Core needle biopsy delivers accurate molecular evaluation of invasive breast cancer
Core needle biopsy (CNB) gives an accurate assessment of the molecular profile of invasive breast cancer and shows that the molecular evaluation does not need to be repeated with surgical specimen (SS), according to a Singapore study.
However, repeat tests with SS are done in cases where CNB is negative for oestrogen receptor (ER), progesterone receptor (PgR) or human epidermal growth factor receptor 2 (HER2/neu) and when cancer is shown to be weakly positive.
“CNB has high concordance with SS in the evaluation of the molecular profile of invasive breast cancer,” researchers said. “Thus, molecular evaluation does not need to be repeated with SS except for ER-, PgR- and HER2/neu-negative CNB results.”
A total of 560 patients were included in this study that analysed the concordance rate, sensitivity, specificity, positive predictive value (PPV) and negative predictive value of CNB and subsequent SS in assessing levels of ER, PgR and HER2/neu. The study also evaluated the revised American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines for ER/PgR positivity.
Researchers analysed the breast cancer database of KK Women’s and Children’s Hospital in Singapore from 1 June 2005 to 30 December 2012.
There was high concordance of ER (96.1 percent), PgR (89.1 percent) and HER2/neu (96.8 percent) positivity between CNB and SS. [Singapore Med J 2017;58:145-149]
When the “ER ≥10 percent positive” group was compared with the “ER ≥1 percent positive” group, specificity rose from 79.7 to 92.5 percent and PPV from 93.9 to 97.5 percent. When the “PgR ≥10 percent positive” group was compared with the “PgR ≥1 percent positive” group, specificity improved from 84.2 to 89.3 percent and PPV from 89.7 to 92.9 percent.
Since nearly three in four breast cancers are hormone receptor-positive, avoiding a repeat test with SS will lower the cost of medical expenditure for both the patient and hospital, according to researchers.
The revised ASCO/CAP guidelines also resulted in more precise ER and PgR status on CNB, with discordant results reduced by >50 percent for ER and by 18.2 percent for PgR.
“In other words, the revised ASCO/CAP guidelines have made the interpretation of CNB results more accurate and reliable in predicting both ER and PgR status,” researchers said.
“Although SS has traditionally been considered the gold standard for molecular profiling, ASCO and CAP jointly recommend the preferential use of CNB samples for ER and PgR testing; this recommendation is based on their empirical observations that CNB samples are more likely to fix better in formalin than SS samples,” they added. [Breast Cancer Res Treat 2001;69:13-9]
However, using CNB samples for molecular profiling has certain disadvantages. In previous studies, a tendency toward upscoring had been reported in CNB as compared to SS. This finding could be caused by the better fixation that was achieved with CNB as compared to SS. [Ann Oncol 2009;20:1948-52]
In addition, CNB samples are likely to crush artefacts, leading to false positive results. Furthermore, the biological profile of the tumour may not be accurately reflected by CNB, as sampling error may occur because of the heterogeneous distribution of the antigens within the tumour.