NEW YORK (Reuters Health) – Particle beam radiation has been available since 1954, but a systematic literature review has failed to turn up statistically or clinically significant differences in survival or in serious adverse events with this treatment modality.

While a supposed advantage of this therapy is precise delivery of radiation doses, researchers at Tufts Medical Center, Boston, point out that its use is controversial, for at least two reasons: “documented clinical superiority over other…techniques is lacking and it is expensive.”

The group, headed by Dr. Teruhiko Terasawa, identified 8 randomized with 1276 patients and 9 nonrandomized clinical trials with more than 4000 subjects. Targeted cancers were in the prostate, skull-base and brain, pancreas, and eye.

According to the definitions used by the investigators, charged-particle radiation therapy involved “irradiation with protons, helium-ions, or heavier ions,” with neutrons or other particles excluded. Conventional radiation therapy was defined as “external photon-beam radiation guided by 2- or 3-dimensional imaging…without beam-intensity modulation.”

In an early online release by the Annals of Internal Medicine for September 15, Dr. Terasawa and associates report that none of the trials had a large enough sample size or long enough follow-up to yield statistically significant differences in overall or cancer-specific survival. Still, 3 of 4 trials favored charged-particle radiation therapy for its better local control rates.

“Overall,” the investigators report, “no study found that charged-particle radiation therapy is statistically significantly better than alternative treatments with respect to patient relevant clinical outcomes.”

The authors did observe that particle beam radiation may be a good alternative for selected rare and specific types of cancer – such as head and neck cancer – in which critical structures close to the tumor are at high risk from conventional treatments.

The investigators point out that 7 facilities in the US provide particle beam irradiation, and 4 others are under construction. Costs of construction are estimate to range between $100 and $225 million.

Still, they surmise, costs may decrease as availability increases.

The research team concludes: “Comparative studies in general, and randomized trials in particular (when feasible), are needed to document the theoretical advantages of charged-particle radiation therapy in specific clinical situations.”

Reference:
Ann Intern Med 2009.