Date Published: June 3, 2019
Publisher: Public Library of Science
Author(s): Claudio Ceccarelli, Antonio De Leo, Pasquale Chieco, Claudio Zamagni, Alice Zamagni, Daniela Rubino, Mario Taffurelli, Donatella Santini, Fernando Schmitt.
Our goal has been to evaluate the importance that the incorporation of Bcl2 in the ER/PGR/Her2/Ki67 bio-profile can have as predictor of the Oncotype Dx categories.
156 consecutive cases of HR+/Her2- pN0/1 primary breast carcinoma were sent to the Oncotype Dx test. Immunohistochemical determination of Bcl2/ER/PGR/Ki67/Her2 expression was evaluated for each case. After the selection of the appropriate cut-off values for PGR and Ki67, explorative as well as confirmative statistical analyses were performed to build and validate predictive risk-of-recurrence immunohistochemical only bio-profiles.
The predictive capacity of these immunohistochemical profiles was compared with both traditional and TAILORx Oncotype Dx risk class classification. This comparison showed that immunohistochemical bio-profiles select those cases not associated with high risk-of-recurrence of disease (luminal-A/B and luminal A/B Bcl2) and those that are instead at high risk and therefore worthy of chemotherapy (luminal-B ki67 and luminal-B Bcl2/Ki67), strongly suggesting to only submit PGR-positive/Bcl2-Ki67 altered cases to Oncotype Dx, thus reducing the number of cases to be tested.
Our results indicate that the addition of Bcl2 to an immunohistochemical bio-profile definitely improves its predictive capacity to correctly select which cases to send to the Oncotype Dx test. We have also suggested that institutions with a significant number of breast carcinomas sent to the Oncotype Dx test can use these latter to derive their own PGR and Ki67 cut-off values, overcoming the drawbacks of sharing common inter-laboratory values. Validation of these bio-profiles as predictors of the Oncotype Dx categories is ongoing in a prospective series of new cases.
The most recent TNM AJCC classification (8th edition)  has defined breast cancer as a group of diseases with different molecular characteristics, and promoted the addition of specific biomarkers to guide personalized systemic therapies. In the light of this perspective, the determination of ER, PGR and Her2 expression using immunohistochemistry (IHC) or multigene panels is today part of TNM AJCC prognostic staging. Risk assessment is crucial to plan correct therapies in breast cancer, and in the light of this need, it is important to properly distinguish those Hormonal Receptor (HR)-positive/Her2-negative cases that required chemotherapy. This risk assessment has gained significant improvement by the introduction of Oncotype Dx molecular assay (Genomic Health, Redwood City, CA, USA). This molecular 21-gene assay quantifies the risk of distant recurrence at 10 years from diagnosis (Recurrence Score—RS) giving a retrospective (NSABP B14 and B-20) and prospective (TAILORx) validated indication of the potential benefit of chemotherapy for those HR-positive/Her2-negative N0 cases [2,3]. In addition, the Oncotype Dx report contains qRT-PCR results for ER, PGR and Her2, all of which are further classified using specific cut-off values.
The study was approved by the CE-AVEC (Comitato Etico—Area Vasta Emilia Centro) register n° 668/2018/Oss/AOUBo. All patients signed an informed consent permitting the use of the data necessary for the study.
Many studies already exist in literature disputing about a simpler predictive value attributed to immunohistochemical bio-profile as opposed to the most expensive but validated Oncotype Dx assay. Of note, at least PGR and proliferation emerge as main players from these studies [13,25,26], in accordance to the predominant role in the RS algorithm presented by Paik et al. . PGR IHC determination was already demonstrated equal to its Oncotype counterpart, especially when H-score method was used . Moreover, when its expression is classified into Negative vs Positive cases an overall concordance between PGR IHC and Dx ranging from 85.8% to 91.3% was reported [28–32], and an inverse relation with RS is also convincingly demonstrated [28–31,33]. Our results are in line with these previously reported observations. Linear regression analysis showed a good relationship between PGR IHC and its molecular counterpart (R2 = 0.731). Principal component analysis on Oncotype or IHC ER, PGR, Her2 and RS confirmed the strong inverse relation between RS and PGR [25,26], and multinomial logistic regression analysis demonstrated an independent association to RS predictive risk-of-recurrence value for PGR IHC. Estrogen Receptor seems to play a minor role in this situation also if a relationship between ER IHC and its Oncotype counterpart was reported . In our cases, the comparison between IHC and Oncotype ER and PGR values showed a relationship for PGR, but not for ER. Moreover, principal component analysis showing the absence of correlation between ER IHC and RS, suggests that the predictive role of ER IHC is irrelevant here, contributing this latter only to define cases as “luminal”.
In conclusion, we have shown that for the best selection of cases to be submitted to the Oncotype Dx test it is advantageous to add Bcl2 to the IHC bio-profile and to select on its own dataset PGR and Ki67 cut-off values tailored on Oncotype Dx results rather than to apply “prognostic” cut-off values. If these results will be confirmed in the new patient dataset being collected, the addition of Bcl2 to IHC bio-profiles will strongly suggest to submit only those PGR-positive Ki67 or Bcl2/Ki67 altered cases to Oncotype Dx test, and directly indicate the need of chemotherapy for those PGR-Negative Ki67 or Bcl2/Ki67 altered cases, showing this immunohistochemical bio-profiles as a useful pre-selection tool for Oncotype Dx referral at the time of pathological diagnosis.