Clinical UM Guideline

This document addresses tumor marker Carcinoembryonic Antigen (CEA) testing.

Note: Please see the following related documents for additional information:

• CG-LAB-32 Cancer Antigen 125 Testing
• CG-LAB-35 Cancer Antigen 19-9 Testing

Medically Necessary:

1. CEA testing is considered medically necessary for either clinical scenario (A or B) and the following conditions (C):
   1. As part of initial evaluation for suspected or diagnosed disease; or
   2. To determine whether residual tumor exists post-surgical therapy;
      and
   3. Conditions:
      1. Ampullary adenocarcinoma; or
      2. Appendiceal adenocarcinoma; or
      3. Biliary tract cancer (gallbladder, cholangiocarcinoma); or
      4. Colorectal cancer; or
      5. Malignant pleural mesothelioma; or
      6. Medullary thyroid carcinoma; or
      7. Metastatic breast cancer; or
      8. Multiple Endocrine Neoplasia Type 2 (MEN2); or
      9. Ovarian, primary peritoneal, or fallopian tube cancer; or
      10. Pancreatic neoplasms; or
      11. Rectal cancer or;
      12. Small bowel adenocarcinoma (duodenum, jejunum, ileum).
2. CEA testing is considered medically necessary for the evaluation of occult primary cancer.
3. Repeat CEA testing* is considered medically necessary when used to:
   1. Monitor response to therapy; or
   2. Assess for recurrence when suggested by clinical factors.

*See Discussion/General Information section below for additional information on medical society guideline recommendations regarding the clinical appropriateness of testing frequency.

Not Medically Necessary:

CEA testing is considered not medically necessary when the above criteria are not met, including, but not limited to, as a screening test in an average risk individual.

The following codes for treatments and procedures applicable to this guideline are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member’s contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services are Medically Necessary:

Carcinoembryonic antigen (CEA) is a protein normally found in embryonic or fetal tissue. Serum levels of CEA disappear almost completely after birth, but small amounts may continue to be present in the colon. In adults, CEA may be elevated in malignancies that produce the protein, particularly mucinous cancers associated with the gastrointestinal tract or ovaries. CEA is a tumor biomarker, but its low specificity and sensitivity makes it unsuitable for cancer diagnosis. CEA testing does have value when used to monitor progression or regression following treatment of specific conditions.

A Cochrane Review by Nicholson (2015) found that CEA is insufficiently sensitive to be used alone for the evaluation of colon cancer, even with a low threshold. The authors concluded that trying to improve sensitivity by adopting a low threshold resulted in high numbers of false recurrence concerns. The authors recommend augmenting CEA monitoring with another diagnostic modality when used in the evaluation of colorectal cancer recurrence, and applying the highest CEA cut‐off assessed (10 µg/L).

Neither current literature, the United States Preventive Services Task Force (USPSTF), or the National Cancer Institute (NCI) support routine screening for colon cancer with CEA testing. CEA testing recommendations are based predominately on the American Society of Clinical Oncology (ASCO) and National Comprehensive Cancer Network^® (NCCN) guidelines.

Serum CEA testing has additional uses as a prognostic indicator for appendiceal carcinoma, as well for the evaluation and treatment of certain cancers when a more specific marker is not expressed by the tumor. These conditions include cholangiocarcinoma, gallbladder cancer, medullary thyroid cancer, metastatic breast cancer, mucinous ovarian cancer, Multiple Endocrine Neoplasia (MEN)-Type 2, or some occult primary cancers.

Serum CEA is also used for the evaluation of jaundice, abnormal liver function tests, obstruction or abnormality of the bile duct, and to exclude a diagnosis of some types of mesothelioma.

CEA levels may be measured in other body fluids, for example pancreatic cyst fluid, to differentiate mucinous pancreatic cysts from other cyst types.

Ampullary Adenocarcinoma

Ampullary cancers originate from the ampulla of Vater (ampulla, the intraduodenal area of the bile duct, and the intraduodenal area of the pancreatic duct) or from periampullary areas (head of the pancreas, distal bile duct, duodenum). The 2024 NCCN ampullary adenocarcinoma guidelines recommend baseline CEA testing.

