ARCHIVED

Medical Policy

Policy Num:       11.001.020
Policy Name:     Detection of Circulating Tumor Cells in the Management of Patients With Cancer
Policy ID:           [11.001.020]                          [Ar B M- P ]                   [2.04.37]

Last Review:       May 30, 2019
Next Review:      May 30, 2020
Issue:                   5:2019

ARCHIVED

Related Policies:  

2.04.33 Genetic and Protein Biomarkers for the Diagnosis and Cancer Risk Assessment of Prostate Cancer

2.04.36 Assays of Genetic Expression in Tumor Tissue as a Technique to Determine Prognosis in Patients With Breast Cancer

Detection of Circulating Tumor Cells in the Management of Patients With Cancer

Summary

The prognosis of cancer patients is often determined by the occurrence of metastatic disease. Studies have suggested that the presence of circulating tumor cells (CTCs) in patients with metastatic carcinoma is associated with shortened survival. The detection of CTCs might be useful for assessing prognosis and guiding cancer therapy. While studies have shown that the level of CTCs is associated with the presence of metastatic disease and prognosis, the prospective use of this information to impact care has not been demonstrated. Given that insufficient evidence is available to evaluate the impact on patient management or health outcomes and additional remaining questions (eg, the optimal cutoff to use for various conditions) the assessment  of CTCs is considered investigational.

Objective

The objective of this evidence review is to determine whether the impact on patient management or health outcomes and additional remaining questions is sufficient .

Policy Statements

Detection and quantification of circulating tumor cells is considered investigational in the management of patients with cancer.

Policy Guidelines

There are CPT category I codes for this testing: 86152: Cell enumeration using immunologic selection and identification in fluid specimen (eg, circulating tumor cells in blood); 86153: physician interpretation and report, when required.

Benefit Application

BlueCard/National Account Issues

State or federal mandates (eg, FEP) may dictate that certain devices approved by the U.S. Food and Drug Administration may not be considered investigational, and thus these devices may  be assessed only  on the basis of their medical necessity.

Background

Circulating tumor cells (CTCs) are malignant cells that are found in the peripheral blood and originate from primary or metastatic tumors. CTCs could potentially provide prognostic information that could guide treatment decisions or aid in the monitoring of response to treatment. CTCs have been documented in multiple tumor types, such as breast, prostate, lung, and colorectal carcinomas; the largest body of data comes from studies of women with metastatic breast cancer. CTCs have also been investigated as an  additional prognostic factor in nonmetastatic breast cancer and could be used to determine the need for additional adjuvant chemotherapy. Research has focused on the development of methodologies with improved sensitivity and specificity. Physical techniques such as size filtration, density gradient centrifugation, and microscopic morphology continue to be used. However, biological techniques such as immunomagnetic isolation, flow cytometry, immunofluorescent microscopy, reverse-transcriptase polymerase chain reaction, polymerase chain reaction, and fluorescence in situ hybridization have been added to provide required specificity. The CellSearch® System (Janssen Diagnostics) is an example of immunofluorescent technology. The technique involves identification of the circulating tumor cells in blood, which are tagged using antibodycoated magnetic beads that recognize cell surface antigens. The cells are then labeled with fluorescent dyes, which can then be quantified by a semiautomated fluorescent-based microscopy system. Note: This evidence review does not address techniques for the detection of bone marrow disseminated  tumor cells or circulating cell-free DNA

Regulatory Status

The CellSearch® System (Janssen Diagnostics, formerly Veridex) was cleared for marketing by the U.S. Food and Drug Administration through the 510(k) process for monitoring metastatic breast cancer (January 2004), for monitoring metastatic colorectal cancer (November 2007), and for monitoring metastatic prostate cancer (February 2008). The system uses automated instruments manufactured by Immunicon Corp. for sample preparation (CellTracks® AutoPrep) and analysis (CellSpotter Analyzer®),  together with supplies, reagents, and epithelial cell control kits manufactured by Veridex. FDA product code: NQI.

