BlueCross and BlueShield of Montana Medical Policy/Codes
Laboratory Testing to Determine 5-fluorouracil (5-FU) Area Under the Curve (AUC) for Targeted 5-FU Dosing for Cancer Patients
Chapter: Medicine: Tests
Current Effective Date: October 25, 2013
Original Effective Date: October 25, 2013
Publish Date: July 25, 2013

Dosing of 5-fluorouracil (5-FU) in cancer patients to a predetermined area under the curve (AUC) target has been proposed as a method to reduce variability in systemic exposure to 5-FU, reduce toxicity, and improve tumor response. Accurate AUC determination relies on sampling at a pharmacokinetically appropriate time, as well as on an accurate method of 5-FU laboratory measurement. Available measurement methods are complex and require the expertise to develop an in-house assay, making them less amenable to routine clinical laboratory settings. One commercially available alternative is Myriad Genetics’ OnDose™, a diagnostic test that is designed to measure colorectal cancer patients’ exposure to 5-FU, help oncologists adjust and 5-FU dosing, and improve patient outcomes.


5-Fluorouracil (5-FU) is a widely used antineoplastic chemotherapy drug with a narrow therapeutic index; doses recommended for effectiveness are often limited by hematologic and gastrointestinal toxicity. Moreover, patients administered the same fixed dose, continuous infusion regimen of 5-FU, have wide intra- and inter-patient variability in systemic drug exposure, as measured by plasma concentration or, more accurately, by AUC techniques. AUC is a measure of the systemic drug exposure in an individual over a defined period of time.

In general, the incidence of grade 3 to 4 toxicity (mainly neutropenia, diarrhea, mucositis, and hand-foot syndrome) increases with higher systemic exposure to 5-FU. Several studies have also reported statistically significant positive associations between 5-FU exposure and tumor response. In current practice, however, 5-FU dose is reduced when symptoms of severe toxicity appear, but seldom increased to promote efficacy.

Based on known 5-FU pharmacology, it is possible to determine a sampling scheme for AUC determination and to optimize an AUC target and dose adjustment algorithm for a particular 5-FU chemotherapy regimen and patient population. For each AUC value or range, the algorithm defines the dose adjustment during the next chemotherapy cycle most likely to achieve the target AUC without overshooting and causing severe toxicity.

In clinical research studies, 5-FU blood plasma levels have most recently been determined by high-performance liquid chromatography or liquid chromatography coupled with tandem mass spectrometry. Both methods require the expertise to develop an in-house assay and may be less amenable to routine clinical laboratory settings. One commercially available alternative is Myriad Genetics OnDose™, a diagnostic test that is designed to measure colorectal cancer patients' exposure to 5-FU to help oncologists adjust and optimize 5-FU dosing.

Regulatory Status

The OnDose™ test is offered by Myriad Genetics as a laboratory-developed test. Other clinical laboratories may offer in-house assays to measure 5-FU AUC. Clinical laboratories may develop and validate tests in-house and market them as a laboratory service; laboratories offering such tests as a clinical service must meet the general regulatory standards of the Clinical Laboratory Improvement Act (CLIA) and must be licensed by CLIA for high-complexity testing. Myriad Genetics is a CLIA-licensed laboratory.


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Blue Cross and Blue Shield of Montana (BCBSMT) considers laboratory testing to determine 5-fluorouracil (5-FU) area under the curve (AUC) in order to adjust 5-FU dose for cancer patients (i.e., colorectal or other cancer) experimental, investigational and unproven, including but not limited to OnDose™ testing or other types of assays.


Literature Review

This policy was created with a search of the MEDLINE database through February 2013. The following is a summary of the key literature to date.

5-Fluorouracil and Clinical Use

5-Fluorouracil (5-FU) is a pyrimidine analog that is an antineoplastic antimetabolite; 5-FU has been useful for many years in the treatment of solid tumors, including colorectal adenocarcinoma. Potentiated by leucovorin (LV), 5-FU is the basis for several standard treatment regimens currently recommended by the National Comprehensive Cancer Network (NCCN) in the treatment of colorectal cancer. (1) While it is recommended that adjuvant therapy for stage II colorectal cancer be limited primarily to disease with high-risk features and individualized for each patient, oxaliplatin in combination with 5-FU/LV is the preferred standard of care for treating patients with stage III disease. (1) Based on the results of the European “Multicenter International Study of Oxaliplatin/5-Fluorouracil/Leucovorin in the Adjuvant Treatment of Colon Cancer” (MOSAIC) trial, (2) in which the addition of oxaliplatin to a regimen of LV and infusional 5-FU every 2 weeks (i.e., a FOLFOX [leucovorin calcium fluorouracil, oxaliplatin] regimen) significantly increased disease-free and overall survival, the FOLFOX regimen is recommended for patients with stage III colorectal cancer. (1) A FOLFOX regimen also improves progression-free survival (PFS) in patients with advanced (i.e., metastatic) colorectal cancer who are able to tolerate intensive versus single-agent 5-FU therapy. (3, 4) Other 5-FU-based combination chemotherapy regimens are also options in advanced disease. (1) FOLFOX may also be considered for individual patients with high-risk stage II disease. In terms of administration, infusional 5-FU regimens are considered less toxic than bolus regimens and are inappropriate when administered with either irinotecan or oxaliplatin. (1)

