ADT, bone architecture, and “virtual bone biopsies”
Posted Oct 11 2010 12:00am
A recent study reported in the Journal of Clinical Endocrinology and Metabolism has been receiving a good deal of media attention, although its immediate clinical importance wouldn’t appear to be particularly high.
Hamilton et al. have used a sophisticated new type of CT scan to assess changes in the bone structure among a cohort of 26 men with non-metastatic prostate cancer during their first year of treatment with ADT.
Their results were as follows:
The men had an average age of 70.6 ± 6.8 years.
After 12 months of ADT
The “distal radius” means the lower end of the thinner of the two bones in your arm below the elbow. The “distal tibia” refers to the lower end of the larger and stronger of the two bones in your leg below the knee.
The authors go on to explain that these reductions in bone density are associated with reductions in cortical volumetric bone mineral density (BMD) and trabecular density. They further note that total testosterone levels were independently associated with total and corrected cortical volumetric BMD at the tibia. Estradiol levels were not.
Cortical bone is the hard, outer shell of the bone, whereas trabecular bone is the softer, “spongy” inner bone structure. Hamilton and her colleagues have explained that the new type of CT scan (high-resolution peripheral quantitative CT) allowed them to take what they have described at “virtual bone biopsies” as a method to carry out this research.
The authors conclude that, “Sex steroid deficiency induced by ADT for prostate cancer results in microarchitectural decay. Bone fragility in these men may be more closely linked to testosterone than estradiol deficiency.”
From a scientific viewpoint, this study certainly adds to our understanding of bone fragility in men receiving ADT. However, from a clinical viewpoint, the whole objective of ADT is to reduce testosterone levels in order to delay prostate cancer progression, so it is hard to see that this study will actually add a great deal to the way we can treat advanced prostate cancer at the present time. We suspect that the term “virtual bone biopsy” gave the study media attention, although it is not likely that most men on ADT will be receiving this type of CT scan in the near future.
Men receiving long-term ADT are generally advised to receive treatment with bisphosphonates to prevent bone loss. Of course bisphosphonate therapy itself is associated with some risk for side effects, so a careful risk-benefit analysis needs to be carried out for each individual patients to assess the most appropriate form of preventive therapy.
For additional commentary on this paper, see reports on the MedPage Today and the HealthDay web sites (among others).