Introduction and Objective:
Locally advanced rectal cancers witha high risk of recurrence need multimodal treatment Rusing neoadiuvant preoperative chemoradiotherapy or preoperative radiotherapy. Both rectal cancer surgery and the additional chemoradiotherapy or radiotherapy may cause late sequelae. The aim of the study is to present a clinical situation in which a pelvic recurrence of rectal cancer has to be distinguished from therapy side effects. Insufficiency fracture (IF) is one of the therapy side-effects. It can cause pain and decrease mobility and it is a well-known late complication to pelvic radiotherapy, but can be misinterpreted as a local recurrence.

Conclusions:
It is extremely important to distinguish IF from metastases, which may require biopsies and initiation of potentially toxic treatments such as chemotherapy. MRI and CT scans are complementary modalities to make an accurate diagnosis of IF.