This is a limited coverage policy for next-generation sequencing (NGS) assays
performed on solid tumor cell-free DNA in plasma, from here on called "liquid
biopsies."

**Criteria for Coverage**

Guardant360 is covered only when **all** of the following conditions are met:

  * Patient has been diagnosed with a recurrent, relapsed, refractory, metastatic, or advanced solid tumor that did not originate from the central nervous system. Patients who would meet all of the indications on the FDA label for [larotrectinib ](https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/211710s000lbl.pdf)if they are found to have an NTRK mutation may be considered to have advanced cancer, **and**
  * Patient has not previously been tested with the Guardant360 test for the same genetic content. For a patient who has been tested previously using Guardant360 for cancer, that patient may not be tested again unless there is clinical evidence that the cancer has evolved wherein testing would be performed for different genetic content. Specifically, in patients with previously tested cancer, who have evidence of new malignant growth despite response to a prior targeted therapy, that growth may be considered to be sufficiently genetically different to require additional genetic testing, **and**
  * Patient is untreated for the primary cancer being tested, or the patient is not responding to treatment (e.g., progression or new lesions on treatment), **and**
  * The patient has decided to seek further cancer treatment with the following conditions:
    * The patient is a candidate for further treatment with a drug that is either FDA-approved for that patient's cancer, or has an NCCN 1 or NCCN 2A recommendation for that patient's cancer, **and**
    * The FDA-approved indication or NCCN recommendation is based upon information about the presence or absence of a genetic biomarker tested for in the Guardant360 assay, **and**
  * Tissue-based, CGP is infeasible ( _e.g_., quantity not sufficient for tissue-based CGP or invasive biopsy is medically contraindicated) **or** specifically in NSLC Tissue-based CGP has shown no actionable mutations. 

If no alteration is detected by Guardant360 or if ctDNA is insufficient/not
detected, tissue-based genotyping should be considered.

Other liquid biopsies will be covered for the same indications if they display
similar performance in their intended used applications to Guardant360".

A wide array of cancer treatments have developed ranging from surgery to
medications. One of the newer approaches to the medical treatment of cancer
has been to use drugs based on genetic features of a malignancy. While many
patients will not benefit from genetic testing to select treatment, for those
whose cancers have select biomarkers, the treatment of choice often includes
therapy targeting that specific biomarker or therapy being avoided because of
a biomarker.1-13

In spite of the importance of actionable biomarker identification in cancer,
research has shown that many patients do not receive genetic testing for the
presence of actionable mutations in their cancers, and there are geographic
disparities in testing with patients in rural areas and those receiving care
at community treatment centers being less likely to receive testing.14-16 In
addition, logistical challenges to testing such as adequate tissue and the
availability of any tissue have been identified as barriers to tissue-based
genomic testing.15 Additionally, even among patients whose cancers were
genomically profiled at diagnosis and found to have a mutation for which they
are receiving targeted treatment, resistance to the initial targeted treatment
may emerge. For some patients, the identification of a new mutation, not
present in the original tissue sample and found in the blood, may allow the
selection of a new targeted life-prolonging therapy.17

Clinical utility of comprehensive genomic profiling using plasma-based testing

Traditionally, tumor genotyping has been conducted by direct interrogation of
tumor tissue obtained through invasive tissue sampling procedures. This
diagnostic approach, however, is limited by the availability of sufficient
tumor tissue and the ability of patients to undergo invasive procedures. In a
recent study of over 100 community-based oncologists, nearly one-third of
NSCLC patients were not tested for EGFR or ALK, over 75% were not tested for
ROS1 fusions, and fewer than 10% were tested for all guideline-recommended
alterations.15 These results were similar to a study in a single academic
center where only 58% of non-squamous NSCLC were tested for EGFR and 40% for
ALK fusions, despite 13% of patients undergoing repeat invasive biopsies to
obtain sufficient tissue for genomic testing.18 Tissue availability was
similarly limited in several recent series, some of which reported that more
than 50% of NSCLC patients had insufficient or unobtainable material for
tissue-based CGP.19-21

Even when successful, tissue acquisition procedures pose a significant
morbidity and mortality risk to Medicare patients. In a recent report, 19% of
all lung tissue acquisition procedures resulted in a serious adverse event,22
while the National Lung Cancer Screening Trial reported 1-2% mortality rates
in their cohorts.23 The FDA has also specifically approved a medication for
patients who have cancer (cancer type unspecified on the label) for which
there is a high risk associated with surgical resection.24 Given the high
rates of inadequate genotyping described above, plasma-based CGP can provide
an opportunity for non- and under-genotyped patients to benefit from therapy
matched to a genetic biomarker. Early studies suggested that plasma-based CGP
can identify potential genomic targets in both the first and second lines,
with response rates similar to those of patients identified using tissue-based
CGP and tissue-based CoDX.20,21,25-27

