Digital breast tomosynthesis (DBT) performs better than two-dimensional digital mammography (DM) as screening mammography in women aged 65 years and older; researchers report. “Tomosynthesis leads to the detection of more invasive (rather than in situ) cancers and fewer node-positive cancers; compared to conventional digital 2D mammography, suggesting that with tomosynthesis we are finding clinically important cancers at an earlier stage,” said Dr. Manisha Bahl of Massachusetts General Hospital in Boston.
Digital breast tomosynthesis
“The goal of screening mammography is to detect breast cancers early, when treatment is more effective and when there are more options for less-aggressive treatments;” she told Reuters Health by email. Breast cancer incidence and mortality rates increase with advancing age, but there are limited data on the benefits and risks of screening mammography in older women and on the relative performance of two-dimensional DM and DBT in these women.
Dr. Bahl and colleagues compared performance metrics between the two modalities among women aged 65 years and older, including 15,019 (mean age, 72.7 years) who underwent more than 30,000 DM examinations and 20,646 (mean age, 72.1 years) who underwent more than 41,000 DBT examinations. In the combined groups, the overall cancer-detection rate was 7.6 per 1,000 examinations and the abnormal-interpretation rate (AIR) was 5.7%.
The positive predictive value 1 (PPV1, the% of positive examinations resulting in a tissue diagnosis of cancer within one year) was 13.3%; PPV2 (the percentage of examinations recommended for tissue diagnosis or surgical consultation that resulted in a tissue diagnosis of cancer within one year); was 57.8%; and PPV3 (the percentage of all known biopsies performed as a result of positive examinations that resulted in a tissue diagnosis of cancer within one year) was 60.8%.
AIR was lower among women 80 years and older, sensitivity was lower in the 70-74 years and 80-84 years groups, and specificity was higher among women 80 years and older; compared with women aged 65-69 years. Cancer detection rates were similar between the DM (6.9 per 1,000 examinations) and DBT groups (8.2 per 1,000 examinations).
But the DBT group had a statistically significantly lower AIR (5.7% vs. 5.8%, P<0.001), higher PPV1 (14.5% vs. 11.9%, P=0.03), higher specificity (95.1% vs. 94.8%, P<0.001); lower false-positive rate (4.8% vs. 5.1%, P<0.001) and higher true-negative rate (94.3% vs. 94.1%, P<0.001). PPV2, PPV3, sensitivity and false-negative rates did not differ significantly between the DM and DBT groups, the researchers report in Radiology; online April 2.
There were similar trends in a subanalysis that included only women who underwent both DM and DBT. The DBT group had a higher proportion of invasive relative to in situ cancers (81.1% vs. 74.4% in the DM group); as well as fewer node-positive cancers (10.2% versus 16.6%, respectively); though these differences fell just short of statistical significance.
“Our study provides data about the risk-benefit ratio of screening mammography in the older population, and we hope that this information is used by patients; physicians, and policymakers to inform future guidelines,” Dr. Bahl said. “Since the benefits of screening mammography continue with advancing age; and the potential risks of false-positive examinations are lower with tomosynthesis; our study supports guidelines recommending that screening decisions be based on individual preferences rather than age alone;” she concluded.
Dr. Liane Philpotts from Yale School of Medicine, in New Haven;l Connecticut, who co-authored an accompanying editorial; told Reuters Health by email; “Older women in general have less-aggressive tumors, so what I found most interesting is that DBT did have an effect on finding more cancers with lower tumor stage. This is important as it permits less-aggressive treatment.”