5-FU has for many years been a component, with cisplatin, of induction therapy for squamous cell carcinoma of the head and neck in patients with advanced locoregional disease, yielding high rates of overall and complete clinical response. The addition of docetaxel was shown to improve survival, and this 3-drug combination is now considered the standard of care for induction chemotherapy. (1, 5) Typical 5-FU administration is also by continuous infusion. (6) 5-FU is also a component of several combination chemotherapy regimens that can be considered for primary systemic therapy administered in conjunction with radiotherapy and of 2 combination regimens recommended for recurrent, unresectable, or metastatic disease. (1)

Metabolism of 5-Fluorouracil

5-FU is a pyrimidine antagonist, similar in structure to the normal pyrimidine building blocks of RNA (uracil) and DNA (thymine). Approximately 85% or more of administered 5-FU is inactivated and eliminated via the catabolic pathway; the remainder is metabolized via the anabolic pathway. Catabolism of 5-FU is controlled by the activity of dihydropyrimidine dehydrogenase (DPD). Because DPD is a saturable enzyme, the pharmacokinetics of 5-FU are strongly influenced by the dose and schedule of administration. (7) For example, 5-FU clearance is faster with continuous infusion compared to bolus administration, resulting in very different systemic exposure to 5-FU during the course of therapy.

Measuring Exposure to 5-Fluorouracil

Patient exposure to 5-FU is most accurately described by estimating the area under the curve (AUC), the total drug exposure over a defined period of time. 5-FU exposure is influenced by method of administration, circadian variation, impaired liver function, and the presence of inherited DPD-inactivating genetic variants that can greatly reduce or abolish 5-FU catabolism. As a result, both inter- and intra-patient variability in 5-FU plasma concentration during the course of administration is high.

As noted, determination of 5-FU AUC requires complex technology and expertise that may not be readily available in a clinical laboratory setting. In the U.S., Myriad Genetics offers a commercial service called OnDose™ that quantitates plasma 5-FU concentration from a blood sample drawn during continuous infusion at steady state, calculates AUC by multiplying 5-FU concentration by the infusion duration, and compares the results to a target AUC range established for colorectal cancer patients. According to information from Myriad’s website, “OnDose test results are used to help optimize an individualized dose for the next cycle of 5-FU chemotherapy.” Myriad technical specifications for the 5-FU immunoassay describe the method and a summary of analytic validity data (replication, linearity, reportable range, interference, cross-reactivity, recovery, detection limit, stability, and comparison of methods), comparable to data summaries included in U.S. Food and Drug Administration [FDA]-cleared diagnostic test kits. Review of the data indicates thorough technical validation and reasonable assay performance. (8) The OnDose™ test result itself does not include a dose adjustment algorithm, but the references for published algorithms are provided. Although searches of large clinical laboratories did not find tests for 5-FU AUC on their listings, it is possible that other clinical laboratories measure 5-FU levels by methods other than the specific method used by Myriad Genetics.

Modifying 5-Fluorouracil Exposure to Improve Outcomes

Evidence supporting the use of 5-FU AUC measurement to help modify subsequent 5-FU treatment doses in order to improve response and reduce toxicity has been summarized and evaluated in a Blue Cross Blue Shield Association (BCBSA) Technology Evaluation Center (TEC) Special Report. (9) Early evidence from small, cohort studies showed that in general, the incidence of grade 3 to 4 toxicity (mainly neutropenia, diarrhea, mucositis, and hand-foot syndrome) increases with higher systemic exposure to 5-FU. This association has been studied extensively in head and neck cancer and in colorectal cancer. In addition, a majority of studies reported statistically significant positive associations between 5-FU exposure and tumor response.