Rationale

This evidence review was originally created in November 2004 and was updated regularly with searches of the MEDLINE database. The most recent literature review was conducted through April 21, 2015. Following is a summary of the key literature to date. Numerous studies have reported the association of circulating tumor cells (CTCs) with prognosis and/or response to treatment in patients with various types of cancer. However, despite these correlational studies, to complete the causal chain, there must be evidence that patient management decisions based on CTC levels increases the duration or quality of life or decreases adverse events. Literature searches have not identified any published studies that prospectively evaluate patient treatment decisions and/or health outcomes in patients managed with and without the monitoring of CTCs. Following is a description  onitoring of CTCs. Following is a description o of the available literature, organized by clinical condition. 

Population Reference No. 1

Metastatic Breast Cancer

In 2012, Zhang et al published a comprehensive meta-analysis of studies on the association between CTCs and health outcomes in patients with breast cancer.1 The analysis included studies of more than 30 patients; used reverse transcriptase-polymerase chain reaction (RT-PCR), CellSearch, or another immunofluorescent technique to detect CTCs; and reported survival data stratified by CTC status. A total of 49 studies met eligibility criteria. In a pooled analysis of 12 studies on metastatic breast cancer, CTC positivity was associated with a significantly increased risk of disease progression (hazard ratio [HR], 1.78; 95% confidence interval [CI], 1.52 to 2.09). CTC positivity was associated with a significantly increased risk of death in patients with metastatic breast cancer (HR=2.23; 95% CI, 2.09 to 2.60; 19 studies). The authors presented a subgroup analysis by detection method; this analysis included studies on nonmetastatic and metastatic breast cancer. Pooled analyses of studies using CellSearch found that CTC positivity significantly increased the likelihood of disease progression (HR=1.85; 95% CI, 1.53 to 2.25; 12 studies) and death (HR=2.45; 95% CI, 2.10 to 2.85; 18 studies). Studies using RT-PCR also found that CTC positivity was significantly associated with disease progression and death. A previous 2011 meta-analysis by Zhao et al considered only studies on CTC detected by RT-PCR.2 A total of 24 studies met inclusion criteria, 5 of which included metastatic breast cancer. The authors did not conduct a separate analysis of studies on metastatic breast cancer. In a pooled analysis of data from 15 studies with 2894 patients, the presence of CTCs was significantly associated with a lower overall survival (OS; HR=3.00; 95% CI, 2.29 to 3.94) and a lower relapse-free survival (RFS; HR=2.67; 95% CI, 2.09 to 3.42). The authors noted substantial heterogeneity among studies including differences in sampling time, detection methods, and demographic or clinical characteristics of the study population. Representative prospective studies using CellSearch immunofluorescent technology for identifying CTC in women with metastatic breast cancer are described next.

In 2004, Cristofanilli et al published a multicenter study that included 177 patients with measurable metastatic breast cancer who were followed up for 38.7 weeks or longer.3 Using the CellSearch System, investigators measured the number of circulating tumor cells before initiating a new line of therapy and at first follow-up (mean [SD], 4.5 [2.4] weeks after baseline sample). Also tested were 145 normal subjects and 200 patients with benign breast diseases. The authors detected 2 or fewer epithelial cells per 7.5 mL of blood in all normal subjects and patients with benign breast diseases. Using a statistically validated threshold of 5 cells per 7.5 mL of blood, they found that patients below threshold at baseline (n=90; 51%) had longer median progression-free survival (PFS; 7.0 months vs 2.7 months, respectively; p<0.001) and OS (18 months vs 10.1 months, respectively; p<0.001) than those above threshold (n=87; 49%). Survival duration of a subgroup (n=33) with values above threshold at baseline but below threshold at first followup (ie, after the first cycle of therapy) was similar to that of patients below threshold at baseline. This subgroup’s median survival also was significantly longer than survival of those who remained above threshold despite therapy. Multivariate analysis showed that being below threshold for level of CTCs was the most statistically significant independent predictor of longer PFS and OS of all parameters studied, including hormone receptor status, HER2/neu status, site of metastases, etc.

