WASHINGTON: Treating cancer with surgery, chemotherapy or radiation may sometimes cause tumours to spread and US researchers said on Thursday they may have nailed down one of the causes – a compound called TGF-beta.

Tests in mice show that using the chemotherapy drug doxorubicin or radiation both raised levels of TGF-beta, which in turn helped breast cancer tumours spread to the lung.

But using an antibody to block TGF-beta stopped the process, Dr Carlos Arteaga and colleagues at Vanderbilt University in Tennessee reported.

Developing drugs that block TGF-beta might help prevent cancer from recurring, Arteaga’s team reports in the May issue of the Journal of Clinical Investigation.

“The repopulation and progression of tumours after anti-cancer therapy is a well-recognised phenomenon,” the researchers wrote. “It has been shown to occur following radiotherapy, chemotherapy, and surgery.”

Cancer experts have wondered if the so-called primary tumour – the first and biggest tumour – might somehow suppress the growth of other tumours, and that removing or destroying the first tumour might allow other, undetectable, tumors to then grow.

TGF-beta, which is involved in both the growth and suppression of tumours, may hold part of the answer, Arteaga’s team said.

When mice infected with human breast cancer cells were treated with radiation or doxorubicin, they had higher levels of TGF-beta in their blood. They also had more tiny tumour cells in their blood, and these cells metastasised, or spread, to the lungs. When the mice were treated with an antibody that suppresses TGF-beta, the spread stopped. And this spreading process did not occur at all in mice bred to lack the TGF-beta protein.—Reuters