Neoadjuvant systemic therapy may be considered, particularly in individuals at high risk, including those with elevated CEA levels. After adjuvant therapy, CEA and/or CA 19-9 levels should be measured during surveillance every 3 to 6 months for 2 years, then every 6 to 12 months for up to 5 years or as clinically indicated.

Appendiceal Adenocarcinoma

Primary appendiceal adenocarcinoma is a rare type of cancer. Primary appendiceal mucinous adenocarcinoma has an age-adjusted incidence of 0.12 per million per year, appendiceal cancer is frequently discovered incidentally during an appendectomy following acute appendicitis. Management is based upon the classification, grade and stage of the neoplasm. The use of tumor markers as a prognostic factor in individuals undergoing treatment has been evaluated, CEA has been determined to be an independent marker regarding progression-free and overall survival, or indicative of higher disease burden (Fackche, 2021).

The NCCN Clinical Practice Guideline on colon cancer (V4.2024) note that for appendiceal adenocarcinoma, CA 19-9 and CEA levels should be measured at clinical presentation and abnormal measurements trended. These two tumor markers are used as prognostic indicators for individuals receiving treatments such as cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.

Biliary Tract Cancers (gallbladder, intrahepatic cholangiocarcinoma, and extrahepatic cholangiocarcinoma)

Gallbladder cancer is the most common type of biliary tract cancer, although it is considered to be rare with an estimated 12,350 new cases diagnosed and 4530 deaths in 2024 (American Cancer Society). Compared to CCA, gallbladder cancer is associated with poorer outcomes (NCCN V3.2024).

The 2024 NCCN biliary tract cancer guideline recommends CEA testing after initial hepatobiliary surgery as part of a post-operative work up for gallbladder cancer, or when a mass on imaging or jaundice are present, as well as for surveillance after resection, as clinically indicated.

Cholangiocarcinoma (CCA), also known as bile duct cancer can start in any part of the bile duct system. Bile duct cancer types are based on their origin. Nearly all bile duct cancers are CCAs, a type of adenocarcinoma that may start in the gland cells that line the bile duct (American Cancer Society, 2021).

The 2015 American Hepato-Pancreato-Biliary Association expert consensus statement on intrahepatic CCA note that the tumor markers CA19-9 and CEA are not sufficiently sensitive enough to definitively rule out intrahepatic CCA when the levels are normal. However, discordance between tumor marker elevation and imaging results may suggest combined hepatocellular carcinoma and cholangiocarcinoma. CEA tumor markers are indicated as part of the workup for CCA. CEA is elevated in 15-20% of CCA cases.

The NCCN recommends CEA testing to assist detection of intrahepatic CCA during the evaluation of an isolated intrahepatic mass when the imaging characteristics are consistent with malignancy but not consistent with hepatocellular carcinoma, as well as when there is a clinical suspicion of biliary tract cancer in the presence of pain, jaundice, abnormal liver function tests, mass, or obstruction on imaging. The guidelines note that CEA is not a specific tumor marker, and that CEA testing should not be done to confirm a diagnosis of biliary tract cancer.

The NCI also recommends CEA tumor marker to detect, diagnose, and stage bile duct cancer (NCI, 2018).

Colorectal Cancer

Worldwide, colorectal cancer is the third most common form of cancer. In 2020, there were an estimated 1.93 million new cases of colorectal cancer and 935,173 deaths. Colorectal cancer affects the sexes almost equally. Among all racial groups in the United States, Black individuals have the highest colorectal cancer incidence and mortality rates. Serum CEA testing is not a valuable screening tool for rectal cancer because of its low sensitivity and low specificity. Postoperative CEA testing is valuable in individuals who are potential candidates for further intervention with stage II or III rectal cancer, and those with rectal cancer who would be candidates for resection of liver metastases (NCI, 2024).

A 2019 ASCO guideline for the treatment of individuals with early-stage colorectal cancer recommends CEA testing for post-treatment surveillance at the following testing frequencies (Costas-Chavarri, 2019):

• Every 6 months for 3 to 5 years for treated individuals with stage II colorectal cancer at standard or high risk
• Every 6 months for 3 to 5 years for treated individuals with early-stage rectal cancer at standard risk
• Every 6 months for 5 years for treated individuals with early-stage rectal cancer at high risk

In their 2020 guideline for the treatment of individuals with late-stage colorectal cancer, ASCO recommends CEA testing every 6 months for 5 years after curative resection of metastatic disease for late-stage colorectal cancer (Chiorean, 2020).

