- - Former “Bachelorette” Katie Thurston’s Oncologist Explains the Risk Factors for Breast Cancer in Young Women (Exclusive)

Kim HubbardFebruary 14, 2026 at 12:47 AM

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Dr. Julia McGuinness; Katie Thurston

Brooke Alexander (Studio Brooke); Michael Loccisano/Getty

For doctors who treat breast cancer today, there is good news and bad news: survival rates have risen dramatically in recent years, yet at the same time more women under 50 and even under 40 are being diagnosed. “We’re seeing an increase of one to two percent a year in these young onset cases,” says Julia McGuinness, an oncologist and Assistant Professor of Medicine at Columbia University Irving Medical Center who cares for patients with breast cancer and those at high risk of developing it.

McGuinness, who is former Bachelorette Katie Thurston’s oncologist, tells PEOPLE what every young woman should know about the disease. “A lot of my patients who are young come in and they say, ‘How did I get breast cancer?’” she says. “It’s important to raise awareness — and for everyone to know their own risk.”

How common is breast cancer in women under 40?

It’s about 4 percent of breast cancer cases, but young women are definitely getting breast cancer at higher rates than in the past.

Do we understand why?

Obesity is probably a significant contributor. Other things they’re looking at are later childbearing or earlier start of menstruation, as well as childhood nutrition and activity levels and whether that early environment sets you up for an earlier onset breast cancer. Everyone is looking at different environmental influences, but no one has really been able to pin it down.

Dr. Julia McGuinness

Brooke Alexander (Studio Brooke)

Does breast cancer present differently in younger women?

There are two differences. One is that women under 40 typically aren’t getting screening mammograms so they’re presenting with a symptom, which often means the cancer is at a higher stage — stage 2 or 3 or, God forbid, stage 4. The whole goal of screening mammograms is that you’re capturing cancer before you have symptoms, which typically corresponds to an earlier, more treatable stage. But there is also something different about the biology. More aggressive types of cancer are somewhat more common in young women, especially in minority women.

At what age do you suggest women begin getting yearly mammograms?

If someone is at average risk, they probably don’t need to start until age 40. We consider earlier mammograms for people who have a strong family history, specifically a family history of earlier onset breast cancer. We usually say you should start breast cancer screening at least ten years before the age when your earliest affected relative was diagnosed. And it’s not just family history that can bump up risk — as I mentioned there are things like not having a child until after age 30 or never having children and having dense breasts or prior breast biopsies. The threshold for being at high risk is at least a 20 percent risk of developing breast cancer over your lifetime. Average risk is about 13 percent.

How can you determine your personal risk level?

There are online tools like the Tyrer Cuzick risk assessment model. Using that could be lifesaving for people. Olivia Munn used a risk assessment tool and discovered that because of her family history she was high risk even though she had negative genetic testing. So, she had a screening breast MRI — and was diagnosed with breast cancer at a very early stage, even though a recent mammogram had not shown any signs of cancer. Everyone should try to become aware of her own risk, and if your risk is high — particularly if you have dense breasts, a strong family history or a genetic mutation—consider adding breast MRIs or ultrasound in addition to regular mammograms.

Katie Thurston PEOPLE Health cover

Allison Michael Orenstein

Do you recommend genetic testing across the board?

This is very controversial actually. For now, universal testing isn’t recommended, it’s still based on family history. But the problem is it’s not just a family history of breast cancer you should be aware of. It’s family history of things like ovarian, prostate, pancreatic, colon cancer. A lot of those actually can be linked by mutations and hereditary cancer syndromes.

Should women do monthly self-exams?

The guidelines don’t recommend them as breast cancer screenings — I think they don’t want people to think that’s sufficient compared to mammograms. But I still advocate for breast awareness — be aware of what your normal is. That can include monthly self-exams to notice when something is definitely different. Breast cancer can kind of present like anything: a painless mass, a painful mass. It can even just feel like the breast is swelling or bigger without a mass. You also want to be aware of any swollen lymph nodes in your arm pits and any changes like redness, swelling in the skin, nipple changes, nipple discharge. Any change, especially if it’s just in one side, should raise the alarm.

Is there anything women can do to lower their risk?

There’s actually a lot of overlap between the recommendations for breast cancer prevention and heart disease prevention. Maintaining a healthy weight, getting adequate exercise— moderate intensity exercise of 150 minutes a week or high intensity of at least 75. Also having a balanced diet, eating fruits and vegetables, eating fiber. And there’s increasing awareness that any amount of alcohol is potentially a carcinogen and increases your risk of cancers including breast and colon. In general, we say you want to limit your number of drinks per week to no more than 7. But the fewer the better, especially if you’re higher risk.

A lot of my patients who are young come in and they say, how did I get breast cancer? Unfortunately, there’s only so much you can do in life to control your health. But having the information, knowing your risk and seeing if you can do anything about it are important.

Doctor looking at a patient's mammogram

Getty

Are breast cancer survival rates improving?

Yes, and that’s true for younger patients as well as older. We have so many more advanced therapies now, newer treatments that are being approved every few months or more frequently. So, the survival actually has dramatically improved. It’s a completely different cancer than 20 or 30 years ago, even 10.

Do you think there will be a cure for metastatic breast cancer — cancer that has spread beyond the original site — someday?

For metastatic breast cancer it’s hard to promise a cure at this point, though I think we all hope for that. But I think women are going to be living longer as more treatments evolve and the disease becomes more chronic—something like diabetes, where you have to be on lifetime medication with the goal of controlling your disease for as long as possible with minimal side effects. I also think we’re going to see fewer and fewer women with early breast cancer having relapses, because we’re improving the treatments we give to prevent a recurrence that would then be metastatic.

And if I could just put in a plug for science: we have to keep doing the research. I’m so thankful for the persistence of the people doing it—I hope that despite all the changes in healthcare people are still inspired to go into this field. And I’m thankful for all the patients who have participated in clinical trials. It’s a huge leap of faith, one that takes courage, and it’s the only reason we have any of these advanced therapies.

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