Pelvic Exenteration

Approximately 5%–8.8% of patients who present with colorectal cancer (CRC) will have tumors that spread beyond the anatomic landmarks of a standard total mesorectal excision (TME) resection.[1][2] T4 tumors have a worse overall prognosis than T1–T3 cancers, and decision-making for patients with T4 lesions must be multidisciplinary and highly individualized considering the higher likelihood of the patient requiring a multivisceral resection.[3] For patients who have the physiologic reserve to undergo aggressive treatment and are willing to accept a higher degree of treatment-related morbidity, surgery with curative-intent may be pursued. In this context, the most important goal in surgical planning is obtaining a histologically negative margin (curative [R0] resection), even when resection of multiple organs is required to obtain this margin.[4]

Care of these patients begins with a thorough, patient-specific evaluation including imaging, medical evaluation, preoperative counseling of functional expectations, and potential stoma counseling and education.[1] The extension of tumor beyond the confines of the mesorectum is best assessed by magnetic resonance imaging (MRI).[2] Once identified, these patients require care from a multidisciplinary team, with surgical (e.g., colorectal surgery, gynecology, neurosurgery, orthopedic surgery, plastic and reconstructive surgery, spine surgery, urology), oncological, radiation oncological, radiologic, and pathology expertise and experience in pelvic exenteration. Nearly all patients with locally advanced primary tumors (i.e., beyond the normal TME planes) undergo chemoradiation therapy prior to surgery.[5][6][7]

Optimal patient selection begins with a thorough assessment of the patient’s performance status and overall health. Patients with significant functional impairments and comorbidities may not be appropriate surgical candidates for resections of this magnitude. A patient’s emotional preparedness for undergoing this extensive treatment should also be evaluated, and each patient should be well informed of the functional effects of the planned surgery as well as the short- and long-term risks of complications.[3]

The next step in this process requires the assessment of the anatomical relationships of the tumor and its potential involvement of adjacent pelvic organs and structures. The primary goal of surgery is the achievement of an R0 resection—that is, resection with histologically negative margins. Surgical planning with the aid of a high-resolution MRI can best plan for the required en bloc resection of the victimized organs and structures.[8][9]

A positron emission tomography (PET)–computed tomography (CT) in addition to the usual CT of the chest, abdomen, and pelvis may aid in the detection of occult extra pelvic disease. This imaging modality may assist in excluding patients from futile radical resections in attempts at cure.[10]

The presence of any metastatic disease complicates the decision to pursue pelvic exenteration. Extensive metastatic disease is a contraindication to exenteration; however, patients with limited metastatic disease may be considered for extensive surgery. The role of a multidisciplinary tumor conference is essential in establishing a patient-specific treatment plan. All patients with locally advanced rectal cancer are referred for neoadjuvant chemoradiation therapy. Multimodality therapies, including external beam radiation therapy (EBRT) and neoadjuvant/adjuvant chemotherapy, and, if applicable and available, intraoperative radiation therapy (IORT), should be considered to maximize local control and improve patient survival. Although there are inherent limitations with post-treatment imaging, patients with these types of tumors should generally be rescanned after completing treatment but prior to surgery.[11][12]

The contraindications and limitations of resectability are debated, with the limitations concentrating on the ability to achieve an R0 resection with an acceptable risk for postoperative morbidity. In general, these decisions are best made at experienced centers with the appropriate expertise in pelvic exenteration.

There are four main anatomical categories of tumors requiring extended proctectomy:[13]

1. Axial tumors involve the central pelvic organs and do not invade the anterior, posterior, or lateral pelvic walls.
2. Anterior tumors invade the bladder, vagina, uterus, seminal vesicles, and/or prostate.
3. Posterior tumors invade the sacrum and/or coccyx.
4. Lateral tumors are the most challenging; they involve the pelvic sidewall, including the iliac vessels, pelvic ureters, lateral lymph nodes, pelvic autonomic nerves, and sidewall musculature.

Pelvic exenteration can be described using these anatomic regions; for example "anterior exenteration" for rectal cancer involves excision of the rectum and mesorectum en bloc with anterior structures (Figure 1).

Figure 1, Anterior Structures

The contraindications to pelvic exenteration are patient preference, lack of required phsyiologic reserve, inoperable metastatic disease, and tumor extending to the S1 level of the sacrum. The relative contraindications are distant metastases, metastases to paraaortic lymph nodes, and tumor fixed to more than one nonaxial pelvic structure.[3] It is institution-dependent when lateral recurrences are contraindicated for pelvic exenteration. Many surgeons perform this surgery with experienced teams after careful assessment of requirements to attain an R0 resection.[14] Evidence of bilateral ureteral obstruction may be associated with involvement the bladder trigone, bilateral pelvic sidewall infiltration frozen pelvis, or peritoneal or lymph node metastases.[15][15][16]

Preoperative enterostomal therapist counseling for marking and education is critical to the successful postoperative outcomes associated with the potential need for a colostomy and/or urostomy. Urological consultation for placement of ureteral stents is helpful to assist identification of the ureters and their potential involvement in the required resection. Plastic surgical consultations for perineal defect reconstruction are essential in minimizing risks of wound complications. The options for perineal soft tissue coverage include a rectus myocutaneous flap,[17][18][19] gracilis muscle flap,[20] gluteal rotational flap,[19] free flap,[21] or biological mesh with omentoplasty.[17][22]

It is critical in successful planning for a pelvic exenteration to include a discussion regarding functional outcomes and expectations, including the quality-of-life changes associated with a potential colostomy and/or urostomy as well as bowel, sexual, and urinary dysfunction.[23]