Gina Kolata wrote a fascinating piece this week on the subject of The War on Cancer, first declared by President Richard Nixon back in 1971. The main focus of her article is how elusive a “cure” is turning out to be, and how expensive the search has become.
As she points out, over the past 50 years the age-adjusted death rate from cancer has fallen a mere 5%, despite the federal government having spent well over $100 billion on cancer research. Details of cancer research funding can be found here.
What really caught my attention, though, was not the fact that a “cure for cancer” is so elusive, but rather her acknowledgement that the public believes that cancer is almost always preventable, and that failing prevention, if caught early enough it is almost always curable.
To some extent, these ideas are true. Quitting smoking clearly decreases a person’s risk of developing lung cancer. But does this mean all lung cancer is preventable? No. As discussed in this recent article in the Journal of Clinical Oncology, 10% of lung cancer patients in the US have never smoked a cigarette. Lung cancer in never smokers (LCINS) is a distinct entity, with its own epidemiology, risk factors, molecular biology, and treatment outcomes. A focus on cigarettes as the major cause of lung cancer is appropriate, because 90% of lung cancer is smoking-related, and lung cancer remains one of the most common types of cancer in the US (lung cancer causes more deaths in women than breast cancer), but by focusing on smoking almost exclusively, are we complicit in making the public believe that all lung cancer is preventable?
Numerous other interventions have been proposed to decrease the risk of cancer, including low fat diets, high fiber diets, the use of antioxidants, taking vitamins – but rigorous testing has rarely shown a benefit to these lifestyle changes when it comes to cancer.
What about early detection? Localized cancer is clearly easier to treat than metastatic cancer, and some cancers are readily detected by screening (including breast cancer, colon cancer, and prostate cancer). However, some types of cancer, such as pancreatic and ovarian cancer, remain difficult if not impossible to detect by a screening program.
Does early detection by screening actually save lives? On the surface, it seems the answer would have to be “Yes.” But in reality, not every screening program saves lives. Two very recently published articles failed to demonstrate a decrease in prostate cancer-related death in men randomized to an intensive screening program compared with “usual care.”
How is this possible? The benefit to screening and early detection of cancer is based on the idea that cancer progresses in an orderly fashion from a pre-cancerous lesion to a localized tumor and finally to metastatic disease.
If a pre-cancerous lesion or a localized tumor is detected on a screening test and treatment is begun immediately, the belief is that metastatic disease can be prevented and lives will be saved. But what if some cancers are more aggressive than others and have already spread when the primary tumor is detected? Early detection of cancers like this will not change the disease-specific death rate (the death rate attributed specifically to cancer) because metastatic disease, which is what usually kills patients, will not be prevented from developing. What if the tumor that is detected is one that grows slowly and only rarely kills? Finding a tumor like this early may not save lives.
So does that mean screening programs don’t work? Not at all. But it does mean that such programs need to be rigorously tested. The introduction of Pap smears has had a profound impact on death from cervical cancer. Screening programs for breast and colon cancer have been shown to decrease cancer-related death from these diseases. However, screening for prostate cancer may not. Prostate cancer is a slow growing disease, and most tumors picked up by screening tests are small enough that they do not need to be treated – men with these tumors are more likely to die of something else (a heart attack or a stroke) rather than dying of prostate cancer. So finding this tumor early does not save lives. As future screening tests become available, they will need to be tested carefully to determine whether or not they should be widely applied.
What does all this mean? I think it means we as a medical community need to be very careful in how we discuss concepts like screening, prevention, and even treatment. Words are powerful. We need to choose ours carefully. We need to avoid complicity in misleading the public into believing that if they just eat right, exercise, and submit to a variety of screening procedures, they won’t die from cancer.
As Ms. Kolata also points out, “Research lurches from fad to fad — cancer viruses, immunology, genomics. Advocacy groups have lobbied and directed research in ways that have not always advanced science.”
Those of us involved in cancer research must continue to carry the fight forward, guided by science, so that one day cancer will be no more feared than high blood pressure.
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