Frequent clonal relations between metastases and non-index prostate cancer lesions

Primary prostate cancer lesions are clonally heterogeneous and often arise independently. In contrast, metastases were reported to share a monoclonal background. Because prostate cancer mortality is the consequence of distant metastases, prevention of metastatic outgrowth by primary tumor ablation is the main focus of treatment for localized disease. Focal therapy is targeted ablation of the primary index lesion, but it is unclear whether remaining primary lesions metastasize at a later stage. In this study, we compared copy number aberration profiles of primary prostate cancer lesions with matching pelvic lymph node metastases of 30 patients to establish clonality between a lymph node metastasis and multiple primary lesions within the same patient. Interestingly, in 23.3% of the cases, the regional metastasis was not clonally linked to the index primary lesion. These findings suggest that focal ablation of only the index lesion is potentially an undertreatment of a significant proportion of prostate cancer patients.