ESTRO 2024 - Abstract Book

S1223

Clinical - Head & neck

ESTRO 2024

studies has been to empirically establish the direct correlation between an escalating DOI and an elevated propensity of patients to experience nodal metastasis. OSCC forms the ninth most common cancer worldwide and the second most common cancer in India.[1], [2] Oral tongue squamous cell carcinoma (OTSCC) forms the most common subsite of OSCC with the worst prognosis compared to other subsites. The question regarding the importance of DOI in predicting treatment, especially in early OTSCC remains a point of concern for most treating oncologists. The role of elective neck dissection using DOI as a cut-off has been established.[3] However, the impact of DOI in deciding post-operative radiotherapy (PORT) has always been a clinical dilemma. Hence, the study aims to assess the role of PORT with a DOI cut-off of 5mm.

Material/Methods:

The retrospective study was approved by the institutional review board. The institutional database was reviewed from January 2014 to December 2021. Patients diagnosed with OTSCC (and restaged as per AJCC 2018) with pT1,2 and pN0 were selected. Patients with incomplete data and with DOI > 10mm (upstaged to T3 as per AJCC 2018) were excluded. Baseline disease and treatment characteristics were collected and divided into two groups using a DOI cut- off of ≤ 5 vs > 5mm. All statistical analyses were performed using the statistical package for social science system (SPSS v22, SPSS Inc, Chicago, IL). Continuous variables were written as mean (along with standard deviation) and median (along with range). Categorical variables were represented as frequency and percentages. Intercohort testing was performed using chi-square for categorical variables and independent-t/nonparametric tests for continuous variables. Survival analysis for independent variables was performed using the Kaplan-Meier product limit method, and Cox’s model was used to estimate relative hazards (hazard ratio [HR] with 95% confidence interval [CI]). A 2-sided P < .05 was considered significant.

Results:

Patient and treatment characteristics: Two hundred and fifty-five patients were identified as per the inclusion criteria. The baseline patient and treatment characteristics were similar between the groups (Table 1). However, there was a significantly higher percentage of perineural invasion (PNI) in the patients with DOI > 5mm.

The median follow-up for the entire cohort was 37 months (range, 8 – 138 months). Whereas, the median follow-up for DOI ≤ 5mm vs > 5mm was 38 (range, 8 – 124) and 37 (range, 9 – 138) months respectively.

Table 1: Baseline patient and treatment characteristics

DOI

≤

5mm

Character

p-value

Effect Size

DOI

>

5mm

n = 73

n = 182 (%)

Age (mean in years)

50.93 ± 10.2

50.75 ± 13.3

0.918

-

Grade

Well-differentiated

7 (9.6)

27 (14.8)

Moderately-differentiated

65 (89.0)

152 (83.5)

0.525

0.071

Poorly-differentiated

1 (1.4)

3 (1.6)

Pathological T size (mean ± SD in cm)

2.04 ± 0.74

2.17 ± 0.77

0.257

-

Lymphovascular Invasion (present)

5 (6.8)

21 (11.5)

0.263

0.035