Clinical practice guidelines are clear that sentinel lymph node biopsy (SLNB) is not warranted in most cases of ductal carcinoma in situ (DCIS). However, a sizeable and apparently growing proportion of patients do undergo this procedure, studies suggest, despite an increasing body of evidence detailing an increased rate of side effects and uncertain benefit.
That body of evidence now includes a relatively large retrospective cohort study showing that SLNB was not linked to significant improvements in recurrence, occurrence of ipsilateral invasive breast cancer, or mortality specific to breast cancer in nearly 13,000 women 67 years of age or older with DCIS that was amenable to breast conservation.
|Our study found that SLNB has no long-term benefits for older women with DCIS, and since the risk of complications are already known, therefore, SLNB should be avoided.|
|The research, just published in JNCI Cancer Spectrum, bolsters current recommendations to avoid SLNB when breast-conserving therapy is the initial treatment approach, according to investigator Shi-Yi Wang, MD, PhD, of Yale University, New Haven, Conn.
“Our study found that SLNB has no long-term benefits for older women with DCIS, and since the risk of complications are already known, therefore, SLNB should be avoided,” Dr. Wang said in a press conference.
These findings highlight the number of DCIS patients inappropriately undergoing SLNB today, according to breast oncology specialist Laura Esserman, MD, who was not associated with this study but also spoke in the press conference.
“I think the problem here is that people tend to think that more is better, but more is not better—it’s just more, and in this case more is worse, because you take the side effects without the benefits,” said Dr. Esserman, director of the UCSF Carol Franc Buck Breast Care Center.
|That lower-than-previously-reported 15.6% rate of SLNB in part reflects the older age of the Medicare beneficiaries in this study, but is nonetheless “shocking,” given that none of the patients in this cohort should have undergone the procedure.|
SLNB on the rise
Lumpectomy without lymph node surgery is recommended as part of primary treatment for many patients with apparent pure DCIS, according to clinical practice guidelines from the National Comprehensive Cancer Network (NCCN); by contrast, SLNB should be “strongly considered” in DCIS patients when mastectomy is intended, or if excisions are in locations that could compromise future sentinel lymph node procedures.
However, use of SLNB in DCIS remains controversial, with some proponents citing concerns that occult disease may not be detected histologically, according to Dr. Wang.
Rates of axillary evaluation do appear to be on the rise in DCIS patients. In one recent retrospective review of the National Cancer Data Base (NCDB), the rate of SLNB increased from just 7.2% in 1998 to 39.4% in 2011 in a cohort of 55,349 patients with DCIS who underwent breast conserving therapy.
“In most of the women in this cohort undergoing breast conserving therapy, we could not identify a clear indication for SLNB,” those investigators said in a 2017 report in BMC Surgery, noting that just 15.5% of the procedures could be accounted for by tumor location that would preclude sentinel lymph node mapping at a later date.
No benefit of SLNB in most DCIS
Some of the latest data on SLNB in DCIS, as reported by Dr. Wang and colleagues in JNCI Cancer Spectrum, included 12,776 women aged 67 to 94 years in the US Surveillance, Epidemiology, and End Results (SEER)-Medicare dataset who received a diagnosis of DCIS between 2001 and 2013 and underwent breast-conserving surgery.
There were no long-term benefits of SLNB for these DCIS patients over 5.8 years of follow-up, Dr. Wang reported. The long-term mastectomy rate was 3.9% with SLNB and 3.7% without; invasive breast cancer developed on the same side of the biopsy in 1.4% of cases with SLNB and 1.7% without; and breast cancer-related deaths were at 1.0% with SLNB and 0.9% without. None of those numerical differences were statistically significant, the researcher said.
In that cohort, SLNB was performed in 1,992 patients (15.6%). Factors linked to SLNB in this cohort included younger age, estrogen receptor (ER) positivity, comedonecrosis, larger or higher-grade tumors, and – echoing results of the BMC Surgery report – a diagnosis occurring in more recent years of the study.
“Shocking” result from “indication creep”?
That lower-than-previously-reported 15.6% rate of SLNB in part reflects the older age of the Medicare beneficiaries in this study, but is nonetheless “shocking,” given that none of the patients in this cohort should have undergone the procedure, said Dr. Esserman, the breast cancer expert.
“We shouldn’t even be looking for DCIS in people 67-94,” she said in the press conference. “That’s not the intention of screening, to be looking for a precancer in women over 65.”
Exactly why sentinel lymph node procedures were performed in these patients could not be evaluated based on the data set. However, Dr. Wang noted that for invasive breast cancers, SLNB has been included in the Merit-Based Incentive Payment System (MIPS) implemented by the Centers for Medicare & Medicaid Services.
“This might create a financial incentive for providers to perform sentinel lymph node biopsy, even for noninvasive conditions,” he said.
That undesirable dynamic would be a vivid example of “indication creep,” or promotion of an intervention beyond the target population or approved indication, Dr. Wang and co-authors said in their published report on the study.
The research on long-term outcomes of SLNB in DCIS in JNCI Cancer Spectrum was funded by an award from the Patient-Centered Outcomes Research Institute. Dr. Wang reported no disclosures, while coauthors provided disclosures related to Genentech, Eisai, Pfizer, Johnson & Johnson, and 21st Century Oncology.