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Maximal Tumor Diameter, biochemical recurrence in organ confined high-grade prostate cancer.
Stephen T. Ryan, MD, Christine Duarte, PhD, Moritz Hansen, MD, Patrick Murray, MD. Maine Medical Center, Portland, ME, USA.
BACKGROUND - With MRI criteria developed for the identification of high-grade prostate cancer (Gleason score ≥7 = HGPCa), there is a potential to increase the detection of small tumors of uncertain clinical significance. Studies suggest that prostate cancers are clinically significant if their volume is > 5 cc, corresponding to a maximum tumor diameter (MTD) of 1 cm. However this prior work has predominantly focused on low-grade prostate cancers with a Gleason score ≤ 6 (LGPCa). Our intent is to investigate the relationship between biochemical recurrence (BCR) and MTD to determine if this relationship varies based on the presence of HGPCa. METHODS - Pathologic data and BCR rates were obtained prospectively from 1999 to 2012 from a single tertiary care center’s prostatectomy database. Inclusion criteria were organ-confined pathology (pT2a – T3a), negative surgical margins, and minimum of 12 months follow-up. Exclusion criteria were androgen deprivation therapy, prior TURP, seminal vesicle invasion, or nodal metastases. Two groups were compared; LGPCa versus any lesion with HGPCa. Index lesion MTD was measured in 1mm increments and divided into 7 groups: ≤0.5 cm, 5-10 mm, 10-15 mm, 15-20 mm, 20-25 mm, 25-30 mm, >30 mm. The relationship between BCR and MTD was assessed using a Cochran-Armitage Trend Test. A Cochran-Mantel-Haenszel analysis tested difference in association between BCR and MTD for LGPCa and HGPCa groups. The relationship between BCR and grade (LGPCa and HGPCa) was tested using a chi-squared test. RESULTS - 1048 men were followed for a median period of 54 months (12-156 months). 73 (6.9%) men with organ-confined disease had a BCR. Median time to BCR was 22.5 months. Rates of BCR for LGPCa and HGPCa were 2.7% and 9% respectively (p=0.0002). Overall the relationship between BCR vs MTD was significant (p=0.03), but not for either the LGPCa vs. HGPCa groups independently. The Cochran-Mantel-Haenszel statistic for difference in trend for high vs. low grade was also not significant. CONCLUSIONS - In a large contemporary cohort of patients with organ confined prostate cancer, MTD is a predictor of BCR. HGPCa lesions have BCR rates significantly greater than for LGPCa lesions. There is no evidence to suggest that a small HGPCa <1cm has a lower BCR than a larger HGPCa. This suggests that MRI identified high-grade lesions in 0.5 – 1 cm range should undergo targeted biopsy.
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