The 2024 NCCN Colon Cancer guideline recommends CEA testing in the initial evaluation of individuals with the following:

• A pedunculated or sessile polyp (adenoma) with invasive cancer when there is a fragmented specimen or the tumor margin cannot be assessed or when unfavorable histologic features are present
• Appendiceal adenocarcinoma
• Suspected or proven metastatic adenocarcinoma

The 2024 NCCN guideline recommends the following CEA testing surveillance protocols after colon cancer treatment for individuals who are candidates for further intervention:

• Stage I disease: CEA surveillance is not recommended
• Stage II, Stage III or Stage IV disease: CEA every 3–6 months for 2 years, then every 6 months for a total of 5 years
• Routine CEA monitoring is not recommended beyond 5 years
• CEA testing is recommended once for initial evaluation in appendiceal adenocarcinoma when abnormal levels are present as necessary to assess the presence of recurrent disease

Additionally, 2024 NCCN Guidelines addressed the management of increasing CEA levels in the following statement:

In a retrospective chart review at Memorial Sloan Kettering Cancer Center, approximately half of elevations in CEA levels after resection of locoregional CRC were false positives, with most being single high readings or repeat readings in the range of 5 to 15 ng/mL. In this study, false-positive results greater than 15 ng/mL were rare, and all results greater than 35 ng/mL represented true positives. Following a systematic review and meta-analysis, the pooled sensitivity and specificity of CEA at a cutoff of 10 ng/mL were calculated at 68% (95% Confidence Interval [CI], 53–79) and 97% (95% CI, 90–99), respectively. In the first 2 years post-resection, a CEA cutoff of 10 ng/mL is estimated to detect 20 recurrences, miss 10 recurrences, and result in 29 false positives.

The American College of Obstetricians and Gynecologists (ACOG) published a Clinical Update in 2022 (Ray, 2022) addressing lower gastrointestinal tract disorders. This clinical update notes that individuals with mutation in the BRCA1 or BRCA2 genes have higher risk to develop colorectal cancer, but no guidelines recommend extraordinary colorectal cancer screening for these individuals. The update goes on to state that:

Until such time as more evidence and directed guidelines are established, breast cancer gene mutation carriers should undergo screening in accordance with recommendations for the general population (or sooner if positive family history). After a diagnosis is established, CEA is useful to monitor the patient’s response to treatment.

Lung Cancer

Nasralla (2020) published a meta-analysis of the predictive value of CEA tumor marker in 4666 individuals with clinical stage I non-small cell lung cancer. The meta-analysis was performed to determine the association of high CEA with death within 5 years and as a predictor of lymph node involvement. The most common tumor sub-type was adenocarcinoma, and the most frequently performed procedure was lobectomy. The analysis revealed that elevated CEA level was associated with increased rates of lymph node involvement and increased mortality. High CEA had an Odds Ratio (OR) of death within 5 years that is 3.17 times that of low CEA (95% CI, 1.75 to 5.73; p=0.0001). For nodal status, high CEA had an increased odds of positive nodal metastases (95% CI, 2.64 to 5.62; p<0.00001) compared to low CEA. The authors concluded that there is correlation between the CEA level and both nodal involvement and survival. Measuring preoperative CEA in early stage non-small cell lung cancer may identify individuals with advanced disease not detected by CT scans, candidates for invasive mediastinal lymph node staging, and assist in planning the most efficacious therapy.

However the 2020 ASCO Thoracic Cancer guideline (Schneider, 2020) Recommendation # 4 states:

Clinicians should not use circulating biomarkers as a surveillance strategy for detection of recurrence in patients who have undergone curative-intent treatment of stage I-III Non-small cell lung cancer or small cell lung cancer. While several studies have demonstrated an association with elevated CEA in the postoperative period and reduced survival, other studies have failed to confirm these findings. Importantly, most of these studies were restricted to stage I patients and used different cutoff values for “positivity.” In addition, coexisting inflammatory conditions like chronic obstructive pulmonary disease and smoking have been known to cause false elevations in CEA, which could affect the interpretability of results. Given these inherent challenges, coupled with the inconsistent data, CEA is not recommended as routine surveillance after curative-intent approaches for non-small cell lung cancer. (Informal consensus; Evidence quality: Intermediate; Strength of recommendation: Moderate).

