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Test Code PIK3B Cell-Free DNA PIK3CA Test, Blood


Shipping Instructions


1. Samples should be transported at ambient temperature or refrigerated (4° C)

2. Samples are viable for 7 days in the Streck Black/Tan Top Tube Kit



Specimen Required


Supplies: Streck Black/Tan Top Tube Kit (T715)

Specimen Volume: Two, 10-mL Streck cell-free DNA (cfDNA) blood collection tubes

Additional Information:

1. Only blood collected in Streck cfDNA tubes will be accepted for analysis.

2. Whole blood will be processed to produce platelet-poor plasma before cfDNA isolation.


Useful For

Identification of hormone receptor positive and human epidermal growth factor receptor 2 negative (HR+/HER2-) advanced breast cancer tumors that may be eligible for treatment with targeted kinase inhibitor therapy (eg, alpelisib).

Method Name

Polymerase Chain Reaction (PCR)

Reporting Name

cfDNA PIK3CA Test, Blood

Specimen Type

Whole blood

Specimen Minimum Volume

One 10 mL Streck cell-free DNA tube

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Ambient (preferred) 7 days Streck Black/Tan top
  Refrigerated  7 days Streck Black/Tan top

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Clinical Information

More than 70% of breast cancers are hormone receptor (HR) positive and human epidermal growth factor receptor 2 (HER2) negative (HR+/HER2-). Approximately 40% of patients with HR+/HER2- advanced breast cancer have activating mutations in the gene PIK3CA, inducing hyperactivation of the alpha isoform (p110 alpha) of phosphatidylinositol 3-kinase, a key upstream component of the PI3K pathway. Mutations in PIK3CA are associated with tumor growth, resistance to endocrine therapy, and a poor overall prognosis.

 

Patients with HR+/HER2- advanced breast cancer identified to have a PIK3CA mutation may be eligible for treatment with targeted kinase inhibitor therapy (eg, alpelisib).

 

This test uses circulating tumor DNA extracted from blood to evaluate for the presence of 10 clinically actionable PIK3CA mutations:

E542K (c.1624G>A)

E542K (c.1633G>A)

E545D (c.1635G>T)

E545G (c.1634A>G)

E545A (c.1634A>C)

H1047Y (c.3139C>T)

C420R (c.1285C>T)

Q546E (c.1636C>G)

H1047L (c.3140A>T)

H1047R (c.3140A>G)

Reference Values

An interpretive report will be provided

Interpretation

The interpretation of molecular biomarker results includes an overview of the results and the associated diagnostic, prognostic, and therapeutic implications.

Cautions

A negative (wildtype) result does not rule out the presence of a mutation that may be present but below the limits of detection of this assay. It also does not rule out the presence of other types of alterations in the PIK3CA gene outside those that the assay was designed to detect.

 

This test is not designed to differentiate between somatic and germline alterations. Additional testing may be necessary to clarify the significance of results if there is a potential hereditary risk.

 

Not all tumors that have PIK3CA mutations will respond to targeted therapies.

 

Rare genetic alterations exist that could lead to false-negative or false-positive results.

 

This test has not been clinically validated for use as a tool to monitor response to therapy or for early detection of tumors.

 

Test results should be interpreted in context of clinical findings, tumor sampling, and other laboratory data. If results obtained do not match other clinical or laboratory findings, please contact the laboratory for possible interpretation. Misinterpretation of results may occur if the information provided is inaccurate or incomplete.

Method Description

A polymerase-chain reaction (PCR)-based assay employing real-time PCR and allele-specific PCR technologies is used to test for 10 mutations within PIK3CA (C420R, E542K, E545A, E545D, E545G, E545K, Q546E, H1047L, H1047R, and H1047Y).(Package insert: therascreen PIK3CA RGQ PCR Kit. Qiagen; 05/2019)

Day(s) Performed

Monday through Friday

Report Available

5 to 10 days

Specimen Retention Time

Whole blood: 2 weeks (if available); Extracted DNA: Indefinitely

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

81309

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PIK3B cfDNA PIK3CA Test, Blood 60034-6

 

Result ID Test Result Name Result LOINC Value
616647 Result Summary 50397-9
616648 Result 82939-0
616649 Interpretation 69047-9
616650 Additional Info 48767-8
616651 Specimen 31208-2
616652 Source 31208-2
616653 Released By 18771-6

Forms

If not ordering electronically, complete, print, and send an Oncology Test Request (T729) with the specimen.