Longitudinal Changes in Bone Mineral Measurements Inside and Outside Radiation Fields Used for Cervical Cancer Treatment

We compared the magnitude of changes in bone mineral density (BMD), within and outside the radiation field, among women who received pelvic radiation therapy (RT) with or without chemotherapy for cervical cancer.In this secondary analysis of a prospective study, we analyzed serial computed tomography scans and dual-energy x-ray absorptiometry scans from 78 patients who received definitive RT or chemoradiation therapy (CRT) for cervical cancer at a single institution from 2008 to 2015. BMD values at L1, L2, L3, and L4 were measured. We compared changes in BMD within the radiation field (ie, at L4) with those outside the field (ie, at L1). Linear mixed models were also used to examine the effect of RT on changes in BMD over time and covariate adjustment.The median age of the 78 patients was 45.5 years (range, 23-88 years); all received RT and 76 (97%) received concurrent CRT. Treatment was associated with significant declines in BMD in all 4 lumbar vertebral bodies over time (P < .05), with nadir at 3 months for L4 and at 1 year for L1. Pairwise comparisons at 3 months and 2 years after treatment indicated that BMD in L4 (within the RT field) had improved (P = .037), but BMD in L1 (outside the RT field) was no different at 3 months and 2 years.Significant BMD declines were observed in all lumbar vertebral bodies immediately after RT. However, in-field vertebral bodies reached nadir BMD earlier than those located outside the RT field. Our results suggest that treatment and patient-related factors other than RT may contribute to declines in BMD after treatment for cervical cancer. Routine bone density screening and post-RT therapy with hormones may be beneficial for selected patients who receive CRT for cervical cancer.