Nole et al (2008) tested 80 patients with metastatic breast cancer for CTC levels before starting a new treatment and after 4 weeks, 8 weeks, at the first clinical evaluation, and every 2 months thereafter.4 Forty-nine patients had 5 or more cells at baseline. In multivariate analysis, baseline number of CTCs was associated with PFS (HR=2.5; 95% CI, 1.2 to 5.4). The risk of progression for patients with 5 or more circulating tumor cells at the last available follow-up was 5 times the risk of patients with 0 to 4 CTCs at the same point (HR=5.3; 95% CI, 2.8 to 10.4). Patients with rising or persistent counts of 5 or more CTCs at last available follow-up showed a statistically higher risk of progression compared with patients who had fewer than 5 CTCs at both times of blood sampling.

In 2012, Pierga et al in France reported on a prospective series of 267 patients with metastatic breast cancer who were starting first-line chemotherapy.5 CTCs were analyzed before starting treatment, before the second cycle of treatment, and at the first radiologic evaluation before the third or fourth cycle of treatment. At baseline, 44% of patients were positive for CTC (>5 CTC per 7.5 mL blood). Patients were followed for a median of 14.9 months. During follow-up, there were 57 deaths (21%), and 161 (60%) experienced tumor progression. Baseline CTC count was a strong predictor of PFS (p<0.001). Median PFS was 19.9 months in patients with 0 CTCs and 8.2 months in patients with more than 5 CTCs per 7.5 mL blood. Baseline CTC was also significantly associated with OS (p<0.001). In multivariate analysis, baseline CTC positivity was an independent prognostic factor for both PFS and OS.

Metastatic Prostate Cancer

A 2014 meta-analysis by Ma et al examined studies on the role of CTCs and disseminated tumor cells (DTCs) on the prognosis of prostate cancer (localized, as well as metastatic).6 To be included in the review, studies needed to report the correlation of CTCs or DTCs with 1 or more survival outcomes. The authors assessed 54 studies for eligibility. Thirty-three studies, 27 on CTCs and 6 on DTCs met the inclusion criteria. A pooled analysis of all studies found significantly lower OS in patients with circulating tumor cells (HR=2.43; 95% CI, 2.07 to 2.86). Eight studies with a total of 946 patients used CellSearch technology to detect CTCs. A pooled analysis limited to these studies also found a significant association between CTCs and OS (HR=2.36; 95% CI, 1.95 to 2.85).

Previously, in 2011, Wang et al published a meta-analysis of studies on the association between CTCs and prognosis in patients with metastatic castration-resistant or hormone refractory prostate cancer.7 The authors searched the literature for studies with at least 30 patients and sufficient data to calculate relative risk (RR) of OS. The authors identified 19 relevant articles, 4 of which met study inclusion criteria. The total number of included patients was 486. All studies used the CellSearch System to detect CTCs. In a pooled analysis of the studies, OS was significantly higher in patients with lower levels of CTC compared with those with higher levels (>5 CTC in 7.5 mL blood; RR=2.51; 95% CI, 1.96 to 3.21). In a sensitivity analysis removing the study with the largest sample size (de Bono et al8 ), the RR was marginally higher (RR=3.25; 95% CI, 2.01 to 5.24). The test for study heterogeneity was not statistically significant.