Based on these early results, various strategies have been tried to reduce the variability in 5-FU pharmacokinetics, improve treatment efficacy, and decrease toxicity. In particular, individual pharmacokinetic dose adaptation can be accomplished by monitoring plasma 5-FU AUC at steady state during each treatment cycle and adjusting administered 5-FU dose for the next treatment cycle to achieve a target AUC value established as maximally efficacious and minimally toxic. The hypothesis is that individual 5-FU dose modulation to a target AUC value that is just below the threshold for severe toxicity could minimize toxicity while improving response.

The results of single-arm trials of AUC-targeted 5-FU dose adjustment in advanced colorectal cancer patients suggested consistency of improved tumor response. (10-12) Similar, although less compelling results were seen in single-arm trials of AUC targeted 5-FU dosing in head and neck cancer. (13, 14) The best contemporary evidence in support of AUC targeted dosing consists of 2 randomized, controlled trials (RCTs), one enrolling patients with colorectal cancer and the other patients with head and neck cancer. No trials of any design were identified for 5-FU dose adjustment in other malignancies.

Gamelin et al. (10) developed a chart for weekly dose adjustment based on the results of an earlier, similar single-arm study (15) in which dose was increased by prespecified increments and intervals up to a maximum dose or the first signs of toxicity. In an RCT enrolling patients with metastatic colorectal cancer, Gamelin et al. (16) reported significantly improved tumor response (33.6% versus 18.3%, respectively; p=0.0004) and a trend toward improved survival (40.5% versus 29.6%, respectively; p=0.08) in the experimental arm using AUC-targeted dosing. However, the authors also reported 18% grade 3 to 4 diarrhea in the fixed-dose control arm, higher than reported in comparable arms of 2 other large chemotherapy trials (5-7%).(2, 3) In the latter 2 trials, delivery over a longer time period for both 5-FU (22 hours vs. 8 hours) and leucovorin (2 hours vs. bolus), which is characteristic of currently recommended 5-FU treatment regimens, likely minimized toxicity. The administration schedule used in the Gamelin et al. (16) trial is “rarely used in current practice in most countries” as described in an accompanying editorial by Walko and McLeod (17) and is absent from current guidelines. (1) Additional optimization studies would be needed in order to apply 5-FU exposure monitoring and AUC-targeted dose adjustment to a more standard single-agent 5-FU treatment regimen, with validation in a comparative trial versus a fixed-dose regimen.

The same group more recently conducted a retrospective analysis of their dose adjustment protocol used in a FOLFOX regimen administered to patients with colorectal cancer (n=118) and compared to patients treated with FOLFOX administered in standard fashion according to body surface area.(n=39). (18) In the dose-adjusted group, the therapeutic dose at 3 months was 110% of the theoretic dose. Grade 3/4 toxicity was 1.7% for diarrhea, 0.8% for mucositis, 18% for neutropenia, and 12% for thrombopenia; corresponding numbers were 12%, 15%, 25% and 10%, respectively, in the standard group. In the dose-adjusted group, the objective response rate was 70% at 3 months and 56% at 6 months; the corresponding result at 3 months for the standard group was 46%. Median overall survival and median progression-free survival in the dose-adjusted arm were 28 and 16 months, respectively; corresponding numbers for the standard group were 22 and 10 months. As the authors note, this proof of principle study needs confirmation in a randomized trial.

Fety et al., in an RCT in patients with locally advanced head and neck cancer, used a different method of dose adjustment and reported overall 5-FU exposures in head and neck cancer patients that were significantly reduced in the dose-adjustment arm compared to the fixed-dose arm. (19) This resulted in reduced toxicity but no improvement in clinical response. The dose adjustment method in this trial may have been too complex, as the 12 protocol violations in this treatment arm (of 61 enrolled) were all related to 5-FU dose adjustment miscalculations. Because patients with protocol violations were removed from analysis, results did not reflect the “real world” results of the dose adjustment method. In addition, the induction therapy regimen used 2 drugs, not the current standard of 3 and, therefore, these results are also limited in generalizability to current clinical practice.

