Anterior, Posterior, and Total Pelvic Exenteration

Seth I. Felder

Martin R. Weiser

INDICATIONS/CONTRAINDICATIONS

Pelvic exenteration is a radical approach to resecting pelvic disease, generally involving the rectum and pelvic viscera. The goal is a margin-negative resection often requiring en bloc removal of the rectum with the bladder, lower ureters, uterus, fallopian tubes, and either ovaries or seminal vesicles and prostate. Extirpation may include lateral pelvic lymph nodes; internal iliac vessels; nerves; pelvic peritoneum; and portions of the bony pelvis, muscles, and ligaments. Multivisceral or extended exenterative rectal resections offer the best chance of curing locally advanced primary rectal cancers and locally recurrent disease confined to the pelvis. The distorted tissue planes, aggressive biology, and prior irradiation increase the risk and technical difficulty of these operations, necessitating meticulous surgical planning. Despite the technical challenges associated with pelvic exenterative operations, the rates of operative mortality and morbidity have sharply declined in recent years because of improvements in patient selection, advances in the quality of imaging, and emphasis on multidisciplinary perioperative care. Although better oncologic outcomes are now anticipated, the magnitude of resection obligates the surgeon to carefully consider the effects of the expected morbidity on the patient’s quality of life. Once a patient has committed to undergoing pelvic exenteration, achieving a microscopic negative (R0) resection margin becomes the surgeon’s primary objective. An R0 resection margin remains the most important prognostic factor for long-term survival in patients with locally advanced primary and recurrent rectal cancers.

Indications

Locally Advanced Primary Rectal Cancer

For the nearly 15% of rectal cancers adherent to adjacent pelvic viscera, neoadjuvant therapy and multivisceral resection are required. In contrast to many other solid tumors, large locally advanced primary rectal tumors are not necessarily indicative of concurrent distant disease. Curative resection is therefore potentially attainable. Because malignant infiltration cannot be clearly differentiated from inflammatory adhesions on surgical exploration, aggressive resection of adherent organs is often necessary. Many studies have shown that if negative margins are achieved, en bloc resection of the anatomic structures invaded by the tumor can lead to long-term survival approaching 60% at 5 years after surgery. In contrast, the prognosis for locally advanced primary rectal cancer left untreated is poor, with median survival being less than 1 year and the 5-year survival rate being less than 5%.

Recurrent Rectal Cancer

After a curative rectal cancer resection, 3-30% of patients experience local recurrence. In the absence of surgical intervention, the mean survival for such patients is 7 months. Although metastatic disease subsequently develops in up to 70% of patients with recurrent rectal cancer, up to 50% of patients die with local disease only. Approximately 20% of patients with recurrent pelvic disease are amenable to a repeat radical resection, which improves 5-year survival to 18-46%. The majority of
local recurrences are detected within 48 months of the primary surgery. Radiation and chemotherapy may partially alleviate symptoms; but with medical therapy alone, patient survival is less than 5% at 5 years. Pelvic exenteration remains the only form of treatment that is potentially curative and, in some select instances, effectively palliative for recurrent rectal cancer.

Metastasectomy/Palliative Surgery

The benefit of pelvic exenteration for patients with metastatic disease remains unclear. Metastatic disease does not necessarily disqualify a patient from operative consideration. In a highly select group of patients with limited and resectable visceral metastases, pelvic exenteration has produced acceptable outcomes, with survival beyond 5 years. Selective use of exenteration may also be reasonable for palliation in patients with unmanageable perineal wounds, disabling pain, bleeding, obstruction, and recurrent infections, even if resection of the disease is incomplete.

Contraindications

Patients with significant comorbidities and poor performance status such as American Society of Anesthesiology IV-V are rarely candidates for the extensive surgery required. Likewise, exenteration should not be performed in patients for whom complete resection is not possible or patients for whom surgical morbidity is likely to be excessive. Other contraindications for exenteration include the following:

Invasion of the sciatic notch or sciatic pain with sciatic nerve involvement
S1 or S2 bony or neural involvement
Extensive peritoneal involvement
Unresectable extrapelvic metastases including para-aortic lymphadenopathy
Multifocal local recurrence and multiple threatened margins or circumferential pelvic sidewall involvement
Bilateral ureteral obstruction

Traditionally, peritoneal carcinomatosis, high sacral involvement, encasement of the external iliac vessels, invasion of the sciatic notch, bilateral ureteral obstruction with bilateral hydronephrosis, and the presence of gross lower limb edema have been considered absolute contraindications to curative pelvic exenteration. The categorization of many of these conditions as contraindications has recently been reevaluated and challenged, particularly at expert high-volume centers, where several of the traditionally absolute contraindications are now considered relative.