The study by de Bono et al (2008) was prospective and included patients with castration-resistant progressive prostate cancer who were initiating a new cytotoxic therapy.8 CTC levels were measured using the CellSearch System at baseline and before each course of therapy until disease progression or for up to 18 months. A total of 276 patients were enrolled; of these, 33 were subsequently found to not meet eligibility criteria (eg, did not have an evaluable baseline blood sample or scan or lacked progressive disease) and 2 patients withdrew consent, leaving 231 patients in the analysis. At baseline, 219 patients were evaluable for CTCs; of these, 125 had elevated levels (≥5 cells per 7.5 mL of blood), and 94 had less than 5 cells per mL. The primary study outcome was the association between elevated CTCs 2 to 5 weeks after initiating treatment and OS. An evaluable CTC level was available for 203 patients at the 2- to 5-week follow-up, and CTCs were elevated in 39 (19%). The group of patients with elevated CTCs after initiating treatment had a significantly shorter median survival time (9.5 months) than those without elevated CTC (20.7 months; p<0.001). Moreover, patients with elevated CTCs at all time points (n=71) had the shortest median OS, 6.8 months. OS in this group was significantly shorter compared with other groups, specifically the group of patients with elevated baseline CTCs who converted to a nonelevated level after treatment (n=45; median OS=21.3 months) and the group of patients with nonelevated CTCs throughout the study (n=88; median OS >26 months). There were only 26 patients who had nonelevated CTCs at baseline and elevated CTCs after treatment; this group had a mean OS of 9.3 months. A limitation of the study was that only 203 (74%) of the 276 enrolled patients were included in the primary analysis.

Metastatic Colorectal Cancer

In 2015, Huang et al published a meta-analysis of studies on the association between CTCs detected with the CellSearch system and colorectal cancer (CRC) prognosis.9 Eleven studies with a total of 1847 patients met eligibility criteria. Pooled data analyses found that detection of CTCs in patients with CRC was associated with a significantly worse OS (HR for death, 2.00; 95% CI, 1.49 to 2.69; 9 studies) and PFS (HR for progression or death, 1.80; 95% CI, 1.52 to 2.13; 8 studies). In addition, a pooled analysis of 3 studies found that the response to adjuvant chemotherapy was significantly lower in patients with detectable CTCs than those without CTCs (RR=0.79; 95% CI, 0.63 to 0.99).

Previously, a 2013 meta-analysis by Groot Koerkamp et al reviewed studies on the prognostic value of CTCs, as well as studies on the detection of DTCs in bone marrow.10 To be included in the review, studies had to include at least 20 patients with metastatic CRC and report long-term outcomes. A total of 16 eligible studies were included, and 12 had data suitable for meta-analysis. Most studies included detection of CTCs; only 4 included detection of DTCs. Pooled analyses found that detection of CTCs or DTCs in patients with metastatic CRC was associated with a worse OS (HR for death, 2.47; 95% CI, 1.74 to 3.51; 11 studies) and a worse PFS (HR for progression or death, 2.07; 95% CI, 1.44 to 2.98; 9 studies).

Studies have used different cutoffs of CTCs. CellSearch materials recommend using a cutoff of at least 3 CTCs in CRC. 11 This was the cutoff used in the 2008 multicenter industry-sponsored study by Cohen et al.12 Eligible participants needed to be initiating any first- or second-line systemic therapy, or third-line therapy with an epidermal growth factor receptor inhibitor. CTC cells were assessed at baseline and at regular intervals after starting treatment. In a preplanned interim analysis, the authors determined that at least 3 CTCs per 7.5 mL blood was the optimal cutoff to use to indicate elevated CTC level. The primary outcome was the agreement between CTC level at the 3- to 5-week follow-up and response to therapy. Agreement was defined as either a nonelevated level of CTC corresponding to lack of disease progression or an elevated level corresponding to progressive disease. A total of 481 patients were enrolled, and there were 430 evaluable patients, 320 of whom were assessable for the primary outcome. Thirty-eight (12%) of 320 patients had elevated levels of CTCs 3 to 5 weeks after starting treatment. By the end of the study, 20 (53%) of these 38 patients had progressive disease or were unavailable because they had died before receiving a follow-up imaging study. In comparison, 54 (19%) of the 282 patients without elevated CTCs at the 3- to 5-week follow-up had progressive disease or had died (p value not reported). OS and PFS were reported as secondary outcomes. Patients with elevated baseline CTC levels (at least 3 per 7.5 mL blood) had shorter mean PFS and OS than patients with nonelevated baseline CTCs (<3 per 7.5 mL blood). Median PFS was 4.5 and 7.9 months, respectively (p<0.001), and median OS was 9.4 and 18.5 months, respectively (p<0.001). A study limitation is that only 320 (67%) of 481 enrolled patients were included in the primary analysis.

