Definition

PIK3CA is an oncogene that encodes the catalytic subunit of the PI3K/AKT/mTOR pathway; it carries activating mutations in 28-40% of HR-positive/HER2-negative metastatic breast cancers and has been associated with endocrine resistance. The SOLAR-1 trial showed that the combination of alpelisib plus fulvestrant significantly prolonged progression-free survival in PIK3CA-mutant patients.

Gene/region examined

PIK3CA Exon 9, PIK3CA Exon 20

Method

DNA analysis

Accepted sample types

Fresh tumor tissue, FFPE

Description

Diagnosis.

Inheritance

Somatic, it is tested as an acquired mutation in tumor tissue (or ctDNA) and is not associated with a germline syndrome.

Related Tests

Inheritance Patterns

Describes how a genetic condition is passed on within a family. There are five main patterns

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Carrier (Heterozygous / Homozygous)

Why it matters: In autosomal recessive inheritance, when each parent is a carrier (while both appear healthy), the chance of their child being born with the disease is 25% in each

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VUS (Variant of Uncertain Significance)

This is the situation where the test has detected a change in the DNA, but the role of this change in the development of disease is unconfirmed.

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How to Read a Genetic Test Result (Positive / Negative / VUS)

A genetic test result falls into three main categories

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Types of Genetic Tests

A genetic test is a type of medical test that detects changes in genes, chromosomes or proteins. Today there are more than 77,000 genetic tests available.

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