LONDON (AP) – Some breast cancer patients may do just as well with a less invasive surgery to remove selected lymph nodes rather than the aggressive operation normally used to remove them all, a new study says.

In the biggest trial yet to compare the two procedures, North American researchers found early breast cancer patients don't need the more interventionist surgery to live longer.

Most patients with such cancer have surgery to remove the disease. Doctors sometimes decide to get rid of all the lymph nodes to better control the cancer because if the disease spreads, it usually goes first to the nearby lymph nodes. Experts also think there is a relationship between the number of lymph nodes affected and how aggressive a cancer is.

But the invasive operation, an axillary-lymph node dissection, often comes with nasty side effects like nerve damage and reduced use of the arms and shoulders.

Doctors can use another surgery to remove only the first set of lymph nodes, or the sentinel lymph nodes under the arm, but many physicians have assumed the more aggressive surgery gives women a better shot at staying alive.

The study dealt only with victims of early breast cancer, not women needing a mastectomy.

US and Canadian scientists monitored 5,611 early breast cancer patients whose disease had not yet spread to their lymph nodes. About half were assigned to get both surgeries. The other half had operations to remove only some of their lymph nodes. Most patients in both groups also received other treatments like radiotherapy. After tracking the patients for eight years, doctors didn't find any difference in the patients' survival rates.

Among the 1,975 women who got both surgeries, 1,660 were alive after eight years. Among the 2,011 who only got a few lymph nodes removed in the less invasive operation, 1,675 were alive.