More recent studies have used other cutoffs. For example, a 2014 prospective study by Seeberg et al used a cutoff of 2 or more CTCs per 7.5 mL blood.13 The study included 194 patients with colorectal liver metastases. The presence of more than 2 CTCs was associated with significantly shorter survival time in the whole group of patients (p<0.001) and in patients with resectable disease (p=0.037) compared with patients with fewer than 2 CTCs. Moreover, the presence of 2 or more CTCs was associated with significantly shorter RFS in the total patient population (p=0.002) and in resectable patients (p<0.001). A 2015 prospective study by Bork et al used a cutoff of at least 1 cell per 7.5 mL blood.14 The study included 287 patients with potentially curable CRC. CTC detection was significantly associated with worse OS in the entire cohort (48.4 months for CTC-positive patients vs 33.6 months for CTC-negative patients, p<0.001). Additional prospective studies are needed to confirm the prognostic value of the 1 or 2 cells per 7.5 mL blood cutoff.

Other Conditions

Studies have also been published evaluating CTC level as a diagnostic and/or prognostic marker for patients with other types of cancer. There are no U.S. Food and Drug Administration‒cleared tests for these indications, and none of the studies evaluated patient management decisions using levels of CTCs. Conditions studied include lung,15-18 bladder,19-21 pancreatic,22 gastric,23 hepatocellular,24 and head and neck cancer,25 and melanoma.26,27 A meta-analysis on lung cancer predominantly included studies using the CellSearch system. This study was published in 2014 by Zhang et al. 28 The authors identified 7 studies with 440 small-cell lung cancer patients. All studies were prospective, and 5 used the CellSearch system. Meta-analyses found that higher baseline CTC level was associated with a lower OS (HR for death, 1.90; 95% CI, 1.19 to 3.04) and lower PFS (HR for progression or death, 2.60; 95% CI, 1.90 to 3.54). Data from all 7 studies were included in the OS analysis, and only 3 studies contributed data to the PFS analysis. 

Ongoing and Unpublished Clinical Trials

Some currently unpublished trials that might influence this policy are listed in Table 1.

Table 1. Summary of Key Trials

Summary of Evidence

While studies have shown that the level of circulating tumor cells (CTCs) is associated with the presence of metastatic disease and prognosis, the prospective use of this information to impact care has not been demonstrated. Given that insufficient evidence is available to evaluate the impact on patient management or health outcomes and additional remaining questions (eg, the optimal cutoff to use for various conditions) the assessment of CTCs is considered investigational.

Supplemental Information

Practice Guidelines and Position Statements

American Society of Clinical Oncology

Recommendations for the use of tumor markers in breast cancer, published in 2007, indicate that the measurement of CTCs should not be used to make the diagnosis of breast cancer or to influence any treatment decisions in patients with breast cancer.29

National Comprehensive Care Network

Their 2015 Clinical Practice Guidelines do not include recommendations regarding detection of CTCs used in the management of patients with breast, colon or prostate cancer.30-32

National Academy of Clinical Biochemistry

In 2009, the National Academy of Clinical Biochemistry issued a guideline on the use of tumor markers in testicular, prostate, colorectal, breast, and ovarian cancer. The only mention of CTCs was related to prostate cancer. The panel concluded that the measurement of circulating prostate cancer cells was not sufficiently validated to recommend its application in routine clinical practice.33

U.S. Preventive Services Task Force Recommendations

Not applicable.

