Phosphaturic mesenchymal tumors: what an endocrinologist should know

Tumor-induced osteomalacia (TIO), also known as "oncogenic osteomalacia", is a rare cause of osteomalacia. TIO often has an insidious onset characterized clinically by progressive muscle weakness and bone pain with fractures. The hallmark biochemical finding is a persistent low serum phosphorus concentration due to renal phosphate wasting. The vast majority of cases of TIO result from production of the phosphaturic hormone fibroblast growth factor 23 (FGF23) by a histologically distinctive mesenchymal tumor, termed "phosphaturic mesenchymal tumor" (PMT). Circulating FGF23 induces internalization of renal sodium/phosphate co-transporters resulting in reduced proximal tubular phosphate reabsorption. FGF23 also inhibits production of 1α,25-dihydroxyvitamin D which is inappropriately low or normal in the context of hypophosphatemia. Diagnosis is often delayed owing to the rarity of the condition and an underappreciation for the role of phosphorus as a cause for the constellation of symptoms. Primary treatment for TIO is identification of the offending tumor and surgical removal. However, these tumors are notoriously difficult to find, precluding the opportunity for a curative surgery in many. In such cases, phosphate and calcitriol therapy is used to improve symptoms and heal the osteomalacia. Recently, molecular genetic studies have shown recurrent genetic events in PMT, including the novel fusions FN1-FGFR1 and less commonly FN1-FGF1. These fusion events are hypothesized to result in autocrine/paracrine signaling loops within the tumor, spurring tumorigenesis. This review will cover the clinical features, imaging characteristics, pathologic features, molecular genetic aspects, and therapy of PMT, with a brief discussion of other neoplasms that may cause TIO.

[Bone and calcium metabolism associated with malignancy. Tumor-induced osteomalacia.]

Tumor-induced osteomalacia(TIO)is a paraneoplastic syndrome caused by excessive production and secretion of fibroblast growth factor 23(FGF23)from causative tumors which induces hypophosphatemia and osteomalacia. Mesenchymal benign tumors in bone or soft tissue are the most frequent causes for TIO. The first choice treatment of TIO is complete resection of the responsible tumors. In patients whose tumors cannot be completely removed, phosphate salt and active vitamin D are usually prescribed. The effect of anti-FGF23 monoclonal antibody that inhibits the actions of FGF23 is being tested in clinical trials.

[Oncogenic osteomalacia. Report of two cases]

Oncogenic osteomalacia is a rare disease. It is caused by a tumor that produces fibroblast growth factor 23, a hormone that decreases the tubular phosphate reabsorption and impairs renal hydroxylation of vitamin D. This leads to hyperphosphaturia with hypophosphatemia and low calcitriol levels. About 337 cases have been reported and we studied two cases; 44 and 70 year-old men who sought medical attention complaining of suffering diffuse bone pain over a period of approximately one year. In both cases, a laboratory test showed biochemical alterations compatible with a hypophosphatemic osteomalacia. In the first case, a soft tissue tumor of the right foot was removed, one year after the diagnosis. The patient was allowed to diminish the phosphate intake, but symptoms reappeared at this time. Eight years later, a local recurrence of the tumor was noted. A complete excision was now performed. The patient was able to finally interrupt the phosphate intake. In the second case, an F-18 fluorodeoxyglucose positron emission tomography, with computed tomography revealed a 2.26 cm diameter hypermetabolic nodule in the soft tissue of the right forefoot. After its removal, the patient discontinued the phosphate intake. Both patients are asymptomatic and show a regular phosphocalcic laboratory evaluation. The histopathological diagnosis was, in both cases, a phosphaturic mesenchymal tumor, a mixed connective tissue variant. This is the prototypical variant of these tumors.

