Serum concentration of type I collagen metabolites as a quantitative marker of bone metastases in patients with prostate carcinoma

Phase II studies of two different schedules of dasatinib in bone metastasis predominant metastatic breast cancer: SWOG S0622

Bone metastases from breast cancer are common, causing significant morbidity. Preclinical data of dasatinib, an oral small molecule inhibitor of multiple oncogenic tyrosine kinases, suggested efficacy in tumor control and palliation of bone metastases in metastatic breast cancer (MBC). This clinical trial aimed to determine whether treatment with either of 2 dose schedules of dasatinib results in a progression-free survival (PFS) >50 % at 24 weeks in bone metastasis predominant MBC, to evaluate the toxicity of the 2 dosing regimens, and explore whether treatment results in decreased serum bone turnover markers and patient-reported "worst pain." Subjects with bone metastasis predominant MBC were randomly assigned to either 100 mg of dasatinib once daily, or 70 mg twice daily, with treatment continued until time of disease progression or intolerable toxicity. Planned accrual was 40 patients in each arm. The primary trial endpoint was PFS, defined as time from registration to progression or death due to any cause. Median PFS for all eligible patients (79) was 12.6 weeks (95 % CI 9.1-16.7). Neither cohort met the threshold for further clinical interest. There were no significant differences in PFS by randomized treatment arm (p = 0.85). Toxicity was similar in both cohorts, with no clear trend in serum biomarkers of bone turnover or patient-reported pain. Dasatinib was ineffective in controlling bone-predominant MBC in a patient population, unselected by molecular markers. Further study of dasatinib in breast cancer should not be pursued unless performed in molecularly determined patient subsets, or rational combinations.

Serum biomarkers of bone metabolism in castration-resistant prostate cancer patients with skeletal metastases: results from SWOG 0421

BACKGROUND

Prior studies suggest that elevated markers of bone turnover are prognostic for poor survival in castration-resistant prostate cancer (CRPC). The predictive role of these markers relative to bone-targeted therapy is unknown. We prospectively evaluated the prognostic and predictive value of bone biomarkers in sera from CRPC patients treated on a placebo-controlled phase III trial of docetaxel with or without the bone targeted endothelin-A receptor antagonist atrasentan (SWOG S0421).

METHODS

Markers for bone resorption (N-telopeptide and pyridinoline) and formation (C-terminal collagen propeptide and bone alkaline phosphatase) were assayed in pretreatment and serial sera. Cox proportional hazards regression models were fit for overall survival. Models were fit with main effects for marker levels and with/without terms for marker-treatment interaction, adjusted for clinical variables, to assess the prognostic and predictive value of atrasentan. Analysis was adjusted for multiple comparisons. Two-sided P values were calculated using the Wald test.

RESULTS

Sera from 778 patients were analyzed. Elevated baseline levels of each of the markers were associated with worse survival (P < .001). Increasing marker levels by week nine of therapy were also associated with subsequent poor survival (P < .001). Patients with the highest marker levels (upper 25th percentile for all markers) not only had a poor prognosis (hazard ratio [HR] = 4.3; 95% confidence interval [CI] = 2.41 to 7.65; P < .001) but also had a survival benefit from atrasentan (HR = 0.33; 95% CI = 0.15 to 0.71; median survival = 13 [atrasentan] vs 5 months [placebo]; P interaction = .005).

CONCLUSIONS

Serum bone metabolism markers have statistically significant independent prognostic value in CRPC. Importantly, a small group of patients (6%) with highly elevated markers of bone turnover appear to preferentially benefit from atrasentan therapy.

Type I and III collagen degradation products in serum predict patient survival in head and neck squamous cell carcinoma

Cancer invasion induces extracellular matrix remodeling and collagen degradation. The aim of this study was to assess whether serum levels of type I and III collagen degradation products were associated with patient survival in head and neck squamous cell carcinoma (HNSCC). A novel enzyme immunoassay was developed for measuring type III collagen N-terminal telopeptide (IIINTP) in human serum samples. In addition, type I collagen C-terminal telopeptide (ICTP), matrix metalloprotease-8 (MMP-8) and tissue inhibitor of metalloproteases-1 (TIMP-1) were assessed in 205 blood samples from HNSCC patients. High levels of serum ICTP and IIINTP and plasma TIMP-1 were associated with poor survival. The concentration of ICTP was associated with levels of IIINTP and TIMP-1. The plasma concentration of MMP-8 was associated with tumor stage, but not with survival or levels of ICTP, IIINTP or TIMP-1 suggesting that other collagenases/proteases are responsible for the cleavage of type I and type III collagens. The rate of type I and type III collagen degradation is associated with patient survival and can be used as a prognostic marker in HNSCC.

