Mammography:The hard truths behind the screen

As breast cancer rates continue to spiral upward (to 185,000 women in the US and 28,000 women in the UK every year), the pressure is on for women, particularly those over 40, to have regular mammograms.

* Do mammograms help to save lives? No. A Swedish study involving nearly 250,000 women found no survival advantage in women under 50 with regular mammograms (Lancet, 2002, 359: 909-19). Mammography also hasn’t helped save those under 60, according to the Canadian National Breast Screening study (Lancet, 2000; 356: 1087).

In 2002, US cancer experts in the Physician Data Query board (PDG) concluded there is insufficient evidence to show that mammograms prevent deaths (BMJ, 2002; 324: 432).

Also, by the time a mammogram spots a problem, the cancer is already around eight years old, according to Dr Samuel Epstein, a world authority on cancer.

Is it accurate? The latest research shows that more than one-third of mammograms give false readings, with a 64-per-cent rate of false positives (finding cancer present, when it isn’t) after 10 mammograms (N Engl J Med, 1998; 338: 1089-96).

The test is accurate less than half the time in the second half of a woman’s menstrual cycle (Cancer, 1997; 80: 720-4).

Mammography is crude, picking up many benign tumours that would do no harm if left alone. This can falsely raise the incidence of breast cancer by as much as one-half (Lancet, 1992; 339: 810). Routine screening could be behind the huge increase in aggressive treatment of ductal carcinoma in situ (40,000 cases in the US alone). This ‘cancer’ spreads, at most, in 20 per cent of cases (Breast J, 2000; 6: 331-4) and some pathologists report that it simply burns itself out.

Is it safe? No. Screening raises your risk of . . . cancer. Just four breast films (the usual for one session) expose you to 1 rad (radiation-absorbed dose) – about 1000 times more than a chest X-ray. Each rad increases a premenopausal woman’s cancer risk by 1 per cent, so screening for a decade will have raised cancer risk by 10 per cent. In addition, if cancer is present, the extreme compression during a mammogram can help cancerous cells to spread (Lancet, 1992; 340: 122).

What can you do instead? Examine your own breasts monthly and have a health professional do it annually. According to the American Cancer Society, 90 per cent of all cancers are found by self-examination. Women trained to examine themselves and who are also given yearly examinations by a trained health professional have the same odds as women given mammograms (Lancet, 2000; 356: 1087). Self-exams are also more accurate (N Engl J Med, 1998; 338: 1089-96).

If you need to have a lump checked out, a safer alternative without the dangers of radiation is ultrasound screening or thermal imaging carried out by an experienced operator.

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Written by What Doctors Don't Tell You

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