease. Investigations of the molecular basis for genomic instability at specific chromosomal locations may yield important insights into mechanisms of chromosomal loss and rearrangements.

Ninety-six-hour paclitaxel infusion after progression during short taxane exposure: a phase II pharmacokinetic and pharmacodynamic study in metastatic breast cancer.

PURPOSE: A phase II trial of paclitaxel infused over 96 hours in patients with metastatic breast cancer with demonstrated disease progression (PD) during short-infusion taxane treatment was performed to evaluate schedule-dependent activity with prolonged drug exposure. The tolerability of this strategy and its pharmacokinetic profile and pharmacodynamic correlates were also investigated. PATIENTS AND METHODS: Paclitaxel was administered to 26 patients with metastatic breast cancer at 120 to 140 mg/m2 intravenously over 96 hours. Twenty-three patients had demonstrated PD while receiving prior 3-hour paclitaxel, two during 1-hour docetaxel, and one during infusions of docetaxel and then paclitaxel. Twenty-one patients (81%) had no prior response to the short taxane infusion (primary resistance) and five (19%) had prior partial responses (PRs) of brief duration before PD (secondary resistance). Plasma paclitaxel concentrations were assessed at 24, 48, 72, and 96 hours. RESULTS: After delivery of 195 cycles, seven of 26 assessable patients (26.9%; 95% confidence interval, 11.6% to 47.8%) had major objective responses, with a median response duration of 6 months (range, 1 to 13). The predominant toxicities were neutropenia (76% grade > or = 3) and stomatitis (15% grade > or = 3). Despite omission of premedications, no significant hypersensitivity reactions occurred. The median steady-state paclitaxel concentration (Css) in 23 assessable patients was 0.047 mumol/L (range, .023 to .176). Patients who experienced grade 4 neutropenia had significantly decreased paclitaxel clearance and higher Css than those with grade 1 to 3 neutropenia (P < .05). Pretreatment elevation of hepatic transaminases was associated with delayed clearance (P < .01) and increased myelo-suppression and mucosal toxicity. CONCLUSION: Paclitaxel demonstrates activity against metastatic breast cancer when administered over 96 hours to patients with disease that recently had progressed during short taxane exposure. Delayed paclitaxel clearance and consequent increased toxicity occurred in patients with hepatic dysfunction. The activity observed supports preclinical data that suggest variability in efficacy and resistance patterns to paclitaxel based on duration of exposure.

Sequential adjuvant therapy with doxorubicin/paclitaxel/cyclophosphamide for resectable breast cancer involving four or more axillary nodes.

The results of both retrospective and prospective studies suggest that the effectiveness of systemic adjuvant chemotherapy with doxorubicin and cyclophosphamide for breast cancer may be related to the dose intensity of these agents. Recent trials also have demonstrated the high activity of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) against metastatic breast cancer. Clinically, paclitaxel appears to be noncross-resistant with doxorubicin, but the unique and overlapping toxicities of these three agents might preclude concurrent adjuvant administration. A possible solution is sequential rather than concurrent administration, an approach that kinetic modelling predicts to be superior. A pilot study testing dose-intensive sequential administration of doxorubicin/paclitaxel/cyclophosphamide enrolled 42 patients with a median age of 42 years who had resected breast cancer metastatic to four or more ipsilateral axillary lymph nodes. Intravenous treatment, given at 14-day intervals, began with three cycles of doxorubicin 90 mg/m2, followed by three cycles of paclitaxel 250 mg/m2, given as a 24-hour infusion, and, finally, three cycles of cyclophosphamide 3 g/m2. Selected patients received radiotherapy. The median number of positive lymph nodes was eight (range, four to 25), and the median tumor size was 3.0 cm (range, 0 to 11.0 cm). Granulocyte colony-stimulating factor support was given. Both hematologic and non-hematologic toxicity were substantial but manageable. Hospital admission was necessary in 62 (17%) of 369 chemotherapy cycles in 29 patients (69%). As planned, the median intertreatment interval was 14 days through all nine cycles of therapy, and the median delivered dose intensity exceeded 98% for all three agents. The median follow-up from local control surgery in December 1994 was 448 days (range, 82 to 632 days). Three patients (7.2%) had disease relapses, one during the doxorubicin portion of treatment and two (4.9%) who had completed treatment with all three agents. Sequential dose-intensive therapy with doxorubicin/paclitaxel/cyclophosphamide has manageable toxicity and, with short follow-up, is a promising new regimen suitable for randomized testing.

Binding, internalization, and degradation of [125I]insulin by cultured bovine aortic endothelial cells: effects of serotonin.

Cultured bovine aortic endothelial cells bind and internalize [125I]insulin and down regulate insulin receptors. Internalized insulin was not degraded significantly and diffused from the endothelial cells. Neither 5-hydroxytryptamine, methylamine, nor dansylcadaverine have any observable effect on insulin binding, internalization, metabolism, or down regulation of insulin receptors. Transglutaminase activity, however, is inhibited by 5-hydroxytryptamine and methylamine. These data indicate that transglutaminase is not required for insulin receptor-mediated endocytosis by bovine aortic endothelial cells in culture.