A Comprehensive Evaluation of an Emerging Technique of Low Dose Radiation Therapy (LDRT) of Osteoarthritis (OA)
Abstract
Purpose
Given the significant rise in patients receiving 50-cGy x 6 fractions low dose radiation therapy (LDRT) of osteoarthritis (OA), we evaluate this emerging treatment technique.
Methods
Started in April of 2025, we accrued 56 patients for LDRT of 89 Knees, 10 hips, 8 shoulders, 5 hands and 1 ankle. We delineated joint bones, articular cartilage and low-density lymphedema-lipedema-like tissue at the joint as the planning target volume (PTV) and organs at risk (OARs) including the skin of 3-mm thick and ≥ 3-cm beyond superior-inferior field edges. Dose-volume histograms were exported for statistical analysis and doses from other joint fields and portal images were all included for possible acute skin reactions and radiation-induced cancer.
Results
Standard AP/PA X-ray fields (PA-field only for hands with 0.5-cm bolus) provided acceptable target coverage (95% volume by 95% dose) but 41 of 89 knees had superior border missing by 1-4 cm; 7 of 10 hips had medial marginal missing by using 18 MV X-ray fields with edge-matching to the pelvic brim; 3 of 5 hands had either partial ulna mass or distal interphalangeal (DIP) joint missing by blocking. Portal images (1 MU open and 1 MU field) for averaged 5.2 MU per joint added 5-cGy to the joint. The maximal dose to the skin, bowel, rectum, bladder and lungs were 310, 280, 140, 60, and 20-cGy, respectively. The mean skin doses were 40, 55, 90, and 200 for hips, shoulders, knees and hands/ankles, respectively.
Conclusion
We first found that almost half of the patients had missed one target boundary, particularly for retreated patients with larger lipedema-like tissues at the joints. Thus, we recommend using CT simulation images to adjust fields particularly for the superior borders of knees and medial border of hips as well as not blocking nails if patients had DIP joint pains.