The Impact of Serial Low-dose Radon Hyperthermia Exposure on Pain, Disease Activity and Pivotal Cytokines of Bone Metabolism in Ankylosing Spondylitis - A Prospective Study

Introduction: Secondary osteoporosis is a frequent complication in ankylosing spondylitis (AS). Loss of bone mass in AS is the result of an imbalance of catabolic and anabolic mechanisms in bone metabolism in response to different factors. Patients and Method: The effects of serial low-dose radon and hyperthermia exposure in a therapeutic adit (12 visits to the adit in 3 weeks) on pain (VAS), disease activity (BASDAI, BAS-G) and serum levels of the cytokines osteoprotegerin (OPG), receptor activator of NF kappa-B ligand (RANKL) and tumor necrosis factor (TNF)-alpha were investigated in 24 patients with chronic AS (mean age 58 years) and an age-matched group of 24 patients with osteoarthritis (OA). Evaluation of pain and disease activity was performed at baseline, after serial treatment and again 3 months after cessation of the treatment, whereas cytokine measurements were realised only at baseline and after completion of the serial treatment. Medication in both groups was limited to non-steroidal anti-inflammatory drugs (NSAIDs) as needed, whereas treatment with TNF inhibitors or any drugs, which could potentially influence bone metabolism, was excluded. Results: AS patients showed a significant reduction of pain after serial treatment (p < 0.005) that was also prolonged for 3 months (p < 0.005), while OA patients presented a reduction of pain only 3 month after treatment (p < 0.005). Furthermore the AS patients showed an amelioration of the disease activity scores BASDAI and BAS-G. In addition the AS patients presented a tendency towards decrease of TNF-alpha serum levels, whereas OA patients achieved a significant decrease (p < 0.0005). Both groups showed significantly decreased levels of RANKL (AS: p < 0.0005, OA: p < 0.004). Only the AS patients presented a signifi cant increase of OPG (p < 0.0005) and a signifi cant decrease of the RANKL/OPG ratio (p < 0.005). Conclusion: In patients with chronic AS, serial low-dose radon and hyperthermia exposure in a therapeutic adit results in an attenuation of pain, amelioration of disease activity, reduction of osteocatabolic and an increase of osteoanabolic cytokine levels, which is in accord with an inhibition of osteoclastic activity in secondary osteoporosis of inflammatory disease. Thus, serial radon (adit) therapy has an important role in a multimodal treatment strategy for AS.