Endocrine Abstracts

Introduction: Hypoparathyroidism Bone Score (TBS) has been associated with fragility fractures in post-menopausal women. Estrogen-receptor positive breast cancer is usually treated with aromatase inhibitors (AIs), with international guidelines recommending initial bone density (BMD) evaluation, since this therapy is associated with high rates of fragility fractures. Each Country has different thresholds of intervention to recommend pharmacologic treatment for fracture prevention. Patients with normal bone density or osteopenia often miss the chance of receiving any anti-osteoporotic treatment, beyond calcium and vitamin D.

Objective: To describe prevalence of low bone quality measured by TBS in women initiating aromatase inhibitors.

Design: Cross-sectional, observational.

Setting: University hospital.

Patients: From January to December 2021, 75 consecutive unselected ambulatory women with normal BMD or osteopenia referred from the Oncology Department for bone metabolism evaluation with a standardized protocol, after recent diagnosis of estrogen-receptor-positive breast cancer. The patients were naïve to any kind of osteoporotic treatment, including calcium or vitamin D3 supplements. History of clinical or morphometric fractures was an exclusion criterion.

Main outcome measures: TBS, BMD and biochemistries at first endocrine referral before the start of AIs. TBS T-score ≤ -2 was used to discriminate low bone quality.

Results: Twenty-five patients (33.3% of the whole cohort) aged 64.8±10.7 had low TBS (1.238±0.043). TBS negatively correlated with age (r=-0.41, P<0.001), time from menopause (r=-0.312,P=0.012) and positively associated with BMD at all sites (L1-L4, total hip and femur neck, P<0.001). TBS was positively associated with urinary calcium (r=0.238,P=0.047), and negatively with 25(OH)vitamin D levels (r=-0.243,P=0.033). By contrast, BMD was not associated with 25(OH) vitamin D levels. TBS showed no association with PTH, renal function or bone turnover markers. As opposed to TBS, lumbar spine BMD was negatively correlated with Beta-CTX (R=-0.231,P=0.047). Both femur neck BMD T-score (R=-0.233,P=0.044) and total hip BMD T-score (r=-0.299,P=0.009) were negatively associated with PTH levels.

Conclusions: A considerable proportion of women with normal BMD or osteopenia appears to present with low bone quality at the start of hormone adjuvant therapy for breast cancer. TBS could be used as a complementary quantitative clinical tool in the initial evaluation and management of these patients and might be adopted to recommend antifracture treatment in this gray zone. TBS might also be correlated with underlying bone metabolism indices.