Alexander Valdman

Since the 1990s, the treatment results for rectal cancer have improved significantly in Sweden. The main reasons are improvement of the surgical technique and that an increasing proportion of patients receive preoperative radiotherapy. Several randomized studies have shown that preoperative radiotherapy reduces the risk of local recurrence by at least half. The knowledge about the effects and side effects of radiotherapy is based on studies done 10-30 years ago. Under it in the last decade, there has been a noticeable technological development in the area. Currently, however, there are no randomized ones studies on proton therapy in locally advanced rectal cancer. Today, to a much greater extent than before, the radiation dose can be limited to the body volumes that contain it tumor cells. This results in fewer side effects, as these side effects depend on the radiation dose given and treatment volume. A way to further reduce the dose to adjacent normal tissue and thereby reduce side effects is to give treatment with protons at the national proton therapy department Skandion Clinic. This one study intends to compare whether radiation therapy with protons causes less toxicity (side effects) compared to photons in patients with rectal cancer at high risk of recurrence. Treatment with proton radiation can be controlled more precisely than conventional radiation with photons, which can reduce the risk of side effects. However, the effect of proton irradiation in the treatment of rectal cancer is not clearly mapped. The purpose with this national study is to investigate whether radiotherapy with protons can reduce side effects compared to the standard treatment for high-risk rectal cancer. The study may be the basis for introducing proton radiation as a new standard for this patient group.