[73] The Effect of Radiation/Chemotherapy on the Immunophenotype of Soft Tissue Sarcomas

EC Miller, MA Stevenson, MC Gebhardt, ME Anderson, JD Goldsmith. Beth Israel Deaconess Medical Center, Boston, MA; Harvard Medical School, Boston, MA

Background: Many sarcoma centers treat with chemotherapy and radiation prior to definitive excision of intermediate or high grade soft tissue sarcomas (STS); this therapy is anecdotally thought to modify the immunophenotype of these tumors, thus making interpretation of immunohistochemical studies difficult in a post-therapy excision specimen. To our knowledge, however, there is no study that has systematically evaluated the effects of radiation and/or chemotherapy on the immunophenotype of STS.
Design: Patients with pretreatment core or incisional biopsies and post treatment excisions were found by searching the patient database in the department of radiation oncology. Both pre-therapy biopsies and post-therapy excisions were stained in the usual manner with common immunohistochemistry (IHC) stains used in STS (S-100, smooth muscle actin, desmin, screening cytokeratin [AE1-3/CAM 5.2], cytokeratin MNF116, CD34, and HMB45). Stains were examined blindly and separately and categorized as negative, 1+ (<10%), 2+ (10-50%), 3+ (50-100%) based on the fraction of tumor cells that were positive.
Results: Eleven patients with pre-treatment biopsies and post-treatment excisions were analyzed. Mean patient age at original diagnosis was 52 years (range 24-77 years). The female to male ratio was 2.8:1. There were 7 pretreatment core biopsies and 4 pretreatment incisional biopsies. 42 pairs of IHC stains were examined in total. If 1+ and negative, and 2+/ 3+ were grouped and compared, all pre and post-treatment results correlated except for 7 pre/post-treatment stain pairs (83%). However, if the negative and 1+ results were considered separately, 29 of 42 stain pairs (69%) showed correlation. The stains that did not correlate were not limited to particular antibodies.
Conclusions: The immunophenotype of STS shows some fidelity after treatment with chemotherapy and radiation. Based on the results of this pilot study, immunohistochemistry might be used with caution on tissue exposed to radiation and/or chemotherapy.
Category: Bone & Soft Tissue

Monday, March 9, 2009 9:30 AM

Poster Session I Stowell-Orbison/Autopsy Award # 16, Monday Morning