It has been a year of significant advances as well as great upheaval in the world of health and medicine.
When major cancer screening guidelines were revised in both Canada and the United States, fierce debate broke out among cancer experts and advocacy groups. The public was left wondering what to do.
The first bombshell exploded south of the border. In October, the U.S. Preventive Services Task Force said healthy men should no longer get an annual PSA blood test, which can indicate the presence of prostate cancer. (In Canada, only some provinces cover the cost of the test, reflecting the ambivalence about its effectiveness.)
A month later, the Canadian Task Force on Preventive Health Care said most women in their 40s should not have routine mammograms to look for signs of breast cancer. And women over 50 should wait up to three years between tests, rather than the previous recommendation of every two years.
Advocates for wider screening were incensed, arguing that many people would die needlessly from cancer. Indeed, the guidelines seem out of step with the commonly held belief that early detection improves a patient’s chances of beating cancer.
Evidence from several decades of mass screening programs, however, has shown that neither mammograms nor PSA tests are perfect – and, in some cases, may do more harm than good.
A growing body of research has also revealed that not all cancers are the same – or equally deadly. In particular, tumours can be divided into three broad categories. Some are so slow-growing that they will never becoming life-threatening. Others are incredibly aggressive and no amount of treatment can stop them. And then there are those tumours that could be deadly – but may not be if treatment is started at the right time.
The problem with screening programs is that they pick up all three types of cancers – and doctors are not yet very good at distinguishing among them. That means some patients with relatively harmless growths undergo therapy and suffer its side effects.
In the case of prostate cancer, the treatment can damage the nerves and muscles of the bladder and penis. A man can be left incontinent, impotent, or both. Similarly, a woman with a benign breast tumour may receive unnecessary treatments including a mastectomy. Even if treatment isn’t undertaken, or a follow-up assessment indicates it was a “false” positive test, just the thought of having cancer can be extremely stressful.
To further complicate matters, significant advances have been made in mammography technology as well as digital imaging. So there is an increasing likelihood that a test will detect an extremely small, early-stage tumour. At the same time, researchers have developed more than 50 new cancer drugs in the past decade, noted Eitan Amir, a medical oncologist at Princess Margaret Hospital and Mount Sinai Hospital in Toronto.
Several decades ago, surgery was the main way of treating a lot of cancers – and it was considered critically important to remove a tumour before it had a chance to spread. But now patients have many more options and it’s no longer essential that a treatable cancer be detected in its earliest stage.
All told, these developments are changing the landscape of cancer therapy and the role of screening programs. Many experts think the PSA test is just too imprecise to be of much use as a mass-screening tool for prostate cancer. Mammography still has its place.
“Nobody believes that mammographic screening is completely useless. It has benefits, but it needs to be better targeted,” said Dr. Amir. “In other words, we need to be a bit better at giving these screening interventions to women who are most likely to benefit from them.”
Dr. Amir agrees with the new screening guidelines. But he expects it will take a while for the public to accept the idea that not all cancers are killers.
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