Chemotherapy and Angiogenesis in Advanced Cancer: Vascular Endothelial Growth Factor (VEGF) Decline as Predictor of Disease Control during Taxol Therapy in Metastatic Breast Cancer

Advanced treatment strategies in breast cancer: A comprehensive mechanistic review

Breast cancer is a destructive lump type that affects women globally. Despite the availability of multi-directional therapeutic strategies, advanced stages of breast cancer are difficult to treat and impose major healthcare burdens. This situation reinforces the need to identify new potential therapeutic compounds with better clinical features. In this context, different treatment methods were included such as Endocrine therapy, chemotherapy, Radiation therapy, antimicrobial peptide-dependent growth inhibitor, liposome-based drug delivery, antibiotics used as a co-medication, photothermal, immunotherapy, and nano drug delivery systems such as Bombyx mori natural protein sericin and its mediated nanoparticles are promising biomedical agents. They have been tested as an anticancer agent against various malignancies in pre-clinical settings. The biocompatible and restricted breakdown properties of silk sericin and sericin-conjugated nanoparticles made them perfect contenders for a nanoscale drug-delivery system.

Efforts in Bioprospecting Research: A Survey of Novel Anticancer Phytochemicals Reported in the Last Decade

Bioprospecting natural products to find prominent agents for medical application is an area of scientific endeavor that has produced many clinically used bioactive compounds, including anticancer agents. These compounds come from plants, microorganisms, and marine life. They are so-called secondary metabolites that are important for a species to survive in the hostile environment of its respective ecosystem. The kingdom of Plantae has been an important source of traditional medicine in the past and is also enormously used today as an exquisite reservoir for detecting novel bioactive compounds that are potent against hard-to-treat maladies such as cancer. Cancer therapies, especially chemotherapies, are fraught with many factors that are difficult to manage, such as drug resistance, adverse side effects, less selectivity, complexity, etc. Here, we report the results of an exploration of the databases of PubMed, Science Direct, and Google Scholar for bioactive anticancer phytochemicals published between 2010 and 2020. Our report is restricted to new compounds with strong-to-moderate bioactivity potential for which mass spectroscopic structural data are available. Each of the phytochemicals reported in this review was assigned to chemical classes with peculiar anticancer properties. In our survey, we found anticancer phytochemicals that are reported to have selective toxicity against cancer cells, to sensitize MDR cancer cells, and to have multitarget effects in several signaling pathways. Surprisingly, many of these compounds have limited follow-up studies. Detailed investigations into the synthesis of more functional derivatives, chemical genetics, and the clinical relevance of these compounds are required to achieve safer chemotherapy.

Assessment of iodine uptake by pancreatic cancer following chemotherapy using dual-energy CT

Pancreatic cancer remains a major health problem, and only less than 20% of patients have resectable disease at the time of initial diagnosis. Systemic chemotherapy is often used in the patients with borderline resectable, locally advanced unresectable disease and metastatic disease. CT is often used to assess for therapeutic response; however, conventional imaging including CT may not correctly reflect treatment response after chemotherapy. Dual-energy (DE) CT can acquire datasets at two different photon spectra in a single CT acquisition, and permits separating materials and extract iodine by applying a material decomposition algorithm. Quantitative iodine mapping may have an added value over conventional CT imaging for monitoring the treatment effects in patients with pancreatic cancer and potentially serve as a unique biomarker for treatment response. In this pictorial essay, we will review the technique for iodine quantification of pancreatic cancer by DECT and discuss our observations of iodine quantification at baseline and after systemic chemotherapy with conventional cytotoxic agents, and illustrate example cases.

Antiangiogenic Activity of Chemopreventive Drugs

Tumors growing within the host form dynamic aberrant tissue that consists of host components, including the stroma, an expanding vasculature and often chronic inflammation, in addition to the tumor cells themselves. These host components can contribute to, rather than limit, tumor expansion, whereas deprivation of vessel formation has the potential to confine tumors in small, clinically silent foci. Therapeutic inhibition of vessel formation could be best suited to preventive strategies aimed at the suppression of angiogenesis in primary tumors in subjects at risk, or of micrometastases after surgical removal of a primary tumor. Our analysis of potential cancer chemopreventive molecules including N-acetylcysteine, green tea flavonoids and 4-hydroxyphenyl-retinamide has identified antiangiogenic activities that could account -at least in part - for the tumor prevention effects observed with these compounds. These drugs appear to target common mechanisms of tumor angiogenesis that may permit identification of critical targets for antiangiogenic therapy and antiangiogenic chemoprevention.

