Pre- and post-radiotherapy computed tomography in laryngeal cancer: imaging-based prediction of local failure.

PURPOSE

To determine if pre-radiotherapy (RT) and/or post-radiotherapy computed tomography (CT) can predict local failure in patients with laryngeal carcinoma treated with definitive RT.

METHODS AND MATERIALS

The pre- and post-RT CT examinations of 59 patients (T3 glottic carcinoma [n = 30] and T1-T4 supraglottic carcinoma [n = 29]) were reviewed. For each patient, the first post-RT CT study between 1 and 6 months after irradiation was used. All patients were treated with definitive hyperfractionated twice-daily continuous-course irradiation to a total dose of 6,720-7,920 cGy, and followed-up clinically for at least 2 years after completion of RT. Local control was defined as absence of primary tumor recurrence and a functioning larynx. On the pre-treatment CT study, each tumor was assigned a high-or low-risk profile for local failure after RT. The post-RT CT examinations were evaluated for post-treatment changes using a three-point post-RT CT-score: 1 = expected post-RT changes; 2 = focal mass with a maximal diameter of < 1 cm and/or asymmetric obliteration of laryngeal tissue planes; 3 = focal mass with a maximal diameter of > 1 cm, or < 50% estimated tumor volume reduction.

RESULTS

The local control rates at 2 years post-RT based on pre-treatment CT evaluation were 88% for low pre-treatment risk profile patients (95% CI: 66-96%) and 34% (95% CI: 19-50%) for high pre-treatment risk profile patients (risk ratio 6.583; 95% CI: 2.265-9.129;p = 0.0001). Based on post-treatment CT, the local control rates at 2 years post-RT were 94% for score 1, 67% for score 2, and 10% for score 3 (risk ratio 4.760; 95% CI: 2.278-9.950 p = 0.0001). Post-RT CT scores added significant information to the pre-treatment risk profiles on prognosis.

CONCLUSIONS

Pre-treatment CT risk profiles, as well as post-RT CT evaluation can identify patients, irradiated for laryngeal carcinomas, at high risk for developing local failure. When the post-RT CT score is available, it proves to be an even better prognosticator than the pre-treatment CT-risk profile.