Depth of Invasion as an Independent Indication for Postoperative Radiation Therapy in Oral Tongue Squamous Cell Carcinoma
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Published on: July 25, 2011
Sarthak Tandon1, Parveen Ahlawat1, Shaifali Mahajan1
1Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India.
Purpose:
Over the years, scientific literature has highlighted the importance of depth of invasion (DOI) in managing oral squamous cancers, particularly its association with nodal metastasis. However, determining the role of DOI in postoperative radiation therapy (PORT) remains a clinical challenge. This study aimed to evaluate PORT with a DOI cutoff of 5 mm.
Methods And Materials:
Patients diagnosed with oral tongue squamous cell carcinoma (and restaged as per American Joint Cancer Committee 2018) with pT1,2 and pN0 were selected. Baseline characteristics were collected and divided into 2 groups using a DOI cutoff of ≤5 versus >5 mm. The study endpoints were overall survival (OS), disease-free survival (DFS), and locoregional control (LRC).
Results:
The study included 255 patients, with comparable baseline characteristics between groups. A significantly higher incidence of perineural invasion (PNI) was noted among patients receiving PORT in both cohorts. After a median follow-up of 37 months, no statistically significant differences were observed in median OS, DFS, or LRC in patients with a DOI ≤5 mm, irrespective of PORT. Conversely, for patients with a DOI >5 mm, the median OS was 48 months for those not receiving PORT, whereas it was not reached for those receiving PORT (P = .03). Furthermore, patients with a DOI >5 mm who received PORT showed significantly improved median DFS and LRC compared with those who did not receive PORT (36 months vs not reached, P = .001 for DFS; 37 months vs not reached, P < .001 for LRC]. In penalized multivariable Cox regression analysis, PORT emerged as the independent prognostic factor for DFS (hazard ratio [HR], 0.50; 95% CI, 0.31-0.82; P = .01) and LRC (HR, 0.34; 95% CI, 0.20-0.60; P < .001) with statistically insignificant OS benefit (HR, 0.58; 95% CI, 0.33-1.02; P = .06) in patients with a DOI >5 mm.
Conclusions:
Despite a significantly higher distribution of PNI in patients with DOI >5 mm, the use of PORT significantly improved median OS, DFS, and LRC in this retrospective analysis. The penalized Cox proportional hazard model also suggested that the use of PORT in patients with DOI >5 mm increases survival endpoints irrespective of PNI and lymphovascular invasion positivity, especially for DFS and LRC.
