MTAP Deletion Results Explained

CDKN2A co-deletion, PRMT5 inhibitors and trial relevance

What each line of the report means

Specimen: Tumor tissue or blood, as stated
MTAP loss is usually detected as a homozygous deletion on a sequencing panel.
Biomarker / finding: MTAP homozygous deletion
MTAP sits next to CDKN2A on chromosome 9p21, so the two are often deleted together.
Classification: Loss-of-function alteration
A deletion removes the gene entirely; this is interpreted differently from a point mutation.
Clinical interpretation: Trial-matching lead
MTAP deletion creates a metabolic vulnerability targeted by PRMT5 and MAT2A inhibitors, which are currently trial-stage drugs.

How this result is interpreted

  • MTAP deletion occurs in roughly 10-15% of all cancers and is especially common in pancreatic cancer, glioblastoma, mesothelioma and bladder cancer.
  • The deletion creates a dependence on the PRMT5 pathway - the basis for a wave of MAT2A and PRMT5 inhibitor trials that enroll specifically on this finding.
  • Co-deletion of CDKN2A/B usually travels with MTAP loss and carries its own implications; both findings deserve review together.

What this result cannot tell you

  • Panel tests vary in how confidently they call homozygous deletions, especially in low-purity samples - the report's copy-number confidence matters.
  • A listed PRMT5/MAT2A trial is a lead for discussion, not a guarantee of eligibility; enrollment depends on cancer type, prior therapy and organ function.
  • Blood-based tests can miss copy-number losses when circulating tumor DNA levels are low.

Questions to ask your oncologist

  • Was MTAP reported as a homozygous deletion, and did the report also cover CDKN2A and CDKN2B?
  • How confident is the copy-number call given my sample's tumor content?
  • Are there open MAT2A or PRMT5 inhibitor trials for my cancer type right now?
  • If my result came from blood only, should the deletion be confirmed on tissue?

Frequently asked questions

Is MTAP deletion treatable today?

There is no approved drug that targets MTAP loss directly yet, but several PRMT5 and MAT2A inhibitors are in clinical trials that enroll specifically on this alteration. For most patients its practical value today is trial matching.

Can a deletion call be wrong?

Copy-number calls are less reliable in samples with little tumor DNA or low tumor purity. If the finding is central to a decision, confirmation on a better specimen can be warranted.

Can someone independently review this result?

Yes. A Clarity Report can assess the deletion call, co-alterations, cancer type and the current trial landscape, then return findings in writing.

Sources

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