We thank the authors for compiling what is known about impingement syndrome of the shoulder (1).
Regrettably, however, they did not mention that even low-dose radiotherapy can have a good analgetic effect. Furthermore, in individual case reports, periarticular calcifications regressed after radiotherapy (2). Retrospective studies have shown a reduction in pain or even absence of pain in 58–100% of patients. The results are better for early symptoms. Radiotherapy is recommended in the form of orthovoltage irradiation or by a linear accelerator with total reference doses of 3–6 Gy in 2–5 × weekly individual fractions of 0.5–1 Gy (2), which amounts to 1–3 weeks of radiotherapy.
Earlier randomized trials from 1952 and 1969, which did not establish any superiority of radiotherapy over placebo, should be regarded with caution because of low patient numbers, questionable endpoints, occasionally unusual indications, and unsatisfactorily short follow-up periods. A study published in 2014 on the painful shoulder syndrome (3), which compared individual doses of 0.5 Gy (total reference dose 3.0 Gy) and 1 Gy (total reference dose 6.0 Gy), showed a good response to radiotherapy on the one hand, but on the other hand it was found that the mentioned doses were isoeffective. Many institutions halved their doses afterwards. Studies comparing radiotherapy using a conventional dose with placebo (or a very low dose) are lacking for impingement syndrome. Gross et al. published a comparison with an alternative method (extracorporeal shockwave therapy, ESWT) (4); they showed equivalent results.
Local adverse reactions, such as skin irritations, have been observed very rarely. The risk of secondary tumors is extremely low when the appropriate technique is used and used sparingly in very young patients (<30 years).
On behalf of the German Working Group on Radiotherapy of Benign Diseases in the German Society of Radiation Oncology (DEGRO)
References
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