Short-term Therapeutic Outcomes of Robotic-Assisted Laparoscopic Radical Prostatectomy for Oligometastatic Prostate Cancer: A Propensity Score Matching Study
Prostate cancer (PCa) remains one of the most commonly diagnosed malignancies in men and a leading cause of cancer-related deaths worldwide. In China, due to limited access to prostate-specific antigen (PSA) testing and economic disparities, many patients are diagnosed with metastatic prostate cancer (mPCa) at their initial medical consultation. Traditional systemic treatments, such as androgen deprivation therapy (ADT), have been the cornerstone of mPCa management for decades. However, recent advancements in surgical techniques and imaging technologies have sparked interest in the role of local treatments, particularly in cases of oligometastatic prostate cancer (OPC). This study investigates the short-term therapeutic outcomes of robotic-assisted laparoscopic radical prostatectomy (RALP) for OPC compared to localized PCa, using propensity score matching to minimize selection bias.
Background and Rationale
The concept of oligometastases, introduced by Weichselbaum and Hellman, describes an intermediate state between localized and widespread metastatic disease. This hypothesis suggests that targeted local treatment of oligometastases could improve overall survival (OS) and potentially offer a cure in select patients. Advances in imaging techniques, such as whole-body MRI and PET-CT, have facilitated the early detection of oligometastatic disease, enabling timely intervention. Studies across various cancers, including lung, breast, and colorectal malignancies, have demonstrated the benefits of surgical resection in oligometastatic settings. Similarly, emerging evidence supports the role of local treatment in OPC, with radical prostatectomy showing promise in improving progression-free survival (PFS) and OS. However, data on the use of RALP specifically for OPC remain limited.
Study Design and Methods
This retrospective study analyzed 508 consecutive patients who underwent RALP as a first-line treatment for PCa between April 2012 and October 2017. Patients were categorized into two groups based on their metastatic status: the OPC group (n = 41) and the localized PCa group (n = 467). Oligometastatic disease was defined as the presence of two or fewer metastatic lesions, confirmed through whole-body bone scans, MRI, or PET-CT. Patients with visceral metastases or extensive lymph node involvement were excluded.
To ensure comparability between the two groups, propensity score matching was employed, accounting for variables such as age, BMI, pre-operative PSA, pathological Gleason score (GS), and pathological T stage. A total of 41 matched pairs were generated for analysis. The primary endpoints included biochemical recurrence (BCR), defined as two consecutive PSA levels >0.2 ng/mL, and OS. Secondary outcomes included operative time, blood loss, positive surgical margin (PSM) rates, post-operative hospital stays, and urinary continence recovery rates.
Surgical Technique and Follow-up
RALP was performed using a standardized technique, with pelvic lymph node dissection conducted in all OPC patients and intermediate-to-high-risk localized PCa patients. Post-operative pathological analysis assessed surgical margins and GS. Patients were followed up at 6 weeks, monthly for the first year, and biannually thereafter. PSA levels were monitored to detect BCR, and urinary continence was evaluated based on pad usage.
Results
After propensity score matching, no significant differences were observed in baseline characteristics between the OPC and localized PCa groups. The median operative time was 140 minutes in the OPC group versus 130 minutes in the localized PCa group (P = 0.267), and median blood loss was 160 mL versus 150 mL (P = 0.632). The overall PSM rate was 36.6% in both groups, with no significant differences in upper or lower margin positivity. Post-operative hospital stays were identical at a median of 6 days (P = 0.939).
Urinary continence recovery rates at 3, 6, and 12 months were 51.2%, 75.6%, and 93.8% in the OPC group, compared to 62.6%, 74.7%, and 82.3% in the localized PCa group (P = 0.915). The 4-year BCR-free survival (BRFS) rates were 56.7% and 60.8% in the OPC and localized PCa groups, respectively (P = 0.804). The 5-year OS rates were 96.3% and 100%, respectively (P = 0.326). Only one patient in the OPC group died of PCa during follow-up.
Subgroup Analysis
A subgroup analysis of patients with single metastatic lesions (n = 27) revealed no significant differences in BRFS based on the site of metastasis. However, patients with thoracolumbar or pelvic metastases showed a trend toward faster progression compared to those with rib or other bone metastases.
Risk Factor Analysis
Cox proportional hazards modeling identified pre-operative PSA, pathological GS, and pathological T stage as independent predictors of BCR. Pre-operative PSA levels >20 ng/mL (HR = 6.606, P = 0.0001) and 10–20 ng/mL (HR = 3.651, P = 0.0108) were associated with higher BCR risk. Similarly, a post-operative GS >7 (HR = 7.381, P = 0.0015) and pathological T stage ≥T3a (HR = 1.932, P = 0.0183) were significant risk factors. Notably, the oligometastatic state itself was not an independent predictor of BCR (P = 0.6816).
Discussion
This study provides evidence supporting the safety and efficacy of RALP in patients with OPC. The comparable peri-operative outcomes, BRFS, and OS between the OPC and localized PCa groups suggest that RALP is a viable treatment option for select patients with oligometastatic disease. The findings align with the oligometastasis hypothesis, emphasizing the potential benefits of local treatment in delaying disease progression and improving survival.
The absence of significant differences in operative parameters and post-operative complications underscores the feasibility of RALP in this patient population. Furthermore, the high urinary continence recovery rates in the OPC group highlight the functional benefits of this approach. The identification of pre-operative PSA, pathological GS, and T stage as independent predictors of BCR reinforces the importance of these factors in risk stratification and treatment planning.
Limitations
This study has several limitations. Its retrospective design and lack of a control group receiving ADT alone limit the generalizability of the findings. Additionally, the relatively short median follow-up of 26.4 months in the OPC group restricts the assessment of long-term oncological outcomes. Future randomized controlled trials comparing RALP with systemic therapies are needed to validate these results.
Conclusion
In conclusion, this propensity score-matched study demonstrates that RALP is a safe and effective treatment for patients with OPC, offering comparable short-term outcomes to those with localized PCa. The oligometastatic state does not independently influence BCR, emphasizing the role of primary tumor characteristics in predicting disease progression. These findings contribute to the growing body of evidence supporting local treatment in oligometastatic settings and provide a foundation for further research in this evolving field.
doi.org/10.1097/CM9.0000000000000590
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