[869] Characterizing the Dominant/Index Lesion in Prostate Cancer: Implications for Grading and Staging

Samson W Fine, Kent Kanao, Kazuma Udo, Hikmat A Al-Ahmadie, Ying-Bei Chen, Anuradha Gopalan, Satish K Tickoo, Victor E Reuter. Memorial Sloan-Kettering Cancer Center, New York, NY

Background: Gleason score (GS) and pathologic stage of prostate cancer are major prognostic features in radical prostatectomy (RP) specimens. Empiric experience suggests that the dominant/index lesion will have the largest tumor volume (TV), highest GS and be the stage-determining tumor. However, the incidence with which volume, grade and stage do not coincide within one dominant/index lesion have not been well-studied.
Design: We created digitized tumor maps for 266 whole-mounted and entirely submitted RP specimens. For each case, TV was calculated and GS/pathologic stage were assessed for all tumor nodules to determine whether largest TV, highest GS/stage coincided in one dominant/index lesion ("congruous") or not ("incongruous").
Results: Incongruous dominant/index lesions:
In 47 (18%) cases, largest TV and highest GS/stage were not localized to the same nodule. 32 were organ-confined/margin negative [pT2], i.e largest TV and highest GS were in distinct nodules, 15 of which had > 1 GS discrepancy from the nodule with largest TV. 12 cases showed extraprostatic extension (EPE). Of these, 1 unique case had three separate tumor nodules with largest TV, highest GS and the stage-determining lesion, respectively. The remaining 11 pT3 cases had 2 incongruous tumor nodules: largest TV/highest GS nodule v. stage-determining nodule [n=5]; largest TV/stage-determining nodule v. highest GS nodule [n=3]; highest GS/stage-determining nodule v. largest TV nodule [n=3]. In 3 cases, one nodule had largest TV/highest GS while a second showed a (+) margin in otherwise organ-confined tumor [pT2+].
Congruous dominant/index lesion:
In 219 (82%) cases, the three features were localized to the same tumor nodule. 207 dominant/index nodules had mean tumor volume=1.46 cm3 [range: 0.002 to 14.24 cm3]; GS 6 [n=50], GS 3+4=7 [n=94], GS 4+3=7 [n=49], GS 8 [n=10] and GS 9 [n=4]; pathologic stage: pT2/margin negative [n=149], pT2+ [n=7], EPE [n=38], seminal vesicle invasion [n=13]. The 12 remaining cases showed multiple minute foci of GS 6 cancer only (mean TV: 0.023 cm3).
Conclusions: Largest TV and highest GS/stage are not present within the same tumor nodule in nearly 1/5 of prostate cancer cases. Specifically, 1/3 of "incongruous" cases have a highest GS nodule that is > 1 GS higher than the largest TV nodule. Likewise, the stage-determining nodule may not have the largest TV/highest GS. As it is crucial for the pathology report to provide prognostically useful information, these findings suggest that the best method of grade/stage assignment in "incongruous" cases awaits future clinical outcome studies.
Category: Genitourinary (including renal tumors)

Monday, March 4, 2013 1:00 PM

Poster Session II # 150, Monday Afternoon


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