Peritoneal carcinomatosis from a colorectal primary represents one of several metastatic pathways. Colorectal cancers may spread by lymphatic and hematogenous dissemination in addition to contiguous and transperitoneal spread. The most common metastatic sites include the liver, lung, regional lymph nodes, and peritoneum. Although peritoneal carcinomatosis is often considered a late stage of disease progression, transcoelomic spread of colorectal cancer is reported to be encountered in 7% of patients undergoing primary surgery.¹

Several factors impact the overall prognosis of colorectal cancer at presentation including local tumor extent, regional lymph node metastases, the presence of mesenteric tumor deposits, and completeness of resection. Residual tumor after definitive surgical therapy is an adverse prognostic factor for patients with colorectal cancer. Patients who are diagnosed with early-stage colorectal cancer (stage I to III) and undergo successful tumor resection have a 60% to 90% 5-year survival. However, the 5-year survival drops to 8% in patients with stage IV disease. Patients particularly with peritoneal carcinomatosis have a very poor prognosis, with median survival ranging from 6 to 12 months with chemotherapy alone.^2,3

Cytoreductive surgery (CRS) with or without hyperthermic intraperitoneal chemotherapy (HIPEC) has been shown to have a role in patients with peritoneal carcinomatosis secondary to colorectal cancer. Traditionally, malignant seeding of the peritoneal cavity had been thought to indicate abdominal contamination, and complete tumor resection was not considered as a potential treatment option. In the 1930s, CRS was first advocated by Meigs⁴ for patients with ovarian cancer. In the 1960s and 1970s, Munnell⁵ and Griffiths⁶ further developed cytoreduction techniques, demonstrating a survival benefit in patients with ovarian cancer who underwent more radical surgery. Sugarbaker⁷ later demonstrated the benefit of cytoreduction followed by HIPEC in patients with peritoneal disease from various gastrointestinal cancers. Since that time, several studies have been performed investigating the efficacy of CRS/HIPEC using a wide variation of intraperitoneal chemotherapies for multiple peritoneal malignancies including appendiceal cancer, colorectal cancer, and peritoneal mesothelioma.

A comprehensive evaluation is critical in determining the appropriate management of patients with peritoneal carcinomatosis. Patient selection is a key factor to optimize those patients best suited for CRS. Imaging studies, including computed tomography (CT) scans and magnetic resonance imaging (MRI), are commonly used to evaluate the extent of peritoneal disease to guide the appropriate treatment. Diagnostic laparoscopy also plays a role in determining disease extent and may be useful in those patients with indeterminate imaging studies. The goal of surgical cytoreduction is to remove all gross tumor, leaving no residual disease behind. However, radical cytoreduction is associated with increased morbidity, and the degree of morbidity is clearly related to the extent of surgical resection. Some studies quote morbidity after CRS/HIPEC to be as high as 40% to 60%.^8,9

Despite the high surgical morbidity, patients with peritoneal carcinomatosis from colorectal cancer undergoing CRS/HIPEC have been shown to have an improved overall survival and progression-free survival compared to those patients receiving systemic chemotherapy alone.^2,8,10  However, only one radomized trial has been conducted. Furthermore, patient survival is directly related to the extent of disease seen at presentation and the residual disease left behind during surgery. As such, surgical input in guiding the management of patients with peritoneal carcinomatosis from colorectal cancer is necessary to provide the best possible chance to extend survival.

Colorectal cancer is the third most common cancer and the third leading cause of cancer death in men and women in the United States. In 2016, an estimated 70,820 men and 63,670 women were diagnosed with colorectal cancer and 26,020 men and 23,170 women died of the disease.¹¹ Colon cancer is more common in men than women, and more than two-thirds of colorectal cancers are diagnosed in patients older than 65 years.¹² In the United States, the lifetime incidence of colorectal cancer is approximately 5%, but has been decreasing 2% to 3% per year over the past 15 years.¹³ Similarly, the death rates from colorectal cancers have progressively declined over the past 20 years. The improvement in outcomes may be largely explained by detection of colorectal cancers at an earlier stage in conjunction with the development of improved chemotherapy agents.

