Terrifying as the C word can be, breast cancer today means something very different than it did a decade ago. Doctors know more than ever about what causes cancer in the first place and when it’s best to screen for the disease as well as which cancers are more likely to spread aggressively and which may be able to be monitored and left alone. This knowledge will only grow more refined in the years to come, thanks in part to a handful of landmark studies launched this year.

Mounting evidence shows that the tendency to respond to every breast cancer with every treatment option available–surgery, chemotherapy, radiation–isn’t always necessary, takes a toll in serious side effects and rarely adds years to women’s lives. This is especially critical as doctors learn that not all lesions in the breast can spread–particularly those in Stage 0 breast cancer, or ductal carcinoma in situ–which calls into question the very idea of when a cancer really is a cancer.

“It’s very difficult to get doctors or patients to accept the fact that there is cancer that doesn’t need to be cured,” says Dr. Otis Brawley, chief medical and scientific officer of the American Cancer Society. But that’s what this new understanding of cancer is pointing toward.

Thanks to a more sophisticated view of what triggers cancer in the first place, more-detailed tools like 3-D mammography and MRIs, and genetic tumor tests that can predict the course of some cancers, the treatment options for women are better than they have been–and they will continue to improve. Ultimately, the goal is a more personalized approach to the cancer that affects nearly 250,000 U.S. women a year. Because no two breast cancers are alike, the way malignancies are detected and treated should reflect that. Here’s a closer look at the three major changes shaping breast-cancer care today and down the line.

Screening becomes more tailored

For decades, the mantra around cancer has been that early detection and early treatment save lives. That led to broad recommendations for all women to get mammograms once they reached age 40–and even earlier for women with a family history of the disease.

More recently, some public-health groups have changed their advice, saying most women can begin mammograms at age 50. In order to refine our understanding of who should start screening when, Dr. Laura Esserman, a breast-cancer expert at the University of California, San Francisco, will lead the WISDOM study, which will test a more targeted approach. About 100,000 women across the U.S. will be randomly assigned to either a personalized screening regimen–determining when to have mammograms according to a woman’s individual risk–or to annual mammograms. Their outcomes will provide insight into whether the current universal recommendations need an overhaul.

“Cancer is not just one disease,” says Dr. Shelley Hwang, chief of breast surgery at Duke University. “So the whole approach to cancer, including how we screen for it, has to change.”

There are new risk factors to know about

A disease as complex as breast cancer can result from a combination of factors, both genetic and lifestyle. Everything from the DNA you were born with to the changes in your genes that come from things like smoking, how much you exercise, your radiation exposure, what you eat and even how much you sleep can influence risk. Still, some factors appear stronger than others.

According to the American Cancer Society, as much as 75% to 80% of breast cancers may be tied to lifestyle choices and environmental exposures. (The rest can be traced to genes, including mutations in BRCA1 and BRCA2.) There’s plenty of evidence that women may be able to control a certain amount of their breast-cancer risk by maintaining a healthy weight, eating a healthy diet and getting regular exercise as well as refraining from smoking and from drinking too much. Eating a diet high in plants and healthy fats like olive oil and low in animal fats, for example, may reduce breast-cancer risk by as much as 60%, and regular exercise–the equivalent of about an hour a day–can lower it anywhere from 25% to 30%. In part that’s because a healthy diet and exercise reduce the risk of obesity, a major driver of many kinds of cancer. Experts suspect that body fat behaves like an organ and releases hormones, including estrogen, that can increase breast-cancer risk. That link has led doctors to recommend limiting estrogen therapy–during menopause, for example–to as short a time frame as possible.

But even with the riskiness of some lifestyles now well established, evidence is emerging that other factors appear to increase breast-cancer risk too. According to a growing number of epidemiological studies, as well as lab and animal research, exposure to various chemicals and toxins in the environment may increase the risk of getting breast cancer. Among the chemicals of concern are BPA–which is used in plastics and tin-can linings–and other hormone-disrupting substances found in household cleaners and personal-care products. Although there’s no direct evidence yet that these chemicals can actually cause cancer in humans, they have been linked to an increase in risk.

Personalization will change the avenues of treatment

Today the vast majority of women diagnosed with breast cancer receive surgery of some kind, radiation and chemotherapy, regardless of the prognosis or stage of their disease. “How do I know my cancer isn’t going to be the one that spreads?” is a question every woman grapples with, says Dr. Mehra Golshan, a cancer surgeon at Boston’s Brigham and Women’s Hospital. That’s why many women and their doctors choose to throw every treatment option available at their cancer. But that aggressive approach is, in many cases, overkill.

Difficult as it may be for doctors and patients to stomach, in some cases, women might be better off living with cancer–as long as it’s Stage 0 and under close supervision by physicians–than treating it. Duke’s Hwang is about to launch a study measuring the outcome of surgery with or without radiation against that of active surveillance with no immediate treatment; women with ductal carcinoma in situ will be randomly assigned to one study arm or the other. The trial, called COMET, will begin enrolling women this year. “Right now most women are still making the choice to do what’s aggressive, but I know these people are out there who want an alternative. So it will be interesting to see how many women participate in the study,” says Hwang.

For those with invasive cancers, there may be occasions where less is more. Increasingly, sophisticated genetic testing of tumors can not just identify genetic changes that might signal cancers that are more likely to recur but also predict how effective chemotherapy and hormone-based drugs might be against the tumors. These next-generation tests can help doctors choose a more personalized treatment course, sparing a patient unnecessary chemotherapy or extensive surgery.

This new approach challenges decades of messages from cancer experts that stressed that living with even a little cancer was too dangerous. “As our abilities to find even small lesions have improved, our definitions of cancer have moved from a 19th century definition to a 21st century definition,” says the American Cancer Society’s Brawley. “We understand the biological behavior of some of these smaller lesions may not be the same as the larger lesions we found in the past.”

Hwang is optimistic that more research will support that view. “It’s a very exciting time to be a breast-cancer researcher,” she says, “and on the flip side, there’s never been a better time to be a breast-cancer patient in terms of the good outcomes they can expect from treatment.”

This appears in the October 17, 2016 issue of TIME.

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