Results of a retrospective study evaluating multiple characteristics of a cohort of individuals with untreated estrogen receptor-positive, HER2-negative invasive breast cancers showed a broad range of tumor growth velocities across patients. These findings were published in Breast Cancer Research and Treatment.
Only very limited data on the natural growth history of untreated breast cancer have been collected during the recent, post-breast cancer subtyping era.
This study examined the in-vivo tumor growth kinetics for patients presenting with “missed” ER-positive, HER2-negative invasive breast cancer that had been present, but unidentified, on 1 or more previous serial screening mammographic images performed at least 6 months prior to the diagnosis of breast cancer. Changes in tumor volume over time (ie, tumor growth velocity) and tumor doubling time were estimated for these tumors.
Through secondary review of mammographic imaging data from a single institution, 36 newly diagnosed, ER-positive, HER2-negative invasive breast cancers that met study specifications were identified by 1 of 2 radiologists. Tumor biopsies were available in all of these cases, and the masses of tumor on prior screening mammographic images were measured in 2 or 3 dimensions. The rate of change in tumor volume was measured in units of mm3/day.
In the study cohort, the median patient age was 70 years, and the median tumor volume at breast cancer diagnosis was 1241 mm3. The median delay between first appearance of breast cancer tumor on mammographic imaging and diagnostic breast cancer imaging was 689 days.
While tumor growth velocity was significantly associated with pathologic tumor size (P =.001) and tumor grade (P =.043), it was not associated with patient age, pathologic nodal status, the Oncotype DX score of the tumor, or diagnostic delay time, among other parameters.
At a median follow-up of 689 days, 64% of tumors doubled in size, with a median tumor volume doubling time of 385 days. Median tumor growth velocity was 0.8 mm3/day, although a wide range of tumor growth velocities was observed, spanning -0.4 mm3/day to 24.3 mm3/day.
The study authors noted that these results “demonstrated a variation of in-vivo growth kinetics in an untreated subset of breast cancers and found that the volume change over time could not be predicted.”
They further commented that these results show that more difficult-to-measure factors such as host immune response, tumor microenvironment, and molecular heterogeneity may play a larger role than solely tumor subtype.
Rojas KE, M D-M, Rojas M, et al. The natural history of untreated estrogen receptor-positive, Her2-negative invasive breast cancer. Breast Cancer Res Treat [published online May 12, 2020]. doi: 10.1007/s10549-020-05666-7