Despite improvements in the early detection of colorectal cancer over the past two decades, a subset of patients still presents with advanced disease. Approximately 20% to 30% of patients with colorectal cancer present with synchronous liver metastasis.¹⁴ In addition, peritoneal carcinomatosis is encountered in about 7% of patients at primary surgery for newly diagnosed colorectal cancer and will be the sole site of metastatic disease in about half of these patients. Furthermore, peritoneal carcinomatosis will be diagnosed in 4% to 19% of patients during follow-up after curative surgery, in up to 44% of patients with recurrent colorectal cancer who undergo relaparotomy, and in 40% to 80% of patients who die from progression of disease.¹ In another study reviewing 11,124 patients with colorectal cancer, synchronous or metachronous peritoneal carcinomatosis was found in 924 patients (8.3%), and was the sole site of metastasis in 535 patients (4.8%).¹⁵ Using more sensitive detection techniques including peritoneal lavage and cytology, the incidence of peritoneal seeding during potentially curative laparotomy for primary colorectal cancer was found to be 3% to 28%. Finally, 16% of patients receiving first-line chemotherapy for metastatic colorectal cancer have peritoneal carcinomatosis.¹⁶

Peritoneal carcinomatosis from colorectal cancer is more likely to develop in certain clinical settings. Carcinomatosis is more common in patients with more advanced primary tumors. Patients with larger tumors (T4 disease) and lymph node involvement have been demonstrated to have a higher risk of development of peritoneal carcinomatosis during the course of their disease than patients with early T and N0 cancers. Furthermore, patients with a perforated primary tumor, ovarian metastasis, or limited peritoneal carcinomatosis resected at the time of primary tumor resection have all been shown to be associated with a high risk of developing recurrent peritoneal carcinomatosis.^17,18

The clinical presentation of patients with colorectal cancer varies with the stage, location, and extent of disease. Many asymptomatic patients are identified at screening colonoscopy. Patients with a localized tumor may present with abdominal pain, bleeding, anemia, or a change of bowel habits. Limited carcinomatosis may produce few if any symptoms. Signs and symptoms of more extensive peritoneal carcinomatosis include abdominal distention, pain, early satiety, weight loss, or symptoms of intestinal obstruction.

Unfortunately, peritoneal carcinomatosis is often detected late in the course of the disease. As such, patients at high risk for development of peritoneal carcinomatosis should be closely monitored. Some studies have advocated for second-look laparotomy with the possibility of CRS/HIPEC in patients with early peritoneal detection.^18–20 Furthermore, a recent study developed and internally validated a risk score chart for predicting peritoneal recurrence after curative resection for colorectal cancer to help in the planning of treatment and surveillance in high-risk patients.²¹

The evaluation of the patient with suspected peritoneal carcinomatosis from colon cancer is directed toward confirming the diagnosis, determining the extent of involvement, and selecting the appropriate treatment. The presence of peritoneal carcinomatosis is usually identified at the time of surgery for resectable colon cancer or for palliation of bowel obstruction. It can be identified on staging CT scans obtained at the time of the initial diagnosis or from surveillance scans obtained for follow-up of patients during or after treatment. CT scan findings in patients with peritoneal carcinomatosis include ascites, omental or peritoneal thickening, and enhancement, mesenteric effacement, luminal narrowing, and peritoneal nodules or bulky mass lesions.²² These CT findings may also be noted during the evaluation of symptoms such as increasing abdominal pain, abdominal distention, or weight loss in patients with a history of colon cancer. In most patients, pathological confirmation for the presence of peritoneal carcinomatosis is appropriate. In patients with ascites, this may be obtained via paracentesis and cytological analysis of the ascites. Patients with peritoneal or omental nodules may be candidates for image-guided fine-needle aspiration or core needle biopsy to establish a diagnosis. In patients without biopsy-accessible lesions by imaging, diagnostic laparoscopy may be used to confirm the diagnosis of peritoneal carcinomatosis. In some clinical settings with strong CT scan evidence of peritoneal carcinomatosis, a tissue biopsy may not be necessary to initiate treatment.

Once a diagnosis of peritoneal carcinomatosis is established, a complete staging evaluation should be completed prior to planning appropriate treatment. If not already obtained, a contrast-enhanced CT scan of the chest, abdomen, and pelvis will also identify any additional sites of metastatic disease including lungs, liver, and any nodal disease. A serum carcinoembryonic antigen (CEA) level is obtained and, if elevated, can be useful in monitoring the response to treatment and in long-term patient surveillance. 18-Fluoro-deoxyglucose positron emission tomography (FDG-PET) scans are not routinely obtained but can be occasionally useful in identifying sites of metastatic disease.

