A man in the advanced prostate cancer online support group has asked, “Why the radiation (external beam to relieve bone pain from prostate cancer and to protect the bones from fractures) is given in so many “mini” doses rather than one or two larger doses.

The answer is it doesn’t necessarily have to be delivered in many smaller dosages.

Guidelines from the American Society for Radiation Oncology (ASTRO) support treatment with a single fraction of radiation using a dose of 8 Gy to provide palliation for relief of pain from bone metastases in men with prostate cancer.

Based upon a systematic review of the literature, this approach improved patient convenience and was more cost effective compared with fractionated schedules [1]. The use of a single 8 Gy fraction for pain relief is also supported by a second systematic review of the literature that looked at different doses of radiation administered as a single fraction [2]. That review also concluded that a dose of 8 Gy was more effective than lower doses in providing pain relief.

The ASTRO Guideline

“External beam radiotherapy has been, and continues to be, the mainstay for the treatment of painful, uncomplicated bone metastasis. Although various fractional schemes can provide good rates of palliation, numerous prospective randomized trials have shown that 30 Gy in 10 fractions, 24 Gy in six fractions, 20 Gy in five fractions, or 8 Gy in a single fraction can provide excellent pain control and minimal side effects.
The longer quest has the advantage of a lower incidence of repeated treatment to the same site and the single fraction has proved more convenient for patients and caregivers…. [3].”

1. Lutz S, Berk L, Chang E, et al. Palliative radiotherapy for bone metastases: an ASTRO evidence-based guideline. Int J Radiat Oncol Biol Phys 2011; 79:965.
2. Dennis K, Makhani L, Zeng L, et al. Single fraction conventional external beam radiation therapy for bone metastases: a systematic review of randomised controlled trials. Radiother Oncol 2013; 106:5.
3. Astro Guidelines – Palliative Radiotherapy for Bone Metastastes: An ASTRO Evidence Based Guideline; http://download.journals.elsevierhealth.com/pdfs/journals/0360-3016/PIIS0360301610035777.pdf

Joel T Nowak, M.A., M.S.W.