Zoledronic acid decreased osteolysis but not bone metastasis in a nude mouse model of canine prostate cancer with mixed bone lesions

BACKGROUND

Bone metastasis is the most common cause of morbidity and mortality in patients with advanced prostate cancer and is manifested primarily as mixed osteoblastic and osteolytic lesions. However, the mechanisms responsible for bone metastases in prostate cancer are not clearly understood, in part due to the lack of relevant in vivo models that mimic the clinical presentation of the disease in humans. We previously established a nude mouse model with mixed bone metastases using intracardiac injection of canine prostate cancer cells (Ace-1). In this study, we hypothesized that tumor-induced osteolysis promoted the incidence of bone metastases and osteoblastic activity.

METHODS

We studied the effect of inhibition of osteolysis with zoledronic acid (ZA) on the prevention and progression of Ace-1 bone metastases in nude mice using prophylactic and delayed treatment protocols. Bioluminescent imaging, radiography, and histopathological evaluation were performed to monitor the effect of ZA on the incidence, progression and nature of bone metastases.

RESULTS

Unexpectedly, there was no significant difference in tumor burden and the incidence of metastasis between control and treatment groups as detected by bioluminescent imaging and bone histomorphometry. However, radiographic and histopathological analysis showed a significant treatment-related decrease in osteolysis, but no effect on tumor-induced trabecular bone thickness in both treatment groups compared to controls.

CONCLUSION

Our results demonstrated that the incidence of prostate cancer bone metastases in vivo was not reduced by zoledronic acid even though zoledronic acid inhibited bone resorption and bone loss associated with the mixed osteoblastic/osteolytic bone metastases in the Ace-1 model.

Prostate cancer and markers of bone metabolism: diagnostic, prognostic, and therapeutic implications

Knowledge of bone metastases complicating advanced prostate cancer (CaP) is increasingly relevant in patient selection for novel therapies. Current nuclear bone scintigraphy imaging has limited specificity for prostate metastases. As serum bone markers do correlate with bony lesions, they may play multiple roles in patients with advanced CaP. Currently, these markers play a role in prognostic nomograms for CaP. Recent studies suggest an expanding role for bone markers in the diagnosis and selection of patients for novel therapies. In the future, therapeutic roles for some of these marker pathways will emerge, eventually allowing greater individualization of patient care.

Plasma osteopontin in comparison with bone markers as indicator of bone metastasis and survival outcome in patients with prostate cancer

BACKGROUND

The study was undertaken to evaluate the diagnostic and prognostic value of plasma osteopontin (OPN) in comparison to bone markers as well as the relationships between the markers and clinico-pathological factors in prostate cancer (PCa) patients.

METHODS

OPN and the bone markers carboxyterminal-telopeptide of type I collagen, bone-specific alkaline phosphatase (bALP), and aminoterminal-propeptide of type I procollagen (PINP) were measured in 90 PCa patients with and without bone metastases, 35 patients with benign prostatic hyperplasia, and 29 healthy men.

RESULTS

OPN and bone markers were significantly elevated in patients with bone metastases compared to the other groups. Significant correlations were found between all four-bone markers (r(s) = 0.43-0.79, all P < 0.01). OPN correlated with tumor grade (r(s) = 0.23, P < 0.05). In receiver-operating characteristics (ROC) analyses, OPN and bone markers were effective in distinguishing PCa patients with and without bone metastases showing areas under the curve (AUC) between 0.80 and 0.88 (all P < 0.001). OPN had an AUC of 0.85 that increased in combination with bALP up to 0.93 providing at the point with the highest diagnostic accuracy both a sensitivity and specificity of about 90%. Kaplan-Meier analyses and Cox proportional hazards regression models showed decreased survival of patients with high OPN and bone marker levels, while only high OPN and PINP were independent negative prognostic factors for PCa-related death.

CONCLUSIONS

OPN alone or in combination with bone markers is useful as diagnostic marker in the detection of bone metastases and as prognosticator in the survival prediction in PCa patients.