Perfusion CT imaging of treatment response in oncology

Perfusion CT was first described in the 1970s but has become accepted as a clinical technique in recent years. In oncological practice Perfusion CT allows the downstream effects of therapies on the tumour vasculature to be monitored. From the dynamic changes in tumour and vascular enhancement following intravenous iodinated contrast agent administration, qualitative and quantitative parameters may be derived that reflect tumour perfusion, blood volume, and microcirculatory changes with treatment. This review outlines the mechanisms of action of available therapies and state-of-the-art imaging practice.

The pharmacological bases of the antiangiogenic activity of paclitaxel

In the mid 1990s, researchers began to investigate the antiangiogenic activity of paclitaxel as a possible additional mechanism contributing to its antineoplastic activity in vivo. In the last decade, a number of studies showed that paclitaxel has antiangiogenic activity that could be ascribed to the inhibition of either tubule formation or cell migration, and to an antiproliferative effect towards activated endothelial cells. Furthermore, paclitaxel was shown to downregulate VEGF and Ang-1 expression in tumor cells, and to increase the secretion of TSP-1 in the tumor microenvironment. Moreover, the new pharmaceutical formulations of paclitaxel (such as liposome-encapsulated paclitaxel, ABI-007, and paclitaxel entrapped in emulsifying wax nanoparticles) enhanced the in vivo antiangiogenic activity of the drug. Thus, the preclinical data of paclitaxel may be exploited to implement a novel and rational therapeutic strategy to control tumor progression in patients.

Vascular endothelial growth factor expression and T-regulatory cells in premenopausal breast cancer

Estradiol (E2) plays a key role in human reproduction through the induction of vascular endothelial growth factor (VEGF) and T-regulatory cells (T-Regs), which are also important in breast cancer (BC) growth. The primary endpoint of the present study was the investigation of whether E2 suppression, chemotherapy and radiation therapy decreased the levels of VEGF and T-Regs of premenopausal patients with high-risk early BC. The secondary endpoints were toxicity, progression-free survival (PFS) and overall survival (OS). Between April 2003 and July 2008, 100 premenopausal women with early, high-risk BC were entered into the study. The characteristics of the patients were as follows: median age, 43 years (range, 26–45); median number of positive axillary nodes, 3.3; median Ki-67, 33%. Plasma E2, VEGF and T-Reg were measured at baseline and every year. Treatment comprised luteneizing hormone-releasing hormone (LH-RH) analogue, tailored chemotherapy, radiation therapy and hormonal therapy in oestrogen receptor-positive (ER⁺) tumours. At 4 years, a statistically significant decrease in E2, VEGF and T-Reg levels was observed; the PFS and OS rates were 94 and 98%, respectively. Hot flushes and G1 osteopenia occurred following LH-RH analogue administration, while no unexpected toxicity was observed following chemotherapy. E2 deprivation with an LH-RH analogue, tailored chemotherapy, radiation therapy and hormonal therapy in ER⁺ tumours decreased plasma VEGF levels and T-Regs numbers in premenopausal high-risk ER⁺ and ER- BC patients. In addition, a favorable impact on PFS and OS was observed.

Circulating levels of angiogenic cytokines in advanced breast cancer patients with system chemotherapy and their potential value in monitoring disease course

PURPOSE

The low-dose metronomic chemotherapy was reported to inhibit directly tumor angiogenesis or VEGF secretion. The study aimed to seek for this effect of system chemotherapy by observing the changes in serum levels of angiogenic cytokines during treatment and assessing their value in monitoring the advanced breast cancer.

METHODS

In sixty-one patients with advanced breast cancer, serum levels of vascular endothelial growth factor (VEGF) and endostatin (ES) were compared at baseline (B0), after one cycle (B1), after 3 cycles (B3), and after 5-6 cycles (B5-6) of system chemotherapy using a quantitative ELISA. Data were correlated with treatment response and total survival.

RESULTS

The response to chemotherapy did not correlate with serum VEGF level before therapy or after one cycle, but the changes in VEGF levels after 3 cycles and 5-6 cycles showed good association with clinical responses, i.e., the patients with disease control had a decreased VEGF value, whereas the progressive patients had an increased value. The Cox proportional hazard model revealed that a normalized VEGF level after therapy and an increase in VEGF level after 5-6 cycles were independent predictors for survival.