Comparative anticancer and antioxidant activities of different ingredients of Ginkgo biloba extract (EGb 761)

Flavonoid glycosides are the major constituents of Ginkgo biloba extract (EGb 761) and are well known to be an antioxidant for inhibiting tumor growth. Because it contains several flavonoid glycosides and other bioactive substances, the activities of EGb 761 against cancer in vivo and in vitro remain poorly understood. This situation prompted interest in the compounds for experimental study. We have investigated the anticancer effects of three analogues of EGb 761 samples on sarcoma 108 (S180)-bearing mice and leukemic 1210 (L1210) cell lines. We have also evaluated the changes of endogeneous antioxidant scavenging enzymes, including superoxide dismutase (SOD), glutathione (GST), lipid peroxidation (LPx), and catalase (CAT), in the blood of the S180-bearing mice. The EGb 761, EGb 761-H (containing mainly flavonoid aglycones and terpene trilactones), and EGb 761-DT-H (containing mainly flavonoid aglycones) samples exhibited cytotoxicity and inhibitory activity with IC (50) values of 46.36 +/- 2.43 microM, 10.27 +/- 0.88 microM, and 14.93 +/- 0.73 microM in L1210 cell-based assays, respectively. This resulted in 41.74 %, 60.72 %, and 63.76 % reductions in tumor weight after 10 days of treatment, respectively. In summary, the anticancer activity of EGb 761 can be improved by increasing the concentration of the aglycone form of the flavonoid. Terpene trilactones cannot exert the anticancer effects of flavonoids in vivo. Raising the levels of the free radical scavenger enzymes GST, SOD and CAT may be one of the involved anticancer mechanisms.

Impact of the smallest surgical margin on local control in soft tissue sarcoma

BACKGROUND

The aim was to review a single-institution experience of a prospective treatment protocol for soft tissue sarcoma of the extremity and trunk wall, with particular focus on the smallest surgical margin leading to local control.

METHODS

The study included 270 patients who had surgery for soft tissue sarcoma at Helsinki University Central Hospital between 1987 and 1997. Resection margins were measured prospectively from tumour specimens. Radiotherapy was administered if the smallest margin measured less than 2.5 cm, irrespective of tumour grade.

RESULTS

With a median follow-up of 6.6 years, the 5-year local control rate was 76.4 per cent. On multivariable analysis, the smallest surgical margin around the sarcoma (after radiotherapy) was prognostic for local control. A margin of at least 2.5 cm was associated with a local recurrence-free rate of 89.2 per cent at 5 years. Tumour size, depth or grade and patient's age had no independent prognostic effect on local control.

CONCLUSION

Surgical margin had independent prognostic value for local control. A surgical margin of 2-3 cm provided reasonable local control of soft tissue sarcoma, even without radiotherapy. Radiotherapy is recommended for smaller margins, irrespective of tumour grade.

Enhanced Susceptibility of Mouse Squamous Cell Carcinoma to Photodynamic Therapy Combined With Low-Dose Administration of Cisplatin

PURPOSE

We have investigated the antitumor effect of photodynamic therapy (PDT), using Photofrin as the photosensitizer, combined with low-dose cisplatin (CDDP) on NR-S1 mouse squamous cell carcinoma.

MATERIALS AND METHODS

CDDP (5 mg/kg body weight) was injected intraperitoneally either 1 hour or 3 hours prior to PDT or immediately afterward. Twenty-four hours after each protocol, the antitumor effects were evaluated by percentage area of the tumor necrosis in hematoxylin-eosin stained specimens as well as terminal deoxynucleotidyl transferase-mediated d-UTP nick-end labeling indices. Furthermore, the tumor sizes were evaluated at 3, 7, and 10 days after each protocol.

RESULTS

The antitumor effect of PDT was enhanced by administration of CDDP 3 hours before PDT, whereas the administration of CDDP 1 hour before PDT or immediately after PDT did not potentiate a PDT antitumor effect.

CONCLUSION

Administration of low-dose CDDP 3 hours before PDT appears to be a useful treatment modality.

