Final Report of Radiation Therapy Oncology Group Protocol 9003: Provocative, but Limited Conclusions From Exploratory Analyses

The DAHANCA 6 randomized trial: Effect of 6 vs 5 weekly fractions of radiotherapy in patients with glottic squamous cell carcinoma

PURPOSE

The DAHANCA 6 trial evaluated tumor response and morbidity after moderate accelerated radiotherapy compared to conventional fractionated radiotherapy in patients treated for glottic squamous cell carcinoma (SCC). Further, the failure pattern and incidence of new primary tumors were explored.

PATIENTS AND METHODS

Six hundred and ninety-four patients with non-metastatic glottic SCC were randomized between six or five weekly fractions (fx/w) of radiotherapy to the same total dose. The median treatment time was 38 and 46days, respectively. The primary endpoint was loco-regional failure.

RESULTS

Median follow-up time was 14.5years. Of the 177 failures, 167 involved T-site. The cumulative incidence of loco-regional failure (LRF) was 21.6% in the 6fx/w group and 29.3% in the 5fx/w group and the corresponding hazard rate (HR) of LRF was 0.72 (CI: 0.53-0.97, p=0.04). The effect of acceleration on LRF was especially evident in well differentiated tumors (HR=0.42 (CI: 0.23-0.75) and in T1-2 tumors (HR=0.60 (CI: 0.41-0.89)). The HR of laryngectomy was 0.72 (CI: 0.50-1.04) in the 6fx/w group compared to the 5fx/w group. The hazards of disease-specific death, event-free survival, and overall survival were comparable between the two groups. Significantly more patients experienced severe acute mucositis in the 6fx/w group but the incidence of late morbidity was comparable between the groups. New primary tumors occurred in 22.5% of the patients.

CONCLUSION

Moderate accelerated radiotherapy significantly improved loco-regional control in patients with glottic SCC.