HOW MUCH ENDOCRINE THERAPY IS ENOUGH?

What is Endocrine Therapy?

Endocrine therapy, or hormone therapy, is treatment that tries to block or reduce circulating oestrogens which is what drives the majority of breast cancers. These drugs block or reduce the ability for the body to produce oestrogen which can reduce the risk of breast cancer returning.

Dr Belinda Yeo is a medical oncologist at the Olivia Newton-John Cancer Wellness and Research Centre in Melbourne, who is researching the level of therapy that breast cancer patients require to minimize toxicity and treatment. She was a guest speaker at the 2022 Breast Cancer Trials Annual Scientific Meeting, and we asked Dr Yeo to explain her research project on endocrine therapy.

“My research is predominantly in trying to better work out which patients need what therapy in breast cancer to try and minimize the toxicity that we give with our treatments.”

“Today’s talk was about looking at the data with regards to endocrine therapy in oestrogen driven breast cancers, and comparing the various drugs that we have, how long patients need to take them, their benefit, and of course what the cost for these treatments that actually go for many years.”

“So endocrine therapy, often people use this term interchangeably with hormone therapy, is treatment that tries to either block or reduce circulating oestrogens because the vast majority of breast cancer that we see is driven by oestrogen. So, these drugs actually either block or reduce the ability for the body to produce oestrogen, and both of those strategies reduce the risk of the cancer coming back.”

“Most women who are diagnosed with an ER-positive breast cancer, even if it’s a low risk one, will be offered a form of endocrine therapy, which are usually tablets, for many years.”

“How intensive that needs to be, and how long that needs to go for depends on their risk and most importantly depends on their tolerance to the drugs.”

How Much Endocrine Therapy is Enough?

“That was the topic of my talk but I’m not sure I quite got there. I think if I’m honest if I could answer that in one line, it’s whatever is enough for the patient. So, the data for endocrine therapy is probably best sitting at five years for most patients. But five years is still quite a long time to take these medications.”

“There’s certainly benefit even if they only take it for one year. One year is better than none. Two years are better than one and five years are in fact better than two. The question is beyond five years, the data gets a little bit less strong and there will be some women, particularly those at high risk of the cancer coming back, where longer therapy makes a difference.”

Rate of Toxicity vs Benefits of Treatment?

“I mean this is something that we discuss with patients every day and I’m sure that if you discussed this with patients, this is something that they’re dealing with on a day-to-day basis. So ideally what we would love is to be able to give a treatment that has minimal toxicity and massive benefit.”

“And in the case of endocrine therapy, there’s quite a substantial benefit. But I do believe that there is a quite substantial toxicity. Some of our drugs are better tolerated than others, but it’s up to I guess the individual patient because some side effects are felt by more patients and some patients remarkably can take these medications and go completely unscathed.”

“I think it really is an individual decision with the patient you have in front of you. For example, some patients will be very concerned about hot flushes, other patients might be very concerned about the risk of their bones thinning and the risk of fractures. And we all perceive these risks very differently. We do that day-to-day.”

“So, I think you have to have the discussion with the patient that’s in front of you to make the best decision.”

What Research and Clinical Trials are Happening in Endocrine Therapy?

“Yes, so, we’re still debating how long you need to go and how intensive you need to go. I guess one of the things we’ve recently seen in the last few years is, for young women, being more aggressive, so blocking virtually as much oestrogen as you can, does seem to make quite a substantial difference to their outcome.”

“The problem is that young women have a lot of oestrogen and of course blocking a lot of oestrogen means that you’re almost certainly going to get side effects. So, I think the research where we’re going now is to try and work out which women need that more intensive treatment, and of course then for how long? Because maybe you only need to do it for a few years and then you could stop or do something a little bit easier.”

“So, there’s some research in that capacity. I guess some of the other research that we still don’t quite know the answer to is when we’re looking at endocrine therapy and chemotherapy, it’s working out are the benefits with endocrine therapy above chemotherapy, and vice versa. Are the benefits of chemotherapy above endocrine therapy?”

“So that’s something that our trials are still looking at, particularly for young women, which is the theme of our meeting.”

Dr Yeo’s Hope for the Future

“Well, obviously I would love to not have to give any of this, and the drugs that we spoke about today are also very good at preventing breast cancer in the first place. Of course, prevention is always better than having to treat cancers, but most of us don’t really want to take a tablet for a disease that we haven’t had yet.”

“You know, we tend to only take something if we really need it and that’s the kind of the scenario of being diagnosed with breast cancer.”