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HER2-low is less aggressive than HER2-positive and HER2-negative, but the new designation allows for targeted therapies that may be helpful
A diagnosis of breast cancer is typically followed up by a need for answers. How fast will it grow? How fast has it grown? What kind of breast cancer do you have? What kind of treatments can you do? And what can you expect in terms of survival?
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These questions and more come up quite often. If you’ve been diagnosed with HER2-low metastatic breast cancer, you might have more specific questions about what exactly that means and what you can expect considering it’s a relatively new designation for breast cancers.
Palliative medicine specialist Nivia Ruiz, MD, shares how HER2-low is different from HER2-positive breast cancers, along with ways your life may change when you’re living with this type of cancer.
HER2-low breast cancers have low levels of human epidermal growth factor receptor 2 (HER2) proteins. These proteins are responsible for breast cell growth and repair. Having a HER2-low diagnosis doesn’t mean you don’t have HER2 proteins or HER2 gene expression — it just means there isn’t enough of these proteins or gene expression for the cancer to be classified as HER2-positive breast cancer.
Healthcare providers use two tests to diagnose and determine an HER2 status:
Historically, the results from these tests would go one of two ways:
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Now, healthcare providers are looking more closely at HER2-low: People who fall within these ranges and have an IHC score of 1+ or 2+ with a negative FISH test result. The reason? More than half of people with breast cancer fall into this HER2-low category, and HER2-low breast cancers can rely on targeted therapies even when they’re considered triple-negative because of the presence of HER2 receptors.
“That’s an important distinction because triple-negative cancers tend to have the worst prognosis because they often spread first to your organs like your lungs, brain or your liver,” explains Dr. Ruiz. “Triple-negative cancers also don’t have the same targeted therapies, so you have fewer chances of responding to treatments if you don’t have those hormonal receptors. With HER2-low, we’re able to target those receptors more effectively.”
HER2-low is an aggressive, fast-growing breast cancer. And like HER2-positive and HER2-negative, HER2-low breast cancers can metastasize or spread to other areas of your body, like your brain or bones, in advanced stages.
For example, we know that up to half of the cases of HER2-positive metastatic breast cancer can spread to the brain over the course of its progression. A Turkish retrospective study from 2022 showed higher rates of brain metastases for people with HER2-low compared to HER2-negative and HER2-positive, but more research is needed to show how HER2-low spreads and how quickly it evolves compared to other cancers.
A retroactive study of 3,500 women in Iran found that people with HER2-low had a better survival rate and less aggressive traits compared to those who had HER2-positive.
Still, a 2024 analysis of 24,636 people diagnosed with metastatic breast cancer between 2008 and 2015 found that half of all patients were still alive after 43.7 months (or 3.5 years). In that same study, researchers found that one-third of people with HER2-low who were hormone receptor-negative and less than half of the people with HER2-low who were hormone receptor-positive were still alive within three years.
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“If you’re hormone receptor-positive, you may respond better to targeted therapy because we can target specific hormonal receptors of the cancer,” explains Dr. Ruiz. “If you don’t have a targeted therapy or a specific treatment for your cancer, you may have to go on general treatments like chemotherapy.”
The U.S. Food and Drug Administration approves Enhertu® (fam-trastuzumab-deruxtecan-nxki) as a targeted treatment for HER2-low that can’t be removed by surgery or has spread to other parts of your body. It’s also approved for those who’ve already received chemotherapy for:
Although research suggests that up to 10% to 15% of people who take Enhertu can develop interstitial lung disease as a side effect of treatment, research has also shown that people with HER2-low metastatic breast cancer can live nearly twice as long without the cancer growing, and up to six months longer overall. This new foray into targeted therapy for HER2-low suggests further research is needed to see what other targeted therapies may be effective.
Understanding what it means to have HER2-low metastatic breast cancer and how it will affect your life can be a big undertaking. For some, it might take a little time to take it all in and process the information before knowing what kinds of questions to ask your healthcare provider. For others, the questions to ask your provider might come more easily and can include ones like:
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“The questions you ask depend on how much you want to know as a patient,” says Dr. Ruiz. “When you get a diagnosis for cancer, regardless of what kind it is, it’s a big impact. There are a lot of resources and answers we can provide as questions come up for you at any stage of the process.”
When you’re living with HER2-low metastatic breast cancer, the goal of treatment is to slow down the speed and spread of the cancer growth, reduce the severity of your symptoms, improve your comfort and quality of life, and prolong your life as much as possible. There’s no cure for metastatic breast cancer, which means your life will likely take on a new reality in a few different ways.