CONCLUSIONS

System chemotherapy for advanced breast cancer lead to a significant decrease in serum VEGF level in patients with disease control, and this anti-VEGF efficacy may be mainly due to the reduction in tumor burden. Sequential measurement of serum VEGF could be useful for evaluating treatment efficacy and prognosis.

Phase I/II trial of metronomic chemotherapy with daily dalteparin and cyclophosphamide, twice-weekly methotrexate, and daily prednisone as therapy for metastatic breast cancer using vascular endothelial growth factor and soluble vascular endothelial growth factor receptor levels as markers of response

PURPOSE Preclinical studies indicate that metronomic chemotherapy is antiangiogenic and synergistic with other antiangiogenic agents. We designed a phase I/II study to evaluate the safety and activity of adding dalteparin and prednisone to metronomic cyclophosphamide and methotrexate in women with measurable metastatic breast cancer (MBC). PATIENTS AND METHODS Patients received daily dalteparin and oral cyclophosphamide, twice-weekly methotrexate, and daily prednisone (dalCMP). The primary study end point was clinical benefit rate (CBR), a combination of complete response (CR), partial response (PR), and prolonged stable disease for > or = 24 weeks (pSD). Secondary end points included time to progression (TTP), duration of response, and overall survival (OS). Biomarker response to treatment was assessed by using plasma vascular endothelial growth factor (VEGF) and soluble VEGF receptors (sVEGFRs) -1 and -2. Results Forty-one eligible patients were accrued. Sixteen (39%) had no prior chemotherapy for MBC; 15 (37%) had two or more chemotherapy regimens for MBC. Toxicities were minimal except for transient grade 3 elevation of liver transaminases in 11 patients (27%) and grade 3 vomiting in one patient (2%). One patient (2%) had CR, six (15%) had PR, and three (7%) had pSD, for a CBR of 10 (24%) of 41 patients. Median TTP was 10 weeks (95% CI, 8 to 17 weeks), and median OS was 48 weeks (95% CI, 32 to 79 weeks). VEGF levels decreased but not significantly, whereas sVEGFR-1 and -2 levels increased significantly after 2 weeks of therapy. There was no correlation between response and VEGF, sVEGFR-1, or sVEGFR-2 levels. CONCLUSION Metronomic dalCMP is safe, well tolerated, and clinically active in MBC.

Class III beta-tubulin isotype predicts response in advanced breast cancer patients randomly treated either with single-agent doxorubicin or docetaxel

PURPOSE

To evaluate the role of microtubule-associated variables as potential predictors of response and clinical outcome in patients with advanced breast cancer receiving single-agent docetaxel or doxorubicin chemotherapy.

EXPERIMENTAL DESIGN

The analysis was done on 173 tumor samples from patients with locally advanced or metastatic breast cancer who have participated in the TAX-303 phase III trial in which patients were randomly assigned to receive docetaxel or doxorubicin. Expression of total alpha- and beta-tubulin, classes II to IV beta-tubulin isotypes, and tau protein was evaluated by immunohistochemistry on formalin-fixed, paraffin-embedded tumors from the primary breast cancer.

RESULTS

We observed that patients with "high" expression of class III beta-tubulin isotype had a higher probability of response to docetaxel than to doxorubicin treatment (odds ratio, 1.9; 95% confidence interval, 1.01-3.7; P = 0.05). No difference was observed in terms of time to progression or in terms of overall survival.

CONCLUSIONS

This study suggests that the superiority of docetaxel over doxorubicin seems to be confined to the subgroup of patients with "high" expression of class III beta-tubulin isotype.

Daily low-dose/continuous capecitabine combined with neo-adjuvant irradiation reduces VEGF and PDGF-BB levels in rectal carcinoma patients

Metronomic low-dose chemotherapy regimen was found to have an antiangiogenic effect in tumors. However, its effect on levels of circulating pro-angiogenic and anti-angiogenic factors is not fully explored.

MATERIALS AND METHODS

The levels of both VEGF and PDGF-BB were measured in three time points, in the serum of 32 rectal carcinoma patients receiving daily reduced-dose/continuous capecitabine in combination with preoperative pelvic irradiation.

RESULTS

We found a significant decrease in VEGF and PDGF-BB serum levels during the combination treatment (p < 0.0001), followed by an increase in the successive rest-period (p < 0.0001). In addition, substantial changes in platelets counts were observed during treatment in correlation with the changes of VEGF and PDGF-BB serum levels.

