Purpose: To identify the risk factors for moderate to severe subcutaneous fibrosis after whole neck irradiation.
Materials and methods: We analyzed 233 cases of patients who had undergone whole neck irradiation with 4-MV X-ray or 8-10-MeV electrons, or both, and had been followed with regard to their skin condition for at least 1 year. The prescribed dose to the whole neck ranged from 19.2 to 72.4 Gy (median 50). The skin-absorbed dose was specified as that at a depth of 4.1 mm (d4.1-mm(depth)), and a biologically equivalent dose (BED) of d4.1-mm(depth) was also estimated (BED(1.8) 4.1-mm(depth)).
Results: Univariate analysis revealed that previous neck dissection, concurrent chemotherapy, corticosteroid administration as a part of chemotherapy, fractionation, and BED(1.8) 4.1-mm(depth) were significant prognostic variables. Multivariate analysis showed that BED(1.8) 4.1-mm(depth) and previous neck dissection were the only prognostic variables for moderate to severe subcutaneous fibrosis.
Conclusion: A high dose to a 4.1-mm depth of the skin and a history of neck dissection were identified as the predominant risk factors for moderate to severe subcutaneous fibrosis after whole neck irradiation. A subcutaneous dose should be considered in radiotherapy treatment planning involving the whole neck, especially in cases in which patients have undergone previous neck dissection.