Effects of androgen deprivation therapy and bisphosphonate treatment on bone in patients with metastatic castration-resistant prostate cancer: results from the University of Washington Rapid Autopsy Series

Abstract

Qualitative and quantitative bone features were determined in nondecalcified and decalcified bone from 20 predetermined bone sites in each of 44 patients who died with castration-resistant prostate cancer (CRPC), some of which received bisphosphonate treatment (BP) in addition to androgen-deprivation therapy (ADT). Thirty-nine of the 44 patients (89%) had evidence of bone metastases. By histomorphometric analysis, these bone metastases were associated with a range of bone responses from osteoblastic to osteolytic with a wide spectrum of bone responses often seen within an individual patient. Overall, the average bone volume/tissue volume (BV/TV) was 25.7%, confirming the characteristic association of an osteoblastic response to prostate cancer bone metastasis when compared with the normal age-matched weighted mean BV/TV of 14.7%. The observed new bone formation was essentially woven bone, and this was a localized event. In comparing BV/TV at metastatic sites between patients who had received BP treatment and those who had not, there was a significant difference (28.6% versus 19.3%, respectively). At bone sites that were not invaded by tumor, the average BV/TV was 10.1%, indicating significant bone loss owing to ADT that was not improved (11%) in those patients who had received BPs. Surprisingly, there was no significant difference in the number of osteoclasts present at the metastatic sites between patients treated or not treated with BPs, but in bone sites where the patient had been treated with BPs, giant osteoclasts were observed. Overall, 873 paraffin-embedded specimens and 661 methylmethacrylate-embedded specimens were analyzed. Our results indicate that in CRPC patients, ADT induces serious bone loss even in patients treated with BP. Furthermore, in this cohort of patients, BP treatment increased BV and did not decrease the number of osteoclasts in prostate cancer bone metastases compared with bone metastases from patients who did not receive BP.

Figure 1

(A) Summary of qualitative analysis of bone response in ADT and bisphosphonate treated PCa decalcified paraffin embedded bone metastatic specimens from 44 patients. Histologically we determined the predominant phenotype of each bone metastasis sample. Five categories were used: predominantly osteoblastic (red), osteoblastic with a small component of osteolysis (pink), osteolytic with a small component of osteoblastic (light green), osteolytic (dark green) and no bone change (blue). The number in each colored square represents the number of bone samples having each of the bone phenotypes. White squares indicate no bone metastases were observed. Asterixes indicate those patients that were treated with BP. In the majority of patients there exists a spectrum of bone phenotypes from osteoblastic to osteolytic or no bone change in response to tumor. Six patients had no bone metastases. Two patients (3 and 19) were predominantly osteolytic. There appears to be no major qualitative difference in bone response between BP and NBP treated patients. (B) Summary of the quantitative analysis in methylmethacrylate (MMA) embedded bone specimens of bone response in 44 ADT and BP treated patients. Bone specimens were obtained at rapid autopsy from the right femoral neck (RF), left femoral neck (LF), right iliac (RI), left iliac (LI), lumbar vertebrae 1-5 (L1-5), thoracic vertebrae 8-12 (T8-12), sternum (St), rib, right humeral head (RH), and left humeral head (LH) in each patient. White squares identify samples that could not be measured due to technical reasons. In grey, the bone sample did not contain tumor. Blue squares represent metastatic specimens with BV less than the age matched control. The majority of sites are red representing metastatic specimens with BV greater than the age matched control. Asterixes indicate patients treated with BP. Crosses indicate samples that were positive for tumor in the paraffin embedded cores, but negative or had no sample available for analysis in MMA. Eight patients had no bone metastases. An additional six bone sites with no tumor and 8 with tumor were also analyzed.

Figure 2. Osteoclasts were still observed in bone metastases of patients treated with zoledronic acid

(A) Metastatic osteoclast numbers were not significantly different in the NBP no treatment (No Tt) biopsy group, as compared to any of the zoledronic acid (Zol) treatment duration groups. In the pamidronate (Pam) group, a low number of osteoclasts were observed. In an alendronate patient (Aln), osteoclasts number was high. (B) When the osteoclast data were sorted by the number of their nuclei, giant osteoclasts were observed in the bone metastases of the alendronate (Aln) treated patient and in bone metastases of patients with <1 year through >3 years of zoledronic acid treatment. Only 9-12 nuclei (or less) containing osteoclasts were found in bone metastases from NBP patients and in pamidronate treated patients.

Figure 3. Morphologic characteristics of bone and osteoclasts of ADT and BP treated bone metastases

(A) The osteolytic aspect of a bone metastasis in an 86 year old patient androgen ablated for 20 years and receiving zoledronic acid for over 3 years before death. (B) The osteoblastic aspect of a bone metastasis in the same patient. In both biopsies tumor fills the spaces between bone trabeculae. Goldner’s stain X2.5 magnification. (C) A 20 nuclei osteoclast untreated with BP. (D) Goldner’s staining of a giant osteoclast with more than 20 non-apoptotic nuclei in the right iliac bone of a patient treated with alendronate for 42 months. (E) Goldner’s staining of a nest of osteoclasts with a variable number of non-apoptotic nuclei in a biopsy specimen of the right iliac bone in a patient treated with zoledronic acid for 10 months. Note the osteoclast with a single large nucleus with a large nucleolus (arrow). (F) Twelve nuclei (or less) osteoclasts in a sacrum biopsy specimen of a patient treated with pamidronate for 6 months. (G) Sixteen nuclei giant osteoclast in a right iliac bone of a patient treated with zoledronic acid for 4 years. (H) Six pyknotic nuclei in an osteoclast in a left iliac bone of the same patient as in G. Goldner’s stain, X40 magnification. (I) Osteoblastic bone metastasis of a patient treated with zoledronic acid for 6 months. TRAcP staining X5 magnification. (J) Same as in I, observed under polarization showing small areas of lamellar bone and mainly woven bone, representing 89% of the total bone. TRAcP staining X5 magnification with polarization.