Abstract 82P
Background
Current guidelines do not recommend retesting biological parameters on breast cancer (BC) surgical specimens (SS) after an initial tumor biopsy (TB).
Methods
We retrospectively gathered data from the TB and SS of 193 BC specimens collected in the Pathology Department of the Policlinico “G. Rodolico - S. Marco” in Catania between 2012 and 2022. Patients receiving neoadjuvant treatment were excluded. Differences between TB and SS in estrogen receptor (ER), progesterone receptor (PR) and Ki67 were tested using paired t-test, while changes in HER2 immunohistochemistry (IHC) score, tumor grade and intrinsic subtypes (according to IHC values) were evaluated with the Wilcoxon rank-sum test.
Results
Mean ER and PR expression were 88% and 55% in TB and 89% and 59% in SS. Mean Ki67 value was 15% in TB and 16% in SS. HER2 IHC score was 0 in 119 TB vs 140 SS, 1+ in 31 TB vs 26 SS, 2+ in 41 TB vs 21 SS and 3+ in 2 TB vs 6 SS. Tumor grading was 1 in 41 TB vs 36 SS, 2 in 128 TB vs 112 SS and 3 in 24 TB vs 45 SS. PR and HER2 expression were significantly lower in SS compared to TB (p 0.008 and 0.007, respectively), while tumor grade was significantly higher in resected samples (p 0.0004). No differences emerged between TB and SS in terms of ER expression and Ki67. After surgery, intrinsic variants changed in 41 (21.2%) tumors. 25/61 luminal B-like BC were reclassified: 22 as luminal A-like and 3 as triple-positive cancers (p 0.0004). 15/119 luminal A-like cases were also reclassified: 13 in luminal B-like and 2 in triple-positive malignancies (p 0.0001). 1/7 triple-positive BC in the TB failed to confirm HER2-positivity in the SS. No changes occurred among HER2-enriched and triple-negative BC.
Conclusions
We detected a significant variability in PR, HER2 and tumor grading between TB and SS, while ER and Ki67 showed no significant differences. Moreover, a relevant proportion of tumors were reclassified in different variants after surgery, with the greatest variability observed among luminal B-like tumors. While our findings require confirmation in a larger cohort, initial results indicate that reassessing biological parameters on SS after an initial TB may have meaningful prognostic and therapeutic value.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
G.M. Vecchio: Financial Interests, Personal, Invited Speaker: Daiichi Sankyo. F. Martorana: Financial Interests, Personal, Invited Speaker: Pfizer, Novartis, Lilly, Istituto Gentili; Financial Interests, Personal, Advisory Board: Amgen; Financial Interests, Personal, Other, Travel grant: Roche; Financial Interests, Personal, Invited Speaker, Travel grant: Gilead. P. Vigneri: Financial Interests, Personal, Invited Speaker: AstraZeneca, Lilly, Gilead, GSK, Istituto Gentili, Novartis, Teva, Pfizer; Financial Interests, Personal, Research Grant: Pfizer, Novartis. All other authors have declared no conflicts of interest.