WASHINGTON (Reuters) — Scientists who have proposed a controversial theory that surgery to remove a breast tumour may actually help the cancer to spread said on Wednesday their ideas may also explain why black women have been more likely to die of breast cancer in the past.While they stressed that women should always get screening and quick treatment for breast cancer, they said their theory could also help explain the belief, widespread in parts of Africa and the United States, that removing a tumour can hasten death.

“I must say that I am sure there is more to this than just a myth,” said Michael Retsky of Children’s Hospital and Harvard Medical School in Boston. His latest hypothesis, which he admits is not supported by any new direct research, is published in the International Journal of Surgery.

He stressed that any woman with breast cancer should get the tumour removed. And he noted that in the United States, the women who could be considered at risk of having their cancer spread now get chemotherapy anyway, which would stop cancer’s spread.

“At this time we are not suggesting any change in clinical practice. We think this is a subject that needs far more research,” Retsky, who has worked with other scientists in South Carolina and Italy, said in a telephone interview. The American Cancer Society also stressed that women should always get mammograms, and questioned the theory.

“No woman should delay getting treatment for breast cancer,” oncologist Dr. Len Lichtenfeld of the American Cancer Society said in a telephone interview.

“What we do know ... is that by early detection, we find the cancer early, we have less risk of lymph node involvement, we have greatly improved the outlook for women with breast cancer,” Lichtenfeld added.

“Whether or not the theory is correct, I have difficulty with the logic that they employed to get there.”

Retsky and colleagues studied several databases on women who have had breast cancer surgery. They published one study in 2005 suggesting that surgery might cause the activation of tiny tumours that had already spread. Retsky believes there may be two mechanisms at work. One idea is that surgery itself, by wounding the body, causes it to produce growth factors that fuel the growth of the other, tiny tumours. The other holds that a primary, or main tumour, secretes some sort of factor that holds the other tumours in check.