Diagnosis of Bone Metastasis in Men with Prostate Cancer by Measurement of Serum ICTP in Combination with Alkali Phosphatase and Prostate-specific Antigen

AIMS

Carboxy-terminal telopeptide of type I collagen (ICTP) is a parameter of bone absorption, and has recently been introduced to monitor bone metastases. The aim of this retrospective study was to investigate the potential of ICTP as a candidate serum marker of bone metastasis in prostate cancer.

MATERIALS AND METHODS

Serum markers in 155 men pathologically diagnosed with prostate cancer were measured. The serum levels of ICTP, prostate-specific antigen (PSA), and alkali phosphatase (ALP) were compared to assess the extent of disease (EOD) scores from bone scans and then analysed statistically.

RESULTS

The serum ICTP levels were not well correlated with the EOD scores in the total group of men, men newly diagnosed with prostate cancer, or men previously diagnosed with prostate cancer who were followed up. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of ICTP (cut-off value, 5.0 ng/ ml) of the men newly diagnosed with prostate cancer were 78.6%, 88.0%, 78.6%, and 88.0%, respectively. In these men, the specificity and PPV of ALP (cut-off value, 335 IU/l) were 100%, whereas the sensitivity and NPV of PSA (cut-off value, 40 ng/ml) were 100% in this study. The serum levels of ICTP in the men with low ALP (< 335 IU/l) and high PSA (> or = 40 ng/ ml) clearly separated the men with or without bone metastasis, as judged by bone scans.

CONCLUSION

We found that the ICTP is not a superior serum marker for bone metastases compared with ALP or PSA. Our study suggests, however, that the ICTP measurement is useful in a certain subset of men with the combination of PSA and ALP in distinguishing men with bone metastasis from those without.

Evaluation of the clinical value of bone metabolic parameters for the screening of osseous metastases compared to bone scintigraphy

Background

Bone metastases are common in many types of cancer. As screening methods different imaging modalities are available. A new approach for the screening of osseous metastases represents the measurement of bone metabolic markers. Therefore aim of this study was to evaluate the usefulness of the determination of bone metabolic markers aminoterminal propeptide of type I procollagen (PINP, osteoblastic activity) and the carboxyterminal pyridinoline cross-linked telopeptide of type I collagen (ICTP, osteoclastic activity) for the detection of bone metastases associated with other malignancies.

Methods

88 patients aged 21 – 82 years with malignant tumors were prospectively studied. The serum concentrations of PINP and ICTP were measured and compared to the results of bone scintigraphy, radiological bone series, CT, MRI and clinical follow-up.

Results

Osseous metastases were found in 21 patients. 19 of them were correctly identified by bone scintigraphy (sensitivity: 90%). For bone metabolic markers results were as follows: ICTP sensitivity: 71%, specificity: 42%; PINP sensitivity: 24%, specificity: 96%.

Conclusions

As markers of bone metabolism PINP and ICTP showed low sensitivity and/or specificity for the detection of osseous metastases. The presented markers did not seem to be sufficient enough to identify patients with bone metastases or to replace established screening methods.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Follow-up of collagen crosslink excretion in patients with oral squamous cell carcinoma and analysis of tissue samples

The presence of an oral squamous cell carcinoma (OSCC) may be associated with increased urinary excretion of the markers of collagen degradation, hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP). We investigated the possibility of these markers predicting the presence of active disease. Patients from a current study on HP and LP were included as follows: Group 1a (OSCC with confirmed mandibular bony infiltration, n=12), group 1b (group 1a patients >6 months after successful treatment), group 2a (OSCC without evidence of mandibular bone infiltration, n=8), group 2b (group 2a patients >6 months after successful treatment), group 3a (recurrent OSCC, n=8), group 3b (group 3a patients >6 weeks later, symptoms unchanged) and group 4 (control group, n=74). Tissue samples from tumour tissue and adjacent healthy mucosa were additionally investigated for HP and LP concentrations (n=8). The decrease in the urinary concentrations of HP and LP was statistically significant between groups 1a and 1b (P<0.001 for HP and LP), but not between groups 2a and 2b (P=0.07 for HP and LP), while values in groups 1b and 2b were within the normal range. When comparing groups 3a and 3b, a significant increase was observed for LP (P=0.050), but not HP (P=0.208). In conclusion, successful treatment of OSCC with bony involvement may be associated with a reduction of urinary HP and LP, whereas ongoing disease may result in an increase of LP. HP and LP may both be useful markers of tumour progression in patients with OSCC.

