A Promising New Treatment for ER-Positive Metastatic Breast Cancer

It is not fair yet to say that this new drug is a game-changer, but the results of a Phase I clinical trial of TTC-352 are very encouraging. The results were recently published in the journal, Breast Cancer Research and Treatment.

Having a new kind of breast cancer treatment that can fight the cancer without impairing our quality of life is very big progress.

Before getting into any details about TTC-352, let's quickly review the landscape of treatment for metastatic/Stage IV/advanced breast cancer. Women in this situation generally can expect to be on some kind of anti-cancer therapy for the rest of their lives. Any single treatment is used for as long as it is useful, and it is impossible to predict how long that will be for any one woman.

The catch is that cancer cells eventually become resistant to a drug, and their constant changes/mutations make it harder for drugs to be effective. There is a cliché: The dumbest cancer cell is smarter than the smartest doctor.

It is unfortunately true that the cancer always figures out how to outsmart the drug. The strategy for women and their doctors is to stay well as long as possible and to sustain the best possible quality of life. Making the best decisions about treatment, when to change medications and which ones to choose, always are tough and require thoughtful consideration and discussion, balancing the potential anti-cancer activity and the possible side effects.

Women with ER-positive breast cancers are usually treated with anti-estrogen/hormonal therapies for as long as possible. Since there are several — tamoxifen, AIs, faslodex, and new companion drugs — this strategy can last for years. It is always difficult when these drugs are no longer useful, and a woman must switch to chemotherapy agents that, inevitably, have more side effects.

Most, but not all, chemo drugs are given by infusion, so this switch also means that women have to spend much more time at the hospital than they did when taking the anti-estrogen therapies which are usually pills. No one wants to spend additional time at the Cancer Center, and it is also distressing to again be so clearly reminded of one's medical situation.

And this brings us to the good news about this new drug with the catchy name: TTC-352. Granted, we only have the results of a single Phase 1 clinical trial, but the early reports are encouraging. TTC-352 is used for women with ER-positive breast cancer whose cancer has stopped responding to the hormonal therapies.

In this first trial, 15 women with metastatic breast cancer who had been treated with hormonal therapies and, in some cases, chemotherapy, were treated with the new drug. Over the course of the trial, six women had stable disease with no progression, two women had no progression for 6 months, and four women were stable for 3 months. Clearly it would be better if these times were longer, but here is the positive news: even at the highest doses, there were no toxic side effects. This means nothing about taking this drug made women feel ill or impaired their quality of life. The conclusion is that TTC-352 is a safe and tolerable choice as an alternative to chemotherapy for women who have been already treated with hormonal therapies.

Any of us who have been treated with chemotherapy are well aware of the side effects and impact on our lives. Even if nausea is well controlled with meds and other side effects are minimal, we remember the general state of chemo fog and overall malaise. Even if we didn't feel terrible, we certainly didn't feel well.

Having a new kind of breast cancer treatment that can fight the cancer without impairing our quality of life is very big progress. I suspect that, following this early success, there will be other drugs developed with a similar profile, and we may be making real progress in the fight to stay as well as possible for as long as possible.