Does location of prostate cancer by sextant biopsies predict for relapse after (125)I seed implant brachytherapy?

Brachytherapy

PubMedID: 26249125

Hill J, Hackett C, Sloboda R, Menon G, Singhal S, Pervez N, Pedersen J, Yee D, Murtha A, Amanie J, Usmani N. Does location of prostate cancer by sextant biopsies predict for relapse after (125)I seed implant brachytherapy?. Brachytherapy. 2015;.
PURPOSE
To report on the importance of cancer location from diagnostic prostate biopsies in predicting biochemical relapse for patients treated with (125)I seed implant brachytherapy as monotherapy for favorable risk disease; specifically, to assess the clinical significance of potentially underdosing the base region of the prostate gland.

METHODS AND MATERIALS
Of 1145 consecutive patients, 846 had pretreatment biopsies allowing for sextant analysis and consequent evaluation of biochemical failure tendencies. Biochemical failure was defined as a posttreatment rise in the nadir prostate-specific antigen (PSA) by at least 2 ng/mL. Patient and tumor characteristics, dosimetry, the use of hormone therapy, source strength, and postimplant PSA kinetics were analyzed between sextant subgroups.

RESULTS
Sixty-two patients (7.3%) with sextant pathology had biochemical failure. There was no significant difference between the failure locations. There were 528 patients (62.4%) with some element of base involvement (BI), and 318 patients (37.6%) with no evidence of BI. Of the 62 patients with biochemical failure, 42 (67.7%) showed BI on biopsy and 20 (32.3%) had no BI. The 10-year relapse-free survival rate is 88.2% (95% confidence interval: 84.3%, 92.2%) and 92.0% (95% confidence interval: 88.4%, 95.8%) for the BI and no BI groups, respectively (p = 0.17). The mean D90 delivered to the base, midgland, and apex was 140.8 (±21.8) Gy, 170.8 (±22.5) Gy, and 177.9 (±29.5) Gy, respectively, for all patients.

CONCLUSIONS
There are no significantly worse outcomes for patients treated with an (125)I seed implant for favorable risk prostate cancer with some element of BI, despite lower doses of radiation delivered to the base region.