Modern Diagnostic Imaging in the Evaluation of Late Complications Radiation Therapy in Patients with Squamous Cancer of the Anal Canal

Purpose: There are some descriptions of different bones’s stress fractures in radiation therapy, among them fractures of os sacrum and femoral heads. We estimated radiotherapy dose on bones mentioned above and collated them with the revealed stress fractures in selected patients.

Material and methods: Since 2011 till 2015 129 patients with morphologically proven squamous cell anal cancer were treated with chemoradiotherapy – IMRT and mytomycin-based CT.

Results: Stress fractures of a sacrum without any symptoms was diagnosed on MRI scan in 5 (3,9 %) patients, aged 54–75, with stages IIIA/IIIB within one year since treatment finished. In our patients no one of those with stress fracture hadn’t radiotherapy dose more than 45 Gy on sacrum. For dose estimation on femoral heads they were contoured as separate structure in 10 patients: D_{2 %} was 41.62 ± 0.84 Gy, V₄₅ – 3.08 ± 1.75 cm³.

Conclusion: Stress fractures are rare but important complication of modern radiation therapy and call for modern diagnostic methods  (MRI). State-of-art  treatment  involves radiotherapy  and  chemotherapy,  and  higher  doses of radiotherapy on distinct regions of pelvic bones may increase the risk of stress fracture.

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