Interval Cancers Are More Aggressive in Nondense Breasts vs Screen-Detected Cancers
In a Swedish study reported in the Journal of Clinical Oncology, Holm et al found that interval cancers in women with low mammographic density breasts were more aggressive vs screen-detected cancers in these women and vs interval cancers in women with dense breasts. Use of hormone replacement therapy and family history of breast cancer were associated with increased risk of interval cancers.
Interval Cancers in Women With Nondense Breasts
The study involved data on tumor characteristics (n = 4,091) and mammographic density (n = 1,957) from women diagnosed with invasive breast cancer from 2001 to 2008 in Stockholm.
Compared with 389 women with low mammographic density (≤ 20%) with screen-detected cancers, interval cancers in 100 such women had significantly higher rates of aggressive features, including higher frequencies of grade 3 disease (odds ratio [OR] = 3.43, 95% confidence interval [CI] = 1.44–9.16), estrogen receptor–negative status (OR = 4.05, 95% CI = 2.24–7.25), progesterone receptor–negative status (OR = 2.63, 95% CI = 1.58–4.38), HER2-positive status (OR = 5.17, 95% CI = 1.64–16.01), triple-negative status (OR = 5.33, 95% CI = 1.21–22.46), tumor size > 40 mm (OR = 4.90, 95% CI = 1.85–13.05), and lymph node involvement (OR = 3.55, 95% CI = 1.74–7.13).
Interval Cancers in Women With Denser Breasts
Compared with 197 screen-detected cancers in women with high breast density (> 40.9%), there were no significant differences in characteristics of 293 such women with interval cancers except for tumor size (OR = 1.53, 95% CI = 1.03-2.29, for 20–40 cm) and estrogen receptor–negative status (OR = 2.06, 95% CI = 1.11–3.82). The overall phenotype of interval breast cancers relative to screen-detected breast cancer was significantly more aggressive among women with nondense breasts (P = .004; P =.008 excluding histology).
Factors Predictive of Interval Cancers
Factors significantly associated with interval breast cancer vs screen-detected breast cancer after adjustment for age and mammographic density were family history of breast cancer (OR = 1.32, 95% CI = 1.02–1.70), current use of hormone replacement therapy (OR = 1.84, 95% CI = 1.38–2.44), and body mass index > 25 kg/m2 (OR = 0.49, 95% CI = 0.29–0.82).
The investigators concluded: “Interval breast cancers in women with low mammographic density have the most aggressive phenotype. The effect of [hormone replacement therapy] on interval breast cancer risk is not fully explained by mammographic density. Family history is associated with interval breast cancers, possibly indicating disparate genetic background of screen-detected breast cancers and interval breast cancers.”
Johanna Holm, MSc, of the Karolinska Institutet, is the corresponding author for the Journal of Clinical Oncology article.
The study was supported by the Swedish Research Council, Swedish Cancer Society, Stockholm County Council, and Cancer Risk Prediction Center. The study authors reported no potential conflicts of interest.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
