Correlation of degree of acute radiation dermatitis (RD) with skin dose distribution in head and neck squamous cell carcinoma patients treated with definitive concurrent chemoradiation.

Background: Radiation dermatitis (RD) or skin toxicity is one of the most common acute side effects of radiation in head and neck cancer patients. This study aims to correlate the pattern of volumetric-modulated arc therapy (VMAT) dose distribution to the skin with the grades of RD.

Materials and methods: 80 plans of histopathologically proven squamous cell carcinoma head and neck patients already treated with definitive concurrent chemoradiation [66-70 Gy in 33-35# or 66 Gy in 30# in simultaneous integrated boost (SIB), with concurrent Cisplatin 100 mg/m² 3 weekly] at our institution between November 2022 and November 2023 were retrieved from our digital archives. For each plan, 1 ring structure was created 3mm below the external skin surface, and the parameters V₄₀, V₅₀, V₆₀ and D_max were collected from the same. These parameters were correlated with grades of RD as per Common Terminology Criteria for Adverse Events (CTCAE) v5.0. The statistical analysis was done using MedCalc software version 22.021.

Results: The incidence of G2/G3 RD was 52.5%, and its incidence was significantly correlated with all of the four parameters. Statistically significant (p < 0.001) dosimetric predictive accuracy was provided by 71.66 cc, 29.98 cc and 7.624 cc of the 3mm skin ring V_40, V₅₀ and V₆₀, respectively.

Conclusion: The dose distribution pattern to a skin layer stationed 3mm below the surface may help predict the development of severe RD in head and neck cancer patients receiving concurrent chemoradiation.