Is Oral Paclitaxel Better Than IV Paclitaxel for Metastatic Breast Cancer?

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Women diagnosed with metastatic breast cancer who were treated with an oral form of the chemotherapy medicine called paclitaxel seemed to have a better response to treatment and less neuropathy compared to women treated with the IV version of paclitaxel, according to a study.

Still, a number of experts questioned whether people would be able to follow the somewhat complicated dosing schedule.

The research was presented on Dec. 13, 2019, at the San Antonio Breast Cancer Symposium. Read the abstract of "Oral paclitaxel with encequidar: The first orally administered paclitaxel shown to be superior to IV paclitaxel on confirmed response and survival with less neuropathy: A phase III clinical study in metastatic breast cancer."

About paclitaxel

Taxol is the brand name of paclitaxel, but the patent expired, meaning the medicine is available as a generic. Paclitaxel is a type of chemotherapy called a taxane. Taxanes work by interfering with cancer cells’ ability to divide. Paclitaxel is usually given in combination with other chemotherapy medicines intravenously, which means the medicine is delivered directly into your bloodstream through an IV or a port.

To allow the medicine to enter the bloodstream, intravenous paclitaxel is mixed with solvents. These solvents can make paclitaxel difficult to tolerate while it’s being given. People usually take steroids before receiving paclitaxel to minimize any reactions to the solvents.

Paclitaxel is used to:

  • reduce the risk of early-stage breast cancer coming back
  • treat advanced-stage and metastatic breast cancer after it stops responding to other chemotherapy regimens

Paclitaxel also can cause a number of side effects, including infusion site reactions and neuropathy. Neuropathy is the general term for pain or discomfort caused by damage to the nerves of the peripheral nervous system. Your peripheral nervous system is made up of the many nerves that bring signals from the brain and spinal cord to other — or peripheral — parts of the body, such as the hands and feet. Chemotherapy medicines, such as paclitaxel, travel throughout the body, where they can cause damage to the nerves. Damage to those nerves can affect the way the body sends signals to muscles, joints, skin, and internal organs. This can cause pain, numbness, loss of sensation, trouble walking, balance issues, and other symptoms.

Because of the need for pretreatment steroids and the side effects, researchers have been looking for a way to give paclitaxel orally, as a pill or capsule.

About the study

The study included 402 women diagnosed with metastatic breast cancer. Metastatic breast cancer is advanced-stage breast cancer that has spread to parts of the body away from the breast, such as the bones or liver.

None of the women had brain metastases, and none of the women had been treated with taxane chemotherapy within the past year.

The women were randomly assigned to one of two treatment groups:

  • oral paclitaxel and encequidar 3 days per week; encequidar is a medicine that allows the oral paclitaxel to be absorbed into the bloodstream (265 women)
  • an IV infusion of paclitaxel every 3 weeks; the infusion took 3 hours to administer (137 women)

The dosing schedule for the oral paclitaxel is quite involved and stringent:

  • a person must fast for 4 hours before taking the encequidar tablet
  • after taking the encequidar capsule, a person must wait for 1 hour before taking the paclitaxel capsules; the person takes a total of 11 capsules
  • a person must then wait 4 hours before eating
  • this schedule must be followed for 3 days in a row each week

Virginia Kaklamani, M.D., a medical oncologist at UT Health San Antonio who moderated the media briefing on the study, said she thought the regimen would be problematic for some patients and wondered whether adherence would be an issue. Other researchers at the media briefing echoed her concerns about the schedule.

The researchers who did the study looked to see how the cancers responded to the two forms of paclitaxel.

Overall, 35.8% of the cancers treated with oral paclitaxel responded to the treatment compared to 23.4% of cancers treated with IV paclitaxel.

The researchers also looked to see how long the cancers responded to treatment:

  • 51% of the cancers that responded to the oral paclitaxel had the response last for more than 150 days
  • 38% of the cancers that responded to IV paclitaxel had the response last for more than 150 days

Progression-free survival was:

  • 9.3 months for women treated with oral paclitaxel
  • 8.3 months for women treated with IV paclitaxel

While progression-free survival was slightly better in the group treated with oral paclitaxel, this difference was not statistically significant, which means that it could have been due to chance and not because of the difference in treatment.

Progression-free survival is how long the women lived without the cancer growing.

Side effects

Compared to women treated with IV paclitaxel, women treated with oral paclitaxel had higher rates of:

  • gastrointestinal side effects
  • low white blood cell counts
  • infection

Still, women treated with oral paclitaxel had much lower rates of neuropathy — 17% compared to 57% for women treated with IV paclitaxel, and 8% of women treated with IV paclitaxel had severe neuropathy compared to 1% of women treated with oral paclitaxel.

Women treated with oral paclitaxel also had less hair loss than women treated with IV paclitaxel.

“This oral form of paclitaxel provides a new therapeutic option for patients, in particular, for those who cannot easily travel,” said Gerardo Umanzor, M.D., of Centro Oncologico Integral in San Pedro Sula, Honduras. “While blood counts still need to be monitored, oral administration allows patients to remain home during therapy, and avoid spending significant time in the chemotherapy unit. We were pleasantly surprised that responses were durable, conferring an early survival advantage with minimal neuropathy.”

What this means for you

If you’ve been diagnosed with metastatic breast cancer and are deciding on chemotherapy, the results of this study may sound very promising to you.

Still, there are some things to keep in mind:

  • The dosing schedule for the oral paclitaxel means that you can’t eat for 9 hours. This happens for 3 days in a row each week. At the media briefing, Umanzor did not discuss the long time people must go without food, but he did say that people were very excited to be able to have an oral treatment.
  • This study compared oral paclitaxel to IV paclitaxel given every 3 weeks. We know now that giving IV paclitaxel every week offers the same benefits as the every-3-week dose but causes fewer side effects. The results of this study only apply to IV paclitaxel given every 3 weeks. So, we don’t know how oral paclitaxel compares to IV paclitaxel given every week.

This form of oral paclitaxel also is not approved by the U.S. Food and Drug Administration yet, so if you’re interested in trying it, you would have to enroll in a clinical trial.

Stay tuned to Breastcancer.org for the latest news on oral paclitaxel and if and when it might be widely available.

Written by: Jamie DePolo, senior editor


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