Session Item

Precision radiotherapy is the essence of modern day treatment for head and neck cancers, which utilizes accurate delineation of target volumes for accurate dose delivery. Volumetric measurement of the tumour depicts the number of clonogenic cells present and thus can predict the treatment outcomes. This volume defined as GTV in the routine radiotherapy planning has been limited for mere contouring purpose and its potential as prognostic factor is less explored.

The data of 150 patients of head and neck cancer undergoing IMRT and weekly cisplatin (40mg/m²) between April 2015 and December 2019 at our Institution were retrospectively analyzed. GTVp (primary), GTVn (node) and GTVcombo (primary + node) contoured on eclipse treatment planning system version 13 were used to generate the volumetric parameters. The prognostic value of these tumour volumes with respect to treatment outcomes was analyzed using SPSS version 16.

Median age at presentation was 58.5 years. 73% were male. 42.6%, 36.6% and 20.6% had Oropharynx, Hypopharynx and Larynx primaries respectively. 16%, 62%, 19% and 3% had T2, T3, T4a and T4b disease; 32%, 23%, 41% and 3% had N0, N1, N2 and N3 disease respectively.  50% had stage III disease. Mean GTVp was 44.5cc (range 2.4 – 169.3), mean GTVn was 13.4cc (range 0 – 156.1) and mean GTVcombo was 57.9cc (range 2.4 – 227.2). All patients completed 70Gy in 33-35 fractions; median chemotherapy cycles were 6. 64% had complete response (CR). Comparison of GTV with CR rates was done using Pearson Chi-Square test, GTVp <30cc had better CR rates than GTVp >30cc (82.6% v/s 51.9%, p=0.00), GTVn <4cc had better CR rates than GTVn >4cc (74% v/s 58.4%, p=0.04) and GTVcombo <50cc had better CR rates than GTVcombo >50cc (81.5% v/s 47.8%, p=0.00). At median follow up of 21.4 months (range 3 – 71) OS was 60% and median OS was 32.3 months. Estimated 3 and 5 year OS was 49% and 42%.  On Univariate analysis the median OS in patients with GTVp < 30cc was better than GTVp >30cc (59.2 v/s 21.4 months, p=0.003); GTVn <4cc was better than >4cc (59.2 v/s 22.2 months, p=0.019); and GTVcombo <50cc was better than >50cc (59.2 vs 19.8 months, p=0.001).

GTV should not just be limited for contouring but also has to be recognized as an important prognostic factor.