Malignant Pleural Mesothelioma

A 2018 ASCO treatment guideline recommends immunohistochemistry exam in conjunction with biomarkers expected to be positive in mesothelioma, as well as biomarkers expected to be negative in mesothelioma (for example, CEA) to exclude a diagnosis of malignant pleural mesothelioma (Kindler, 2018).

Medullary Thyroid Cancer and Multiple Endocrine Neoplasia type 2

Medullary thyroid cancer, or MTC, is a cancer that forms in the thyroid. MTC occurs when the parafollicular cells of the thyroid gland become cancerous. MTC is the rarest type of thyroid cancer accounting for 3% to 4% of all thyroid cancers. About 1000 people are diagnosed each year in the United States. MTC is also more common in natal females than natal males. Twenty-five percent of MTC cases run in families. MTC may be passed down when families carry a change in the RET gene that causes a condition called Multiple Endocrine Neoplasia type 2, or MEN2. MEN2 is a genetic syndrome that increases the risk of developing MTC and other types of endocrine cancers. Individuals with MEN2A have a high chance (90%) of getting MTC and other cancers. MEN2A is rare, affecting 1 in 40,000 people (NIH, 2019).

The 2024 NCCN Neuroendocrine and Adrenal Tumor Guidelines recommends CEA testing for MEN-Type 2 evaluation, and also recommends a baseline CEA for 2-3 months postoperatively in medullary thyroid carcinoma diagnosed after initial surgery. If the basal serum CEA is within reference range, then the CEA level should be tested annually, if the basal CEA is elevated then CEA should be repeated every 6–12 months (NCCN V3.2024 – Medullary Thyroid Carcinoma).

Metastatic Breast Cancer

The 2012 ASCO Breast Cancer Follow-Up and Management After Primary Treatment Guideline Update states that breast cancer tumor marker CEA testing is not recommended for routine surveillance of individuals with breast cancer after primary therapy.

In their Invasive Breast Cancer Guideline, the NCCN (2024) states that rising levels of serum tumor markers (for example, carcinoembryonic antigen [CEA], CA 15-3, CA 27.29) can be used as unequivocal evidence of ineffective therapy or acquired resistance to establish disease progression or recurrence.

Occult Primary Cancer (also known as Cancer of Unknown Primary origin [CUP])

Cancers are named based on their primary site regardless of where in the body they spread. The NCI defines Occult Primary Cancer as a cancer in which the site of the original tumor cannot be found. When metastatic carcinoma is histologically confirmed in the absence of clinical, radiographic, or pathologic findings of the primary site, it is called occult primary cancer or cancer of unknown primary (CUP). CUP can sometimes be classified in categories that predict the primary site and target therapies to increase survival (Conner, 2015).

The NCCN 2024 Occult Primary Cancer Guideline identified CEA as a useful marker for CUP, specifically when medullary thyroid carcinoma, hepatocellular carcinoma, or mesothelioma is suspected.

Ovarian, primary peritoneal, or fallopian tube cancer

Ovarian tumors consist of several histopathologic entities with epithelial ovarian cancer accounting for approximately 90% of cases. Epithelial cancer subtypes include endometrioid, carcinosarcoma, clear cell, mucinous, and borderline epithelial tumors. Approximately 12-15% of all ovarian tumors are categorized as primary mucinous tumors. The majority of primary mucinous tumors are benign (75%) with the rest classified as borderline (10%) and malignant (15%) (Cho, 2014).

The 2021 ASCO Assessment of Adult Women With Ovarian Masses and Treatment of Epithelial Ovarian Cancer guideline recommends a CEA test to differentiate primary mucinous carcinoma of the ovary from metastatic gastrointestinal cancer when a biopsy cannot be performed. Cytologic evaluation combined with a serum cancer antigen 125 to CEA ratio > 25 can confirm the primary diagnosis.

