Permanent alopecia after radiotherapy of primary brain tumours: The most influential factors.

Purpose: Alopecia is a distressing side effect of radiotherapy in patients undergoing treatment for primary brain tumours. This study aimed to investigate the most influential clinical, demographic, and dosimetric factors associated with permanent scalp alopecia in patients with brain tumours treated with intensity-modulated radiations.

Patients and methods: Eighty patients with brain tumors treated with intensity-modulated radiations were enrolled. Inclusion criteria were having a primary brain tumour and patients with at least 18 months of radiotherapy. Scalp alopecia was evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) v5.0. The scalp location with hair loss was marked and delineated on their follow-up MRI, and the planning dosimetric parameters, including D_0.1cm³ (as maximum dose), mean dose, and various volumetric parameters such as V_16Gy-43Gy (with about 5Gy interval) were recorded. In addition, receiver operating characteristic (ROC) curve analysis was employed to identify predictive parameters for chronic alopecia.

Results: The hair loss severity was grade 1 for 70 % of cases, and grade 2 for 30 %. Male gender, history of chemotherapy, and family history of hair loss were significantly associated with increased volume of hair loss follicles. The correlation and ROC analysis revealed that regions receiving doses of 30Gy or higher (i.e., V_30Gy) were associated with a higher risk of developing grade 2 alopecia. The resulting areas under the curve of 0.694 were indicators for moderate correlations between the considered dose-volume histogram parameters and patients' permanent alopecia. Even if these results were not statistically significant, these findings suggest that specific dosimetric parameters, such as V_30Gy to V_43Gy, maybe the strongest predictors of grade 2 chronic radiation-induced alopecia. The cut-off values were also about 13.5 to 8 cm³ for V_30Gy to V_43Gy, respectively, which can be played as an indicator of the dose-volume histogram threshold above which permanent alopecia will be expected after brain intensity-modulated radiotherapy.

Conclusion: The incidence of permanent alopecia after intensity-modulated radiotherapy is influenced by demographic, dosimetric, and clinical factors such as gender, history of chemotherapy, and family history, and the skull follicle regions receiving doses of 30Gy or higher.