Presumptive downstaging from preoperative irradiation for bladder cancer as determined by flow cytometry: Preliminary report
Presumptive tumor downstaging was evaluated in 28 patients with grade II or III, solid, muscle-infiltrating bladder cancer (clinical category T3) treated by integrated irradiation (2000 rad to the whole pelvis in 5 days) and cystectomy (1-14 days later) by comparing the results of flow cytometry (FCM) on barbotage specimens obtained before and after irradiation (at the time of cystectomy) and the results of pretreatment clinical stage (T category) and post cystectomy pathological stage (P category). The patients were divided into three groups: (1) P greater than T, (2) P = T, and (3) P less than T. All of the patients in this study had positive FCM specimens with an aneuploid stemline in the pre-irradiation specimen. A complete radiation response (CRR) was defined by FCM as disappearance of the aneuploid stem cell line. Of the 5 patients in the P less than T group, 4 showed a CRR; of 20 patients in the P = T group, 8 showed a CRR; of the 3 patients in the P greater than T group, none showed a CRR. The proportion of patients in the various T/P groups is consistent with that previously observed in patients receiving integrated irradiation (2000 rad in 5 days) and cystectomy (1-14 days later). The overall downstaging response of 43%, as determined by FCM, correlates well with the pathological downstaging rates of 40%-68% reported by others following high dose (4000-5000 rad) integrated irradiation cystectomy regimens; however, it is more than the 27% rate reported with the low dose short course (2000 rad in 5 days) regimen. The correlation of the FCM findings with clinico-pathological downstaging is consistent with the possibility that FCM may be useful in identifying a favorable radiation response.