Comparison three-dimensional conformal radiotherapy versus intensity modulated radiation therapy in local control of head and neck cancer

Abstract

Background: About 74% of head and neck cancer (HNC) patients need to undergo either definitive or postoperative radiation therapy because of aggressive nature of disease. The transition from two-dimensional conventional radiotherapy to three-dimensional conformal radiotherapy (3D-CRT) and further technological evolutions led to the successful clinical implementation of intensity modulated radiation therapy (IMRT), which constitutes an evolution of 3D-CRT. The IMRT technique gives the ability to create treatment fields with varying beam intensity using inverse planning and optimization algorithms to treat irregularly shaped target volumes with high precision. IMRT is in existence in clinical practice since 1995. Since then, presuming its clinical benefit a significant amount of patients has been treated by this technique. PARSPORT was the first multi-institutional prospective trial comparing IMRT with conventional RT in the treatment of HNC. It has shown a reduction in severe xerostomia but no difference in other toxicity and locoregional control after 24 months' follow or overall survival. Except for early T1, 2 N0 stages, the prognosis for patients with oral cavity cancer (OCC) is dismal than for carcinoma in other sites of the head and neck (HNC).

Aim: The aim of this study was to assess the outcome of OCC following IMRT.

Materials and methods: Between January 2013 and January 2015, 40 patients of carcinoma buccal mucosa and carcinoma alveolus were treated by postoperative (19) or definitive (21) radiation therapy by IMRT technique. Of these, 28 patients (70%) presented with locally advanced T3/4 or recurrent tumor. Total radiation doses delivered was between 60 and 70 Gray at 2 Gray/fraction. Of these 31 patients (78%) has received concurrent cisplatin-based chemotherapy. Another group of 42 similar patients treated by 3D-CRT as definitive or postoperative adjuvant treatment over the same period has been selected. Comparisons were performed between these two groups.

Statistical analysis: Data were entered into Excel spreadsheet and expressed as mean and standard deviation for deriving P value, and unpaired t-test was used to calculate 95% confidence interval. Local control (LC) was analyzed using Kaplan-Meier curve. Of all assessed treatment subgroups, LC rate was highest for patients treated with postoperative IMRT (89% LC at 2 years) followed by postoperative 3D-CRT patients (79% LC at 2 years); and finally, poorest LC rates (43% and 32% at 2 years) were seen in definitively irradiated patients with IMRT and 3D-CRT, respectively. LC rate for T1 stage (83%, n = 6) was significantly higher, than that for T2-4 (LC 55%, n = 76) as expected.

Conclusion: Postoperative IMRT of carcinoma buccal mucosa and alveolus resulted in the highest LC rate of all the treatment subgroups assessed hence should be generously recommended in such cases especially ones with unfavorable features such as close resection margin, nodal involvement, locally advanced tumor (>T1N0), or recurrent disease, respectively. Despite definitive IMRT, locoregional control in carcinoma buccal mucosa and alveolus remain unsatisfactory, comparable to that following definitive 3D-CRT.

Keywords: Three-dimensional conformal radiotherapy; definitive radiotherapy; intensity modulated radiotherapy; local control; postoperative radiotherapy.