[Gastrointestinal stromal tumors: a broad clinical spectrum from incidental -discovery to acute gastrointestinal bleeding]

Three cases of gastrointestinal stromal tumors (GIST) are reported as typical examples of the broad clinical spectrum in which these rare tumors can be detected. The first case describes an 82-year-old patient with a hemorrhagic shock due to upper gastrointestinal bleeding from a GIST of the stomach. GIST most frequently present with either gastrointestinal bleeding, abdominal pain or a detectable mass on physical examination or by ultrasound imaging. Clinically asymptomatic tumor growth also occurs as demonstrated by the second case of a 44-year-old -woman with an incidental finding of GIST during surgery of the esophagus. The cases are used to discuss the consequences for therapy and prognosis resulting from the heterogeneity of this tumor entity; the relevant immunohistochemical markers used to distinguish between various tumor subtypes of gastrointestinal mesenchymal tumors (GIMT) are listed. Since gastrointestinal stromal tumors (GIST) represent the most common subgroup of GIMT, we focus on the clinicopathological prognostic factors of GIST. The third case of a 40-year-old patient with a malignant GIST recurrence after surgery and exhibiting secondary resistance after one year of successful therapy with the receptor tyrosine kinase inhibitor imatinib (Gleevec), antagonizing pathogenetically relevant constitutive c-KIT activation, illustrates the potential and limitations of the only effective drug treatment for advanced GIST.

Treatment with STI571, a tyrosine kinase inhibitor, for gastrointestinal stromal tumor with peritoneal dissemination and multiple liver metastases

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are usually refractory to standard chemotherapeutic agents. We successfully treated a patient with a tyrosine kinase inhibitor (STI571) for GIST with peritoneal dissemination and liver metastases.

METHODS

In a 32-year-old man presenting with abdominal pain from diffuse peritonitis, a GIST and associated perforated small intestine were resected. Multiple liver metastases were present. After therapies with microwave coagulation, ethanol injection, and local and systemic antineoplastic drugs (fluorouracil, cisplatin, tegafur-uracil, and tegafur) failed, investigational treatment with a tyrosine kinase inhibitor was initiated (STI571, 300 mg, p.o. daily).

RESULTS

Anorexia and abdominal fullness resolved within a few days. At 24 days after initiation, positron emission tomography showed a remarkable decrease in the abdominal uptake of [18F] fluorodeoxyglucose. Adverse effects of STI571, including mild alopecia and anemia, were minimal.

CONCLUSIONS

The tyrosine kinase inhibitor STI571 may be effective against GISTs.

Identification and treatment of chemoresistant inoperable or metastatic GIST: experience with the selective tyrosine kinase inhibitor imatinib mesylate (STI571)

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. The concept of GIST and the definition of GIST pathology have evolved greatly over the past 5 years. GIST has been shown to share immunohistochemical, ultrastructural and histogenic similarities with the interstitial cells of Cajal. Both GIST and the interstitial cells of Cajal express KIT, the receptor tyrosine kinase that is the protein product of the c-kit proto-oncogene. KIT is universally phosphorylated in GISTs. Sequencing of c-kit complementary DNA from human GIST cells has demonstrated a high frequency of mutations that lead to constitutive activation of the KIT tyrosine kinase in the absence of stimulation by its physiologic ligand (stem cell factor). This, in turn, causes uncontrolled stimulation of downstream signaling cascades with aberrant cellular proliferation and resistance to apoptosis. Historically, malignant GIST has been highly refractory to conventional cytotoxic therapy. Signal transduction inhibition as cancer therapy was first tested successfully with imatinib mesylate (formerly known as STI571), a selective small-molecule tyrosine kinase inhibitor, with the initial target being blockade of Bcr-Abl, the oncogene with tyrosine kinase activity responsible for the pathogenesis of chronic myelogenous leukemia (CML). Imatinib was subsequently shown to block activity of the KIT tyrosine kinase as well, and in laboratory studies this led to apoptotic death of GIST cells. The first GIST patient to receive imatinib exhibited dramatic benefit despite far-advanced metastatic disease that was previously refractory to all chemotherapy. Subsequently, multicenter clinical trials have been performed to assess the safety, efficacy and biologic activity of imatinib in patients with advanced GIST. The results from these studies have established imatinib as an effective new therapeutic alternative for the majority of patients with advanced GIST, a solid tumor for which no prior chemotherapy has ever shown antitumor efficacy. This work provides proof of concept to the hypothesis that selective inhibition of aberrant signal transduction can provide important anticancer activity, if the proper signaling pathways are identified and blocked.

