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Risk of Radiation-Induced Malignancy After Low-Dose Radiation Therapy for Nonmalignant Musculoskeletal Disorders: A
Robert Maximilian Blach1, Mathias Sonnhoff2, Ralph Muecke3
1Department of Radiotherapy, Hannover Medical School, Hannover, Germany.
Purpose:
Musculoskeletal disorders are conditions with substantial medical and economic consequences. Low-dose radiation therapy (LDRT) is regaining large-scale global significance as a cost-effective conservative treatment that can provide significant symptomatic relief because of its anti-inflammatory and antiproliferative effects. This study aimed to appraise the potential risk of secondary malignant neoplasms (SMN) following functional LDRT for nonmalignant musculoskeletal disorders in a long-term analysis.
Methods And Materials:
Single-center retrospective observational analysis. All patients who received low-dose radiotherapy for nonmalignant musculoskeletal disorders between January 1, 1994 and December 31, 2011 were included. Data on newly diagnosed malignant neoplasms, overall survival, and cause of death were documented. Overall survival was estimated using Kaplan-Meier analysis. Solid malignancies were considered SMN if they occurred within the irradiated field. For hematologic malignancies, treatment regions were categorized by the presence or absence of active red bone marrow based on International Commission on Radiological Protection data for adults.
Results:
A total of 4699 patients underwent LDRT (mean age 64 years); n = 5614 treatment series were conducted. Kaplan-Meier estimates showed an expected post-low-dose radiotherapy life expectancy of 21 years. Treatment sites were classified as distal joints (62%), proximal joints (37%), and others (1%). Three solid malignancies were observed within previously irradiated regions, corresponding to an incidence of 0.064%. At 12.5 years, hematologic malignancy-free survival was 99.0% in the non-marrow-adjacent group compared with 97.7% in the marrow-adjacent group, corresponding to an absolute difference of 1.3 percentage points (P = .002; relative risk, 1.013). Hematologic malignancy-free survival was significantly different when comparing non-marrow-adjacent regions to the shoulder (P = .001) and trunk/pelvic region (P = .003).
Conclusions:
The greatest theoretical risk of SMN arises from LDRT of central trunk regions, where potential risks for systemic and solid cancers overlap. Overall, contemporary LDRT appears safe for peripheral indications, while treatments near marrow-rich or central trunk structures should be applied judiciously.
