P5-14-08: Impact of Progesterone Receptor Semiquantitative Immunohistochemical Result on Oncotype DX® Recurrence Score: A Quality Assurance Study of 1078 Cases.

Background: The oncotype DX® recurrence score (RS) is predominantly dependent on estrogen and progesterone receptor content of the tumor, proliferation and HER2 status. We have previously shown (Mod Pathol. 2008;21:1255–1261) that using a regression equation that incorporates the above along with tumor grade components is capable of estimating the RS [RS=13.424+5.420 (nuclear grade) +5.538 (mitotic count) −0.045 (ER immunohistochemical score) −0.030 (PR immunohistochemical score) +9.486 (HER-2/neu)]. Subsequent studies have also shown similar findings including a few that suggests an even more important role for progesterone receptor. In order to identify the role of semiquantitative progesterone receptor immunohistochemical (IHC) result in a simplistic manner, we evaluated the PR IHC score (H-score) for different categories of RS (low, intermediate, and high) within each tumor grade (I, II, III). Design: As a continuing quality assurance program at our institution, all cases sent for oncotype DX® testing that have available tumor grade, and RS were included in this study. Hormone receptor results at our institution are reported using an H-score like method which details the percentage of positive cells showing none, weak, moderate, or strong staining. The score is given as the sum of the percent staining multiplied by an ordinal value corresponding to the intensity level (0=none, 1=weak, 2=moderate, 3=strong). With four intensity levels, the resulting score ranges from 0 (no staining in the tumor) to 300 (diffuse intense staining of the tumor). Results: A total of 1078 cases were analyzed (see table below). Conclusions: Within each grade, PR IHC score is inversely related to the RS. The dramatic impact of PR IHC score on RS is noteworthy. If PR IHC score is combined with traditional histopathologic features (nuclear grade, mitotic activity score), and other IHC variables (ER IHC score, HER2 status, Ki-67 labeling index), then a tumor9s risk of recurrence and need for chemotherapy can be reasonably estimated. Oncotype DX® test may not be necessary in more than half of cases that are currently sent for testing. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-14-08.