It has been shown that the region of DNA sequenced is important, since
alterations may occur outside the sequenced region or involve complex
alterations (e.g. indels, copy number alterations, or rearrangements) that are
not detectable by certain tests.28 Newer techniques such as next-generation
sequencing (NGS), offer the possibility of not only increased analytical
sensitivity but also the ability to detect a broader range of genomic
alterations.29

While the evidence appears most developed for clinically actionable targets in
NSCLC, targeted therapy for cancer has been recommended for a number of other
cancers as well. Genetic biomarkers associated with specific guideline
recommended targeted therapies for a number of conditions is summarized below
in Table 1. These guidelines are updated frequently, so new genes not listed
in the table may also become part of guideline-consensus recommendations.

**Table 1**

Non-small cell lung cancer6

|

EGFR  
BRAF  
MET  
HER2 / ERBB2  
ALK  
ROS1  
RET  
MET  
KRAS  
  
---|---  
  
Colorectal3,10

|

KRAS  
NRAS  
BRAF  
  
Breast2

|

HER2 / ERBB2  
BRCA1  
BRCA2  
  
Endometrial13

|

HER2 / ERBB2  
  
Gastric and Gastroesophageal4

|

HER2 / ERBB2  
  
Gastrointestinal Stromal Tumor11

|

KIT  
PDGFRA  
BRAF  
  
Melanoma5

|

BRAF  
KIT  
  
Ovarian7

|

BRCA1  
BRCA2  
  
Pancreatic8

|

BRCA1  
BRCA2  
  
Prostate9

|

BRCA1  
BRCA2  
  
Thyroid12

|

BRAF  
RET  
  
Chordoma1

|

EGFR  
  
Additionally, there are now medications, which are FDA approved for cancers
based on the presence of genetic mutations, regardless of the tissue of
origin.

**Microsatellite instability**

Microsatellite instability structures are composed of repeated nucleotide
sequences that emerge due to defects in mismatch repair during DNA
replication.30 The importance of them in cancer, is that Microsatellite
Instability High (MSI-H) tumors have been found to respond to immunotherapy,31
and one immunotherapy drug, pembrolizumab, now has an FDA indication for the
treatment of patients with unresectable or metastatic, MSI-H solid tumors.32

**NTRK**

The tropomyosin receptor kinase (TRK) receptor family is family of
transmembrane proteins, some of which are encoded by the NTRK1, NTRK, and
NTRK3 genes. Of these, Guardant360 tests for NTRK1 mutations including
fusions. Fusions in the NTRK genes lead to chimeric TRK proteins, which have
oncogenic potential, and have been viewed as a potential therapeutic target
for cancer.33

Larotrectinib, a TRK inhibitor, has received FDA approval for NTRK positive
(without a known resistance mutation) tumors in patients with metastatic
disease or where surgical resection is likely to result in severe morbidity,
and who have no satisfactory alternative treatments or that have progressed
following treatment.24

**Guardant360  **

Guardant360 is a comprehensive genomic profiling test that identifies
mutations in 73 genetic mutations. It has demonstrated targeted therapy
response rates similar to tissue-detected genomic targets in numerous
published NSCLC studies. 20,21,25-28 In addition to sequencing accuracy,
research has been done evaluating the ability of the test to identify
actionable mutations across cancers originating in a number of organ systems.

In a study by Rozenblum et al., tissue biopsies from 101 advanced NSCLC
patients were tested locally for EGFR mutations and ALK fusions.34 Tissue-
based CGP identified 15 EGFR and ALK alterations missed locally, but could
only be performed in 82 of the 101 (81%) patients because of tissue
exhaustion. Guardant360 was used in the 19 remaining patients and two (11%)
additional sensitizing EGFR mutations were found that had been missed with
local tissue genotyping. In addition, alterations including MET amplification,
ERBB2 (HER2) mutation, and two RET fusions were also identified (missed with
local non-CGP genotyping), for a total of 6 driver alterations in 19 patients
(32%). Thus, Guardant360 changed treatment in 32% of patients with
insufficient samples for tissue-based CGP, with five receiving matched
therapy. These five patients achieved a 60% objective response rate and 100%
disease control rate.

