P53 as a predictor of tumor burden in lymph nodes (LN) in colon cancer (Cca) patients (pts) undergoing sentinel lymph node (SLN) mapping (M)

Abstract

3617 Background: p53 and LN status(S) are important prognostic markers in Cca. Our study was done to evaluate whether p53 S could predict tumor burden in LNs in Cca undergoing SLNM. Methods: Pts with Cca underwent SLNM to determine the LN S. A portion of tumor was used for detection of p53 S by IHC.p53 Histo Score (HS) was defined as (Intensity of stain in cells from 0–4 +1) × (% cells staining). HS of 180 was taken as cut off for significance based on previous studies on solid tumors. Metastatic foci in SLNs and nonSLNs were measured in greatest diameter by ocular micrometer. For overall tumor burden in SLNs and nonSLNs,all metastatic foci were added for each pt. Results: SLNM was successful in 100% of the 117 consecutive pts with Cca. Pts with distant metastasis (mets) (18) and skip mets (9) were excluded. Of the remaining 90 pts,39% were SLN positive (+ve) and 61% were SLN negative (-ve). HS of ≤ 180 was found in 66% and HS >180 was found in 34% of the pts. In 55 SLN -ve pts 76% had HS ≤ 180 while 24% had HS >180. In 35 SLN +ve pts, 49% had HS of ≤ 180 and 51% had HS >180. ( Table ) Of SLN +ve pts, size of metastatic tumor in LNs was available in 86% of pts. Average (av.) non SLN met size was 0.95 cms in pts with HS ≤ 180 and 3.4 cms in pts with HS > 180. Av. SLN met size was 0.63 cms in pts with HS ≤ 180 and 0.9 cms in pts with HS>180 ( Table ). No statistical significance was found among T stage of pts with HS >180 vs ≤ 180. Conclusion: Pts with p53 HS >180 showed significantly greater tumor burden in both SLNs and non SLNs as compared to pts with HS ≤ 180. Also probability of having SLN -ve disease is higher in pts with HS ≤ 180 as compared to pts with HS >180 in Cca. Thus,even in SLN -ve pts, high HS may indicate a worse prognosis. Hence,a high p53 HS might predict pts with Cca having higher tumor burden in LNs and thus identify an aggressive subgroup of pts. [Table: see text] No significant financial relationships to disclose.