PSMA-PET/MRI-Ultrasound Multimodal Fusion Navigation for Da Vinci Robot-Assisted Radical Prostatectomy: A Randomized Controlled Trial

Prostate cancer, the second most prevalent malignancy in men globally, has long grappled with a core dilemma in radical surgery: balancing functional preservation against oncological efficacy. Although nerve-sparing techniques significantly improve postoperative urinary control and sexual function (with robotic surgery achieving >80% continence recovery rates), conventional approaches relying on intraoperative visual tumor boundary assessment result in positive surgical margin (PSM) rates of 11%- 38%, increasing biochemical recurrence risk exceeding 40% [1,2]. For locally advanced cases, sacrificing functional structures to ensure oncological radicality leads to postoperative erectile dysfunction rates up to 95% and urinary incontinence exceeding 50% [3].The essence of this conflict lies in: Extended resection reduces PSM rates but damages neurovascular bundles (NVBs) governing micturition and erectile function; Limited resection preserves function yet increases PSM risk due to residual microlesions-particularly in anatomically complex zones like the prostatic apex and anterior wall, where visual localization errors typically exceed 3 mm.

Preoperative imaging limitations exacerbate this: MRI offers high anatomical resolution (0.5 mm³) but cannot track intraoperative organ deformation; PSMA-PET/CT detects micrometastases with 98% sensitivity, yet spatial registration errors between metabolic/anatomical data exceed 2 mm [4]. Current multimodal fusion approaches are inadequate: MRI-based fusion misses early-stage lesions due to limited tumor contrast; PSMA-PET/CT fusion suffers from metabolic-anatomical misalignment.

Thus, a navigation system enabling simultaneous subclinical lesion detection and dynamic deformation compensation is imperative to resolve the function-versus-curability dilemma.

We have adopted the following approaches to complete the construction of the intraoperative navigation system: (1) On the PET/MRI before the operation, the prostate and the lesion were delineated: at least two nuclear medicine physicians independently reviewed the images and then provided a unified report; the external contour of the prostate and the three-dimensional lesion schematic diagram of the lesion were then delineated by a urologist; (2) On the intraoperative ultrasound, the prostate was delineated: the prostate image was captured in real time by BK ultrasound and then the external contour of the prostate was delineated by a urologist; (3) The multimodal fusion of the three-dimensional lesion delineated by BK ultrasound and PSMAPET/MRI was achieved through the MIM software built into the BK ultrasound; (4) The intraoperative resection was guided by the Da Vinci Tilepro functional module. So far, 6 cases have been successfully completed and compared with 6 T3a patients randomly selected from previous conventional surgeries. Currently, due to the small sample size, although the differences in the surgical margins have not reached a statistically significant difference, a trend of difference has been demonstrated. Due to the short follow-up period, the postoperative PSA and urination conditionshave not been included in the statistical cohort.

Inclusion criteria

• Target Population: Patients with clinical stage T3a, or T2 (with the lesion close to the surface of the prostate) scheduled for robot-assisted radical prostatectomy (RARP), who have been diagnosed with prostate cancer.

• Age 50 - 80 years old;

• Pathologically confirmed as prostate adenocarcinoma (Gleason score 6 - 10);

• PSMA-PET/MRI indicates extracapsular invasion of the lesion; ④ Signed informed consent and committed to completing follow-up.

Exclusion criteria

• ① Metastasis (M1 stage) or lymph node metastasis (N1 stage);

• Previous pelvic radiotherapy or endocrine therapy history;

• Severe cardiopulmonary dysfunction (ASA grade ≥ III); ④ Mental illness or cognitive impairment that cannot cooperate with assessment; ⑤ Participating in other interventional clinical trials.