Using primary tumor volumetry to predict treatment outcome for patients with oropharyngeal cancer who were treated with definitive chemoradiotherapy.

AIM: This study aimed to determine predictive values for volumetric measures in patients with oropharyngeal cancer who received definitive chemoradiotherapy (CCRT).

METHODS: Contrast-enhanced computed tomography (CT) scans were obtained before radiotherapy (RT) (I), after delivering a median RT of 50.6 Gy (R) and three months after RT (F). Primary site gross tumor volumes (GTV) were assessed using these scans (GTVI , GTVR and GTVF ). The percentage volume change between GTVI and GTVR (GTV change) was calculated. Volumetric analyses of primary site local control (LC) and progression-free survival (PFS) were performed.

RESULTS: In total, 35 patients were evaluated, with a median 31 months of follow-up. The 2-year LC rates (LCRs) were 95.0% for patients with GTVI <23 cc, and 42.9% for those with GTVI ≥23 cc (P = 0.001); the 2-year PFS rates were 85.9% and 21.9% (P = 0.002), respectively. Using GTVR classifications <11 cc or ≥11 cc, log-rank tests demonstrated differences in 2-year LCR (95.2% vs 33.3%, P < 0.001) and 2-year PFS (86.5% vs 0%, P < 0.001). There was no local progression in patients with GTV change ≥75%, and GTV change predicted poor PFS (P = 0.026). On multivariate analysis, GTVR ≥11 cc was a significant predictor of poor LCR (hazard ratio [HR] = 26, P = 0.009) and PFS (HR = 8.33, P = 0.046).

CONCLUSION: For patients with oropharyngeal cancer treated with definitive CCRT, GTVI , GTVR and GTV changes predicted LC and PFS; GTVR was the most significant predictor of LC and PFS. RT intensification should be considered for patients with larger remaining tumors after CCRT.