Cavity Shave of Margins in Breast Cancer

Chagpar et al report on their article in NEJM the results of a 235 patients trial with breast cancer stage 0 to III who were undergoing partial mastectomy, with or without resection of selective margins, and further cavity shave margins resected.

The median age of the patients was 61 years (range, 33 to 94). On pathological testing, 54 patients (23%) had invasive cancer, 45 (19%) had ductal carcinoma in situ, and 125 (53%) had both; 11 patients had no further disease. The median size of the tumor in the greatest diameter was 1.1 cm (range, 0 to 6.5) in patients with invasive carcinoma and 1.0 cm (range, 0 to 9.3) in patients with ductal carcinoma in situ.  The rate of positive margins after partial mastectomy (before randomization) was similar in the shave group and the no-shave group (36% and 34%, respectively; P=0.69). After randomization, patients in the shave group had a significantly lower rate of positive margins than did those in the no-shave group (19% vs. 34%, P=0.01), as well as a lower rate of second surgery for margin clearance (10% vs. 21%, P=0.02).

The authors concluded that cavity shaving halved the rates of positive margins among patients with partial mastectomy.

N Engl J Med 2015; 373:503-510

Screening mammography has not saved lives

Harding, et al in their article published in JAMA Intern Med report on associations between screening mammography and the incidence and mortality from breast cancer, as well as tumor size.

A study of 16 million women 40 years or older who resided in 547 US counties reporting to the Surveillance, Epidemiology, and End Results cancer registries during the year 2000. Of these women, 53 207 were diagnosed with breast cancer that year and were followed up for the next 10 years.

Across the US counties, there was a positive correlation between the extent of screening and breast cancer incidence but not with breast cancer mortality. An absolute increase of 10 percentage points in the extent of screening was accompanied by 16% more breast cancer diagnoses but no significant change in breast cancer deaths. In an analysis stratified by tumor size, they found that more screening was strongly associated with an increased incidence of small breast cancers (≤2 cm) but not with a decreased incidence of larger breast cancers (>2 cm). An increase of 10 percentage points in screening was associated with a 25% increase in the incidence of small breast cancers and a 7% increase in the incidence of larger breast cancers.

They found that screening mammography results in the diagnosis of additional small cancers but no concomitant decline in the detection of larger cancers, which might explain the absence of any significant difference in the overall rate of death from the disease. Together, these findings suggest widespread overdiagnosis.