T4 disease is divided as T4a (moderately advanced) and T4b (very advanced) for oral cavity cancers as per American Joint Committee on cancer (AJCC) 7th edition. Liao et al showed no statistical difference in the 5-year survival rates between the T4a and T4b groups. But it was a retrospective study with a small sample size. Thus, there was a need of a prospective study comparing the survival outcomes between T4a and T4b lesions.
This is a prospective study of 210 treatment naïve biopsy proven T4 buccal mucosa cancer patients operated between January 2010 to December 2013.Surgery was the primary modality of treatment followed by adjuvant therapy. Patients with Extracapsular spread(ECS) and margin positivity received chemoradiation and remaining patients received radiation alone. Follow up was done every 3 months. In the case of clinical suspicion of recurrence, confirmation was done using biopsy and or imaging.
The mean age was 49 years (26-73 years) with a male to female ratio of 4.6:1. T4a disease was seen in 135(64.3%) patients and T4b in 75(35.7%) patients. The mean disease-free survival(DFS) in T4a and T4b group was 41 months and 30 months respectively(p-0.001).The mean overall survival was 46 months for T4a lesion and 30 months for T4b lesion(p-0.0012). Differences in the DFS of the patients who received chemoradiation and those who received only radiation is given in the Table below. As expected, it is seen that patients with Extracapsular spread(ECS) and margin positivity have poor survival. But it is difficult to explain why patients with T4b disease without ECS or positive margins also have poor survival. Intensification of treatment in these select group of patients is important which might improve outcomes. Also, the rate of distant metastasis in patients with T4b disease was 19% and among those with T4a disease was 11%.3 –year DFS T4a T4b Chemo-radiation(with ECS & margin positivity) 41.6% 33.6% Radiation alone 72.2% 42.1% p-value 0.000 0.074
T4b is more aggressive disease than T4a.Treatment intensification with the addition of chemotherapy to radiation may benefit select patients with T4b buccal mucosa cancers and might help in reducing the rate of distant metastasis.
Manish Mair
None
All authors have declared no conflicts of interest.