PREOPERATIVE PLANNING

Before the operation, the surgeon must carefully evaluate the clinical symptoms, the extent of local and distant disease, the patient’s fitness for major surgery, and the patient’s cognitive awareness of the rehabilitative process. It is crucial that patients with multifocal distant metastases not undergo such a potentially morbid treatment. Recurrent disease should be verified usually by computed tomography (CT)-guided biopsy before an operation of such magnitude is undertaken. Many efforts have been made to identify factors associated with complete resection, which could aid surgeons in selecting patients who are truly suitable for exenteration. Because a spectrum of opinions regarding suitability for exenteration exists, a consensus survey of experienced surgeons has been conducted. Among 58 clinical criteria for patients with recurrent rectal cancer, “history of pain” and “pelvic bone pain” were among the highest ranked variables associated with an anticipated negative effect on the surgical outcome.

Physical Examination

Although many surgeons consider modern imaging modalities to be the most effective means of tumor staging, a thorough physical examination, including detailed digital rectal and vaginal examinations, remains essential. Physical examination can provide an experienced surgeon with valuable information on the tumor’s extent and its fixation to adjacent organs and/or the bony pelvis. In some cases, adequate examination may need to be performed under anesthesia. A thorough pelvic examination is usually the simplest, most direct method of determining whether sphincter-sparing surgery is feasible or multivisceral resection or exenteration is necessary. To exclude synchronous primary tumors, a complete colonoscopy should also be performed.

Radiologic Imaging

Contrast-enhanced CT is the most frequently used imaging modality for assessing a tumor’s extent and/or the presence of metastatic disease. CT can provide an approximate idea of tumor size, but it does not always accurately differentiate tumor margins from the surrounding viscera. A more accurate indication of pelvic involvement and of the potential need for multivisceral resection can be obtained with magnetic resonance imaging (MRI). Several comparative studies have demonstrated the superiority of MRI in predicting extrapelvic visceral involvement in both primary and recurrent diseases. A negative predictive value of 93-100% for invasion into critical structures has been reported for MRI. However, treatment-related fibrosis has been shown to result in overstaging, particularly for recurrent tumors along the pelvic sidewall.

MRI remains the most valuable tool for delineating the extent of tumor involvement in the four main pelvic compartments: anterior, axial/central, posterior, and lateral sidewall. Tumor involvement of central and anterior structures, with the potential exception of bone involvement, indicates a high likelihood of obtaining negative margins. Lateral pelvic sidewall disease identified on preoperative imaging, however, portends a worse surgical outcome and represents the most common site for a positive margin because of the anatomic constraints of the bony pelvis. For this reason, intraoperative radiation to the pelvic sidewall soft tissue, ureters, iliac vessels, sciatic nerve, piriformis muscle, and pelvic bones may need to be considered. Even with pelvic sidewall involvement, recent series have reported R0 resection rates approaching 53%, with overall survival as high as 69% at 19 months, although these operations often required vessel reconstruction with bony and ligamentous resections.

Fluorodeoxyglucose positron emission tomography can image tumor metabolic activity and provide useful information regarding the presence of metastatic disease. This technology can be a valuable tool in detecting pelvic recurrence, with potential advantages over CT or MRI in differentiating fibrosis from viable tumor. Nonetheless, false-positive interpretations of physiologic fluorodeoxyglucose uptake in displaced pelvic organs, such as bladder, seminal vesicles, uterus, and small-bowel loops, as well as radiation-induced inflammation, reduce its specificity.

Neoadjuvant Therapy

The single most important factor in curing rectal cancer is complete excision of the tumor with negative margins, thus achieving an R0 resection. In primary rectal cancer, preoperative chemoradiation has been shown to prevent local recurrence more effectively than postoperative therapy, without necessarily extending overall survival. Although radiotherapy and chemotherapy may allow for palliation and symptom control, prolonging survival by 10-17 months, surgical resection remains the only curative option. A significant benefit of preoperative chemoradiotherapy is its potential to downsize the tumor, which may facilitate complete resection of locally advanced disease. Indeed, neoadjuvant chemoradiation has become standard practice in treating most locally advanced rectal cancers.

In efforts to enhance the likelihood of complete resection of advanced rectal cancer, the intensity and sequence of preoperative therapy have been actively studied, and recommendations continue to evolve. One such strategy for potentially improving R0 resection rates is induction chemotherapy followed by standard chemoradiation. Chua et al. conducted a phase II study of 105 poor risk patients with rectal cancer treated with induction capecitabine-oxaliplatin before receiving standard chemoradiation. Poor risk was defined according to MRI findings as (a) tumor extending to within 1 mm of, or beyond, the mesorectal fascia; (b) T3 low-lying tumor at or below the levators; (c) tumor extending 5 mm or more into the perirectal fat; and (d) T4 tumor. Of the 97 patients in the study, 93 eventually underwent complete negative-margin resections. The EXPERT-C phase II study, which included 165 patients with “high-risk” rectal cancers defined on the basis of MRI findings, treated with four cycles of induction chemotherapy, reported a similar, 96% R0 resection rate.

