Should the excised tumor tissue be sent for molecular testing despite currently having no evidence of disease after surgery and chemoradiation?

Should You Use the Biopsy Tissue Specimen Post Excision for Molecular Testing?

Yes, you should absolutely send the excised tumor tissue for comprehensive molecular testing even when there is currently no evidence of disease after surgery and chemoradiation. This tissue represents an irreplaceable resource that may be critical for future treatment decisions, clinical trial eligibility, and prognostic information.

Why This Matters

The excised tumor tissue is often the only source of viable tumor material you will have, particularly if the patient achieves a complete pathologic response. Once this tissue is discarded, it cannot be recovered, and future molecular profiling opportunities are permanently lost 1.

Key Reasons to Preserve and Test Tissue:

For Immediate Clinical Utility:

• Molecular markers provide prognostic information that pathologic staging alone cannot capture 2, 3
• Results guide adjuvant therapy decisions and intensity of surveillance
• Identifies targetable alterations that may inform treatment at recurrence 4, 5
• Determines eligibility for clinical trials requiring specific molecular profiles

For Future Clinical Needs:

• If recurrence occurs, the original tumor molecular profile serves as baseline for comparison 6
• Resistance mechanisms at progression can be understood in context of original mutations
• Liquid biopsy (ctDNA) monitoring requires knowledge of the original tumor's molecular signature 7, 8
• New targeted therapies are continuously being developed; archived tissue allows retrospective testing 9

Recommended Tissue Handling Protocol

Based on the most recent expert consensus 1:

Immediate Processing (within 30 minutes of resection):

1. Formalin-fixed paraffin-embedded (FFPE) tissue - for routine diagnostics and most molecular testing
2. Fresh frozen tissue in liquid nitrogen - stored at -80°C or colder for optimal preservation of RNA, proteins, and metabolites
3. Both formats should be banked - FFPE is more stable but frozen tissue preserves analyte quality better 1

Minimum Testing Panel:

The specific markers depend on tumor type, but the principle is universal: test comprehensively upfront rather than sequentially exhausting tissue 4, 5.

For gliomas specifically (based on your context): IDH mutation status, 1p/19q codeletion, MGMT promoter methylation, and other WHO-required markers 2, 3

Storage Requirements:

• Do not discard excess tissue - store indefinitely with proper patient consent 1
• Frozen samples should not be exhausted until final diagnosis is established 1
• After diagnosis, excess tissue can be released for biobanking 1
• Maintain samples for at least 10 years, as new clinically relevant tests emerge 10

Critical Pitfalls to Avoid

1. Assuming "No Evidence of Disease" Means Testing is Unnecessary

• Molecular markers provide prognostic stratification independent of current disease status
• Post-treatment tissue changes make future biopsies less reliable 1
• Recurrence risk assessment requires baseline molecular data 7, 8

2. Exhausting Tissue on Sequential Single-Gene Tests

• Use multiplexed assays or NGS panels to conserve tissue 4, 5
• Coordinate with molecular pathology before sectioning blocks 1

3. Improper Tissue Preservation

• Delays in fixation/freezing degrade nucleic acids 1
• Document time from resection to preservation 1
• Avoid long-term formalin storage of unfixed tissue 1

4. Failing to Obtain Patient Consent for Biobanking

• Required before large-scale sequencing or research use 1
• Should be obtained prospectively, not retrospectively 1

Practical Implementation

Turnaround Time: Results should be available within 10 working days for treatment planning 4

Tissue Adequacy: Even small samples (1 mm³) can yield diagnostic molecular results, but larger volumes reduce sampling bias 1. All resected viable tissue should be preserved if storage capacity allows 1.

Quality Assurance: Fresh tissue yields higher quality sequencing data than FFPE, avoiding formalin-induced artifacts 11. However, FFPE remains the standard and is sufficient for most clinical molecular testing 1, 3.

The Bottom Line

The excised tumor tissue is a finite, irreplaceable resource. Comprehensive molecular testing and proper biobanking should be standard practice for all resected tumors, regardless of current disease status. This approach maximizes future treatment options, enables precision surveillance strategies, and ensures patients can access emerging targeted therapies and clinical trials 1, 9.