Additionally, the 2024 NCCN Ovarian Cancer, Fallopian Tube Cancer, and Primary Peritoneal Cancer guideline recommends a CEA test for suspected or confirmed mucinous neoplasms of the ovary. The guideline for mucinous ovarian cancer recommends surveillance with repeat CEA testing for individuals with Stage I, II, III, and IV after primary treatment if the CEA tumor marker was initially elevated.

Pancreatic neoplasms

CEA is increased in 30%–60% of individuals with pancreatic cancer. Although carbohydrate (or cancer) antigen 19-9 (CA19-9) is the most important serum biomarker in pancreatic cancer, the diagnostic and prognostic value of CEA is increasingly being recognized.

In 2015, the American Gastroenterological Association (AGA) published a Technical Review on the Diagnosis and Management of Asymptomatic Neoplastic Pancreatic Cysts. Mucinous cysts include Intraductal Papillary Mucinous Neoplasm (PMN) and mucinous cystic neoplasms, both of which have malignant potential. Nonmucinous cysts, such as serous cysts and pseudocysts, have very low or no malignant potential. The review determined that the largest prospective study concluded that measurement of CEA level was most useful. Endoscopic ultrasonography morphology and cytology were also evaluated individually and in combination. Although the combination of endoscopic ultrasonography morphology, cytology, and CEA level had a higher sensitivity than CEA level alone (91% compared to 75%, respectively), the combination had a lower specificity than the CEA level (p<0.0001) (Scheiman, 2015).

Meng (2017) published a systematic review and meta-analysis of the diagnostic and prognostic value of CEA in pancreatic cancer. The authors pooled data for 3650 participants enrolled in 19 studies to assess the diagnostic accuracy of various biomarkers used in the diagnosis and prognosis of pancreatic cancer. The pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of a CEA-based panel were 0.45 (95% CI, 0.41–0.50), 0.89 (95% CI, 0.86–0.91), 5.39 (95% CI, 3.16–9.18), and 0.55 (95% CI, 0.41–0.72), respectively. The CEA-based panel had increased diagnostic accuracy compared with CEA or CA19-9 alone (p=0.011). In a subgroup analysis by ethnicity, 6 studies were conducted in an Asian population and the remaining 5 in a Caucasian population. Regardless of ethnicity a high level of CEA was a predictor of poor overall survival of pancreatic cancer (Asian: HR, 1.56; 95% CI, 1.35–1.80), (Caucasian: HR, 1.37; 95% CI, 1.23–1.52,). The authors concluded that a biomarker panel including CEA level is better at diagnosing pancreatic cancer than CA125 or CA19-9 alone, but that this finding should be confirmed by further multicenter, prospective clinical studies to enable a definitive conclusion to be made.

The 2024 NCCN Pancreatic Adenocarcinoma Guideline recommends CEA testing for neoplastic pancreatic cysts to distinguish mucinous from non-mucinous malignant cyst types and to determine baseline levels for individuals with Lewis Antigen negative cysts. Approximately 5-10% of individuals are Lewis antigen negative These are individuals that are non-secreting of CA19-9, the most important biomarker for pancreatic cancer, and will have a normal CA19--9 level. In such individuals CEA testing is recommended.

Rectal Cancer

Rectal cancer is a type of cancer that forms in the tissues of the rectum. Colorectal cancer is caused by certain changes to the way colorectal cells function, especially how they grow and divide into new cells. There are many risk factors for colorectal cancer, but many do not directly cause cancer. Instead, they increase the chance of DNA damage in cells that may lead to colorectal cancer. When found in higher than normal amounts CEA can be a sign of rectal cancer.

The 2024 NCCN Guideline for rectal cancer with or without proven metastases recommends CEA testing as part of the clinical work up (NCCN V2.2024).

The 2024 NCCN and ASCO guidelines recommend surveillance CEA testing in individuals with Stage I, II, III, and IV disease every 3–6 months for 2 years, then every 6 months for a total of 5 years.

Small Bowel Adenocarcinoma (duodenum, jejunum, ileum)

The small intestine is the longest segment of mucosa in the gastrointestinal tract. Small bowel adenocarcinoma or cancer of the small intestine is an uncommon disease, representing only 0.06% of all new cancers diagnosed each year (Chen, 2018).