“It’s very important for people living with cancer to modify their lives around this new reality so they can still regain control of what that is so they can have a better, positive outlook,” notes Dr. Ruiz. “Just because research says the median survival rate is around three years, that doesn’t mean that’s for you. It could be different. So, you have to focus on what you can do to continue living.”
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Here are some areas to focus on after receiving a diagnosis of metastatic breast cancer:
From day one, you’ll want to think about who you have as part of your support system — like family, friends, neighbors, healthcare providers, instructors and social workers. Together, this team of individuals can band together and help you at every step of the way, from getting you to and from your appointments to providing meals, helping with childcare and spending quality time together. Finding community with others who share your diagnosis can also be empowering and helpful.
“A lot of times, people don’t know when to ask for help, or they feel ashamed they’re going through this journey and feel as if they need to go through this alone because they don’t want to be a burden on their family,” empathizes Dr. Ruiz. “When you’re so focused on starting treatment, you don’t often think about how it’s affecting you on a deeper level and it may be difficult to open up at first. But mental, physical and emotional support should be something that’s talked about from day one.”
Weight loss can be an unwanted side effect of cancer and cancer treatment. To prevent unnecessary weight loss, healthcare providers may advise you to try and gain weight or work with a registered dietitian and nutritionist to make sure you’re getting enough nutrients during treatment. That said, you don’t have to give up the things you love like a sweet treat every now and then either.
“There’s no evidence that eating sugar can worsen your cancer,” shares Dr. Ruiz. “Eat as healthy as possible but enjoy the experience. If you’re losing weight, you want to try to regain those calories and maintain your weight so you can tolerate your treatments.”
For some, a career and employment can be a source of empowerment. If continuing to work is important to you, you can and should keep working for as long as you’re able and comfortable doing so. In some situations, you may have to modify some of your working responsibilities like changing your hours, dropping down to part-time or switching to less physically taxing responsibilities. But it comes down to knowing what you can handle physically, mentally and emotionally and what’s right for you during treatment.
“Being able to work comfortably gives someone a sense of control as long as they feel well and the treatment isn’t giving them side effects,” explains Dr. Ruiz. “If you feel like you’re having more bad days than good days, then maybe you can ask for medical leave, apply for the Family Medical Leave Act (FMLA) or other accommodations.”
Financial assistance is also available through the Cancer Financial Assistance Coalition and other nonprofit organizations, or you can apply to federal Social Security programs that offer additional disability benefits.
Social workers are a big resource you’ll be connected to early on who can help you with a number of things, like financial assistance, social support, community networking and transportation to and from appointments.
“If you don’t have much family nearby, or you don’t have anybody to take you to your appointments and you have multiple appointments, it can feel burdensome and stressful,” recognizes Dr. Ruiz.
“So, we can set you up with transportation to any appointment, not just to your oncologist, but for your infusions and treatments, when you go in for blood work, when you touch base with your doctor or nurse practitioner, your dietitian or nutritionist, your psychologist or psychiatrist, or even when you’re getting a CAT scan, an ultrasound or an MRI of the breast. It can feel overwhelming, but that’s why we help.”
In between appointments, you’ll want to monitor your symptoms and keep track of any changes in your weight or any new symptoms that you experience. Every couple of months, your healthcare provider will request a new series of diagnostic tests and blood work to make sure treatment is working and to monitor the progression of your cancer.
This is also where palliative care can become an important piece of the pie, as they can work with you to make sure your needs are met — not just physically, but emotionally and mentally, too.
“We can help with symptom management and make sure your mental health is OK,” says Dr. Ruiz. “It’s OK to ask for help if you’re feeling anxious or down or if you’re having a bad day. We’re here to make sure you have a support system and have people to talk to.”
Coming to terms with how your life expectancy may change is perhaps the hardest part of this process. But rather than focus on how much time you do or do not have left, Dr. Ruiz advises focusing instead on how you can make the most out of the life you do have.
“Treatment is designed to prolong your life for as long as possible,” she notes. “So, it’s important to plan ahead of time, talk to your loved ones about what’s important to you and take it one day at a time. It’s OK to take time to yourself when you want to be alone. It’s OK to be with friends and family when you want to. It’s OK to have a bad day.
“Sometimes, it’s about having the recognition that you’re not always going to have good days moving forward, but what can you do with the good days you do have and how can you adjust when you have a bad day?”
For example, if you once ran three miles a day and now find yourself only going on walks or running a half-mile twice a week instead, those modifications can still be viewed as successful for a life with cancer, illustrates Dr. Ruiz.
“A lot of it is about self-care and focusing on the things you can do,” she encourages. “Your will to live is actually correlated with prognosis, too, and patients have better outcomes when they have a more positive mindset.”
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