One of the difficulties of this investigation was in choosing a cut-off point for what is considered significant.

As aforementioned, the distribution of CA 19-9 is skewed to the right; many patients might only have a slightly elevated marker level, which may not be clinically meaningful. In analyzing the DPAM/PMCA-I/D group, we chose to split the group rather arbitrarily based on degree of marker elevation (≤40 U/mL, 40-100 U/mL, >100 U/mL and >1,000 U/mL). We found that arbitrary grouping or splitting into quartiles all resulted in demonstrating the same pattern of behavior, however, our method allows for setting a practical cut-off that can be utilized in clinical practice or further research protocols. More specifically, Inhibitors,research,lifescience,medical we believe that CA 19-9 >100 U/mL may be a more appropriate discriminator than marker FK228 concentration positivity itself and given the findings, should be Inhibitors,research,lifescience,medical incorporated as part of a staging scheme for PMP. This could potentially identify patients with DPAM/PMCA-ID who may benefit from adjuvant

chemotherapy, which is not Inhibitors,research,lifescience,medical currently standard practice. Using CA 19-9 as part of a staging system may also provide some objectivity in dealing with tumors classified as PMCA-I/D. In most studies, patients with PMCA-I/D tend to exhibit a similar biological behavior to that of frank PMCA (1,4). However, in the current cohort, the PMCA-I/D group appeared to portend a survival time similar to the DPAM group. Presently the histopathological

critieria defining this group of patients remains Inhibitors,research,lifescience,medical complex and insufficient attention has been given in the pathological analysis. As Bradley et al. have described from their institutional experience, the bi-grouping of PMP may be appropriate as in our context, given the similar outcomes of both PMCA-I/D and DPAM (5). Ronnett’s criteria defines PMCA-I/D as peritoneal lesions that contain predominantly features of DPAM but with focal areas of well-differentiated mucinous adenocarcinoma or discordant features. Use of the word ‘predominantly’ Inhibitors,research,lifescience,medical thus leaves room for ambiguity as there are no specific cut-offs per se. Due to this ambiguity, our institution recognizes that there are limitations in relying solely on Ronnett’s criteria in determining prognosis. Perhaps the treatment decision Rutecarpine should be more heavily based on the pre-operative CA 19-9 level, given that even in patients with PMCA, 88% of CA 19-9 negative patients survive to 5-year. Our study suggests an intimate relationship between CA 19-9 and PMP which should be further scrutinized, not only for the purpose of developing novel treatments but more pertinently, rationalizing current treatment strategies. As some authors have done for other gastrointestinal malignancies, the potential role of CA 19-9 in mediating tumor cell adhesion and disease progression in PMP merits investigation in a laboratory setting to deepen our understanding of the disease’s inherent biological behavior.