The 2024 NCCN Small Bowel Adenocarcinoma guideline recommends CEA for the evaluation of jejunum, ileum, gastrointestinal, and metastatic adenocarcinoma. The surveillance protocol recommendations include CEA every 3-6 months for a period of 2 years, then every 6 months for a total of 5 years.

Other relevant information

FDA labeled indications exists for a number of assays for quantitative measurement of CEA in serum and plasma to aid in the management of individuals with cancer in whom changing concentrations of CEA are observed.

The Centers for Medicare & Medicaid Services (CMS) National Coverage Determination (NCD)190.26 titled, Carcinoembryonic Antigen was last updated 11/25/2002. This document establishes when CEA testing is covered for Medicare enrollees.
Available at: https://www.cms.gov/medicare-coverage-database/view/ncd.aspx?ncdid=118&ncdver=1&keyword=CEA&keywordType=starts&areaId=all&docType=NCD&contractOption=all&sortBy=relevance&bc=1.

Conclusion

The use of CEA testing in oncologic disease is in accordance with generally accepted standards of medical practice and considered clinically appropriate for the evaluation, staging, treatment planning, monitoring of treatment response, and surveillance.

Carcinoembryonic Antigen (CEA): A glycoprotein molecule that is associated with specific forms of cancer, particularly colorectal cancer. CEA may be used as a biomarker in diagnostic and prognostic evaluations.

Hepatobiliary cancers: An aggressive grouping of cancers which originate in the liver. These cancers include hepatocellular carcinoma (HCC), gall bladder, and intrahepatic and extrahepatic cholangiocarcinoma (bile ducts).

Progression: Disease worsens or spreads without ever having gone away.

Recurrence: Cancer that has returned post treatment, often undetected for a certain period of time. The recurrence can happen at the same location as the initial tumor or at a different site in the body.

Screening Test: A test administered to individuals when there are no signs or symptoms of a specific condition.

Surveillance: Used to detect early signs of recurrence in diseases, particularly cancer, or to monitor individuals at an increased risk of a disease.

Peer Reviewed Publications:

1. Chen EY, Vaccaro GM. Small Bowel Adenocarcinoma. Clin Colon Rectal Surg. 2018; 31(5):267-277.
2. Cho HY, Kyung MS. Serum CA19-9 as a predictor of malignancy in primary ovarian mucinous tumors: A matched case-control study. Med Sci Monit. 2014; 20:1334-1339
3. Conner JR, Hornick JL. Metastatic carcinoma of unknown primary: diagnostic approach using immunohistochemistry. Adv Anat Pathol. 2015; 22(3):149-167.
4. Fackche N, Schmocker RK, Kubi B, et al. The utility of preoperative tumor markers in peritoneal carcinomatosis from primary appendiceal adenocarcinoma: an analysis from the US HIPEC collaborative. J Gastrointest Surg. 2021; 25(11):2908-2919.
5. Meng Q, Shi S, Liang C, et al. Diagnostic and prognostic value of carcinoembryonic antigen in pancreatic cancer: a systematic review and meta-analysis. Onco Targets Ther. 2017; 10:4591-4598.
6. Nasralla A, Lee J, Dang J, et al. Elevated preoperative CEA is associated with subclinical nodal involvement and worse survival in stage I non-small cell lung cancer: a systematic review and meta-analysis. J Cardiothorac Surg. 2020; 15(1):318.

Government Agency, Medical Society, and Other Authoritative Publications:

1. Chiorean EG, Nandakumar G, Fadelu T, et al. Treatment of patients with late-stage colorectal cancer: ASCO resource stratified guideline. JCO Glob Oncol. 2020; 6:414-438.
2. Costas-Chavarri A, Nandakumar G, Temin S, et al. Treatment of patients with early-stage colorectal cancer: ASCO Resource-Stratified Guideline. J Glob Oncol. 2019; 5:1-19.
3. Centers for Medicare and Medicaid Services (CMS). National Coverage Determination: Carcinoembryonic Antigen. NCD #190.26. Effective November 25, 2002. Accessed on March 26, 2024. Available at: https://www.cms.gov/medicare-coverage-database/view/ncd.aspx?ncdid=118&ncdver=1&keyword=CEA&keywordType=starts&areaId=all&docType=NCD&contractOption=all&sortBy=relevance&bc=1. Accessed on April 5, 2024.
4. Khatcheressian JL, Hurley P, Bantug E, et al.; American Society of Clinical Oncology. Breast cancer follow-up and management after primary treatment: American Society of Clinical Oncology clinical practice guideline update. J Clin Oncol. 2013; (7):961-965.
5. Kindler HL, Ismaila N, Armato SG 3rd, et al. Treatment of malignant pleural mesothelioma: American Society of Clinical Oncology clinical practice guideline. J Clin Oncol. 2018; 36(13):1343-1373.
6. National Cancer Institute. Bile Duct Cancer Diagnosis. Updated May 18, 2022. Available at: https://www.cancer.gov/types/liver/bile-duct-cancer/diagnosis. Accessed on March 27, 2024.
7. National Cancer Institute. Colorectal Cancer Prevention (PDQ^®)-Health Professional Version. Updated August 18, 2023. Available at: https://www.cancer.gov/types/colorectal/hp/colorectal-prevention-pdq. Accessed on March 27, 2024.
8. National Cancer Institute. Rare Tumors. Medullary Thyroid Cancer (MTC). February 27, 2019. Available at: https://www.cancer.gov/pediatric-adult-rare-tumor/rare-tumors/rare-endocrine-tumor/medullary-thyroid-cancer. Accessed on June 14, 2023.
9. National Cancer Institute. Rectal Cancer (PDQ)-Health Professional Version. Updated February 15, 2024. Available at: https://www.cancer.gov/types/colorectal/hp/rectal-treatment-pdq. Accessed on June 7, 2024.
10. National Cancer Institute. Tumor Marker Tests in Common Use. Updated December 7, 2023. Available at: https://www.cancer.gov/about-cancer/diagnosis-staging/diagnosis/tumor-markers-list. Accessed on March 27, 2024.
11. NCCN Clinical Practice Guidelines in Oncology^®. © 2024 National Comprehensive Cancer Network, Inc. For additional information visit the NCCN website: http://www.nccn.org/index.asp. Accessed on July 26, 2024.
    • Ampullary Carcinoma (V.1.2024). Revised December 13, 2023.
    • Biliary Tract Cancers (V.3.2024). Revised July 2, 2024.
    • Breast Cancer (V.4.2024). Revised July 3, 2024.
    • Colon Cancer (V4.2024). Revised July 3, 2024.
    • Intrahepatic Cholangiocarcinoma (V.3.2024). July 2 19, 2024.
    • Neuroendocrine and Adrenal Tumors (V.1.2024). Revised August 2, 2023.
    • Occult Primary Cancer (V2.2024). Revised April 29, 2024.
    • Ovarian Cancer Including Fallopian Tube Cancer and Primary Peritoneal Cancer (V3.2024). Revised July 15, 2024.
    • Pancreatic Adenocarcinoma (V.2.2024). Revised April 30, 2024.
    • Rectal Cancer (V3.2024). Revised July 3, 2024.
    • Small Bowel Adenocarcinoma (V.4.2024). July 3, 2024.
    • Thyroid Carcinoma – Medullary Carcinoma (V.3.2024). Revised June 18, 2024.
12. Nicholson BD, Shinkins B, Pathiraja I, et al. Blood CEA levels for detecting recurrent colorectal cancer. Cochrane Database of Syst Rev. 2015;(12):CD011134.
13. Ray J, LaBundy J. Lower Gastrointestinal Tract disorders: clinical updates in women's health care primary and preventive care review. Obstet Gynecol. 2022; 139(6):1201.
14. Scheiman J, Hwang J, Moayyedi P. American Gastroenterological Association technical review on the diagnosis and management of asymptomatic neoplastic pancreatic cysts. Gastroenterology 2015;148:824–848.
15. Schneider BJ, Ismaila N, Aerts J, et al. Lung cancer surveillance after definitive curative-intent therapy: ASCO Guideline. J Clin Oncol. 2020; 38(7):753-766.
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Carcinoembryonic Antigen
CEA

The use of specific product names is illustrative only. It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.