Comparing daily versus weekly imaging checks in radiation therapy for prostate cancer

This study aimed to investigate the best timing of treatment verification imaging used in radiation therapy for patients with prostate cancer. This study found that patients undergoing daily imaging had less risk of their cancer returning and had reduced rectal side-effects.

One main treatment option for prostate cancer is radiation therapy. This involves the local use of high dose x-rays to kill tumor cells. Radiation therapy treatment for the prostate is generally spread out over several weeks (up to 6-7) and takes place each day. Each treatment is delivered to the exact same area as prescribed by a radiation oncologist. However, this area of the body is movable. Imaging (low dose x-rays) can be used before or during radiation treatment to verify the target area will be treated correctly. This technique is called image-guided radiotherapy (IGRT). This can be carried out every day or it can be carried out on days 1-3 and weekly thereafter (weekly imaging). It is unclear which imaging schedule is more effective for accurate treatment.

470 patients from different centers were included in this study. They were randomly assigned to have imaging once a week (234 patients) or daily (236 patients). Patients who had weekly imaging were also imaged days 1,2 and three before proceeding to weekly. All patients were followed up for an average of 4 years.

At the end of the study, patients undergoing daily imaging had a 19% lower risk of their cancer returning. However, the overall survival (time patients are still alive) was two times lower in the daily group, compared to the weekly group.

Side-effects such as rectal bleeding were more common in the weekly group (11%) compared to 6% in the daily group.

The authors concluded that patients undergoing daily imaging had a lower risk of their cancer returning and had fewer rectal side-effects.

This study did not have a long enough follow-up period for this to be considered a high level of evidence. Further studies are needed to determine the best timing for IGRT.