An evaluation of national treatment trends for ductal carcinoma in situ from 1991 to 2010 and their impact on survival revealed “a substantial shift in locoregional treatment patterns for ductal carcinoma in situ,” Mathias Worni, MD, of Duke University Medical Center, Durham, North Carolina, and colleagues reported in the Journal of the National Cancer Institute. “The use of lumpectomy with radiation increased by almost 100%, whereas use of unilateral mastectomy dropped by 60%,” the investigators stated. Overall survival was higher for lumpectomy with radiation therapy than for mastectomy, which was higher than for lumpectomy alone.
These findings were based on 121,080 patients with ductal carcinoma in situ identified through the Surveillance, Epidemiology, and End Results (SEER) registry from 1991 to 2010. Overall, the greatest proportion of patients was treated with lumpectomy and radiation therapy (43.0%), followed by lumpectomy alone (26.5%) and unilateral mastectomy (23.8%) or bilateral mastectomy (4.5%), and 2.3% had no surgical treatment. There were, however, “significant shifts over time.”
The proportion of patients undergoing lumpectomy plus radiation therapy increased from 24.2% in 1991 to 46.8% in 2010. The proportion of patients treated with bilateral mastectomy increased from 0% to 8.5% during those years, which the authors noted was “likely driven by prophylactic contralateral mastectomy rather than by bilateral ductal carcinoma in situ.” The proportion of patients receiving no treatment increased from 1.2% to 3.2%. “In contrast, there was a statistically significant reduction in the rate of unilateral mastectomy (44.9%–19.3%) and lumpectomy alone (29.8%–22.3%, Ptrend < .001 for all groups),” the investigators reported.
Increase in Sentinel Lymph Node Biopsies
For patients undergoing mastectomy, the rate of sentinel lymph node biopsy increased from 9.7% in 1991 to 67.1% in 2010, and axillary dissections dropped from 62.9% to 15.3% (Ptrend < .001 for both comparisons). For those patients treated with lumpectomy, the rate of sentinel lymph node biopsy increased from 1.4% to 17.8%, whereas the rate of axillary dissections decreased from 14.2% to 2.8% (Ptrend < .001 for both comparisons).
“The low prevalence of node involvement in the setting of ductal carcinoma in situ and minimal impact of lumpectomy on feasibility of subsequent axillary surgery supports a more restrained use of sentinel node biopsy with lumpectomy for ductal carcinoma in situ,” the investigators commented. They pointed out, “current rate of axillary surgery overall, and of axillary dissection specifically, remains higher than indicated based upon the recent ASCO clinical practice guidelines and represents both a source of concern as well as a target for further education.”
Striking Regional Differences
The investigators also found “striking differences” by region in the rate of radiation use following lumpectomy. “Reasons for such geographical variation remain unclear and are of concern, as these data suggest that treatment decisions are much more strongly driven by the geography where the diagnosis was made, rather than by ductal carcinoma in situ disease characteristics,” the authors wrote.
“Compared with mastectomy, overall survival was higher for lumpectomy with radiation (hazard ratio [HR] = 0.79, 95% confidence interval [CI] = 0.76–0.83, P < .001) and lower for lumpectomy alone (HR = 1.17, 95% CI = 1.13–1.23, P < .001),” the researchers reported. The 10-year inverse probability weight–adjusted disease-specific survival was also highest for lumpectomy with radiation therapy (98.9%), followed by mastectomy (98.5%) and lumpectomy alone (98.4%). The greater differences in overall survival than disease-specific survival were “likely reflecting both a prevailing patient selection bias as well as clinically negligible differences in breast cancer outcomes between groups,” the authors noted.
“The choice of locoregional treatment had a strikingly small impact on breast cancer–specific survival, calling for a more thoughtful and restrained treatment approach for this disease,” the researchers concluded. “Consideration of an individual’s health and life expectancy as well as implementation of less invasive treatment options, including active surveillance in thoughtfully selected patients, could yield the greatest benefit and treatment-related harms for future patients diagnosed with ductal carcinoma in situ.” ■
Worni M, et al: J Natl Cancer Inst. September 30, 2015 (early release online).