Breast cancer patients with even the most minute spread of the disease to a lymph node have a much higher risk of it recurring years later and may need more treatment than just surgery, a new study by Dutch researchers suggests.

For years, doctors and patients have struggled with what to do about a microscopic tumour or stray cancer cells in a lymph node.

'For the first time, it suggests that isolated tumour cells or micrometastases do have biological significance.'— Dr. Daniel Hayes

Women with "micro tumours" usually are given estrogen-blocking drugs, chemotherapy or both; those with isolated cancer cells usually are not, because those were thought to be of low concern.

The new study challenges that view. It suggests that either type of metastasis, or spread, raises a woman's risk of having cancer show up in the breast or anywhere else in the next five years by about 50 per cent.

"This took an area that was very grey and I think made it black and white," said Dr. Linda Vahdat, director of breast cancer research at Weill Cornell Medical College and an adviser for the breast cancer patient website of ASCO, the American Society of Clinical Oncology.

'Our biases are wrong'

"I think it will influence treatment," Vahdat said of the study. "If we're considering treating the patient, we probably should."

Dr. Daniel Hayes, director of breast cancer treatment at the University of Michigan, agreed.

"It really does look like our biases are wrong," he said. "For the first time, it suggests that isolated tumour cells or micrometastases do have biological significance."

Vahdat and Hayes had no role in the study, which was done by researchers throughout the Netherlands. Results are in Thursday's New England Journal of Medicine.

The study is not ideal: It just observed a large number of women rather than assigning some to get treatment and comparing how they fared to others who were not treated. The study also was done at a time when treatment was less aggressive and in a country where doctors had been treating breast cancer more conservatively than in the United States.

In the U.S., many women with early stage breast cancer are given hormone blockers.

"The big issue is, should these patients also get chemotherapy?" Hayes said.

However, not all women benefit from chemotherapy even when their risk of a recurrence is high, said Dr. Eric Winer, breast cancer chief at the Dana-Farber Cancer Center in Boston.

"Patients are looking for more specific treatment" tailored to their individual tumour type — not necessarily more or less treatment, he said.

Tumour guidelines change

The Dutch study involved more than 2,700 women with low-risk, early stage cancer — small tumours that did not seem aggressive.

Weightlifting helps prevent painful arm swelling in breast cancer survivors, according to a second study in Thursday's New England Journal of Medicine.

Women who have had radiation to the armpit, or lymph nodes removed to check for cancer, can suffer lymphedema — a buildup of fluids that causes painful and unsightly swelling of the arms or hands.

The study looked at 141 breast cancer survivors who had suffered lymphedema. Half were told not to change their exercise habits. The rest were given 90-minute weightlifting classes twice a week for 13 weeks at community gyms.

They wore a custom-fitted compression garment on the affected arm and gradually worked up to more challenging weights and repetitions.

For the next 39 weeks, they continued these exercises on their own.

The women's arms were measured monthly. After one year, fewer weightlifters had suffered lymphedema flare-ups — 14 per cent versus 29 per cent of the others. Weightlifters reported fewer symptoms and greater strength. Rates of change in arm size due to swelling were similar in both groups.

Weighlifters in the study also made fewer trips to doctors or physical therapists for lymphedema flare-ups (77 versus 195), which could help save money, Wendy Demark-Wahnefried, of the University of Texas M.D. Anderson Cancer Center in Houston, said in a journal editorial.

All had surgery to remove their breast tumours. All of their armpit lymph nodes or a few key ones called "sentinel" nodes were removed and checked for signs of cancer. Doctors do this by examining tissue slices from the nodes and using special stains to make cancer cells show up.

Larger tumours in lymph nodes already trigger further treatment. A micro tumour is a cluster of cells less than two millimetres.

Most, but not all, doctors would treat these, too. Isolated tumour cells are even tinier — "you can essentially count them" in a tissue sample, Winer said — and do not typically spur further treatment under current guidelines.

The Dutch researchers compared patients based on whether they received treatment beyond surgery and whether cancer of various amounts was found in a lymph node.

In most cases, breast cancer doesn't return after surgery. Among women in the study who were given no additional treatment, 86 per cent of those with no cancer in lymph nodes were free of cancer five years later. Only 76 per cent of those with micro tumours and 77 per cent of those with isolated cancer cells were cancer-free.

That translates to a roughly 50 per cent greater risk of recurrence if any sign of cancer was present in a node.

Also, women with micro tumours or stray cells who were given additional treatment had a 43 per cent lower risk of a cancer recurrence than similar women not treated beyond surgery.

The differences should lead doctors to reconsider guidelines for how tumours are classified, which guides the amount of treatment a woman receives, the authors write. Now, a micro tumour is considered "node positive" cancer, warranting further treatment, while isolated cells are called "node negative."

A new version of the guidelines is due out soon, Hayes said.