The efficacy of a serum carboxyterminal pyridinoline cross-linked telopeptide of type I collagen as a quantitative screening marker for bone metastases in patients with urological malignancies

In order to ascertain whether carboxyterminal pyridinoline cross-linked telopeptide of type I collagen (ICTP) might be useful as a serum screening parameter for bone metastases from non-prostate urological malignancies as well as prostate cancers, as series of 210 patients were examined. In addition to ICTP, serum alkaline phosphatase (ALP) and also prostate specific antigen (PSA) in the prostate cancer cases were assayed using commercial kits. The areas under the receiver operating characteristic (ROC) curves were 0.7846 for ICTP (cut-off point 9.6 microg/l), 0.8304 for ALP in prostate cancer cases, and 0.8278 for ICTP (cut-off point 10.6 microg/l), and 0.7139 for ALP in non-prostate cancer cases. While significance was only observed for ICTP and PSA in prostate cancer cases, borderline significance was also evident with ICTP for non-prostate malignancies, and with ALP for prostate cancer case. The results suggest that serum ICTP may be useful in combination with ALP as a quantitative clinical marker for low cost screening for bone metastases in patients with all types of urological malignancies.

Collagen crosslink excretion and staging of oral cancer

Lysylpyridinoline (LP) and hydroxylysylpyridinoline (HP) are collagen crosslink residues of which the urinary concentration reflects the level of connective-tissue turnover. HP is ubiquitous in tissue, whereas LP is specific for bone. The purpose of this investigation was to assess the sensitivity and specificity of an increased urinary concentration of both HP and LP in indicating infiltration of mandibular bone by an oral squamous cell carcinoma (OSCC) or recurrence of the disease after successful therapy. We investigated the history and urine levels in 116 adult patients, who were divided into the following groups. Group 1: patients with OSCC with bone infiltration (n=17); group 2: patients with confirmed OSCC (n=12) without evidence of bone infiltration; group 3: patients with recurrence of an OSCC (n=13); group 4: patients without clinical evidence of disease (n=74). The range and upper limit of normal values (HP(max) and LP(max)) were measured from the normal controls in group 4. Levels of LP and HP were measured by HPLC and fluorescence detection. There was a significant difference in the average urinary levels of LP and HP between groups 1-4 (P<0.001). The presence of mandibular bone infiltration could be detected with a sensitivity and specificity of 100% when comparing groups 1 and 2. Presence of tumour tissue could be detected with a sensitivity of 90%. In conclusion, a normal LP concentration in patients with an OSCC strongly suggests that bone invasion by the disease has not taken place. If both urinary HP and LP are elevated, disease recurrence is highly likely.

Bone markers in the management of patients with skeletal metastases

BACKGROUND

Biochemical markers of bone remodeling have been used as surrogate markers to manage patients with metastatic bone disease. Markers of the bone resorptive process, such as the bone collagen breakdown products N-telopeptide and C-telopeptide, are useful markers for monitoring the response and efficacy of antiresorptive therapy and to assess disease progression in patients with osteolytic bone disease. Recently discovered markers of osteoclastogenesis, osteoprotegerin (OPG) and the soluble form of the receptor activator for nuclear factor (NF)-kappaB (RANK-L), also are candidate markers of the bone metastases process and offer potential as surrogate markers of tumor-induced osteoclastogenesis.

METHODS

Immunoassays have been developed that can determine blood and urine levels of the telopeptides associated with bone collagen breakdown. In addition, immunoassays now are available that can measure both OPG and the soluble form of RANK-L in blood and tissues as markers of osteoclastogenesis.

RESULTS

The measurement of bone collagen breakdown products and specific factors associated with the process of osteoclastogenesis have been applied to the management and assessment of patients with metastatic bone disease. Results indicate that these surrogate markers can be useful in determining response to antiresorptive therapy, in selecting optimal dosage, and as markers of disease progression.

CONCLUSIONS

Although they show promise, questions remain whether blood measurements of surrogate markers of osteoclastogenesis, like OPG and RANK-L, will be useful in both assessing and managing patients with metastatic bone disease.

Metastasis to bone: causes, consequences and therapeutic opportunities

The most common human cancers --lung, breast and prostate -- have a great avidity for bone, leading to painful and untreatable consequences. What makes some cancers, but not others, metastasize to bone, and how do they alter its physiology? Some of the molecular mechanisms that are responsible have recently been identified, and provide new molecular targets for drug development.