None of these studies used the OnDose™ test. For technical validation, OnDose was directly compared to liquid chromatography-tandem mass spectrometry (20); the slope of the correlation was 1.03 (ideal: 1.00) and the r-value was 0.99 (ideal: 1.00). This test is clinically validated only for patients with colorectal cancer to determine 5-FU exposure and subsequent dose modification. Myriad Genetics cites Gamelin et al. (16) for clinical validation of AUC-targeted 5-FU dose adjustment and for information on how to modify the dose once 5-FU exposure has been determined. Gamelin et al. used high-performance liquid chromatography, similar to liquid chromatography-tandem mass spectrometry, to measure AUC. Thus, OnDose clinical validation is indirect; the only published clinical study using OnDose was reported in a commentary by Saam et al. describing the results of an observational analysis of sequential patients treated with constant infusion 5-FU using current adjuvant or metastatic treatment protocols with or without bevacizumab. (21) Samples were drawn at least 2 hours after the start of and before the end of each infusion and sent to Myriad Genetics Laboratories for analysis. Sixty-two patients were studied longitudinally across 4 sequential sample submissions (i.e., four 5-FU treatment infusions), of which only about 5% were within the target AUC after the first infusion. By the fourth infusion, this number rose to 37% and outliers were reduced. The use of bevacizumab did not affect results. No information on response or toxicity was reported.

Given the limitations of the existing evidence, the evidence is insufficient to draw conclusions about the impact of 5-FU exposure measurement and AUC-targeted dose adjustment on outcomes of patients administered contemporary chemotherapy regimens for colorectal or head and neck cancer. Given the lack of relevant studies, a similar conclusion is reached for use of 5-FU in other cancers.

Clinical Trials

One clinical trial was started that was intended to directly compare OnDose-guided 5-FU dosing compared to standard dosing; the status of a non-U.S. trial is unknown; no other clinical trials have been found.

  • NCT01468623 received November 2011, sponsored by Myriad Genetic Laboratories; the purpose of the study was to compare OnDose®-guided 5-FU dosing versus standard body surface area (BSA)-based dosing in patients with metastatic colorectal cancer treated with mFOLFOX6, with or without bevacizumab, to determine if the use of OnDose® achieves an improvement in the Overall Response Rate (ORR) relative to BSA dosing response. The study was terminated due to slow enrollment.
  • NCT00943137 (Singapore) will determine the proportion of Asian patients achieving a target area under the curve using a pharmacokinetically guided 5-fluorouracil dose; the trial will also determine the safety and tolerability of dose adjusted 5-FU (verified 9-2009; updated information not available). Per the online database, the recruitment status of this trial has not been verified in 2 years. There are no related publications by the principal investigator.


Prior evidence supports the wide variability of 5-fluorouracil (5-FU) plasma levels when patients are placed on a fixed-dose regimen; high exposure is associated with toxicity, but higher exposure up to the limits of toxicity is also associated with better tumor response to treatment. Area under the curve laboratory testing methods to better measure 5-FU exposure during treatment of cancer and validated algorithms to modify subsequent dosing may improve response and reduce toxicity, but currently available evidence is insufficient to support such testing. Because the impact of this testing on net health outcome is not known, this is considered experimental, investigational and unproven.

Practice Guidelines and Position Statements

National Comprehensive Cancer Network (NCCN) Guidelines

NCCN guidelines for colon cancer (version 3.2013) make no mention of the use of area under the curve-guided 5-FU dosing.


