Evaluation of acute skin toxicity of breast radiotherapy using thermography: Results of a prospective single-centre trial

Purpose: Radiotherapy is a common adjuvant treatment of breast cancer. Acute radiation-induced dermatitis is a frequent side effect. We hypothesized whether it is possible to capture the increase of local temperature as a surrogate of the inflammatory state induced by radiotherapy. We designed a prospective, observational, single-centre study to acquire data on temperature rise in the treated breast during the course of radiotherapy, establish a possible association with the occurrence of dermatitis and investigate the predictive value of temperature increase in future occurrences of radiation-induced dermatitis.

Patients and methods: All patients presenting for neoadjuvant or adjuvant radiotherapy during the course of breast cancer treatment at the university hospital of Martinique were considered for inclusion. Every week, patients were examined by two trained investigators for the occurrence of radiation-induced dermatitis, graded based on Radiotherapy Oncology Group, Common Terminology Criteria for Adverse Events v.4.0 and Wright scales. A frontal thermal image of torso was taken in strictly controlled conditions, with a calibrated TE-Q1 camera (Thermal Expert, i3systems, Daejeon, Korea). We studied temperature differences between the irradiated breast or thoracic wall and the contralateral area. For each thermal picture, we measured the difference in maximum temperature as well as the difference in minimum temperature and the difference in the average temperature in the considered area. We studied the evolution of these parameters over time week after week, measuring the maximum recorded difference and its correlation to acute radiation dermatitis intensity.

Results: Sixty-four consecutive patients were included. For all patients, we noticed an increase of temperature during the course of radiotherapy. Difference in maximum, minimum and average temperature was higher between the two breasts of patients with a radiation-induced dermatitis grade 2 or above compared to patients with no or mild dermatitis. Higher temperatures were also significantly associated with an increased sensation of discomfort, as recorded by questionnaire (P<0.05).

Conclusion: As expected from the inflammatory phenomena involved in radiation-induced dermatitis, a noticeable increase in temperature during the course of radiotherapy was seen in all patients. Furthermore, high-grade radiation-induced dermatitis was strongly associated with an additional increase in local temperature, which is probably linked to the intense inflammatory reaction. Lastly, with a 1.4°C threshold set beforehand, it is possible to anticipate the occurrence of radiation-induced dermatitis, with interesting positive and negative predictive values of 70% and 77%, respectively in our population. We note that these results need to be confirmed in a dedicated study.