Although the overall prognosis for early-stage oral tongue squamous cell carcinoma is good, a significant portion of patients still experience locoregional recurrence and affect the disease-specific survival. At present, whether more aggressive postoperative radiation therapy in this particular patient population should be taken is still controversial. The analysis exhibited that disease-free survival (OR = 0.53, 95 % CI:0.35–0.81; P = 0.003) and locoregional recurrence-free survival (OR = 0.59, 95 % CI:0.38–0.93; P = 0.022) was significant improved in patients received radiotherapy compared to surgery alone. However, radiotherapy failed to improve overall survival (HR = 1.06 95 % CI:0.42–2.64, P = 0.901). Furthermore, two studies reported overall survival based on depth of invasion as well. The pooled OR was 1.65 (95 % CI:0.31–8.91, P = 0.221) and no survival benefit was observed for early-stage patients underwent adjuvant radiotherapy according to depth of invasion. Current evidence is insufficient to independently support the depth of invasion as an effective indication for radiotherapy of early tongue cancer.