The one very subtle symptom of lung cancer you need to know

Lung cancer—not breast or uterine or ovarian cancer—claims more women's lives every year than any other type of cancer. One of the reasons is that there's no proven screening test for detecting early lung cancer, so the majority of patients (about 70 percent) are diagnosed once the cancer is advanced and has spread elsewhere in the body.

Back pain, headaches, weight loss, and fatigue are all typical symptoms of advanced lung cancer. Bone pain is also common, because that's where lung cancer tends to spread first, Andrea McKee, M.D., chairwoman of radiation oncology at the Lahey Hospital and Medical Center Sophia Gordon Cancer Center in Burlington, Massachusetts, tells SELF.

Symptoms of advanced lung cancer:

But while the majority of people diagnosed with lung cancer don't experience obvious symptoms in its early stages, some people may present with one really simple symptom early on: a chronic cough.

"Sometimes in the periphery [of the lungs] a tumor can just keep growing to a relatively large size before we'll diagnose it because it won't cause very many symptoms," Dr. McKee explains. But if a tumor is pushing on one of the bronchi, the major air passages going to the lungs, it will likely trigger the cough receptors. "It can trigger a cough even if the tumor is relatively small," she explains, if it's pushing on the right spot.

Being able to recognize this super subtle symptom can help you catch lung cancer in its beginning stages—which is crucial.

"There's a big difference in terms of survival between early detection and late detection when it comes to lung cancer," Dr. McKee says. In fact, the five-year survival rate for those diagnosed with late-stage lung cancer is under 10 percent. But when lung cancer is detected in its earliest stages, there's a 90 percent chance the person can be cured, Dr. McKee says.

A cough, though, is a very nonspecific symptom. And when you have one, cancer is not the first thing you think of (nor should it be). The common cold can persist for a few weeks, and if you have sensitive lungs, your cough may linger even after the runny nose goes away. "You don't need to necessarily be worried about lung cancer in that situation if it's associated with a viral illness," Dr. McKee reassures.

If you have a cough that persists for two or three weeks and is not connected to any virus or bacterial infection, you should see a doctor.

Also, if you're ever coughing up blood, see a doctor ASAP. "Some patients will cough up blood if the tumor is close to the bronchi," Dr. McKee explains.

Marlo Palacios, a 42-year-old lung cancer patient in Pasadena, California, was diagnosed after she saw her doctor for a persistent cough. "I developed a cough from what I initially assumed was a cold caught by my son," Palacios tells SELF. After a few weeks, the cough didn't go away. "I didn't want to make a big deal of it, so I didn't see my physician immediately. I had even made an appointment three weeks into the cough, but I cancelled it."

A few weeks later, she finally decided to see a doctor. "I had to come to terms that this cough wasn't going away and that it didn't feel as though it was from a common cold," she says. "The cough was dry, and it would come in intense waves. I would cough uncontrollably when this happened, to the point where I was gagging and couldn't catch my breath." After seeing a handful of doctors, she was diagnosed with stage IV lung cancer. "As a never-smoker, this was an initial shock to me and everyone in my life," Palacios says.

Ashley Rivas, a 35-year-old lung cancer survivor from Albuquerque, New Mexico, shares a similar story about her diagnosis. Her symptoms started as wheezing during exercise, and her doctor prescribed an inhaler for activity-induced asthma. "The medicine helped a little bit but never eliminated the symptoms," she tells SELF.

A few years later, Rivas developed a dry cough. At first, it was just "a lingering annoyance, but nothing that caused much concern," Rivas explains. Within the year, it became more aggressive. "It sounded hollow or drum like. It was coming from deep inside my chest and was very painful. It was worse at night and was accompanied with a fever." The coughing remained, but she never felt sick enough to see a doctor.

Eventually, Rivas went for an X-ray, and was diagnosed with pneumonia. A few weeks later, she was very fatigued and had a fever. She knew something wasn't right—finally, additional X-rays and tests revealed a cancerous tumor had been growing on her right lung.

At the end of the day, you can't go wrong with listening to your body and being cautious.

Seeing a doctor when something doesn't feel right will help you catch lung cancer—or any other health problem—early. While cough isn't the most common symptom of lung cancer, it can be one, and most of the time, happens early on. A chronic cough could also be a sign of acid reflux, asthma, or a side effect of medication, Dr. McKee says. "Those are all things you want your doctor to weigh in on." Even if it's not the worst-case scenario, you'll be glad you got treatment and finally kicked that pesky cough.