[1862] Comparison of Histologic Grading Schemes for Response to Neoadjuvant Therapy in Pancreatic Adenocarcinoma (PDAC)

Madelyn Lew, Theodore Hong, Vikram Deshpande. Massachusetts General Hospital, Boston, MA

Background: Pancreatic ductal adenocarcinoma (PDAC) is known for poor survival rates despite treatment with neoadjuvant therapy. Other gastrointestinal malignancies have shown complete histologic response to neoadjuvant therapy to be a positive prognostic factor. However, complete histologic responses in pancreatic adenocarcinoma to neoadjuvant therapy are rare. Furthermore, the assessment of histologic response to treatment in PDAC is limited by the existence of multiple classification systems. Moreover, no prior published studies have compared results of existing classifications systems with clinical outcome.
Design: The study cohort consisted of 33 pancreaticoduodenectomy resection specimens with PDAC from patients treated with a single neoadjuvant chemoradiation protocol. Each case was evaluated histologically and classified according to published classifications schemes for tumor response to treatment (Ishikawa, Evans, and White). Survival rates after resection were compared within classification schemes to evaluate each system's capability of predicting survival outcome.
Results: The median survival of the study cohort was 15 months. Of the 33 evaluated cases, none showed a complete response to treatment. According to the Ishikawa classification system, a majority of cases showed therapy effect in <33% of tumor cells (58% Grade 1, 24% Grade 2, and 18% Grade 3). When Grade 2 (therapy effect in 33-67% of tumor cells) and Grade 3 (therapy effect in >67% tumor cells) subgroups were combined and compared against Grade 1 (therapy effect in <33% of tumor cells), there was a difference in median survival, although this did not reach statistical significance (P=0.0990). The Evans and White classification systems did not predict outcome.
Conclusions: Of the existing classification systems, the Ishikawa grading scheme was the easiest to apply to surgical resection specimens. None of the classification systems could predict survival outcome to a statistically significant degree. However, a modified two-tiered version of Ishikawa's classification may be useful in predicting survival in patients with PDACs who have received neoadjuvant therapy.
Category: Pancreas

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 273, Monday Morning


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