DISCUSSION

These results suggest that combined chemo-irradiation affect levels of pro-angiogenic factors during treatment, and may reflect an anti-angiogenic window induced during this treatment. The potential implications of this inducible phenomenon, including a possible clinical benefit from the administration of long lasting metronomic chemotherapy immediately following combined chemo-irradiation, would warrant further investigation.

Vascular endothelial growth factor levels in ascites between chemonaive and chemotreated patients

PURPOSE

Vascular endothelial growth factor (VEGF) levels in malignant ascites have high diagnostic value for their discrimination from ascites of non-malignant origin. However, there have been no reports on the comparison of VEGF levels between malignant ascites of chemonaive and chemotreated patients.

MATERIALS AND METHODS

VEGF levels were measured in 44 ascites patients (cirrhosis ascites, 10; chemonaive patients, 21; chemotreated patients, 13) and compared to the level of carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9). The diagnostic parameters of sensitivity, specificity, and correlation among 3 markers were evaluated.

RESULTS

VEGF levels in malignant ascites of chemonaive and chemotreated patients were significantly higher than those in cirrhotic ascites (p<0.05). VEGF levels in ascites of chemonaive patients were significantly higher than those in chemotreated patients (p<0.05). A cutoff value of 10.4 pg/mL was calculated using receiver operating characteristic curves (ROCs) for VEGF in chemotreated and chemonaive patients, which gave sensitivities of 75.0% and 53.8% and specificities of 69.6% and 47.1%, respectively. Positive correlations were observed between VEGF and CEA (r=0.353, p<0.05) as well as between VEGF and CA19-9 (r=0.367, p<0.05) in ascites.

CONCLUSION

VEGF levels could be a useful tumor marker for malignant ascites, but its value should carefully be interpreted because of lesser reliability in chemotreated ones.

Biomarkers predictive for clinical efficacy of taxol-based chemotherapy in advanced breast cancer

BACKGROUND

Several studies looked for tumor biomarkers predictive for paclitaxel sensitivity but till now no reliable biomarkers are available. The aim of this study was to verify the potential predictive value of beta-tubulin III and IV, vascular endothelial growth factor-receptor (VEGFR-1), HER2/neu and microvessel density (mVD), in a group of 70 patients with advanced breast cancer (ABC) treated with paclitaxel-based chemotherapy.

PATIENTS AND METHODS

Immunohistochemical analysis (ICA) of HER2, VEGFR-1, mVd, beta-tubulin III and beta-tubulin IV expression were performed in a series of 72 advanced breast cancer. Furthermore apoptotic fraction with TUNEL analysis was evaluated.

RESULTS

beta-tubulin III ICA expression was predictive of progression after chemotherapy. In fact only 2% of the patients with low beta-tubulin III expression progressed after paclitaxel chemotherapy vs 38% of those with high beta-tubulin III tumor expression (P=0.000; by chi(2)). This evidence was confirmed by a logistic regression analysis (OR 28.789; 95% CI 3.212-258,072; P=0.004). There was not a significant association between other biomarkers' characteristics and clinical response to chemotherapy. A Cox multivariate analysis, with overall survival as a dependent variable, showed that only HER2 expression was independently associated (OR 2.39; 95% CI 1.09-5.23; P=0.03) with overall survival.

CONCLUSIONS

We suggest that class III beta-tubulin immunohistochemical expression analysis could be a potentially relevant tumor biomarker for paclitaxel resistance in advanced breast cancer patients.

Decline in angiogenic factors, such as interleukin-8, indicates response to chemotherapy of metastatic melanoma

