Denosumab for the prevention of skeletal complications in metastatic castration-resistant prostate cancer: comparison of skeletal-related events and symptomatic skeletal events

In this analysis of a phase III trial in patients with castration-resistant prostate cancer and bone metastases, treatment with denosumab reduced the risk of skeletal complications vs zoledronic acid regardless of whether the end point was defined as SSE or SRE. Both SSEs and SREs were associated with development of moderate/severe pain among patients with no/mild pain at baseline.

Background

In a phase III trial in patients with castration-resistant prostate cancer (CRPC) and bone metastases, denosumab was superior to zoledronic acid in reducing skeletal-related events (SREs; radiation to bone, pathologic fracture, surgery to bone, or spinal cord compression). This study reassessed the efficacy of denosumab using symptomatic skeletal events (SSEs) as a prespecified exploratory end point.

Patients and methods

Patients with CRPC, no previous bisphosphonate exposure, and radiographic evidence of bone metastasis were randomized to subcutaneous denosumab 120 mg plus i.v. placebo every 4 weeks (Q4W), or i.v. zoledronic acid 4 mg plus subcutaneous placebo Q4W during the blinded treatment phase. SSEs were defined as radiation to bone, symptomatic pathologic fracture, surgery to bone, or symptomatic spinal cord compression. The relationship between SSE or SRE and time to moderate/severe pain was assessed using the Brief Pain Inventory Short Form.

Results

Treatment with denosumab significantly reduced the risk of developing first SSE [HR, 0.78; 95% confidence interval (CI) 0.66–0.93; P = 0.005] and first and subsequent SSEs (rate ratio, 0.78; 95% CI 0.65–0.92; P = 0.004) compared with zoledronic acid. The treatment differences in the number of patients with SSEs or SREs were similar (n = 48 and n = 45, respectively). Among patients with no/mild pain at baseline, both SSEs and SREs were associated with moderate/severe pain development (P < 0.0001). Fewer patients had skeletal complications, particularly fractures, when defined as SSE versus SRE.

Conclusion

In patients with CRPC and bone metastases, denosumab reduced the risk of skeletal complications versus zoledronic acid regardless of whether the end point was defined as SSE or SRE.

Abstract P3-10-01: Burden of symptoms associated with development of metastatic bone disease in patients with breast cancer

Background: Bone is the most common site of distant metastasis in advanced breast cancer patients (pts). Development of bone metastases (mets) is associated with substantial morbidity including skeletal complications, decreased quality of life, increased pain, and shortened lifespan. Pt burden of symptoms associated with bone mets has been assessed in tumor types other than breast or in metastatic disease not specific to bone. This study characterizes patterns of pt-reported symptoms over time among breast cancer pts with bone mets.

Methods: The Oncology Services Comprehensive Electronic Records (OSCER) database was used to retrospectively identify women with breast cancer who developed bone mets during their care and had ≥1 ACORN Patient Care Monitor (PCM) assessment. The PCM summarizes symptoms on an 11-point scale (0 = not a problem to 10 = as bad as possible). Moderate/severe symptoms were defined by a PCM score ≥4. PCM items relevant to metastatic disease (fatigue, physical pain, trouble sleeping, numbness/tingling, anxious, loss of interest in others) were assessed. A generalized linear mixed model was used to evaluate symptom progression before and after bone mets diagnosis (dx). Kaplan-Meier methods were used to estimate time to development of and proportion of pts with moderate/severe symptoms after bone mets dx.

Results: 1105 pts with breast cancer and bone mets were included. In general, the proportion of pts with moderate/severe symptom burden increased in the months (mos) before bone mets dx (Table 1). The odds (risk) of pts experiencing moderate/severe symptom burden increased in the mos leading up to bone mets dx, with a 9% increase per mo for both fatigue and physical pain, and a 19% increase per mo for numbness/tingling (P&lt;0.001 for all). Non-significant changes were observed in the risk of pts experiencing trouble sleeping (3%), anxiousness (0%), or loss of interest in others (16%). After bone mets dx, the cumulative proportion of pts with moderate/severe symptom burden increased with time (Table 2). Median time to moderate/severe symptoms after bone mets dx was 1.4 mos for fatigue, 1.9 mos for physical pain, 3.9 mos for trouble sleeping, 9.3 mos for numbness/tingling, 20.6 mos for anxious, and was not reached for loss of interest in others.

Table 1. Unadjusted proportion of pts with moderate/severe symptom burden before or at time of bone mets dxSymptom12 mos before dx6 mos before dxAt bone mets dxFatigue35%37%52%Physical pain29%34%47%Trouble sleeping22%25%28%Numbness/tingling16%18%19%Anxious14%16%23%Loss of interest in others4%6%6%

Conclusions: These data from a large number of breast cancer pts treated at community oncology practices show that pts experience increasing symptom burden for a substantial period of time before bone mets dx. Most pts continue to experience burdensome symptoms after bone mets dx. These findings reinforce the need for multiple symptoms to be proactively monitored and managed in these pts.

Table 2. KM estimate: cumulative proportion of pts with moderate/severe symptom burden after bone mets dxSymptom2 mos after dx12 mos after dxFatigue58%82%Physical pain51%74%Trouble sleeping39%64%Numbness/tingling26%53%Anxious27%46%Loss of interest in others9%22%

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-10-01.

Drug enterocyte adducts: possible causal factor for diclofenac enteropathy in rats

BACKGROUND & AIMS

Enteropathy is a frequent complication of diclofenac and other nonsteroidal anti-inflammatory drugs, yet little is known about the underlying mechanism. One possibility is that reactive metabolites of diclofenac form adducts with enterocyte macromolecules, as previously shown for liver. We addressed this possibility by using immunohistochemistry to detect diclofenac adducts.

