Relationship of depth of invasion to survival outcomes and patterns of recurrence for T3 oral tongue squamous cell carcinoma

Highlights

• DOI is an independent predictor of poor survival outcomes in pT3N0M0 OTSCC patients.

• Based on DOI, two prognostic groups may exist within the 8th Ed AJCC pT3N0M0 stage.

• DOI (10–20 mm) has worse overall and disease-specific survival than DOI (≤10 mm).

• DOI (10–20 mm) had more regional recurrence, especially in the contralateral neck.

Abstract

Introduction

Current research is elucidating how the addition of depth of invasion (DOI) to the 8th edition of the American Joint Committee on Cancer (AJCC) TNM staging for oral cavity squamous cell carcinoma influences its prognostic accuracy. However, there is limited research on survival in pT3N0M0 oral tongue SCC (OTSCC) patients when stratifying by DOI.

Objectives

Determine 5-year overall survival (OS), and cancer-specific survival (CSS) for patients with pT3N0M0 oral OTSCC based on shallow DOI (<10 mm) and deep DOI (10–20 mm).

Methods

Retrospective review involving three tertiary care cancer centers in North America. cT3N0M0 OTSCC patients receiving primary surgical treatment from 2004 to 2018 were identified. Inclusion: age > 18 years old and confirmation of pT3N0M0 OTSCC on surgical pathology. Exclusion: patients undergoing palliative treatment or previous head and neck surgery/radiotherapy. Analysis comprised two groups: shallow pT3 (tumor diameter > 4 cm, DOI < 10 mm) and deep pT3 (DOI 10 mm-20 mm).

Results

One hundred and four patients with pT3N0M0 OTSCC were included. Mean age was 59.1 years (range: 18–80.74). Age, gender, and Charlson Comorbidity Index were similar between the two groups (p > 0.05). Recurrence, LVI, PNI, and positive margins were more common in deep T3 tumors (P < 0.05). 5-year OS (50% vs 26%, p = 0.006) and CSS (72% vs 24%, p = 0.005) were worse in deep pT3 tumors. Deep pT3 disease was an independent predictor of OS (p = 0.004) and CSS (p = 0.01) on Cox-Regression analysis.

Conclusion

DOI is an independent predictor of poor survival in pT3N0M0 OTSCC patients. Consideration should be given to escalating adjuvant therapy for deep pT3N0M0 OTSCC patients.

Introduction

Oral cavity squamous cell carcinoma (OCSCC) is the ninth most common cancer worldwide [1], [2]. Oral tongue is the most common subsite within the oral cavity and generally carries a worse prognosis [3], [4]. Occult nodal metastasis is an important predictor of survival, with reported 5-year survival declining from over 80% to 65% if this is present [5], [6]. Within the past decade, primary tumour depth of invasion (DOI) has become established as a predictor of occult nodal metastasis, recurrence, and survival [7], [8], [9], [10]. More recently, DOI has been integrated into the T classification of the 8th edition of the American Joint Committee on Cancer (AJCC) TNM staging for OCSCC [11].

Separating superficial tumors with relatively good prognosis from those with deep invasion has shown a separation in prognosis. This distinction allows for more appropriate allocation of adjuvant treatments to surgery, such as radiation therapy (RT). Along with changes to the other T-classifications, tumors previously classified as pT2 with tumor diameter 2–4 cm are now up-staged to pT3 if DOI is 10–20 mm [5]. There is ongoing focus in the literature on how the addition of DOI influences the prognostic accuracy of the new T-classification system [7], [12], [13], [14], [15].

However, there has been limited research comparing survival outcomes of patients with pT3 oral tongue squamous cell carcinoma (OTSCC) based on tumor diameter (>4 cm) with DOI ≤ 10 mm with patients that have relatively small tumor sizes, but have been upstaged to pT3 based on a DOI of 10–20 mm. These two groups may represent two distinct clinical entities, with different prognostic characteristics. Therefore, we sought to study survival outcomes in patients with pT3 OTSCC based on shallow DOI (≤10 mm) and deep DOI (10–20 mm).