The group, which represents cancer specialists, said the new recommendations should also restrict the number of women who will require further removal of multiple nodes after biopsy, cutting down on painful side effects.
In sentinel lymph node biopsy, a few lymph nodes are removed and checked for signs of cancer -- hence the name "sentinel." Usually, if these lymph nodes have no cancer, it means the remaining, unchecked lymph nodes should also be cancer-free.
The new ASCO recommendations expand eligibility for sentinel node biopsy and will reduce the number of patients who undergo a more invasive procedure called axillary -- underarm -- lymph node dissection, which carries a higher risk of complications, the group said.
In axillary lymph node dissection, most lymph nodes under the arm on the same side as the breast tumor are removed and examined for cancer. This procedure can cause long-term side effects such as pain and numbness in the arm and swelling due to a build-up of lymph fluid.
The new guidelines state that for women whose sentinel lymph nodes show no signs of cancer, removal of more underarm lymph nodes is not recommended.
The guidelines also addressed the case of women who undergo lumpectomy instead of full mastectomy and are also scheduled for whole-breast radiation therapy to help "mop up" residual cancer. If these patients have signs of cancer in only one or two sentinel lymph nodes upon biopsy, they too may opt to avoid further node removal, the ASCO experts said.
Women who have undergone mastectomy but show signs of cancer's spread in sentinel lymph nodes should be offered further node removal, the guidelines reaffirmed.
The ASCO also said women who are diagnosed with certain breast cancers while pregnant can skip sentinel node biopsy.
The ASCO issued initial guidelines on sentinel node biopsy in 2005. The new guidelines, published March 24 in the Journal of Clinical Oncology, are based on the findings of a panel of experts who reviewed studies published between 2004 and 2013.
"The updated guideline incorporates new evidence from more recent studies -- nine randomized controlled trials and 13 cohort studies since 2005," panel co-chairman Dr. Armando Giuliano said in an ASCO news release.
"Based on these studies, we're saying more patients can safely get sentinel node biopsy without axillary lymph node [removal]," he said. "These guidelines help determine for whom sentinel node biopsy is appropriate."
Panel co-chairman Dr. Gary Lyman said, "We strongly encourage patients to talk with their surgeon and other members of their multidisciplinary team to understand their options and make sure everybody is on the same page."
"The most critical determinant of breast cancer prognosis is still the presence and extent of lymph node involvement," he said. "Therefore, the lymph nodes need to be evaluated so we can understand the extent of the disease."
Two breast cancer specialists welcomed the new guidelines.
"Over the past few years, there has been a movement to limit the amount of axillary [lymph node] surgery in patients undergoing breast conservation," said Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City.
Bernik said the new guidelines are important because some doctors have been reluctant to move away from further underarm node removal when a patient has even one affected sentinel node. "This update will give surgeons the confidence to tell patients that a sentinel lymph node biopsy may be enough, even if there is evidence of spread, in patients undergoing [lumpectomy]," Bernik said.
"However, it is still important for surgeons to discuss the pros and cons with a patient, as not all [real-world] patients fit the study criteria," she said. "Furthermore, it needs to be stressed that the more limited surgery does not apply to women undergoing mastectomies."
Dr. Debra Patt is the medical director of an expert panel that assesses cancer care guidelines for the US Oncology Network. She said she was "thrilled" at the new ASCO guidelines because they seem to echo the results of recent studies.
"In 2010, a study presented at the ASCO annual meeting showed that women undergoing breast-conservation surgery with clinically node-negative small breast cancers could safely avoid removing all the lymph nodes from under the arm in most cases," Patt said. "There has been greater variance in treatment patterns in my community practice, and I believe these updated guidelines will direct practitioners to evidence-based patient care."
The American Academy of Family Physicians has more about breast cancer.