Overview of issues related to imatinib therapy of advanced gastrointestinal stromal tumors: a discussion among the experts

Information regarding the activity of imatinib in patients with metastatic gastrointestinal stromal tumors (GISTs) has accumulated rapidly. Nevertheless, several important issues about imatinib therapy as well as these tumors themselves remain to be answered. Importantly, the optimal dose and duration of imatinib therapy are unknown, with daily doses of 400 mg and 600 mg producing comparable response rates in a phase II study. Moreover, the role of surgery following maximal responses to imatinib and those of functional imaging and use of biopsies in monitoring treatment responses need to be investigated. Further understanding of the molecular and pathologic characteristics of GISTs that are responsive or resistant to imatinib is also needed. This paper summarizes a symposium that was held in Helsinki, Finland, in September 2001.

Update of phase I study of imatinib (STI571) in advanced soft tissue sarcomas and gastrointestinal stromal tumors: a report of the EORTC Soft Tissue and Bone Sarcoma Group

In a phase I study conducted by the EORTC Soft Tissue and Bone Sarcoma Group, 40 patients with advanced soft tissue sarcomas, most of whom had gastrointestinal stromal tumors (GISTs), received imatinib at doses of 400 mg q.d., 300 mg b.i.d., 400 mg b.i.d., or 500 mg b.i.d. Dose-limiting toxicities, including severe nausea, vomiting, edema and rash, were seen at the highest dose level; the maximum tolerated dose was therefore 400 mg b.i.d. Imatinib was active in the group of 35 patients with GISTs, producing partial responses in 19 (54%) patients and stable disease in 13 patients (37%). Responding patients have now been followed for a minimum of 10 months. The most common side effects seen in patients continuing on therapy have been periorbital edema (40%), peripheral edema (37.5%), fatigue (30%), skin rash (30%) and nausea/vomiting (25%). Severe late myelosuppression has also been seen occasionally. Eighteen (51%) GIST patients continue to have partial responses and 11 (31%) continue with stable disease. Thus, 82% of patients with GISTs are still obtaining clinically important benefits with continued imatinib therapy. Some patients showed accelerated progressive disease shortly after starting imatinib. On the other hand, following drug withdrawal, 2 patients had reductions in tumor burden and remain alive without drug therapy. In summary, imatinib is generally well tolerated and has significant activity during long-term treatment of patients with advanced GISTs.

Use of positron emission tomography in oncology and its potential role to assess response to imatinib mesylate therapy in gastrointestinal stromal tumors (GISTs)

The reliability of established anatomical imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), is compromised in following response to certain types of treatment if metabolic improvement occurs before morphologic change is apparent. Thus, traditional imaging techniques cannot discriminate early tumor response because they are based on purely visual structural assessments. Recently, the use of positron emission tomography (PET), most commonly employing the radiotracer 18F-fluoro-2-deoxy-D-glucose (FDG), has been shown to improve the assessment of tumor behavior by highlighting early functional changes in tumor glucose metabolism that appear to correlate closely with metabolic tumor response to imatinib mesylate. Like CT and MRI, PET can identify an abnormal mass; its improvement over these techniques lies in its ability to differentiate active tumor from necrosing tissue, malignant from benign tissue, and recurrent tumor from scar tissue. Understanding and using this tool should improve our ability to accurately follow response in GIST patients treated with imatinib mesylate, and permit this new therapeutic approach to be used optimally with accurate follow-up assessments and informed therapeutic decision-making.

