Prognostic impact of tumor growth velocity in head and neck squamous cell carcinoma treated by radiotherapy: A pilot study

Background: When a patient is seen with a newly diagnosed oropharyngeal squamous cell carcinoma, it remains unclear to the treating physicians how fast the tumor growth rate is. Methods: From patients with oropharynx squamous cell carcinoma treated by radiotherapy, the investigators selected comparable diagnostic CT-scan (DiCT) and radiotherapy planning CT-scan (RtCT). Tumor and pathological lymph node volumes were measured in order to calculate tumor progression. Results: From the selection of 19 patients, the mean absolute tumor progression rate was 0.23 ± 0.2 cm³/d and mean relative progression rate was 1.84 ± 1.64%/d. Mean tumor doubling time is 286 days (range 7-1282 days), demonstrating a wide range of tumor growth pattern. Significant tumor progression (>20%) between DiCT and RtCT was shown in 73% of patients, and 53% of the patients were seen a tumor progression of >50% within a mean waiting time of 42.1 days. Kaplan-Meier curves showed a non-significative link between fast progression tumors (>1%/d) and higher risk of recurrence (HR: 2.2; P =.23). Conclusions: Tumor progression can be assessed based on DiCT and RtCT. Treatment delay should be avoided at all cost. Different growth patterns were evidenced. For the fast-growing tumors subgroup, pejorative clinical outcomes were suggested. Prospective studies are needed to confirm a link between fast-growing tumors and higher risk for recurrence.