Benefits of breast screening at age 70+

Written by Professor Alan Rodger, Director of Radiation Oncology, William Buckland Radiotherapy Centre, The Alfred, and Monash University Melbourne, the editorial states that, because invasive cancers detected by screening are smaller, less likely to involve lymph nodes, and more likely to involve fewer nodes, women with screen-detected invasive cancer will probably have a better prognosis and live longer.

"Professor Rodger's comments are made in the light of recent controversy about the value of screening mammography and whether it reduces mortality in women with breast cancer.

The editorial also comments on a recent systematic review of screening mammography in women 70 years and over, conducted from 1966 to July 2000 — the results of which are also published in the latest issue of the Medical Journal of Australia.

The review, by Dr Alexandra Barratt, Professor Les Irwig, and Dr Glenn Salkeld from the Department of Public Health and Community Medicine, University of Sydney, Professor Paul Glasziou from the University of Queensland Medical School, and Dr Nehmat Houssami, Director of the Sydney Square Breast Clinic, assessed the benefits, harms and costs of continuing mammographic screening for women 70 years and over.

The review's key findings were:

For women aged 70-79 years, the relative benefit of screening mammography was estimated as 40-72 per cent of the benefit of screening women aged 50-69 years, while in women over 80 years the benefit was about a third that of 50-69 year old women. With quality of life adjustment, these relative benefits reduced to 18-62 per cent and 14 per cent, respectively;

Of 10 000 Australian women participating in ongoing screening, 400 are recalled for further testing, and 70-112 undergo biopsy, with 19 - 80 cancers detected; and

Cost-effectiveness estimates for extending the upper age limit for screening from 69 to 79 years range from $8119 to $27 750 per quality-adjusted life-year saved.

Breast cancer mortality is known to rise steeply with age (from 21 per 100 000 among women aged 40 - 49 years to 117, 146, and 197 per 100 000 for women aged 75-79, 80-84 and 85 and over, respectively). The results of the review show that extending screening to women over 70 compares favourably with extending screening to women aged 40-49 years, the other group not covered by the national breast screening program.

"Age is the strongest risk factor for breast cancer, as indicated by the increasing number of cancers detected across age groups. However, because older women are at a higher risk of death from other causes, they may only experience the downsides of screening, and not live long enough to experience the benefits.

"Women who are likely to be bothered by screening attendance, who will be made anxious by follow-up investigations and who will not easily tolerate a diagnosis of breast cancer and treatment are less likely to benefit from screening," Dr Barratt said.

In conclusion, the authors said women 70 years and over, in consultation with their doctor, may want to decide for themselves whether to continue mammographic screening, suggesting decision-support materials are needed for women in this age group.

The Medical Journal of Australia is a publication of the Australian Medical Association.