Pharmacology of imatinib (STI571)

Deregulation of protein kinase activity has been shown to play a central role in the pathogenesis of human cancer. The molecular pathogenesis of chronic myelogenous leukemia (CML) in particular, depends on formation of the bcr-abl oncogene, leading to constitutive expression of the tyrosine kinase fusion protein, Bcr-Abl. Based on these observations, imatinib was developed as a specific inhibitor for the Bcr-Abl protein tyrosine kinase. The expanding understanding of the basis of imatinib-mediated tyrosine kinase inhibition has revealed a spectrum of potential new antitumor applications beyond the powerful activity already reported in the treatment of CML. Imatinib has shown activity in vivo against PDGF-driven tumor models including glioblastoma, dermatofibrosarcoma protuberans and chronic myelomonocytic leukemia. Antiangiogenic effects have been demonstrated by inhibition of PDGF-, VEGF (vascular endothelial growth factor)- and bFGF- (basic fibroblast growth factor) induced angiogenesis in vivo, and by inhibition of angiogenesis and tumor growth in an experimental bone metastasis model. Imatinib has been shown to reduce interstitial fluid pressure in an experimental colonic carcinoma model by blocking PDGF-mediated effects on tumor-associated blood vessels and stromal tissue. It is also a potent inhibitor of the Kit receptor tyrosine kinase, and has demonstrated activity clinically against the Kit-driven gastrointestinal stromal tumor (GIST) and experimentally in small-cell lung cancer cell lines. The pharmacology of imatinib and its activity in various tumor models is discussed.

Effect of the cytokine rhTNF-alpha on the population of mast cells in the growth of MethA fibrosarcoma--a TEM study

The aim of the present study was the ultrastructural characteristics of mast cell (MC) involved in host antitumor responses induced by local (i.t.) administration of recombinant human tumor necrosis factor alpha (rhTNF-alpha) in the primary focus of methA fibrosarcoma. MC were involved in tumor interstitium remodeling. Numerous mitochondria, well-developed RER and Golgi apparatus, clusters of polyribosomes, considerable polymorphism of granules and differentiated lamellar structures which frequently presented myelinic forms were observed after rhTNF-alpha application. In the study numerous fibres of the fibrous tissue, richly vascularized, occurred in the peripheral and intermediate tumor zones. Cluster of MC and tumor cells were seen on the border of the necrotic foci. However, proteolytic enzymes released by MC cause interstitial lysis, ensuring the place for tumor growth, and are involved in angiogenesis. Thus, it is not clear whether MC contribute to the inhibition of tumor growth or have an adjunctive role in tumor progression.

Papular elastorrhexis in childhood improved by intralesional injections of triamcinolone

Papular elastorrhexis is a rare disease developing asymptomatic skin-colored small papules in adolescence with histopathological loss of elastic fibers. There has been no established treatment for this disease. A 4-year-old Korean boy had multiple, hard, whitish papules on his chest and back for one year. Histopathologic examination revealed focal loss of elastic fibers in the dermis, and X-ray examination showed no bony abnormalities. His skin lesions were improved by intralesional injections of triamcinolone but recurred after four months.

The role of radiation therapy in the treatment of solitary plasmacytomas

Between 1960 and 1985, 30 patients with solitary plasmacytomas were treated with radiotherapy at the University of Iowa: 13 patients with extramedullary plasmacytomas (EMP) and 17 with solitary plasmacytomas of bone (SPB). The local control rates were 92% for patients with EMP and 88% for those with SPB. Two of nine patients (22%) with EMP treated to the primary tumor only developed regional lymph node metastasis, indicating the need for elective irradiation of this area. The most common pattern of failure in both groups was progression to multiple myeloma. This occurred in 23% of the patients with EMP and 53% of those with SPB. The time course of progression to multiple myeloma differed for the two groups. All of those who progressed to multiple myeloma in the EMP group did so within 2 years, whereas a significant number of those in the SPB group progressed more than 5 years after initial therapy. None of five patients who received adjuvant chemotherapy in the SPB group progressed to multiple myeloma, compared to 75% (9/12) of the patients who did not receive chemotherapy.