Discussion
osteoarthritis, arthrosis, pain
INFLAMMATORY ARTHRITIS, OSTEOARTHRITIS, DEGENERATIVE, RECRUITMENT, ARTHROSIS, ONCOLOGY
The aim of this study was to examine whether the analgesic effect of the standard dose is superior compared to that of a very low dose (taken as a kind of placebo dose). In summary, we found good pain relief in both groups, whereas there were no statistically significant differences between the dose groups. The improvement of pain mainly occurs during the first 3 months after radiotherapy. In the 9 months afterwards, we noticed only marginal additional improvement and pain relief—if achieved—persists over the long term.Patients receiving a second radiotherapy course were classified as nonresponders. Apparently, their initial grade of pain relief was much lower than in the responders. The second radiotherapy course which was offered to those patients a minimum 3 months after primary radiotherapy had only a marginal effect.The KOOS-PS values were significantly different in the time interval between 3 months and 1 year after radiotherapy. This is in agreement with the deterioration of KOOS-PS in this time interval. To our opinion, the functional symptoms—after an initial improvement—worsen over the long term.In our collective, patients with a higher VAS score before radiotherapy had a better response than those with a lower intensity of pain.Retrospective studies published in the past 80 years have shown favorable results concerning pain relief. We are well aware that these trials are of variable quality, the vast majority of the patients were treated using orthovoltage machines and doses of 6 Gy. The older results have been summarized in the S2k guideline of the DEGRO (German Society for Radiation Oncology) [Three patterns-of-care studies have shown that low-dose radiotherapy for painful osteoarthritis is applied frequently in German-speaking countries [Two very well designed randomized, controlled and double blinded trials were published in 2018 and 2019 (Minten et al. [We are well aware of the limitations of this trial. This trial had to be closed prematurely due to slow recruitment of patients. Furthermore, it appears plausible that single patients may have guessed their dosage arm especially when at least two joints in a patient were irradiated with different doses. The influence of oral medication during this trial was not assessed—to our opinion it was not ethical to limit intake of the oral analgesics.It remains an issue of discussion why we found an equally negative result in agreement with the study of the Dutch colleagues irrespective of the fact that our trial was much larger. One reason may be the inhomogeneity in our patient collective. In discussions with the colleagues of the working group it was suggested to record the grade of the OA. Probably, in a relevant number of patients arthrosis was too advanced to allow a good radiation effect. An inflammatory and a degenerative pain component may be assumed. Thus. it may be a point of discussion whether only the inflammatory pain component responds to radiotherapy and not the degenerative one. This theory follows the fact that preclinical studies had an inflammatory arthritis model as a basis and no osteoarthritis model [The optimal dose remains a point of debate. In the radiobiological literature, the highest effect was recorded after a dose of 0.5 Gy, whereas an effect on macrophages was found after 0.1 Gy [