The longer women wait for radiotherapy after breast cancer surgery, the greater the risk their disease will come back, scientists said on Wednesday, in a study likely to pressure health services to cut waiting times.

Researchers from the United States, Canada and Japan studied links between waiting times for radiotherapy after surgery and recurrence of breast cancer, and said their results suggest the best option is to start radiotherapy as soon as possible.

Since breast cancer is the most common women’s cancer, this could add “substantial” costs, they said - a factor that would need to be weighed against a relatively small reduced risk of breast tumours coming back.

“The cost of increasing capacity to ensure uniformly short waiting times could be substantial,” Rinaa Punglia of the Dana-Farber Cancer Institute in Boston, wrote in the study in the British Medical Journal.

“But given the known negative impact of local recurrence on overall survival and the large numbers of women treated with radiotherapy for breast cancer, it seems appropriate to consider whether this is a price we should be prepared to pay.”

Punglia’s team analysed national cancer records for more than 18,000 American women who were diagnosed with early stage breast cancer between 1991 and 2002 at age 65 or older. All women had surgery and radiotherapy, but not chemotherapy.

The results showed that starting radiotherapy more than six weeks after surgery was linked to a “modest but significant increase” in tumour recurrence. Around 30 percent of the women in the study started radiotherapy after six weeks and tumours had come back in 734 (4 percent) of them at five years.

Breast cancer is the most common cancer in women worldwide, accounting for around 16 percent of all female cancers.

It kills around 519,000 people globally each year, and the World Health Organisation says survival rates vary widely from more than 80 percent in the United States, Sweden and Japan to under 40 percent in low-income countries.

The researchers said four to six weeks is generally accepted as a reasonable interval between cancer surgery and radiotherapy, but evidence on the effect of waiting times on breast cancer patients had until now been unclear.

In a commentary on the study, Ruth Jack and Lars Holmberg from King’s College London said healthcare providers should invest and plan ahead to reduce delays between surgery and radiotherapy, but needed to keep a keen eye on costs.

If big investments were needed, they said, the relatively small benefit seen in the study would have to be weighed against other priorities in cancer care.

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* Longer waits mean higher risk of tumours coming back

* Experts says cutting delays may mean “substantial” cost

* Costs to be seen against better outcomes, other priorities

By Kate Kelland

LONDON (Reuters)