Breast Cancer: Where We Are and What’s to Come

Overall survival for breast cancer has improved by about 40% since the 1980s, thanks to improved screening and treatments.

“There are always more improvements to make along the way but the increase in survival is due to those efforts as well as increased advocacy and awareness of the disease,” says Columbia oncologist Katherine Crew, MD, associate professor of medicine at the Vagelos College of Physicians and Surgeons and a member of the Herbert Irving Comprehensive Cancer Center.

Crew spoke recently about advancements in the detection and treatment of breast cancer and the outlook for the future. 

How has genetic testing impacted treatment?

Back in the mid-1990s it was all about BRCA1 and BRCA2 mutations, but in the past several years, we’ve been testing for multiple genes that can predispose to breast cancer as well as other cancers. We’re able to sequence the whole genome much more cheaply and quickly than before. This has led to an increase in our understanding about genetic susceptibility to breast cancer.

We know if a woman has a genetic predisposition, she has the option for enhanced screening, with not just mammography, but more sensitive screening tests like breast MRI. If she has a high penetrance gene she may opt for prophylactic mastectomy.

With more moderate risk genes, it has become harder to know where to draw the line. We don’t want women to have unnecessary surgery that may be potentially harmful. I think we’re still learning what to do with that information.

There are many types of breast cancer. Can you give us the lay of the land of the main subtypes?

The subtypes of breast cancer all behave differently and we treat them differently. The most common is the estrogen receptor-positive breast cancer, which counts for about 70% of all breast cancers, and we know that these types of breast cancers respond very well to anti-estrogen therapy. More recently we’ve been using a class of drugs called aromatase inhibitors in post-menopausal women. In many ways that’s been one of the most effective targeted treatments that we’ve had for breast cancer; we see up to a 50% to 65% relative risk reduction in breast cancer relapse with these drugs.

There is HER2-positive breast cancer, and recently there’s been an explosion of new drugs for treating this subtype. Within just the past few years, at least four or five additional drugs have been approved for HER2-positive breast cancer. Although it is a more aggressive form of breast cancer, it is also a type of breast cancer that responds well and is very sensitive in general to chemotherapy and targeted therapy. Even in patients who have metastatic disease, women are living longer—sometimes for more than five years—with advanced breast cancer.

The most challenging type of breast cancer to treat is triple negative breast cancer, meaning that it is negative for the two hormone receptors—estrogen and progesterone—and for the HER2 receptor. We can’t treat it with anti-estrogen therapy and we can’t treat it with any HER2 targeted therapies. The main treatment option is chemotherapy, which has its own set of side effects associated with it. Recently there was drug approval for immunotherapy for triple negative breast cancer, particularly in combination with chemotherapy.

What are the other exciting areas of breast cancer research right now?

A big trend within oncology is the de-escalation of therapy. Can we spare some patients from unnecessary treatment? We don’t want to overtreat breast cancer. We want to treat the high-risk patients but the ones with a more favorable breast cancer, we want to spare them some of the side effects of chemotherapy, for example.

As we understand the biology of these tumors a little bit better, one breakthrough is that we can better classify patients. There are different molecular tumor tests we use now, including Oncotype Dx, MammaPrint, and breast cancer index, that give us the opportunity to personalize a woman’s breast cancer care. Based upon a woman’s tumor biology, we can assess who needs chemotherapy, who may benefit from extended hormonal therapy, who can do well with just five years of anti-estrogen therapy, and then we can spare them from a lot of the side effects that we’ve seen from some of these drugs.

How has screening for breast cancer evolved or changed?

For a long time we only had 2D digital mammography and now we have 3D mammography, or tomosynthesis. Rather than just having two views of the breast, 3D mammography produces serial slices of the breast. That can help to increase the sensitivity of the mammogram, particularly in women who have dense breast tissue.

We’re trying to move away from a one-size-fits-all for breast cancer screening. For most women who are not high risk, perhaps we can think about cutting back on mammography screenings. Under current guidelines, average-risk women can wait until 50 to get mammograms every two years, rather than yearly. Maybe less frequent screenings can also reduce some of the harms of screenings, like increased biopsies.

Closing thoughts?

More than anything else, having genetic information has really put more tools in our toolbox in terms of what we can offer patients.

The most exciting is this idea of precision medicine, both for prevention and for treatment, and using genetic information to assess breast cancer risk. Having the genetic information of the tumor tissue to assess the aggressiveness of the cancer and being able to tailor treatments specific for individual patients is what we are working towards.