Bone metabolic markers as gauges of metastasis to bone: a review

Currently, imaging techniques are the leading methods used to diagnose of metastasis to bone. However, these techniques are expensive, expose patients to toxic and radioactive compounds, and monitor response to treatment poorly; these drawbacks have prompted the search for alternative screening methods. Therefore, bone metabolic markers have been evaluated as possible methods to diagnose and monitor the development and progression of metastatic bone disease. Although bone metabolic markers are often grouped as either resorption or formation markers, studies have revealed that each marker has its own biologic meaning and clinical relevance. Recent milestones in the use of bone metabolic markers as screening methods for metastatic bone disease and as evaluation methods for treatment response are shown in the following lists. 1. Bone metabolic marker measurements provide insight into mechanisms of metastasis to bone. 2. Although promising data have been reported, bone metabolic markers are not yet considered to be reliable screening methods for metastasis to bone. 3. Bone metabolic markers are reliable indicators of response to both conventional and bisphosphonate therapies. 4. Preliminary results indicate bone metabolic markers might be an independent prognostic factor in patients whose tumors metastasize to bone. 5. New or refined assays for bone metabolic markers are expected to improve the sensitivity and specificity of bone metabolic marker use in diagnosing and monitoring metastasis to bone.

Markers of bone turnover in prostate cancer

Prostate cancer is the most common malignancy in elderly men and is often associated with bone metastases. Although bone metastases are osteosclerotic, histological and biochemical studies clearly indicate an increase of both bone formation and bone resorption, providing the rational for using bisphosphonate as a palliative treatment in these patients. The recent development of specific and sensitive biochemical markers, reflecting the overall rate of bone formation and bone resorption, has improved the non-invasive assessment of bone turnover abnormalities in patients with prostate cancer. The immunoassays for bone-specific alkaline phosphatase and type I collagen propeptides are currently the most sensitive markers to assess bone, formation. The best indices of bone resorption are the immunoassay for the pyridinoline cross-links and the related peptides that can be measured in urine and more recently in serum. A better knowledge of the biochemistry, especially of the age-related post-translational modifications of type I collagen in the abnormal bone matrix, associated with bone metastases from prostate cancer may lead to markers of increased sensitivity. A recent example is the demonstration that the isomerization and racemization of the aspartic acid residue in C-telopeptides of type I collagen is impaired in patients with prostate cancer and bone metastases, a pattern than can be detected with specific conformational antibodies. The most sensitive markers of bone formation and bone resorption are markedly increased in patients with bone metastases compared with patients with cancer but without metastases, the levels correlating with the extent of the bone involvement. However, their sensitivity remains limited, suggesting that the currently available biochemical markers cannot be used as a surrogate for bone scintigraphy in the diagnosis of bone involvement. A few studies have suggested that the measurement of bone markers may be useful in the assessment of response to anti-endocrine therapy, although available data indicate a lower sensitivity than with prostates specific antigen. Additional longitudinal studies are required to assess the potential use of bone markers, especially to identify patients who relapse during the course of the treatment and, more specifically 3 those that result from the progression in bone metastases.Clearly, the established use of bone markers is for monitoring effects of bisphosphonate treatment. Several studies have shown a rapid decrease of bone resorption markers in patients with prostate cancer and bone metastases, the magnitude of the decrease correlating with the efficacy of the treatment in reducing bone pain. Thus, bone markers are likely to become a useful and objective tool to monitor bisphosphonate treatment and individual the therapy scheme.

Bone markers in the management of metastatic bone disease

Newer markers of bone formation and bone resorption are now available. Alone these new markers do not appear to be useful to diagnose metastatic bone disease. Several markers appear to be of prognostic importance and correlate with the extent of tumour in the skeleton. Serial monitoring of bone markers may be useful to monitor the efficacy of bisphosphonate and/or systemic therapy of both lytic and blastic bone metastases.

Biochemical markers and skeletal metastases

BACKGROUND

Skeletal metastases are common occurrences in patients with malignancies such as breast and prostate carcinoma, but they are difficult to diagnose nonradiologically, and treatment is difficult to follow clinically. Recent developments suggest that biochemical markers of bone remodeling, such as the bone collagen breakdown product N-telopeptide and the bone formation marker known as bone specific alkaline phosphatase, hold great promise as clinical tools for the management of patients with metastatic bone disease.

