Purpose:
Approximately 1 in 10 patients without prior prostate biopsy undergoing surgery for lower urinary tract symptoms harbors incidental prostate cancer; however, practice guidelines do not provide recommendations for its management. We aimed at describing the oncologic outcomes of patients with Grade Group (GG) 1 and GG2 prostate cancer diagnosed at transurethral resection of the prostate (TURP).

Materials and Methods:
This was a nationwide, population-based, observational study of patients undergoing TURP in Denmark from 2006 to 2022 using the Danish Prostate Registry. We estimated the cumulative incidence of further biopsies and MRI, curative treatment, endocrine treatment, and cause-specific mortality with competing risk analyses.

Results:
Among 24,494 patients who underwent TURP, there were 1016 men with GG1 and 381 with GG2 prostate cancer. The 5-year cumulative incidence of further MRIs or biopsies was 36% (95% CI 33%-39%) for GG1 and 30% (95% CI 25%-34%) for GG2 disease. Fifteen-year prostate cancer mortality was 8.4% (95% CI 5.3%-11%) for GG1 and 14% (7.5%-21%) for GG2. A total of 270 men with GG1 disease underwent a biopsy after the TURP, and 162 (60%) had no cancer; in this group, prostate cancer mortality after 15 years was 0.6% (95% CI 0%-1.8%). Men with post-TURP biopsy ≥ GG2 had a prostate cancer mortality of 30% (95% CI 9%-50%) 15 years post TURP. The major limitation was the heterogeneous follow-up, which could lead to an overestimation of prostate cancer mortality compared to a more standardized follow-up.

Conclusions:
We observed high prostate cancer mortality after TURP with GG1 or GG2, likely due to unsampled high-grade cancer in the peripheral zone. Patients with incidental prostate cancer should be further investigated to rule out high-grade cancer. For patients with GG1 on TURP, once a subsequent biopsy does not show cancer, follow-up should be lessened similar to that of patients with an initial nonmalignant biopsy.

Transurethral resection of the prostate (TURP) is a standard approach for management of lower urinary tract symptoms unresponsive to medical treatment.1,2 Prostate cancer is found in the surgical specimen in approximately 10% to 20% of cases, most frequently Grade Group (GG) 1.2,3 This is typically referred to as incidental prostate cancer.3

International guidelines do not provide recommendations on prostate cancer diagnostic workup after prostate cancer diagnosed incidentally.2,4 One view is that incidental cancers (stage T1a and T1b) do not differ from T1c cases and usual predictors such as PSA and grade should guide decision-making the same way.5 Others have argued that the natural history of incidental prostate cancer differs from that of T1c tumors and therefore should be included in the guidelines as a unique entity.6 These differing views may be the consequence of a paucity of data on the long-term outcomes of incidental prostate cancer. While many studies have reported on prevalence, few have examined subsequent morbidity and mortality.3,7-10

We previously reported that the risk of dying of prostate cancer after a TURP in which no cancer was found is 1.4% at 15 years. We speculated that if prostate cancer is not found with limited sampling, then the likelihood of harboring aggressive disease in the peripheral zone is low.11 However, it is not known whether, if prostate cancer is found on limited sampling, this is a proxy of unsampled higher-grade cancer.

In Denmark, since 1995, reporting of histopathological findings of tissue retrieved from TURP has been mandatory, and all assessments were stored in a nationwide registry.11 We used this dataset to investigate the clinical follow-up and long-term oncologic outcomes of patients who had an incidental diagnosis of GG1 or GG2 prostate cancer on TURP.