Medicare National Coverage

There is no national coverage determination (NCD). In the absence of an NCD, coverage decisions are left to the discretion of local Medicare carriers.

References

1. Zhang L, Riethdorf S, Wu G, et al. Meta-analysis of the prognostic value of circulating tumor cells in breast cancer. Clin Cancer Res. Oct 15 2012;18(20):5701-5710. PMID       22908097

2. Zhao S, Liu Y, Zhang Q, et al. The prognostic role of circulating tumor cells  (CTCs) detected by RT-PCR in breast cancer: a meta-analysis of published literature. Breast Cancer Res Treat. 2011;130(3):809-816.

3. Cristofanilli M, Budd GT, Ellis MJ, et al. Circulating tumor cells, disease progression and survival in metastatic  breast cancer. N Engl J Med. 2004;351(8-Jan):781-791.

4. Nole F, Munzone E, Zorzino L, et al. Variation of circulating tumor cell levels during treatment of metastatic breast cancer: prognostic and therapeutic implications. Ann Oncol. 2008;19(5):891-897.

5. Pierga JY, Hajage D, Bachelot T, et al. High independent prognostic and predictive value of circulating tumor cells compared with serum tumor markers in a large prospective trial in first-line chemotherapy for metastatic breast cancer patients. Ann Oncol. 2012;23(3-Jan):618-624.

6. Ma X, Xiao Z, Li X, et al. Prognostic role of circulating tumor cells  and disseminated tumor cells in patients with prostate cancer: a systematic review and meta-analysis. Tumour Biol. Feb 22 2014. PMID 24563278

7. Wang FB, Yang XQ, Yang S, et al. A higher number of circulating tumor cells in peripheral blood indicates poor prognosis in prostate cancer patients-a meta-analysis. Asian Pac J Cancer Prev. 2011;12(10):2629-2635.

8. de Bono J., Scher HI, Montgomery RB, et al. Circulating tumor cells predict survival benefit from treatment in metastatic castration-resistant prostate cancer. Clin Cancer Res. 2008;14(19):6302-6309.

9. Huang X, Gao P, Song Y, et al. Meta-analysis of the prognostic value of circulating tumor cells detected with the  CellSearch System in colorectal cancer. BMC Cancer. 2015;15:202. PMID 25880692

10. Groot Koerkamp B, Rahbari NN, Buchler MW, et al. Circulating tumor cells and prognosis of patients with resectable colorectal liver metastases or widespread metastatic colorectal cancer: a meta-analysis. Ann Surg Oncol. Mar 2 2013;20(7):2156-2165. PMID 23456317

11. CellSearch Brochure. https://www.cellsearchctc.com/sites/default/files/docs/cellsearch-ctc-test-brochure.pdf. Accessed May 5, 2015.

12. Cohen SJ, Punt CJ, Iannotti N, et al. Relationship of circulating tumor cells to tumor response, progression-free survival and overall survival in patients with metastatic colorectal cancer. J Clin Oncol. 2008;26(19):3213-3221.

13. Seeberg LT, Waage A, Brunborg C, et al. Circulating Tumor Cells in Patients With Colorectal Liver Metastasis Predict Impaired Survival. Ann Surg. Feb 6 2014. PMID 24509211

14. Bork U, Rahbari NN, Scholch S, et al. Circulating tumour cells and outcome in non-metastatic colorectal cancer:  a prospective study. Br J Cancer. Apr 14 2015;112(8):1306-1313. PMID 25867263

15. Krebs MG, Sloane R, Priest L, et al. Evaluation and prognostic significance of circulating tumor cells in patients with non-small-cell lung cancer. J Clin Oncol. 2011;29(12):1556-1563.

16. Naito T, Tanaka F, Ono A, et al. Prognostic impact of circulating tumor cells in patients with small cell lung cancer. J Thorac Oncol. 2012;7(3):512-519.