A more recent study examined the clinical implications of using plasma-based
testing in addition to tissue-based testing in 229 patients with NSCLC.35 Of
the 229 patients in whom both tissue and plasma testing were ordered, the
addition of plasma increased the percentage of patients eligible for targeted
therapies from 21% (47/229) to 36% (82/229). For the 128 patients with
successful tissue testing results, 55 were found to have a therapeutically
targetable mutation. Of these 55, only 31 had this mutation found in tissue
and plasma, though not necessarily the same actionable mutation(s) in each
testing method. For 16 patients, the mutation was found in tissue only, and
for 8, it was found in plasma only. To further assess whether the selection of
targeted therapy based on the detection of low allele frequency mutations that
Guardant360 is able to identify has a clinical benefit, the authors assessed
the depth of response to targeted mutations identified in plasma-based
testing. A total of 42 patients received a targeted therapy consistent with
the plasma-based testing, 12 of whom had that mutation also detectable in
tissue-based testing as well. Of this 42, there were 36 (85.7%) who achieved a
response of stable disease, partial response, or complete response.

The ability of Guardant360 to identify actionable mutations in multiple types
of cancer, including NSCLC, gastric cancer, and melanoma, was examined in 194
patients with metastatic cancer but no availability of tissue for NGS-based
genotyping.25 Actionable mutations were found in the majority of patients, but
the study also evaluated treatment response when the patients were given
therapy matching a genetic mutation in the test. In the group with NSCLC, 15
received matched therapy, and 13 of them responded to the therapy. Among those
with gastric cancer, a total of nine received matched therapy, and 6 responded
to treatment, with one of those six have a complete response (a patient with
an ERBB2 amplification). Only 2 patients with melanoma received matched
therapy, and one responded to this treatment.

Guardant360 has been validated recently across genetic mutation types (single
nucleotide variants, indels, fusions, and copy number amplifications) and a
range of specific actionable mutations in a study using orthogonal tissue and
plasma-based methods.36,37 Analytical performance of Guardant360 is
summarized in the table below.

**Mutation Type**

|

**LOD95**

|

**Sensitivity**

|

**Positive Predictive Value**  
  
---|---|---|---  
  
**SNVs**

|

>0.25%  
0.05 - 0.25%

|

100%  
63.8%

|

99.2%  
96.3%  
  
**Indels**

|

>0.20%  
0.05 -0.20%

|

100%  
67.8%

|

98.2%  
98.2%  
  
**Fusions**

|

>0.20%  
0.05-0.20%

|

95%  
83%

|

100%  
100%  
  
**CNAs**

|

2.24-2.76 copies

|

95%

|

100%  
  
Additionally, the study assessed the detection rate of tumor DNA using
Guardant360 from 10,585 patients with more than 20 different cancers.
Detection rate was >60% for nearly all cancers and around 80-90% for NSCLC,
breast cancer, colorectal cancer, prostate cancer, gastroesophageal cancer,
and gynecologic cancer. For primary CNS malignancies the detection rate was
less 50%.

While MolDX initially covered the Guardant360 assay for the selection of
targeted therapy in NSCLC, the assay tests for the presence of mutations in
over 70 genes and Microsatellite Instability (MSI). More recent research
looking beyond NSCLC has shown that the analytical and clinical performance of
the Guardant360 assay varies little between mutation type and tissue origin,
with the exception of malignancies arising in the central nervous system.36,37

**Guardant360 Test Description and Intended Use**

Guardant360 analyzes tumor-derived cell-free DNA (also known as ctDNA) to
detect somatic alterations, though it also reports germline alterations.

Guardant360 detects the following classes of alterations:

  * Base pair substitutions (also known as SNVs)
  * Small (20 bp) and large (>20 bp) indels
  * Copy number amplifications (CNAs)
  * Fusions
  * Microsatellite Instability

The analytical performance characteristics of Guardant360 are similar across
mutation types, specific actionable mutations, and tissue types, except
primary CNS cancers.





_Level of Evidence_

Quality: Moderate  
Strength: Limited  
Weight: Limited

The clinical utility of plasma-based genomic testing for patients with
advanced cancer at diagnosis or at progression, as defined in the intended use
above, appears to be a viable alternative to solid tumor genotyping, when
tissue is unavailable. At present, Guardant360, one such assay, appears to
have similar performance to detect mutations regardless of the tissue of
origin or mutation type.

While tissue-based testing remains the preferred tool to test for actionable
mutations in cancer, for patients in whom obtaining this tissue is not
feasible, liquid biopsy with Guardant360 represents an alternative which may
allow more patients to get potentially effective cancer treatment.