Serum concentrations of angiogenic factors have been reported to correlate with tumour burden and prognosis in metastatic melanoma. The present study was performed to assess the value of angiogenic factors in serum in indicating response or failure to chemotherapy and immunochemotherapy in stage IV melanoma. Thirty-five patients suffering from stage IV melanoma according to the American Joint Committee on Cancer (AJCC) criteria were included in this prospective study. Before and following chemotherapy or immunochemotherapy, serum levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF-AB), vascular cell adhesion molecule-1 (VCAM-1) and interleukin-8 (IL-8) were measured. Staging examinations following chemotherapy revealed 15 patients with response to therapy (complete response, partial response, stable disease), 14 patients with progressive disease and six patients with mixed response. Patients who responded to therapy showed a significant decrease in the serum level of IL-8 at the time of staging examinations, whereas patients with progressive disease did not. Following chemotherapy, serum concentrations of PDGF-AB had significantly decreased in both patients with response and patients with progressive disease. Comparing the VEGF and bFGF levels of responders and non-responders after a single administration of cytostatics showed significantly lower concentrations in patients with response to therapy. In all patients, a high intra- and inter-individual variability of serum values was observed during application of therapy. It can be concluded that low IL-8 serum levels after chemotherapy indicate response to chemotherapy in stage IV melanoma patients. The persistence of elevated serum levels of VEGF and bFGF following the initial cytostatic administration may help to identify patients resistant to chemotherapy. The distinct variability of serum levels indicates that processes other than tumour angiogenesis also influence the serum concentration of the examined angiogenic factors.

The effects of standard anthracycline-based chemotherapy on soluble ICAM-1 and vascular endothelial growth factor levels in breast cancer

PURPOSE

The circulating soluble form of intercellular adhesion molecule-1 (sICAM-1) and vascular endothelial growth factor (VEGF) are elevated in women with breast cancer and associated with tumor progression and poor prognosis. This study examined the effects of anthracycline-based chemotherapy on plasma sICAM-1 and VEGF, as well as soluble P-selectin, von Willebrand factor, and interleukin-6 levels.

EXPERIMENTAL DESIGN

Twenty-six women diagnosed with stage I-IIIA breast cancer (mean age, 48.4 +/- 10.4 years; range, 34-79 years) were studied before (week 1) and at weeks 2 and 3 of cycles 1 and 4 of chemotherapy.

RESULTS

The initial effect of chemotherapy was to reduce sICAM-1 levels; compared with pretreatment, sICAM-1 levels were decreased at week 2 of both cycles (P values < 0.01). sICAM-1 levels were elevated, however, at the start of cycle 4 as compared with pretreatment (P < 0.01). Chemotherapy led to an increase in sICAM-1 levels in node-positive but not node-negative patients (P < 0.01). VEGF levels were decreased at week 2 of cycle 4 (P = 0.001) and remained so at week 3. Similar to sICAM-1, VEGF levels were elevated at the start of cycle 4 as compared with pretreatment (P < 0.006). Soluble P-selectin levels decreased during week 2 of cycle 4 (P = 0.026). Neither interleukin-6 or von Willebrand factor were significantly changed in response to chemotherapy.

CONCLUSIONS

The findings support prior studies suggesting that sICAM-1 levels derive from sources other than endothelial cells. In addition, whereas the more immediate effect of chemotherapy is to reduce sICAM-1 and VEGF, continued treatment may lead to significant elevations.

Serum levels of angiogenic cytokines decrease after antineoplastic radiotherapy

Serum levels of angiogenic cytokines decrease after radiotherapy in patients with cancer and their may have an impact on response to treatment and progression-free survival. Here, we have evaluated sera of patients before and after radiotherapy for various tumour types for levels of soluble fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) to assess whether these factors decrease after radiotherapy, and whether their diminution is related to the radiation dose, tumour type, age and haemoglobin level. We demonstrate that levels of FGF-2 and VEGF, but not HGF, decrease significantly, and that the extent of their diminution is related to the radiation dose and response.

Molecular targets as therapeutic strategies in the management of breast cancer

Therapy directed against specific biologic targets has long been used in the treatment of breast cancer; the estrogen receptor is a validated prognostic and therapeutic target, and antiestrogen therapy has been used effectively for decades. Recently, scientific progress and increased comprehension of mechanisms of breast cancer pathogenesis have led to the proliferation of both potential molecular targets and new therapeutic agents. The success of traztuzumab (Herceptin, Genentech, South San Francisco, CA), an anti-HER2 antibody, has spurred the development of other biologically directed therapeutics. In this overview, I discuss three targets relevant to breast cancer (the epidermal growth factor receptor family, angiogenesis, and NF-kappa B), and therapeutic approaches directed against these targets are discussed.