17. Hirose T, Murata Y, Oki Y, et al. Relationship of circulating tumor cells to the effectiveness of cytotoxic chemotherapy in patients with metastatic non-small-cell lung cancer. Oncol Res. 2012;20(2-3):131-137. PMID 23193919

18. Ma XL, Xiao ZL, Liu L, et al. Meta-analysis of circulating tumor cells as a prognostic marker in lung cancer. Asian Pac J Cancer Prev. 2012;13(4):1137-1144. PMID 22799295

19. Guzzo TJ, McNeil BK, Bivalacqua TJ, et al. The presence of circulating tumor cells does not predict extravesical disease in bladder cancer patients prior to radical cystectomy. Urol Oncol. 2012;30(1):44-48.

20. Rink M, Chun FK, Minner S, et al. Detection of circulating tumor cells in peripheral blood of patients with advanced non-metastatic bladder cancer. BJU Intl. 2011;107(10):1668-1675.

21. Gazzaniga P, de Berardinis E, Raimondi C, et al. Circulating tumor cells detection has independent prognostic impact in high-risk non-muscle invasive bladder cancer. Int J Cancer. Mar 6 2014. PMID 24599551

22. de Albuquerque A., Kubisch I, Breier G, et al. Multimarker gene analysis of circulating tumor cells in pancreatic cancer patients: a feasibility study. Oncology. 2012;82(1):3-10.

23. Okabe H, Tsunoda S, Hosogi H, et al. Circulating Tumor Cells as an Independent Predictor of Survival in Advanced Gastric Cancer. Ann Surg Oncol. Mar 17 2015. PMID 25777087

24. Schulze K, Gasch C, Staufer K, et al. Presence of EpCAM-positive circulating tumor cells as biomarker for systemic disease strongly correlates to survival in patients with hepatocellular carcinoma. Int J Cancer. Nov 2013;133(9):2165-2171. PMID 23616258

25. Nichols AC, Lowes LE, Szeto CC, et al. Detection of circulating tumor cells in advanced head and neck cancer using the CellSearch system. Head Neck. Oct 2012;34(10):1440-1444. PMID 22076949

26. Khoja L, Lorigan P, Zhou C, et al. Biomarker Utility of Circulating Tumor Cells in Metastatic Cutaneous Melanoma. J Invest Dermatol. Dec 6 2013;133(6):1582-1590. PMID 23223143

27. Bidard FC, Madic J, Mariani P, et al. Detection rate and prognostic value of circulating tumor cells and circulating tumor DNA in metastatic uveal melanoma. Int J Cancer. Mar 1 2014;134(5):1207-1213. PMID 23934701

28. Zhang J, Wang HT, Li BG. Prognostic significance of circulating tumor cells in small--cell lung cancer patients: a meta-analysis. Asian Pac J Cancer Prev. 2014;15(19):8429-8433. PMID 25339041

29. Harris L, Fritsche H, Mennel R, et al. American Society of Clinical Oncology 2007 Update of recommendations for the use of tumor markers in breast cancer. J Clin Oncol. 2007;25(33):5287-5312.

30. National Comprehensive Care Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Breast Cancer Version 2, 2015. http://www.nccn.org/professionals/physician_gls/pdf/breast.pdf. Accessed April, 2015.

31. National Comprehensive Care Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Colon Cancer Version 2, 2015. http://www.nccn.org/professionals/physician_gls/pdf/colon.pdf. Accessed April, 2015.

32. National Comprehensive Care Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Prostate Cancer Version 1, 2015. http://www.nccn.org/professionals/physician_gls/pdf/prostate.pdf. Accessed April, 2015.

33. National Academy of Clinical Biochemistry (NACB). The use of tumor markers in testicular, prostate, colorectal, breast and ovarian cancer. 2008; http://www.ncbi.nlm.nih.gov/pubmed/19042984. Accessed April, 2015.

Codes

Applicable Modifiers

N/A

Policy History