High-dose taxol (HDT) with G-CSF in patients with advanced breast cancer (ABC) refractory to anthracycline (ANT) therapy

The effect on tumor response of adding sequential preoperative docetaxel to preoperative doxorubicin and cyclophosphamide: preliminary results from National Surgical Adjuvant Breast and Bowel Project Protocol B-27

PURPOSE

The National Surgical Adjuvant Breast and Bowel Project Protocol B-27 was designed to determine the effect of adding docetaxel after four cycles of preoperative doxorubicin and cyclophosphamide (AC) on clinical and pathological response rates and on disease-free and overall survival of women with operable breast cancer.

PATIENTS AND METHODS

Women (N = 2,411) with operable primary breast cancer were randomly assigned to receive either four cycles of preoperative AC followed by surgery (group I), or four cycles of AC followed by four cycles of docetaxel, followed by surgery (group II), or four cycles of AC followed by surgery and then four cycles of docetaxel (group III). Clinical and pathologic tumor responses to preoperative therapy were assessed.

RESULTS

Mean tumor size (4.5 cm) and other key characteristics were evenly balanced among the three treatment arms. Grade 4 toxicity was observed in 10.3% of 2,400 patients during AC treatment, and in 23.4% of 1584 patients during docetaxel treatment. Compared to preoperative AC alone, preoperative AC followed by docetaxel increased the clinical complete response rate (40.1% v 63.6%; P <.001), the overall clinical response rate (85.5% v 90.7%; P <.001), the pathologic complete response rate (13.7% v 26.1%; P <.001), and the proportion of patients with negative nodes (50.8% v 58.2%; P <.001). Pathologic primary breast tumor response was a significant predictor of pathologic nodal status (P <.001).

CONCLUSION

The addition of four cycles of preoperative docetaxel after four cycles of preoperative AC significantly increased clinical and pathologic response rates for operable breast cancer.

Emerging role of taxanes in adjuvant and neoadjuvant therapy for breast cancer: the potential and the questions

Adjuvant chemotherapy has gained increasing prominence in the treatment of nonmetastatic breast cancer, producing gradual improvement in the survival of these patients. The taxanes offer great hope for adding to the progress in adjuvant treatment, but data have been conflicting. Early results of multi-center trials testing the sequential addition of paclitaxel to anthracycline-based adjuvant chemotherapy have perhaps been prematurely reported, but have already made a major impact on patterns of care for node-positive and even some node-negative patients. The early dramatic improvements in CALG 9344 are fading with time, however, and have not been confirmed by a second similar trial, NSABP B-28. Moreover, it cannot be stated with certainty whether the modest improvements observed by sequential addition of paclitaxel reflect the ability of this drug to kill anthracycline-resistant cancer cells or the increased total duration and amount of treatment. By contrast, the early results of the BCIRG 001 trial suggest that combining docetaxel with doxorubicin may significantly increase survival, but these early results should be viewed with caution and do not necessarily mean that docetaxel is superior to paclitaxel. The role of neoadjuvant chemotherapy for breast cancer has also expanded over the past 2 decades, from its initial use for inoperable locally advanced breast cancer (LABC) to its current use for patients with large operable tumors to make BCT feasible. The neoadjuvant approach also has an important role in clinical trials, where it will allow more rapid comparison of treatment regimens than can be accomplished in the adjuvant setting and provides an opportunity to analyze biologic markers as predictors of response. The value of this approach, however, will ultimately depend on a clear demonstration, not yet available, that a change in therapy that increases primary tumor response will also lead to improved long-term survival. The roles of docetaxel and paclitaxel in the neoadjuvant setting has been actively investigated over the past 5 to 10 years, and exciting results are beginning to emerge. Clearly, docetaxel has potent antitumor activity against breast cancer. Several preliminary results suggest that addition of docetaxel to an anthracycline-based regimen, particularly when added sequentially, as in NASBP B-27 and the Aberdeen trial, results in higher clinical and pathologic response rates. Whether this will translate into increased long-term survival, as suggested by the early results of the Aberdeen trial, remains to be seen. Whether sequential addition of docetaxel to doxorubicin is more or less effective than combining these drugs also has not been established. The results from M.D. Anderson suggesting that paclitaxel given on a weekly schedule was more effective than the same drug given every 3 weeks are particularly intriguing, and they may help to explain why the adjuvant studies with paclitaxel given every 3 weeks have not produced more dramatic results, whereas several studies with docetaxel (also given every 3 weeks) seem so positive. It may be that paclitaxel, with activity that is highly schedule-dependent and for which cell killing is more dependent on the duration of exposure, works best when given weekly, whereas the efficacy of docetaxel depends less on scheduling. If this is the case, then weekly paclitaxel may turn out to be equally effective as docetaxel appears to be even when given every 3 weeks. Alternatively, if docetaxel is simply a more active drug, then giving docetaxel weekly may be the most effective taxane regimen. Whether routine use of weekly chemotherapy administration in the adjuvant or neoadjuvant setting is practical or not is largely subjective, but at least it appears that the toxicity of this approach is acceptable. These issues are also being addressed in ongoing trials. Finally, taxanes have produced dramatic increases in response rates in the neoadjuvant setting, but, except for the Aberdeen trial, survival benefits have not yet been shown. If, however, the high pCR rates do translate into overall survival benefits that are greater than adding taxanes to postoperative adjuvant therapy, it might suggest that, unlike other drugs, taxanes are actually more effective before surgery than after, as predicted originally based on laboratory experiments. Clearly, much work remains to be done in this area of research on breast cancer therapy.

A phase II study of paclitaxel in advanced breast cancer resistant to anthracyclines

33 women with advanced breast cancer resistant to anthracyclines were treated with paclitaxel 175 mg/m2 in a 3 h infusion every 3 weeks. The median age was 53 years (range 30-72) and the median performance status was 1 (range 0-2). 24 (73%) patients had visceral metastases while 22 (67%) had > or = two involved sites. 23 (70%) patients received anthracycline or mitoxantrone in an adjuvant setting and 21 (64%) for advanced disease. There were two (6%, 95% confidence interval (CI) 1-20%) complete responses (CRs) and 12 (36%, 95% CI 20-55%) partial responses (PRs). Median dose intensity of paclitaxel delivered was 58 mg/m2/week. Median time to progression was 24 weeks (range 4-61) and median survival was 41 weeks (range 8-66). Grade 3-4 toxicities included leucopenia (9%), stomatitis (3%), alopecia (91%), neurotoxicity (9%), infection (3%) and diarrhoea (3%). In conclusion, paclitaxel at a dose of 175 mg/m2 exhibits significant activity in advanced breast cancer resistant to anthracyclines.

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.

Paclitaxel (Taxol) and docetaxel (Taxotere): not simply two of a kind

Paclitaxel and docetaxel are the two presently clinically available representatives of the new class of taxane drugs. They share major parts of their structures and mechanisms of action, but differ in several other aspects. For instance, there is a difference in their tubulin polymer generation, and docetaxel appears twice as active in depolymerization inhibition. In vitro docetaxel also tends to be more potent in different cell lines and investigational models. While in vitro and in vivo studies suggest that prolonged exposure to paclitaxel is better than a brief exposure, no such tendency is seen for docetaxel, indicating it to be a schedule-independent drug. Clinical studies have not confirmed an advantage for prolonged exposure to paclitaxel; but do show differences in the toxicity profiles of the two drugs. These topics will be addressed in detail.