MTAP Insight

03 · Clinical Planning

A test result is only useful if it changes a decision.

MTAP status crosses disciplines — pathology, molecular diagnostics, medical oncology, and clinical research. The institutions that integrate it best treat MTAP as a workflow question, not just a science question.

The pathway

  1. 01

    At diagnosis

    Reflex MTAP into your standard panel

    Order MTAP IHC or include it on your standard NGS panel at the time of initial tissue diagnosis — not at progression. Tissue is most plentiful, and the result informs trial eligibility from day one.

  2. 02

    Within 7–14 days

    Confirm equivocal results

    If IHC is heterogeneous or NGS purity is borderline, reflex to FISH. A confirmed homozygous deletion is far more actionable than an ambiguous one.

  3. 03

    At report sign-out

    Flag the result for the treating team

    Include an interpretive comment that calls out the therapeutic relevance and recommends molecular tumor board review. A buried copy-number table is easy to miss.

  4. 04

    Before line-of-therapy decisions

    Discuss at molecular tumor board

    MTAP-deleted patients are candidates for PRMT5 inhibitor trials. Identify them while standard-of-care options remain, not after multiple progressions.

  5. 05

    Throughout the journey

    Coordinate with a trial-savvy site

    Even if your institution doesn't run a PRMT5 inhibitor study, the trial directory can identify partner sites for referral. Early conversation prevents missed windows.

Built for your role

What MTAP means at your desk.

The one question

Ask on every new solid-tumor diagnosis:

"Do we know this patient's MTAP status?"

Roughly 10–15% of solid tumors carry homozygous MTAP deletion — higher in pancreatic, mesothelioma, glioblastoma, NSCLC squamous, bladder, and cholangiocarcinoma. If your NGS panel doesn't already report MTAP / CDKN2A copy number, ask your lab to enable it.

When to order

  • ›At initial diagnosis — not at progression, when tissue is scarce.
  • ›Reflex with CDKN2A; the two are co-deleted on 9p21.3.
  • ›Re-test on a new biopsy only if prior tissue is exhausted or QNS.
  • ›Document on the problem list so it travels with the chart.

Acting on a positive result

  • ›Bring to molecular tumor board before the next line of therapy.
  • ›Screen the trial directory for PRMT5 inhibitor studies open in your region.
  • ›Confirm tissue availability for central biomarker confirmation.
  • ›Start the referral conversation early — site activation takes weeks.

Talking to patients

MTAP loss is a tumor feature, not inherited. Frame it as a vulnerability the tumor carries — one that a new class of investigational drugs is designed to exploit. Patients respond well to the idea that their tumor's specific biology is being matched to a specific therapy.

Clinical trials

When testing reveals an MTAP deletion, a trial may be the next conversation.

Investigational PRMT5 inhibitors are being studied in patients whose tumors carry homozygous MTAP loss. Refer eligible patients early — site activation, screening, and consent take time.

Search the trial directory