Endometrial cancer - cancer of the uterine lining - is typically treated with surgery to remove the uterus. For patients with intermediate or high-risk disease, surgeons must also remove surrounding tissues to ensure no cancer cells remain. The challenge is deciding exactly how much tissue to remove while minimizing harm to nearby structures.
Peritoneal mesometrial resection (PMMR) is an approach developed by surgeon M. Hockel based on the concept that cancer spreads along predictable anatomical compartments - tissue regions that developed together during embryonic growth. By removing the entire compartment rather than just the tumor, PMMR aims to achieve what surgeons call "ontogenetic resection" - cutting along natural tissue boundaries.
In traditional surgery, removing a uterus (hysterectomy) takes the organ but may leave microscopic cancer cells at the edges. PMMR instead removes the uterus along with its entire embryological tissue compartment, which includes the parametrium (tissue alongside the uterus) and the peritoneal layer (the membrane lining the abdominal cavity). This compartment-based thinking reduces the chance of leaving cancer behind.
PMMR was originally performed as open surgery - meaning a large abdominal incision was made to access the uterus. Open surgery allows surgeons full visibility and manual control, but comes with longer recovery times, higher infection risk, and greater blood loss. The authors wanted to know whether PMMR could be translated to robotic-assisted laparoscopic surgery.
Robot-assisted surgery uses the da Vinci surgical system, in which a surgeon sits at a console controlling robotic arms that hold miniaturized instruments inside the patient's body. Cameras provide a three-dimensional, magnified view. The advantages include greater precision in tight spaces, less blood loss, smaller incisions, and faster recovery for patients.
The critical question the study addressed was: can the complex, anatomically precise PMMR technique - originally requiring open surgery - be performed just as effectively using robotic tools? The authors adapted the procedure (calling it rPMMR for robotic PMMR) and reported their initial series of 42 patients.
The study included 42 patients with intermediate or high-risk endometrial cancer treated with rPMMR between 2009 and 2012. Intermediate risk was defined by FIGO stage IB, grade 3, or unfavorable histology; high risk included stage II, III, or IV disease. A subset of 14 patients with bulky nodal disease or deep myometrial invasion also underwent therapeutic lymph node excision (tLNE).
The robotic rPMMR procedure involved several key steps: creating a peritoneal window to access the retroperitoneal space, identifying and separating the uterine compartment from surrounding structures like the ureter and bladder, and then removing the uterus along with its full mesometrial tissue in a single en-bloc specimen. The operation was performed using the da Vinci Si system with four robotic arms. Surgeons also removed the pelvic peritoneum as part of the resection.
Patients were followed postoperatively and assessed for complications using the Clavien-Dindo classification - a standardized scale rating surgical complications from grade I (minor, no intervention) to grade V (death). Oncologic outcomes including recurrence and survival were tracked over a median follow-up of approximately 20 months.
The surgical results were encouraging. No patient required conversion to open surgery - meaning rPMMR was feasible in all cases using the robotic approach alone. Median operating time was approximately 260 minutes, which is longer than standard hysterectomy but reflects the added complexity of compartment-based resection.
The overall complication rate was 12%, with complications occurring in 5 of 42 patients. Using the Clavien-Dindo scale, most complications were grade II (requiring medication) or grade IIIa (requiring outpatient intervention). There were no grade IV or V (life-threatening or fatal) complications. One patient had a urinary tract injury that was repaired during the same surgery without long-term consequences.
Blood loss was modest, and the average hospital stay was consistent with minimally invasive approaches. The authors reported that the robotic platform provided excellent visualization of the ureter and pelvic floor structures, which are the most critical anatomical targets to protect during this type of radical surgery.
The most important finding was the oncologic outcome: over a median follow-up of 20 months, the recurrence-free survival rate was 95%. Only 2 of 42 patients developed recurrent disease, and critically, neither recurrence was isolated to the locoregional area - the pelvic region where surgery was performed. Both recurrences were distant metastases, suggesting the surgery successfully cleared the local disease.
This absence of locoregional recurrence is particularly important. Traditional radical hysterectomy for high-risk endometrial cancer is associated with pelvic recurrences in 10-15% of cases. The fact that no patient in this series had a pelvic recurrence supports the theoretical rationale of PMMR - that removing the entire embryological compartment eliminates the tissue substrate where local recurrence typically originates.
Pathological examination of the removed specimens showed negative surgical margins in all cases, meaning the cancer was completely surrounded by normal tissue. Lymph node assessment in the tLNE subgroup provided important staging information that guided decisions about additional adjuvant treatment such as chemotherapy or radiation.
A subset of 14 patients underwent therapeutic lymph node excision (tLNE) in addition to rPMMR. This is a departure from the traditional practice of sentinel lymph node biopsy or systematic lymphadenectomy - where lymph nodes are sampled primarily for staging purposes. In tLNE, the lymph nodes are removed therapeutically, on the assumption that microscopic metastases there should be treated rather than just identified.
The tLNE procedure involves removing the pelvic and para-aortic nodal chains - the lymph node clusters running along the major blood vessels in the pelvis and abdomen. Because these lymph nodes receive drainage from the uterus, they are the most common first site of cancer spread outside the uterus itself.
In the 14 patients who underwent combined rPMMR + tLNE, no locoregional recurrences occurred, even in patients with confirmed nodal involvement. This suggests that therapeutic rather than diagnostic lymph node removal may offer an oncologic benefit, though the small patient numbers make definitive conclusions difficult. The authors advocate for further study of this approach in a prospective trial.
This study demonstrated that rPMMR is technically feasible and oncologically promising for intermediate and high-risk endometrial cancer. The robotic platform appears well-suited to the precise dissection required for compartment-based surgery, particularly in identifying and preserving the ureter while removing surrounding tissue.
The results add to a growing body of evidence that minimally invasive radical surgery - using laparoscopic or robotic techniques - can achieve outcomes comparable to open surgery for gynecologic cancers while offering patients faster recovery and fewer wound-related complications. The challenge for future research is confirming these outcomes in larger patient series with longer follow-up.
The authors conclude that rPMMR should be considered as an option for patients with intermediate/high-risk endometrial cancer at centers with expertise in both robotic surgery and the PMMR anatomical principles. They call for a prospective multicenter trial to validate these findings across different institutions and surgeons, which would be necessary before rPMMR becomes a widely adopted standard of care.