METHODS

Serum levels of the bone formation marker known as bone specific alkaline phosphatase (BAP), along with serum levels of the bone collagen breakdown product carboxyterminal telopeptide of Type I collagen (ICTP) and urine levels of pyridinoline (PYD), deoxypridinoline (DPD), and N-telopeptide (NTx), were measured in a large cohort of patients with newly diagnosed or progressive cancer of the breast, prostate, lung, and other sites. Bone marker levels were correlated with the presence or absence of bone scan-documented metastases; metastatic disease extension in terms of the number of skeletal sites involved; and the type of lesion, whether blastic or lytic. Sites examined included the pelvis, spine, skull, ribs, and long bones.

RESULTS

All of the bone markers examined, including BAP and NTx, were abnormally elevated in a high proportion of patients with confirmed metastases to bone. Urine NTx levels and bone specific alkaline phosphatase were significantly correlated with the number of skeletal sites involved, and a significant correlation between marker level and extent of skeletal involvement was also observed. In addition, both markers were higher in patients with a blastic disease presentation than in patients with osteolytic lesions.

CONCLUSIONS

Biochemical markers of bone resorption and bone formation are abnormally raised in the blood and urine of patients with metastatic bone disease. Markers of bone collagen breakdown, such as N-telopeptide, as well as markers of osteoblast function, such as bone specific alkaline phosphatase, appear to be of use in assessing and managing patients with malignancies that metastasize to bone. In this study, both NTx and BAP showed a significant correlation with both the presence of bone metastases and the extent of skeletal involvement. Biochemical markers of bone remodeling can also be used to guide decision making regarding the treatment of metastatic bone disease and to determine the effectiveness of therapy for patients with cancer to bone whose broad-based symptoms make it difficult to discern true response to therapy.

Markers of bone turnover in bone metastases

BACKGROUND

Bone metastases are a frequent complication of cancer disease. The evaluation of metastatic bone disease is crucial for the primary cancer staging because it will influence the therapeutic decision. The diagnosis of bone metastases usually relies on skeletal X-ray and bone scintigraphy. This latter technique is a sensitive diagnostic tool but lacks specificity. Moreover, the assessment of efficacy in the treatment of bone metastasis is difficult because the increased radionucleotide uptake does not always reflect an active metastatic area but may correspond to a bone reconstruction in patients responding to treatment. Markers of bone remodeling could help the clinician in the diagnosis and follow-up of bone metastases.

METHODS

A common feature of both types of bone metastases (lytic or sclerotic) is an alteration of bone remodeling activity. The rate of formation or degradation of the bone matrix can be assessed either by measuring a prominent enzymatic activity of the bone forming or resorbing cells or by measuring bone matrix components released into the circulation during formation or resorption. They have been separated into markers of formation and resorption, but when both events are coupled and in balance, either of these markers will reflect the overall rate of bone turnover. These markers are of unequal specificity and sensitivity, and some of them have not been fully investigated yet in bone metastases. None of these markers is disease specific.

RESULTS

Several studies of breast carcinoma showed increased levels of pyridinium cross-links in patients with bone metastases. However, in most studies, breast carcinoma patients without evidence of metastatic bone disease excreted pyridinium cross-links at a much higher rate than healthy controls. Similar findings have been observed with other types of primary cancer including lung, prostate, kidney, throat, and digestive carcinoma. Markers of bone formation had a low sensitivity in the diagnosis of bone metastasis, but they could be useful for prostate carcinoma, in which studies have shown that all patients without bone metastasis had normal value of bone alkaline phosphatase. Bone markers can be used for the follow-up of treatment, especially bisphosphonates therapy. Bisphosphonate infusion induces a large decrease of pyridinium cross-link level. Some studies suggest that a high level of resorption markers after treatment could reflect a resistance to the treatment. Moreover, some studies have shown that level of pyridinium cross-links before treatment could be a predictive factor of the response in multiple myeloma and prostate carcinoma.

CONCLUSIONS

Bone markers have improved greatly in terms of sensitivity and specificity and could be useful for an early diagnosis of bone metastases. However, the clinical value of the use of bone markers in the diagnosis of bone metastasis has not been clearly shown yet with the possible exception of BPAL in prostate carcinoma. When bone is the only site of metastases, bone markers may be useful for monitoring patients with bone metastases. Markers of bone resorption are sensitive to changes in bone turnover induced by treatment. Bone resorption markers may be particularly useful for the follow-up of bisphosphonate treatment, which is increasingly used in the management of bone metastases.