Skeletal alkaline phosphatase as a serum marker of bone metastases in the follow-up of patients with breast cancer

Diagnostic value of alkaline phosphatase and bone-specific alkaline phosphatase for metastases in breast cancer: a systematic review and meta-analysis

PURPOSE

Numerous studies had reported the diagnostic value of alkaline phosphatase (ALP) and its bone-specific isoforms (BAP) in the metastases of breast cancer (BC). The purpose of this meta-analysis was to summarize the diagnostic value of serum ALP and BAP in metastatic BC, especially focused on bone metastases.

METHODS

We searched comprehensively in the PubMed, Cochrane Library, and EMBASE for studies to explore the diagnostic accuracy of serum ALP/BAP level for metastatic BC. Qualities of including studies were assessed and pooled sensitivity, specificity, and summary receiver operating characteristic curve were calculated. Publication bias was assessed and meta-regression was conducted.

RESULTS

We finally included 25 studies with a total of 12,155 BC patients (1681 metastatic cases and 10,474 controls). According to the QUADAS-2 tool to assessment the methodological quality, most of the included studies were judged as high risk of patient selection bias. High serum levels of ALP/BAP in bone metastatic BC patients could be found compared with non-metastatic BC patients. The pooled sensitivity and specificity of ALP for BC bone metastases were 0.62 and 0.86, and the area under the curve (AUC) was 0.80. The pooled sensitivity and specificity of ALP for all site metastases (mainly bone and liver) were 0.56 and 0.91, and the AUC was 0.90. The pooled sensitivity and specificity of BAP for BC bone metastases were 0.66 and 0.92, and the AUC was 0.89.

CONCLUSION

Although not promising, serum ALP and BAP could bring useful information for the early detection of BC metastases especially for the bone metastases.

Prognostic value of alkaline phosphatase and bone-specific alkaline phosphatase in breast cancer: A systematic review and meta-analysis

Numerous studies have reported the clinical value of alkaline phosphatase (ALP) and its bone-specific isoforms (bone-specific alkaline phosphatase (BAP)) in breast cancer. The purpose of this meta-analysis was to summarize the prognostic value of serum ALP and BAP in breast cancer, especially focused on bone metastasis and survival. PRISMA guidelines were followed to conduct this review. Observational studies were searched in PubMed, Cochcrane Library and EMBASE to January 1, 2022. Data were extracted to explore the prognostic value of ALP and BAP. The quality of the included studies was assessed and the outcome effects were evaluated. Subgroup and sensitivity analyses were performed to explore the potential sources of heterogeneity. Publication bias was assessed. There was a total of 53 studies with 22,436 patients included. For the primary outcome of survival, high levels of both ALP and BAP were associated with short survival time. The hazard ratio of high ALP level on overall survival was 1.72 (95% CI 1.37, 2.16, P < 0.001). For the secondary outcomes, a high ALP level (not BAP) was detected in breast cancer compared with healthy controls, and high levels of both ALP and BAP were risk factors for bone metastasis, while ALP (not BAP) was a risk factor for non-bone metastasis. This study showed that high levels of both serum ALP and BAP were associated with metastasis (BAP was associated with bone metastasis) and survival in breast cancer. The biomarkers could provide useful information for the early diagnostic assessment and monitoring in the follow-up of breast cancer patients.

Usefulness of Bone Formation Markers in Breast Cancer

The skeleton is the main site affected by metastases and breast cancer is the most frequent tumor to invade bone. The assessment of bone metastases is difficult and biochemical markers of bone formation (BFMs) could be a promising alternative. Although the essential role of osteoblasts in the metastatic process of bone destruction is now well established, little attention has been paid to BFMs. We conducted a Medline search for studies about BFMs in breast cancer. Our review allows us to conclude that BFMs have high specificity but low sensitivity for the diagnosis of bone metastases. The available biochemical markers cannot replace imaging techniques for the diagnosis of bone metastases. Several studies indicate that BFM serum levels reflect total tumor burden in the skeleton. BFM levels are higher in patients with blastic lesions compared to those with lytic lesions. Serial measurements of BFMs could be useful for the clinical assessment of response to antineoplastic treatment or to bisphosphonate therapy. Besides markers of bone resorption, biochemical markers of bone formation are a promising alternative for the assessment of metastatic bone disease, but large prospective studies are needed to address this important issue.

Implications of Cancer Staging Uncertainties in Radiation Therapy Decisions

Introduction . Radiation therapy (RT) for cancer is a critical medical procedure that occurs in a complex environment involving numerous health professionals, hardware, software, and equipment. Uncertainties and potential incidents can lead to inappropriate administration of radiation to patients, with sometimes catastrophic consequences such as premature death or appreciably impaired quality of life. The authors evaluate the impact of incorrectly staging (i.e., estimation of extent of cancer) breast cancer patients and resulting inappropriate treatment decisions. Methods . The authors employ analytic and simulation methods in an influence-diagram framework to estimate the probability of incorrect staging and treatment decisions. As inputs, they use a combination of literature information on the accuracy and precision of pathology and tests as well as expert judgment. Sensitivity and value-of-information analyses are conducted to identify important uncertainties. Results and conclusions . The authors find a small but nontrivial probability that breast cancer patients will be incorrectly staged and thus may be subjected to inappropriate treatment. Results are sensitive to a number of variables, and some routinely used tests for metastasis have very limited information value. This work has implications for the methods used in cancer staging, and the methods are generalizable for quantitative risk assessment of treatment errors.

Human placental alkaline phosphatase: expression in Pichia pastoris, purification and characterization of the enzyme

The soluble form of human placental alkaline phosphatase (PLAP) was expressed in the methylotrophic yeast Pichia pastoris and the expression product was purified and characterized. Yeast-derived PLAP (yPLAP) was secreted into the medium to the level of 2 mg/liter. yPLAP displayed kinetic properties similar to those reported earlier for the membrane-bound PLAP. Purified yPLAP had specific activity of 774 U/mg and appeared in two subunit sizes, ca. 62 and 65 kDa. This difference was due to heterogenous N-glycosylation. Purified yPLAP appeared as multiple forms in isoelectric focusing in pI range of 4.2 to 5.2. The expression system is discussed in comparison to previously reported expression systems.

Biochemical markers in the assessment of bone disease

As the mean age of our population increases, increasing attention has been paid to the diseases associated with aging, including diseases of the skeleton such as osteoporosis. Effective means of treating and possibly preventing such skeletal disorders are emerging, making their early recognition an important goal for the primary care physician. Although bone density measurements and skeletal imaging studies remain of primary diagnostic importance in this regard, a large number of assays for biochemical markers of bone formation and resorption are being developed that promise to complement the densitometry measurements and imaging studies, providing an assessment of the rates of bone turnover and an earlier evaluation of the effects of therapy. In this review, emphasizing the recent literature, the major biochemical markers currently in use or under active investigation are described, and their application in a number of diseases of the skeleton including osteoporosis is evaluated.