904P - Analysis of TP63 immunohistochemistry scores (IHC) by primary site and between primary and metastatic tumours in adenoid cystic carcinoma (ACC)

Background

ACC can be sub-classified based on TP63 IHC, with low TP63 expression (ACC-I) characterised by MYC amplification and NOTCH pathway activation. ACC-I has significantly shorter overall survival (OS) versus TP63-overexpressing ACC-II. To inform application of TP63 IHC in clinical practice, we characterised ACC TP63 expression in different primary sites (major salivary gland vs other) and between primary and metastatic tumours.

Methods

109 patients consented to an ethically approved study. ACC tumour samples were evaluated by TP63 IHC (DAK-P63, Dako) for proportion of tumour cells expressing TP63. Scores were described by primary site (major salivary gland; other) and biopsy site (primary; distant metastasis). Kaplan-Meier analysis was performed and p values calculated (log-rank test) to calculate OS for TP63 positive or negative cases, using a cut-point of >10%.

Results

109 ACC patients (45 male, 64 female; median age 61yrs, range 29-81) were included. Primary sites were major salivary gland (51%), sinonasal (19%), upper aerodigestive (19%) or other exocrine glands (11%). TP63 staining was seen in 94% of cases (median 45%; range 1-85%) and strongly associated with prognosis. For a cut-point of ≤10%, 13/109 (12%) were classed as negative. Median OS from recurrence was significantly reduced in TP63-negative patients (13 v 72.6mo; p=0.0015). Analysis of TP63 staining by primary site found no significant difference. In analysis of TP63 staining by primary and metastatic site: primary tumour 43%, median 45%, range 0-85%; distant metastasis 39%, median 40%, range 1-80%; p=0.2422. There was no significant difference in TP63 scores for solid vs non-solid pathology (39.1%, median 45%, range 0-85% vs 43.8%, median 43.5%, range 0-80% respectively; p=0.3166).

Conclusions

The study confirms single-marker IHC classification (possible in any diagnostic lab) as TP63 positive/negative is prognostic in recurrent/metastatic ACC. No significant differences were found in TP63 scores based on primary tumour site or site of biopsy (primary vs metastatic). This has potential to inform future clinical application of TP63 IHC.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The Christie NHS Foundation Trust.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.