VEGF-165 serum levels and tyrosinase expression in melanoma patients: correlation with the clinical course

Vascular endothelial growth factor (VEGF) is known to play a crucial role in the growth and metastatization of solid tumours. In cancer patients, high VEGF serum levels correlate with tumour status and prognosis, but to date few data have been reported concerning VEGF in melanoma patients. In the present study, immunoenzymatic and reverse transcription-polymerase chain reaction (RT-PCR) techniques were used to detect VEGF-165 serum levels and the presence of tyrosinase mRNA, respectively, in the peripheral blood of a cohort of 155 melanoma patients at different clinical stages (30 stage I, 40 stage II, 40 stage III and 45 stage IV; AJCC classification). Data were compared with both the extent of the disease and the clinical course. The aim was to assess the relationship between VEGF serum levels, the presence of detectable circulating melanoma cells and melanoma progression. A significant increase in VEGF serum levels was found in melanoma patients, in particular in those with metastatic disease; a higher incidence of relapses was found in stage I-III disease-free patients who showed an increase in VEGF during follow-up. VEGF serum levels were significantly higher in patients with detectable circulating melanoma cells than in those with negative tyrosinase mRNA expression. The finding of both an increase in VEGF and the presence of detectable melanoma cells during follow-up was associated with a relapse rate of 81%. The relapse rate was significantly lower when either of the two parameters were present separately. Multivariate analysis of both overall survival and time-to-progression selected baseline tyrosinase expression in peripheral blood but not VEGF serum levels as an independent prognostic factor.

Serum vascular endothelial growth factor levels are elevated in metastatic differentiated thyroid cancer but not increased by short-term TSH stimulation

Solid tumor formation requires the development of a blood supply adequate to meet the metabolic demands of the enlarging tumor mass that cannot be sustained by simple diffusion. One principal stimulant to endothelial cell growth and migration, vascular endothelial growth factor (VEGF), is synthesized and secreted by thyroid cancer cells. Furthermore, VEGF overexpression is associated with an aggressive thyroid cancer phenotype in both animal models and clinical-pathological studies. In other malignancies, elevated serum levels of VEGF often correlate with stage of disease and other poor prognostic clinical features. Therefore, we hypothesized that serum VEGF levels would be significantly higher in patients with persistent or recurrent thyroid cancer than in those cured of the disease. Because TSH stimulates both normal and neoplastic thyroid cells, we also proposed that serum VEGF would be further increased by TSH stimulation. Sixty-nine patients with either papillary or follicular thyroid cancer, status post total thyroidectomy, and prior radioactive iodine ablation, who had undergone routine recombinant human TSH (rhTSH, Thyrogen, Genzyme Transgenics Corp., Cambridge, MA) assisted whole-body radioactive iodine scanning, were included in this study. This cohort (mean age 53 +/- 16 yr, 51% female) included 21 patients with no evidence of disease and 48 patients with local or distant metastases. Stored serum samples obtained for standard Tg determinations before and 72 h following standard rhTSH stimulation were identified and assayed for VEGF 165 (R \[amp ]\ D Systems, Minneapolis, MN). Baseline serum VEGF levels obtained at a time of TSH suppression were significantly higher in patients with known metastatic disease than in those with no evidence of disease (416 +/- 62 pg/ml vs. 185 +/- 25 pg/ml, P = 0.001). Patients with distant metastases had baseline serum VEGF levels that did not differ significantly from patients with only cervical recurrences (455 +/- 90 pg/ml in distant metastases vs. 330 +/- 44 pg/ml for local cervical recurrences). Short-term TSH stimulation, although causing a significant rise in serum Tg, resulted in no significant increase in serum VEGF measured 72 h after rhTSH injection in either the patients with known metastatic disease (416 +/- 62 pg/ml baseline vs. 419 +/- 71 pg/ml after TSH stimulation) or in cured patients (185 +/- 25 pg/ml baseline vs. 191 +/- 33 pg/ml after TSH stimulation). Subgroup analysis revealed that patients with metastatic disease arising from well differentiated primary thyroid cancers had significantly higher serum VEGF levels than patients with metastatic disease arising from poorly differentiated thyroid cancer primaries (485 +/- 74 pg/ml vs. 167 +/- 32 pg/ml, P = 0.003 by ANOVA). Poorly differentiated metastatic thyroid cancers had serum VEGF levels indistinguishable from patients cured of disease (167 +/- 32 pg/ml vs. 186 +/- 25 pg/ml). In summary, serum VEGF is significantly elevated in patients with metastatic differentiated thyroid cancer but not in those with poorly differentiated thyroid cancer metastases. No measurable increase in serum VEGF levels can be detected 72 h after short-term TSH stimulation with rhTSH. We conclude that serum VEGF may serve as a clinical useful marker of residual differentiated thyroid cancer.