For patients with pelvic recurrence who have not previously received radiation, preoperative chemoradiotherapy should be strongly considered. Reirradiation is also a consideration in patients with recurrent disease. In a multicenter study, Valentini et al. reported an 8.5% rate of complete pathologic response and a 29% rate of downstaging following reirradiation. Because robust clinical data on long-term normal tissue recovery and radiation tolerance doses are sparse, reirradiation is controversial, although it has been shown to have acceptable risks of toxicity. Considering the available evidence, reirradiation should be prescribed on a case-specific basis.

Additional Studies

Preoperative evaluation, including physical examination and imaging, will determine the need for any additional studies such as pelvic ultrasound, cystoscopy, or dedicated sacral bone evaluation. Cystoscopy may be necessary before surgery, or it may be intraoperatively performed. Temporary ureteral catheters should be used liberally, especially in cases of recurrent disease. A positron emission tomography scan may identify distant metastatic disease and prevent unnecessary operation with no benefit to the patient and delay systemic chemotherapy.

SURGERY

The expertise of the surgical team should be broad and include specialists in colorectal, urologic, gynecologic, orthopedic, neurologic, and plastic reconstructive surgery. The surgical objective is to achieve complete en bloc resection of the tumor and viscera with negative margins while preserving as much healthy anatomy as possible. Although defining total pelvic exenteration is relatively straightforward, partial exenteration describes a more heterogeneous group of procedures. Total pelvic exenteration is the removal of the rectum with or without sphincter preservation, genitourinary viscera, reproductive organs, regional lymph nodes, and pelvic peritoneum. Anterior pelvic exenteration is defined as the removal of the rectum and genitourinary organs including the bladder, lower ureter(s), prostate, seminal vesicles, uterus, vagina, and cervix. Posterior pelvic exenteration is defined as en bloc resection of the rectum with or without reproductive organs, with bladder preservation. Sacropelvic exenteration is used when the rectal tumor invades or is broadly adherent to the sacrum or the coccyx and requires removal of the bony pelvis.

Preoperative Regimen

Patients who undergo pelvic surgery of such magnitude are at a high risk of major cardiac, respiratory, thrombotic, and wound complications. Medical evaluation to assess surgical risk and optimally treat comorbidity is important. A recent study reported that a dedicated “prehabilitation” program has been beneficial in reducing perioperative risks.

Patients undergo mechanical cathartic bowel preparation and oral antibiotic preparation on the day before surgery. Ureteral stents can be preoperatively placed to help identify and protect the ureters. Parenteral antibiotics are delivered in the operating room along with preoperative deep vein thrombosis prophylaxis. The patient is placed in the lithotomy position, giving the surgeon anterior access to the pelvis and the perineum. Surgery will be performed in one or two stages, depending on the extent of resection, with the potential need to move the patient into the prone position.

Resection

The surgeon first examines the abdomen and evaluates for any hepatic, peritoneal, or retroperitoneal disease, because detection would likely dictate a management change (Figs. 40-1, 40-2, 40-3 and 40-4). It is helpful to identify stable landmarks, including the proximal ureters, the distal aorta, and common iliac vessels, before committing to the deeper pelvic dissection. If dense fibrosis is encountered near the promontory, the iliac veins will be at especially high risk for injury. The most common vein injured in difficult pelvic dissections is the left common iliac vein, because it is typically immobile and fragile and courses from right to left across the midline with little protective tissue overlying it. Apart from the left common iliac vein, other major risk zones for severe bleeding are the retroprostatic or retrovaginal vessels, presacral venous plexus, and pelvic sidewalls.

Lateral dissection begins on the common and external iliac vessels, which are located lateral to the parietal layers of the endopelvic fascia. The medial border of the external iliac vein provides entry onto the medial aspect of psoas major muscle, which, in turn, is the medial border of the obturator internus muscle, which represents the key dissection point for a lateral pelvic sidewall dissection. The obturator internus can be partially removed if it is involved by the tumor, sacrificing the obturator nerve if necessary. The internal iliac artery and vein can be ligated as required. At this point, dissection exposes the lumbosacral trunk, with further caudal dissection exposing the piriformis and splanchnic nerve roots.

If bladder resection is planned, the space of Retzius is dissected, separating the bladder from the symphysis and pubic rami in the retropubic space down toward the levator plate anteriorly. The vesicular veins that drain the bladder into the internal iliac veins should be ligated carefully, because
they are easily torn and difficult to control. Dissection continues until the urethra is encountered and then transected. The anterior levator muscle is resected off the pubic bone and the obturator internus muscle to the ischial spine laterally. If the tumor involves the anterior compartment, then the obturator internus is completely resected.

FIGURE 40-1 In total pelvic exenteration, the lateral dissection begins on the common and external iliac vessels, which are lateral to the parietal layer of the endopelvic fascia. The internal iliac artery and vein are clamped, cut, and tied distal at their origin. The ureter is cut in the pelvis with care to preserve ureter length for reconstruction.

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