Pelvic insufficiency fractures commonly occur in women receiving external beam radiotherapy (EBRT) for gynaecological malignancies (GM). Our study was to determine the effects of EBRT on the skeleton.
24/127 women treated from 2020-23 and who met the entry criteria were evaluated. Their mean age was 63.2 (45-85) years, 21/24 were post-menopausal and 19/24 were non-smoker. Endometrial cancer was the most common primary site (18/24). 9/24 received EBRT to the pelvis and para-aortic nodes and 15/24 only to the pelvis. The total radiation dose and the mean radiation exposure to the third lumbar vertebrae (L3) and left femoral neck (FN) were calculated. BMD of lumbar spine (LS) and FN was performed prior to and within 18 months of EBRT by quantitative computed tomography (QCT). Precision error was 1% for LS and 1.5% for FN.
The mean time from EBRT to follow up QCT was 6.2 (range 1.0-15.1) months. BMD decreased significantly in 20/24 (83.3%) patients at the LS and 13/24 (54.2%) at the FN. The mean change in BMD was -29.1% (95% CI; -17.7% to -40.6%) at LS and -4.1% (95% CI; -0.5% to -8.7%) at FN. The mean change in LS BMD was significantly more pronounced (t (13) = 3.354, p = 0.05) when the treatment field was extended above the L4 (-50.2%, 95% CI; -29.8% to -70.5%) compared to treatment at L4 or below (-16.5%, 95% CI; -6.1% to -16.5%). There was a significant correlation between radiation dose and %change in BMD at L3 (r=-0.739, p>0.001), but not at the FN (r =-0.2, p=0.30). The change in the LS BMD correlated weakly with time since radiotherapy (r=-0.36, p=0.08).
These data demonstrate that women treated with EBRT for GM develop severe radiation-induced osteoporosis. The radiation dose, field size and time since radiotherapy are important variables contributing to skeletal bone loss.