METHODS

Rats were treated orally with diclofenac (10-100 mg/kg) and killed after 1-24 hours, and their gastrointestinal (GI) tracts were evaluated for ulcer number and area. Adduct distribution and intensity were assessed by immunohistochemistry by using a technique to simultaneously process and stain multiple intestinal rings.

RESULTS

Drug treatment led to dose-dependent formation of both adducts and ulcers only in small intestine and only in animals with intact enterohepatic circulation. Adducts formed within enterocytes by 1 hour, translocated to the brush border, preceded ulceration and vascular protein leakage, and were intense at sites of ulceration. Adducts and ulcers exhibited a parallel distribution within intestinal quintiles: 3rd > 5th >> 1st.

CONCLUSIONS

Diclofenac treatment resulted in the formation of drug adducts in enterocytes. Because this molecular change occurred before ulceration, was dose dependent, and exhibited concordant distribution with extent of ulceration, the results suggest a causal role for drug adduct formation in diclofenac enteropathy.

Aging enhances susceptibility of diclofenac-treated rats to gastric ulceration, while attenuating enteropathy

Although clinical reports note aging and gender as risk factors for NSAID therapy associated gastroenteropathy, neither variable has been examined in an animal model. We addressed this unknown by comparing the responses of young (4 months) and old (22 months) rats of both genders to oral treatment with diclofenac (10 or 50 mg/kg). Diclofenac produced gastric ulcers only in old rats, with markedly larger lesions in females. In contrast, the small intestines in old rats of both genders given the 50 mg/kg dosage had >30% fewer ulcers and a fourfold decrease in area of ulceration compared to young rats. The small intestine was the only site of lesions after the 10 mg/kg dosage and showed one gender influence, namely, a transiently faster time course of ulcer development in females. Old and young rats given 50 mg/kg showed similar declines in serum levels of the vascular permeability indices-total protein and albumin-despite reduced intestinal damage in the old animals, which suggests additive vascular leakage across the gastric lesions that were evident only in old animals. Serum biochemistry showed no evidence of hepatotoxicity or dysfunction, consonant with small intestine as the primary target for diclofenac toxicity in rats. We provide the first experimental evidence for an aging influence on the gastrointestinal target site of a nonaspirin NSAID.

Developmental vasculotoxicity associated with inhibition of semicarbazide-sensitive amine oxidase

The endogenous substrate(s) and physiological function(s) of semicarbazide-sensitive amine oxidase (SSAO), a group of enzymes exhibiting highest activity in vascular smooth muscle cells of the mammalian aortic wall, remain undetermined. This study examines the pathophysiological effects in the thoracic aortic wall resulting from specific in vivo SSAO inhibition. Weanling Sprague-Dawley rats were treated acutely or chronically with either semicarbazide hydrochloride or the allylamine derivatives MDL-72274 or MDL-72145 (Marion Merrell Dow Research Institute, Cincinnati, OH). Treatment with these compounds produced acute (6 and 24 h) and chronic (21 day) lowering of SSAO activity in aorta and lung with little effect on the activity of the vital matrix-forming enzyme, lysyl oxidase, in aortas of chronically treated animals. Chronic SSAO inhibition produced lesions consisting of striking disorganization of elastin architecture within the aortic media accompanied by degenerative medial changes and metaplastic changes in vascular smooth muscle cells. No significant difference in the total weight of dry, lipid-extracted aortic elastin and collagen components were observed between chronically SSAO inhibited and control animals. However, the amount of mature elastin was lowered and mature collagen was raised in the aortas of animals treated chronically with semicarbazide. Descending thoracic aortic rings isolated from chronically SSAO-inhibited animals had larger cross-sectional diameters (i.e., exhibited dilation) when compared to corresponding rings from control animals. This study demonstrates that developmental toxicity, characterized by striking vascular lesions and dilated thoracic aortas, can result from specific in vivo SSAO inhibition, suggesting a role for SSAO in connective tissue matrix development and maintenance, and specifically in the development of normal elastin.

Calcium channel blockers induce thymic apoptosis in vivo in rats

We investigated the in vivo effect of structurally different calcium channel blockers (CCB) on rat thymus. Administration of verapamil (40 mg/kg ip), diltiazem (90 mg/kg ip), nifedipine (15 mg/kg ip), or nicardipine (10 mg/kg ip) induced apoptotic indices of 4.3, 4.0, 2.0, and 6.5, respectively, compared to 0.5 in the saline-treated control rats. Apoptosis was assessed by morphology and the apoptotic index was calculated using a computer-assisted image analyzer. Diltiazem had a rapid and substantial effect as evidenced by apoptosis at 1.5 hr and a 36% decrease in thymus weight by 24 hr. We were uncertain about the mechanisms by which CCB induced thymic apoptosis in vivo since in vitro studies have shown that increases in intracellular calcium cause apoptosis and that CCB prevent apoptosis. We sought insight into the mechanism by evaluating potential and known in vivo effects of these drugs. Neither verapamil nor diltiazem was found to elevate serum cortisol levels, a known trigger for apoptosis. Hypotension, a known response to CCB, does not appear to be causal factor since the potent hypotensive agent sodium nitroprusside (10 microg/kg, iv) did not cause a significant increase in thymic apoptosis. Calcium signaling may be important since the calmodulin antagonist chlorpromazine (60 mg/kg ip) was found to induce a 15-fold increase in apoptosis. Our observations suggest that calcium signaling is necessary for the survival of the T lymphocytes in the thymus.