The magnitude of peritoneal carcinomatosis is critical in determining the appropriate treatment and, ultimately, the prognosis of patients with peritoneal carcinomatosis from colon cancer. The extent of disease has been defined most commonly using the peritoneal carcinomatosis index (PCI) devised by Jacquet and Sugarbaker.²³ The PCI quantifies the size and distribution of peritoneal metastases. The abdomen is divided into nine regions and the small intestine into four regions: each region is assigned a lesion-size score of 0–3 based on the size of the largest lesion within each region (see Chapter 133). A CT-PCI (PCI calculated using preoperative CT scan) is estimated and may be useful in selecting patients for CRS.

In patients with advanced colon cancer, CT scans often underestimate the extent of carcinomatosis. Studies comparing the results of CT-PCI with the PCI calculated at surgical exploration have demonstrated that lesion size is calculated accurately in only 60% to 80% of abdominal regions examined.²² In addition, the presence of metastatic disease is missed in 10% to 35% of abdominal regions.²² The false-positive rate for CT scan–detected lesions is low.²² The accuracy for CT is lowest in the pelvis, lower quadrants, and in identifying small intestinal involvement and highest in the upper abdomen.

Despite the low accuracy in characterizing individual regions or lesions, CT scan remains clinically useful in identifying patients who are acceptable candidates for CRS. Esquivel et al²²  examined the accuracy and clinical relevance of CT-PCI in 52 patients with colorectal cancer. Patients were classified as having low (<10), moderate (10 to 20), or severe (>20) PCI scores. Based on prior outcomes analyses, patients with severe PCI scores can be eliminated as surgical candidates. Only 12% of patients with low or moderate CT-PCI scores were upstaged to severe at operative exploration.²²

Diagnostic laparoscopy is also useful in excluding poor candidates for CRS. Laparoscopy is usually performed prior to full laparotomy to identify patients who are better candidates for systemic chemotherapy and to avoid a long recovery prior to beginning treatment. Patients with high-grade colon cancer, intermediate CT-PCI scores, and clinical symptoms including pain, obstruction, or significant weight loss are good candidates for an initial diagnostic laparoscopy. Most patients have had prior surgery, and postoperative adhesions often limit complete visualization of the peritoneal cavity. The extent of disease and the ability to resect it are determined for each visible abdominal quadrant. The proximal and mid-small intestine are carefully inspected. Multiple lesions involving the bowel wall in this location would preclude successful cytoreduction.

Patient selection is critical in achieving a treatment benefit in the majority of patients undergoing CRS. Only patients receiving a complete (CC-0; no gross residual disease) or near complete cytoreduction (CC-1; residual tumor nodules < 2.5 mm) receive a survival benefit from the procedure.^3,8,9,24 Survival in patients following incomplete cytoreduction (CC-2; residual tumor >2.5 mm) is poor (median survival 5 to 10 months) and CRS/HIPEC should be avoided in these patients.^3,8,9,24

A variety of clinical, radiological, and pathological factors are used to select patients who will benefit from CRS with HIPEC. CRS/HIPEC is a major operative undertaking and should be limited to patients with good performance status (ECOG 0 or 1) and limited comorbidities. CRS/HIPEC carries a high morbidity and mortality in patients over 70 years of age and should be considered carefully in the elderly.²⁵ Significant cancer-related symptoms, including pain or intestinal obstruction, suggest more extensive, aggressive disease with a greater likelihood of incomplete cytoreduction. The majority of patients evaluated for CRS/HIPEC have received or are receiving systemic chemotherapy. Disease progression after 2 to 3 months of neoadjuvant chemotherapy also correlates with poor outcome following surgery. CRS/HIPEC is not warranted in most patients with extraperitoneal disease. Carefully selected patients with limited (less than 3) resectable hepatic metastases and low PCI peritoneal metastases have done well following CRS/HIPEC.^26,27 Finally, high tumor grade including signet ring cell histology is also associated with poor survival following CRS/HIPEC.²⁸