Probiotics for rectal volume variation during radiation therapy for prostate cancer.

PURPOSE: To investigate the effect of the probiotic Lactobacillus acidophilus on the percentage volume change of the rectum (PVCR), a crucial factor of prostate movement.

METHODS AND MATERIALS: Prostate cancer patients managed with tomotherapy as a radical treatment were enrolled in the study to take a probiotic capsule containing 1.0×10(8) colony-forming units of L acidophilus or a placebo capsule twice daily. Radiation therapy was performed at a dose of 78 Gy in 39 fractions. The PVCR, defined as the difference in rectal volume between the planning computed tomographic (CT) and daily megavoltage CT images, was analyzed.

RESULTS

Forty patients were randomized into 2 groups. The L acidophilus group showed significantly lower median rectal volume and median PVCR values than the placebo group. L acidophilus showed a significant reduction effect on the PVCR (P<.001). However, the radiation therapy fraction number did not significantly influence the PVCR.

CONCLUSIONS

L acidophilus was useful in reducing the PVCR, which is the most important determining factor of prostate position, during radiation therapy for prostate cancer.