"You smoked for years. Maybe you still do. Now that Medicare promises to begin covering lung cancer screening http should you sign up Thats a difficult question. The eligibility requirements seem fairly clearcut You can receive an annual lowdose CT scan if you are  to  years old have a smoking history of at least  pack years  meaning that you smoked a pack a day for  years or two packs a day for  and so on  and still smoke or quit only within the past  years. More than  million Americans will be eligible for screening the United States Preventive Services Task Force http an independent volunteer panel of national experts has estimated though many of those millions arent yet Medicare recipients. But screening will not help everyone who is eligible experts warn. Like any medical test or procedure it will subject some patients to harm.  How do you make a blanket coverage decision about something thats a good idea for some people and not so good for others said Dr. Michael Gould a pulmonologist and senior research scientist at Kaiser Permanente Southern California and a nonvoting member of Medicares coverage advisory committee. That committee voted last year against covering the procedure saying it found insufficient evidence of benefit. A few months earlier the preventive services task force had come to precisely the opposite conclusion and recommended annual screening httpannals.orgarticle.aspxarticleid which made coverage mandatory for private insurers but not for Medicare. Overriding its own advisory committee Medicare approved coverage http but decided to require  a first  a counseling and shared decisionmaking visit with a physician or other medical professional before reimbursement for a scan. Because the followup testing is invasive biopsies and such and lung cancer has such serious mortality and morbidity risks we wanted to ensure that Medicare beneficiaries were informed said Dr. Patrick Conway chief medical officer at the Centers for Medicare and Medicaid Services http Lung cancer overwhelmingly caused by smoking still causes more deaths than any other cancer http in part because it is hard to detect at more curable stages.  Unlike lumps in breasts for example nothing in your lungs allows you to sense the presence of a nodule or mass said Dr. Douglas Arenberg director of the lung cancer screening program at the University of Michigan Medical School. With treatment usually surgery  percent to  percent of patients with Stage  lung cancer and half of those with Stage  survive for at least five years. But most lung cancer is diagnosed when the disease is more advanced leading to lousy overall mortality rates Just  percent of all lung cancer patients survive for five years. Pulmonologists have tried for years to find ways to detect lung cancer earlier. Experiments using ordinary chest Xrays proved disappointing. Then in  researchers running the National Lung Screening Trial http involving  smokers and former smokers ages  to  reported encouraging findings Patients who received a lowdose CT scan annually for three years were  percent less likely to die of lung cancer http over an average of . years than those tested with Xrays. Those results led to the preventive services task forces endorsement and eventually to Medicares approval. Were covering evidencebased preventive services for beneficiaries which will save lives Dr. Conway said. How many lives While the overwhelming number of people with lung cancer are or were smokers most smokers dont develop lung cancer. So although a  percent reduction in mortality sounds impressive it represents a small number of people. In the national trial those screened with chest Xrays had about a . percent chance of dying from lung cancer http during the study period in the CT scan group it was about . percent. For every thousand people screened with a lowdose CT three fewer died of lung cancer. Lay people struggle to grasp these kinds of numbers. They look at me and say Doc just tell me what to do  Dr. Arenberg said. Or they give a howcanithurt shrug and opt in Maybe theyll be among the three in  saved. The problem is testing can cause harm too httpannals.orgarticle.aspxarticleid. First a high proportion of those tests will trigger a false alarm. CT scans cant distinguish well between small nodules that arent dangerous and those that become lethal. In the national trial close to  percent of participants got positive results from at least one of their three CT scans but more than  percent of these nodules werent cancerous. False positives usually require additional scans over several years to determine whether nodules are malignant. Meanwhile you have to be willing to live with that uncertainty Dr. Gould said. Worse some positive results require more invasive followup particularly biopsies which also have risks though low ones. Twenty to  percent of the time a biopsy causes a pneumothorax http or collapsed lung which usually heals on its own but occasionally requires hospitalization. Biopsies can also produce false negatives or dangerous bleeding. For older people the odds shift somewhat. Their cancer risk rises with age so the scan will detect more lung cancer httpannals.orgarticle.aspxarticleid according to an analysis of the national trial participants over age . But their rate of false positives rose too making invasive diagnostic procedures more likely. At older ages these procedures may not be trivial. Elayne Green a retiree in Boca Raton Fla. learned this in  when she was . Because shed smoked for  years before hypnosis helped her stop at  her health care provider recommended lung cancer screening. She agreed and paid  out of pocket. She wouldnt meet Medicare eligibility requirements now. The CT scan found a hot spot she was told. Regular followup screenings felt like a guillotine over my head she said. So Mrs. Green had diagnostic surgery called wedge resection which found no cancer but caused considerable pain.  I couldnt wear a brassiere for three months she recalled. Among the  to yearolds getting CT scans in the national trial moreover many had other serious health problems  heart disease diabetes hypertension pulmonary disease  which probably contributed to only  percent surviving five years compared with  percent among those under age . Researchers call it competing mortality httparchinte.jamanetwork.comarticle.aspxarticleid. Finding lung cancer is a hollow victory if patients endure testing and treatment then die of another illness before the cancer would have killed them. Most older adults especially smokers have multiple chronic diseases. If I find a teensy lung cancer in a yearold with heart disease I may not have done him any favor Dr. Arenberg said. In fact if screening finds cancer some seniors wont withstand the surgery usually a lobectomy http_index.html_rmoduleinline that may cure it. The postsurgical death rate in the national trial was just  percent but that involved major medical centers with specialized radiologists and surgeons  the ideal setting. Nationally deaths from this operation run two to four times higher and they increase with the patients age. And the trial provides no information on screening results for those older than . So those required shared decisionmaking visits with doctors will involve lots of very individual questions and judgments. Researchers are developing decision aids to guide physicians and consumers beginning to struggle with lung cancer screening. A University of Michigan team has put a helpful one online at shouldiscreen.com http And Medicare has established a registry to see how well largescale screening works. But it is worth remembering that however effective it is screening cant ward off disease. It only finds the damage already done. The only way to prevent lung cancer or reduce your risk Dr. Gould said is to stop smoking."