Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_33_2776 - Tumour Depth of Invasion vs Tumour Thickness in Determining Risk of Nodal Disease in Early Oral Tongue Squamous Cell Carcinoma

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Tumour Depth of Invasion vs Tumour Thickness in Determining Risk of Nodal Disease in Early Oral Tongue Squamous Cell Carcinoma
B. Liu1, R. Amaratunga2, M. Veness3, E. Wong2,3, M. Abdul-Razak1,4, M. Smith1, H. Coleman1, V. Gebski5, and P. Sundaresan1,3; 1Westmead Hospital, Sydney, Australia, 2Westmead Hospital, Westmead, Australia, 3Sydney Medical School, University of Sydney, Sydney, Australia, 4Sydney Medical School, UNiversity of Sydney, Sydney, Australia, 5NHMRC Clinical Trials Centre, University of Sydney, Sydney, Australia

Purpose/Objective(s): Decisions regarding elective nodal treatment in early stage oral tongue squamous cell carcinoma (OTSCC) are based on the risk of sub-clinical metastases in the regional neck lymph nodes. Tumour thickness (TT) and tumour depth of invasion (DOI) have been recognized to correlate with this risk but there is ambiguity in the measurement, reporting and use of these entities. We examined the reporting of these entities at our institution and aimed to establish, for each entity, the cut point which best predicted for regional nodal disease. We also compared the threshold values of 4mm and the 5mm in predicting regional nodal disease.

Materials/Methods: A prospectively collected institutional database was interrogated to identify adult patients with histologically proven OTSCC that measured <4cm and who were treated with curative surgical resection between 1995 and 2012. Additional patient, disease, and treatment data were collected from hospital and cancer service records. The minimum p value method was used to calculate cut point values of TT and DOI that predicted for regional nodal disease. Data concerning TT and DOI were then classified into 3 subgroups: TT and DOI ≤4mm; TT and DOI ≥4mm; and either TT or DOI ≥4mm. The management decisions made in each group were examined and used to determined rates of under treatment and overtreatment. This was repeated for a 5mm threshold value.

Results: Of 145 cases identified, 109 had both DOI and TT parameters reported and recorded. 58 cases (53%) had been assigned identical values or values which differed by ≤ 0.1mm. Logistic regression analysis showed DOI (p=0.00036) and TT (p=0.0001) were highly correlated with risk of nodal disease and each other. The cut points that best predicted for regional nodal disease were 4.5 for DOI and 8mm for TT. Using 4mm as the threshold for either DOI or TT to guide elective nodal treatment, the rates of under treatment and overtreatment were 11% and 47% respectively. The 5mm threshold was associated with a under treatment of 19% and overtreatment rate of 49%.

Conclusion: Both TT and DOI were highly correlated with the risk of regional nodal disease but should be recognized as two distinct entities as their cut points for regional nodal disease prediction were different. In this dataset, a value of 4.5mm was the best cut point for DOI in predicting regional nodal disease. Our findings suggest very little difference between thresholds of 4 and 5mm in terms of guiding decisions on regional nodal neck treatment. This supports the use of the 5mm DOI, which has been incorporated into the staging of OTSCC, as also the threshold value to guide elective regional nodal treatment.

Author Disclosure: B. Liu: None. R. Amaratunga: None. M. Veness: None. E. Wong: None. M. Abdul-Razak: None. H. Coleman: None.

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