Main Session
Sep 29
SS 25 - Nonmalignant 1: Advances in Radiotherapy for Nonmalignant Indications

250 - Risk of Radiation-Induced Malignancies following Low-Dose Orthovoltage Therapy for Painful Joint and Tendon Disorders: A Retrospective Analysis

03:30pm - 03:40pm PT
Room 310-312

Presenter(s)

Robert Blach, MD, MBBS Headshot
Robert Blach, MD, MBBS - Medical School Hannover, Hannover 30625, Niedersachsen

R. M. Blach1, M. Sonnhoff1,2, R. Muecke3, and U. Schaefer4; 1Department of Radiotherapy, Hannover Medical School, Hannover, Germany, 2Zentrum für Strahlentherapie und Radioonkologie, Bremen, Germany, 3Radiation Oncology Rhein-Main-Nahe, Bad Kreuznach, Germany, 4Department of Radiotherapy, Lippe Medical Center, Lemgo, Germany

Purpose/Objective(s): Low-dose orthovoltage radiation therapy is experiencing renewed interest for treating painful joint and tendon disorders. However, this modality involves administering potentially carcinogenic radiation to patients with non-malignant conditions. This study aims to assess the risk of both hematological and solid radiation-induced malignancies in patients that underwent low-dose orthovoltage therapy for benign musculoskeletal pain.

Materials/Methods: We conducted a retrospective analysis of n=4,699 patients treated with orthovoltage radiation therapy between 1994 and 2010 at Lippe Medical Center, Germany. The standard regimen was 6 fractions of 1.0 Gy each. Patient data including age at exposure, gender, treatment sites, survival, cause of death, and incidence and location of any malignancies - were extracted from the hospital information system using anonymized patient identifiers.

Treatment sites were categorized as follows:

  • Distal joints of the extremities: ~62% (e.g., elbow, knee, heel)
  • Proximal joints of the extremities: ~37% (shoulder, hip bursa)
  • Others: ~1% (e.g. trunk)

For solid malignancies (ICD C00 – C80), radiation induction was assumed if the tumor was located within the radiation field (in-field).

Hematological malignancies (ICD C81–C96) were analyzed based on the presence of active red bone marrow (RBM) within the treatment volume. According to ICRP 1991 – Chapter 3, treatment sites were classified into:

  • No active RBM, i.e. distal joints (n=2,906)
  • Low proportion of active RBM, i.e. proximal joints (n=1,736)
  • High proportion of active RBM, i.e. trunk (n=57)

Hematological malignancy-free survival rates were estimated using Kaplan-Meier graphs and compared across RBM groups with log-rank testing (p-values <0.05 were regarded as significant).

Results: Three in-field solid malignancies were observed:

  • One lung cancer 12 years post thoracic spine irradiation
  • Two basaliomas at 8- and 13-years post shoulder joint irradiation

Hematological malignancy-free survival rates were:

  • All non-active RBM regions: 99.3% at 10 years; 98.6% at 15 years. Compared with:
  • All active RBM regions: 98.4% at 10 years; 97.1% at 15 years (p = 0.002)
  • Only shoulder region: 98.2% at 10 years; 96.8: % at 15 years (p = 0.001)
  • Only hip bursa region: 99.0% at 10 years; 98.2% at 15 years (p = 0.633)
  • Only trunk/pelvic region: 98.3% at 10 years; 97.0% at 15 years (p = 0.003)

Conclusion: Despite limitations such as a limited follow-up period, our findings suggest that low-dose orthovoltage therapy for benign musculoskeletal pain in elderly individuals is associated with an almost negligible risk of inducing solid malignancies, potentially limited to skin areas with additional sun exposure, such as the shoulder. However, the risk for hematological malignancies may be elevated, particularly when treating areas containing (even small portions of) active RBM, like the shoulder joint. Thus, caution is advised when considering irradiation of the trunk region.