Taxotere (docetaxel) vs. Taxol (paclitaxel)

Taxotere (docetaxel) has been vastly advertised by its manufacturer Sanofi-Aventis, as a newer, more effective alternative to Taxol (paclitaxel). The older chemotherapy agent produced by Bristol-Myers Squibb has been one of the most widely used drugs in the adjuvant treatment of breast cancer since its approval in 1992, thanks to the considerable volume of high-quality evidence found in the scientific literature that proved its safety and effectiveness in clinical practice. Despite the fact that a full comparison between the two medications proved them to be almost equivalent, Sanofi kept claiming that docetaxel is superior to paclitaxel on most of its initial advertisement campaign. Nonetheless, in the last ten years, the use of Taxol progressively decreased while Taxotere gained substantial traction, even though its price is comparably higher than its counterpart (1, 2)

Docetaxel and Paclitaxel – comparing the two Taxanes

Taxotere and Taxol are two “taxanes”, a group of chemotherapy agents used to treat advanced or metastatic breast cancer in patients that did not respond to prior therapies. They have also been approved for the treatment of other types of malignancy such as prostate and gastric cancer, and non-small cell lung cancer (NSCLC). They act by targeting tubulin, a globular protein that constitutes microtubules, a critical component of the cellular cytoskeleton. Since they are anti-mitotic agents, taxanes suppress cellular division, inhibiting the replication of tumor cells and preventing them from spreading to other organs (metastasis). Although to a less extent, these drugs also target healthy cells, especially those that replicate at a higher speed such as those found in hair follicles, blood and immune system. This toxicity causes several side effects in 9 patients out of 10, which may also have lethal consequences if the medication levels are not closely monitored. Common adverse reactions include weight loss, anemia, recurrent infections, neutropenia, diarrhea and hair loss. Often used in combination with other drugs such as cisplatin and capecitabine, these agents are administered in cycles that consist of a one hour-long intravenous infusion. The main difference between Taxol and Taxotere is that the first one’s cycles must be repeated every week, while the latter can be administered only once every three or four weeks, improving its compliance with patients since they require fewer trips to the oncology clinic (3, 4, 5).

Curiously enough, the decline in the use and prescription of paclitaxel coincided with its patent expiration in 2004. According to data provided by a large study published in the journal Cancer Treatment Reviews that compared the clinical use and consumption of the two chemotherapy agents, from 2004 to 2008 the prescriptions of Taxol dropped by 50%, while the prescriptions of docetaxel increased proportionally by roughly the same amount. However, the cost of a paclitaxel cycle is 20 times cheaper than the cost of a docetaxel one, so hospital oncology wards may spend more than 90% of their yearly taxanes expenditure on docetaxel alone. Before Taxotere’s own patent expired in 2010, it was one of the most used cancer medications globally, with more than $1.2 billion sales just in the United States (1, 2).

Is Taxotere a better or safer drug than Taxol?

In April 2009, the U.S. Food and Drugs Administration (FDA) accused Sanofi of overstating the efficacy of their medication by providing the public (doctors and patients as well) with misleading promotional material that included unsubstantiated superiority claims. In its warning letter, the regulatory agency highlighted how no prior clinical experience ever provided substantial evidence about the fact that docetaxel was safer, better or more effective than paclitaxel. The pharmaceutical company falsely claimed that its drug was associated with significantly higher response rates, longer duration of response, and longer median overall survival when compared to its competitor (6). The manufacturer cited a study in support of these claims that was deemed insufficient by the FDA since it failed to demonstrate statistical significance and has never been replicated in later times (7).

Some of the claims about docetaxel’s purported superiority over paclitaxel also relied on indirect comparisons or statistically unreliable assumptions (1, 8, 11). In 2009, the NICE guidelines determined that a doxorubicin and cyclophosphamide (AC) protocol may be more effective if the two drugs are used in association with a taxane, but never assumed which one was superior to the others. In their final recommendation, they preferred docetaxel regimens (DAC) simply because they had no systemic reviews available that compared their standard comparator to paclitaxel ones (AC-P) since its corresponding treatment cycle was rarely used (9). On the other hand, many other highly authoritative national guidelines never expressed a true preference between the two drugs. For example, the British Columbia Agency only recommended dose-dense regimens in adjuvant therapy instead of traditional paclitaxel treatment, but never defined a preferential cancer protocol with any specific taxane (10, 11). Lastly, other studies such as the E1199 published in the New England Journal of Medicine found that the AC-P regimen improved both disease-free survival (DFS) and overall survival (OS) while the DAC one only improved OS outcomes (12).

Docetaxel’s potency is twice than paclitaxel’s one, but this does not mean it is more effective. The only consequence of an increased potency is that a reduced dose may be required, yet again, some studies showed that Taxol-based regimens are associated with a better tolerability because of its reduced toxicity, especially in the elderly (13). At the same time, Taxotere is susceptible to significantly higher cellular drug resistance caused by various different metabolic mechanisms, and its efficacy can be thus reduced in some subjects (14). In conclusion, the data currently available does not justify the overwhelming preference currently shown for the newer taxane in many hospitals in the U.S. and Europe. If this new drug regimen yields no greater benefits than those including its older counterpart, then this change in consumption pattern is probably unjustified.

Article written by Dr. Claudio Butticè, Pharm.D.
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