Researchers have found that although hormone therapy helps prevent growth of the prostate cancer, the treatment also changes its properties, thereby making the tumour more aggressive.
The new study from Sahlgrenska Academy showed that though treatment prevents growth of the tumour, it might make tumour more aggressive and more liable to form metastases.
According to the researchers, the hormone that is given causes the natural production of male sex hormone to fall, and the tumour stops growing. Pain also usually decreases.
The results showed that patients who have been given hormone therapy have higher levels of the proteins that enable the cancer cells to move through the body and attach to other organs.
One of these proteins is known as "N-cadherin", and this protein is present in higher levels in patients who have been given hormone therapy.
"Our results suggest that the tumour properties change following hormone therapy such that the tumours at a later stage can continue to grow and spread in the body," said pharmacist Karin Jennbacken, author of the thesis.
"For this reason, it is probably necessary to supplement the hormone therapy in order to compensate for these changes", Jennbacken said.
"We don't have any good treatment alternatives in cases where the tumour returns after hormone therapy, and this means that it is particularly important to study how such tumours are controlled and how they behave.
"The properties that we have identified may become targets for new anti-metastatic drugs in advanced prostate cancer", Jennbacken added.