Does the frequency of radiotherapy doses impact its effectiveness and safety for patients with localized prostate cancer?

This study examined if the frequency of the same dose of radiotherapy (RT) changed the effectiveness and safety of patients with localized prostate cancer (PC). The results showed that RT that was given weekly was as effective and safe as RT given every other day.

Radiotherapy (RT) is an effective treatment for patients with localized prostate cancer (PC). RT can be given in different ways and dose schedules. One type of RT is called stereotactic body radiotherapy (SBRT). This type aims multiple beams at the tumor from different angles. It aims to reduce side effects on the surrounding tissues. Often patients receive SBRT once weekly or every other day. These schedules aim to effectively treat PC while reducing serious side effects.

RT can cause serious long-term side effects, particularly in the gut, bladder, and genitals. Methods to protect these organs and therefore reduce side effects have been developed, such as urethra sparing techniques. However, it is unclear if the addition of urethra sparing techniques to RT changes the impact of dosing frequency.

165 patients with localized PC were divided into two groups. Group A received SBRT with urethra sparing every other day (82 patients). Group B received SBRT with urethra sparing once weekly (83 patients). In total, both groups received the same dose of RT five times. Patients were examined before treatment, at the 5^th dose, and 18 months after starting treatment.

International Prostate Symptom Scores (IPSS) were used to measure the severity of symptoms.  In Group A, average IPSS was 6.4 before treatment, 10.9 by the 5^th dose and 5.6 by 18 months. In Group B, the average IPSS was 7.1 before treatment, 10.2 by the 5^th dose and 6.2 by 18 months.

Side effects in the gut, bladder, and genitals were mild for both groups. Patients’ urination quality was 80% before treatment, 62% at the 5^th dose and 90% by 18 months in Group A. In Group B, urination quality was 77% before treatment, 67% by the 5^th dose and 88% by 18 months.

Most patients did not develop serious gut, bladder and genital side effects. By 18 months, 2% of Group A and 3% of Group B had gut-related side effects.  At 18 months, 4% of Group A and 4% of Group B had bladder or genital side effects.

PSA is a protein produced by the prostate which increases as the tumor grows. It is used to evaluate the effectiveness of PC treatment. Over 18 months, patients' PSA reduced from 8.3 ng/mL to 0.53 ng/mL in Group A and from 7 ng/mL to 0.46 ng/mL in Group B. 

The authors concluded that both SBRT schedules were as effective and safe as each other.

This study was limited by the small numbers of patients and relatively short follow-up time.