Objective: This research aimed to evaluate acute and late toxicities of radiotherapy for patients with connective tissue disease (CTD).

Methods: A retrospective review was performed with the medical records of patients with a diagnosis of both cancer and CTD, who have undergone radiotherapy at our institution between January 2010 to December 2020. Acute and chronic adverse effects of radiotherapy were analyzed.

Results: The mean age of the patients at time of RT was 58 years (45-74) and 50 years (35-68) at CTD diagnosis. Fourteen of patients were female (77.7%). Primary tumor location was as; breast 8 (44.7%), cervix 2 (11.1%), rectum 2 (11.1%), prostate 2 (11.1%), brain 1 (5.5%), lung 1 (5.5%), larynx 1 (5.5%) and endometrium 1 (5.5%). Nine patients (50%) had Behçet’s disease, 5 (28%) systemic lupus erythematosus, 2 (11%) systemic sclerosis and 2 (11%) dermatomyositis. Patients in the curative group receiving higher doses of radiation have experienced more acute toxic effects than the others. Thirteen (72%) patients had any grade 1 and 6 (33%) patients had any grade 2 acute toxicities while only 3 (17%) patients with cervical and brain cancers had chronic grade 2 hematological toxicity due to concomitant chemoradiotherapy. The most common acute toxicities were radiation dermatitis, nausea, fatigue and diarrhea. No acute or chronic toxicities higher than grade 2 were recorded. There was not any interruption occured during radiotherapy treatment because of acute toxicities and all patients completed their prescribed course of radiotherapy.

Conclusion: With new radiotherapy techniques there was no increased incidence of acute and chronic risk of toxicity observed and radiotherapy was generally well-tolerated for patients with CTD during the treatment and follow-up. Individualizing treatment strategy for each patient will help improve the results for this group of patients with increased treatment efficacy and decreased toxicity.