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ICD-9 Codes
ICD-10 Codes
C18.0-C18.9, C19
Procedural Codes: 84999, S3722
  1. National Comprehensive Cancer Network (NCCN). Clinical Practice Guidelines in Oncology: Colon Cancer, V.2.2011; and Head and Neck Cancers, V.2.2010. Available at: (Accessed January, 2011).
  2. Andre T, Boni C, Navarro M et al. Improved overall survival with oxaliplatin, fluorouracil, and leucovorin as adjuvant treatment in stage II or III colon cancer in the MOSAIC trial. J Clin Oncol 2009; 27(19):3109-16.
  3. de Gramont A, Figer A, Seymour M et al. Leucovorin and fluorouracil with or without oxaliplatin as first-line treatment in advanced colorectal cancer. J Clin Oncol 2000; 18(16):2938-47.
  4. Giacchetti S, Perpoint B, Zidani R et al. Phase III multicenter randomized trial of oxaliplatin added to chronomodulated fluorouracil-leucovorin as first-line treatment of metastatic colorectal cancer. J Clin Oncol 2000; 18(1):136-47.
  5. Posner M, Vermorken JB. Induction therapy in the modern era of combined-modality therapy for locally advanced head and neck cancer. Semin Oncol 2008; 35(3):221-8.
  6. Beneton M, Chapet S, Blasco H et al. Relationship between 5-fluorouracil exposure and outcome in patients receiving continuous venous infusion with or without concomitant radiotherapy. Br J Clin Pharmacol 2007; 64(5):613-21.
  7. Grem JL. 5-Fluorouracil and its biomodulation in the management of colorectal cancer. In: Saltz LB, ed. Colorectal Cancer: Multimodality Management. Totowa, NJ: Humana Press; 2002.
  8. OnDose® Technical Specifications, Myriad Genetic Laboratories, Inc. June 2010. Available at: (Accessed January, 2011).
  9. TEC Special Report: Laboratory Testing to Allow Area Under the Curve (AUC) –Targeted 5-Fluorouracil Dosing for Patients Administered Chemotherapy for Cancer.  Chicago, Illinois: Blue Cross Blue Shield Association – Technology Evaluation Center Assessment Program (2010 June) 24(10):1-28.
  10. Gamelin E, Boisdron-Celle M, Delva R et al. Long-term weekly treatment of colorectal metastatic cancer with fluorouracil and leucovorin: results of a multicentric prospective trial of fluorouracil dosage optimization by pharmacokinetic monitoring in 152 patients. J Clin Oncol 1998; 16(4):1470-8.
  11. Boisdron-Celle M, Craipeau C, Brienza S et al. Influence of oxaliplatin on 5-fluorouracil plasma clearance and clinical consequences. Cancer Chemother Pharmacol 2002; 49(3):235-43.
  12. Ychou M, Duffour J, Kramar A et al. Individual 5-FU dose adaptation in metastatic colorectal cancer: results of a phase II study using a bimonthly pharmacokinetically intensified LV5FU2 regimen. Cancer Chemother Pharmacol 2003; 52(4):282-90.
  13. Milano G, Etienne MC, Renee N et al. Relationship between fluorouracil systemic exposure and tumor response and patient survival. J Clin Oncol 1994; 12(6):1291-5.
  14. Santini J, Milano G, Thyss A et al. 5-FU therapeutic monitoring with dose adjustment leads to an improved therapeutic index in head and neck cancer. Br J Cancer 1989; 59(2):287-90.
  15. Gamelin EC, Danquechin-Dorval EM, Dumesnil YF et al. Relationship between 5-fluorouracil (5-FU) dose intensity and therapeutic response in patients with advanced colorectal cancer receiving infusional therapy containing 5-FU. Cancer 1996; 77(3):441-51.
  16. Gamelin E, Delva R, Jacob J et al. Individual fluorouracil dose adjustment based on pharmacokinetic follow-up compared with conventional dosage: results of a multicenter randomized trial of patients with metastatic colorectal cancer. J Clin Oncol 2008; 26(13):2099-105.
  17. Walko CM, McLeod HL. Will we ever be ready for blood level-guided therapy? J Clin Oncol 2008; 26(13):2078-9.
  18. Capitain O, Asevoaia A, Boisdron-Celle M et al. Individual fluorouracil dose adjustment in FOLFOX based on pharmacokinetic follow-up compared with conventional body-area-surface dosing: a phase II, proof-of-concept study. Clin Colorectal Cancer 2012; 11(4):263-7.
  19. Fety R, Rolland F, Barberi-Heyob M et al. Clinical impact of pharmacokinetically-guided dose adaptation of 5-fluorouracil: results from a multicentric randomized trial in patients with locally advanced head and neck carcinomas. Clin Cancer Res 1998; 4(9):2039-45.
  20. Salamone SJ, Beumer JH, Egorin MJ et al. A multi-center evaluation of a rapid immunoassay to quantitate 5-fluorouracil (5-FU) in plasma. Hematology/Oncology Pharmacy Association (HOPA) /International Society of Oncology Pharmacy Practitioners (ISOPP) Conference, Anaheim, CA, June 2008.
  21. Saam J, Critchfield GC, Hamilton SA et al. Body surface area-based dosing of 5-fluoruracil results in extensive interindividual variability in 5-fluorouracil exposure in colorectal cancer patients on FOLFOX regimens. Clin Colorectal Cancer 2011; 10(3):203-6.
  22. Laboratory Testing to Allow Area Under the Curve (AUC) Targeted 5-Fluorouracil (5-FU) Dosing for Patients Administered 5-FU for Cancer. Chicago, Illinois: Blue Cross Blue Shield Association Medical Policy Reference Manual (March 2013) Medicine 2.04.68.
July 2013  New 2013 BCBSMT medical policy.  Laboratory testing to determine 5-fluorouracil (5-FU) area under the curve (AUC) in order to adjust 5-FU dose for cancer patients (i.e., colorectal or other cancer) is considered experimental, investigational and unproven, including but not limited to OnDose™ testing or other types of assays. 
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Laboratory Testing to Determine 5-fluorouracil (5-FU) Area Under the Curve (AUC) for Targeted 5-FU Dosing for Cancer Patients