Grade Group 1 Prostate Cancer Outcome by Biopsy Grade and Risk Group

Importance Advocates for removing the cancer label from grade group 1 (GG1) prostate cancer detected on biopsy primarily base their argument on the observation that when only GG1 is detected on prostatectomy, rates of metastasis are rare. However, the frequency with which GG1 prostate cancer on biopsy is associated with adverse clinical features and the long-term cancer outcomes in this context are poorly defined. Objective To assess cancer-specific outcomes of localized GG1 prostate cancer stratified by risk category. Design, Setting, and Participants A population-based cohort study using Surveillance, Epidemiology, and End Results data was performed to assess cancer-specific outcomes in 117 162 men with localized GG1 prostate cancer stratified by National Comprehensive Cancer Network risk groups between January 1, 2010, and December 31, 2020. Competing risk analyses and multivariable regression determined rates of prostate cancer–specific mortality and associations with prostatectomy adverse pathology. Data were analyzed from July 1, 2024, to October 1, 2024. Main Outcomes Prostate cancer–specific mortality and risk of adverse pathology at surgery in GG1 prostate cancer. Results Among 117 162 men with biopsy GG1 prostate cancer, 10 440 (9%) had favorable intermediate-risk disease, 3145 (3%) had unfavorable intermediate-risk disease, and 4539 (4%) had high-risk disease. Median age was 64 years (IQR, 58-69 years). A total of 867 men with high-risk GG1 prostate cancer (60%) had adverse pathology at prostatectomy. The prostate cancer–specific mortality rates for unfavorable intermediate-risk GG1 and for high-risk GG1 were 2.4% and 4.7%, respectively, comparable to the prostate cancer–specific mortality rates for favorable intermediate-risk GG2 and unfavorable intermediate-risk greater than or equal to GG2, which were 2.1% and 4.0%, respectively. In adjusted analyses, favorable intermediate-risk GG1 (adjusted hazard ratio [AHR], 1.60; 95% CI, 1.30-1.96), unfavorable intermediate-risk GG1 (AHR, 2.10; 95% CI, 1.53-2.89), and high-risk GG1 (AHR, 3.58; 95% CI, 2.93-4.38) were associated with increased risk of prostate cancer–specific mortality compared with low-risk GG1. Conclusions and Relevance This cohort study found that approximately 1 in 6 men with GG1 prostate cancer has intermediate-risk or high-risk disease. Biopsy GG1 prostate cancer has heterogeneous long-term outcomes that are reflected in adverse pathology and prostate cancer–specific mortality. These data indicate that not all GG1 prostate cancer follows an indolent course. A subset of men with biopsy GG1 prostate cancer have outcomes comparable to those of men with higher-grade intermediate-risk prostate cancer, a group that often undergoes treatment. These findings should be considered in the reclassification debate.