Image-Guided-Radiotherapy Retreatment of Spine Metastasis: A Case Report and Radiobiological Evaluation

Aims and background

The present case report describes vertebral metastasis retreatment using kilovoltage cone-beam computed tomography (CBCT) for setup error correction, in order to improve target irradiation and prevent spinal cord toxicity. We evaluated the feasibility of the second radiation therapy course on the overlapping treatment volume.

Methods and study design

A patient with metastatic kidney cancer, previously treated to the tenth dorsal vertebra with conventional radiation planning (21 Gy; 3 × 7 Gy), underwent retreatment. In order to deliver 30 Gy (15 × 2 Gy) to the target volume with the second irradiation, we evaluated the residual dose that could be received by the spinal cord. We calculated the biologically effective dose according to the linear-quadratic model, using an α/β ratio of 2 Gy. A 3-dimensional conformal plan was generated; CBCT imaging was used to ensure accurate repositioning.

Results

A total of 15 CBCT scans were performed; the mean setup corrections in the lateral, longitudinal and vertical directions were 3.38 mm (SD 2.09; range, −0.2 mm ÷ 7.6 mm), 2.13 mm (SD 3.38; range, −5.9 mm ÷ 6 mm), and −1.28 mm (SD 2.02; range, −7.1 mm ÷ 0.3 mm), respectively.

Conclusion

Image-guided radiotherapy is an alternative approach for the retreatment of spine tumors; it ensures accurate patient setup correction and high-precision treatment delivery, which are required for target volumes very close to critical structures. Free full text available at www.tumorionline.it

The time factor in oncology: consequences on tumour volume and therapeutic planning

The rules that govern tumour treatment depend largely on clinical stage (tumour volume, localization and/or metastasis presence). These rules are applied assuming that tumor growth is relatively static without considering the time factor, the number of clonogenic cells in the tumour or the volume reduction following initial cytotoxic therapy. Time and neoplastic growth (with a subsequent change in volume) are generally not considered in 90% of clinical trials, where chemotherapy is administered on the first and eighth day and radiotherapy is carried out five days a week with different schedules. In the clinical situation, however, a tumour has more complex growth times that should be appropriately assessed to improve the treatment results (1). The aim of this paper is to stress the influence of the time factor to optimize the schedule of the cytotoxic therapies, based on different mathematical models developed to describe the tumour growth. To better understand the role of the neoplastic growth at its different clinical stages and the subsequent response to cytotoxic therapies, several elements concerning such growth should be thoroughly analyzed.

Pharmacokinetics of 2-(alpha-thenoylthio)-propionylglycine (TTPG) in healthy volunteers--an oral dose-proportionality investigation

The dose linearity of 2-(alpha-thenoylthio)-propionylglycine (TTPG) pharmacokinetics after a single oral administration at three different TTPG doses (180, 540 and 1080 mg) was evaluated in 12 healthy volunteers according to an open, randomized, cross-over study with a 1-week wash-out period between each administration. The duration of the study, for each subject, was 4 weeks. Plasma concentration and urinary excretion of TTPG and its two systemic metabolites, namely propionylglycine (tiopronin) and thiophenecarboxylic acid (TCA) were assayed by a previously well validated HPLC method. Due to differences in the physical and chemical properties of these compounds, two assays were needed, one to measure TTPG and TCA as such, and one to measure derivatized tiopronin. Both used UV detection. TTPG, tiopronin and TCA were quickly detected in plasma, suggesting that the drug administered is rapidly absorbed and biotransformed, in part, in the systemic circulation into the two metabolites noted above. Time-to-peak for all three analytes showed a trend to increase with increasing doses of TTPG, being: 0.42, 0.40 and 0.67 h (P < 0.01) with TTPG; 0.53, 0.47 and 0.73 h (P < 0.05) with TCA; and 1.33, 2.13 and 2.58 h (P < 0.01) with tiopronin. Cmax showed the opposite behaviour with values (ng ml-1) normalized to the dose of 540 mg: 1235, 905 and 513 (P < 0.001) with TTPG; 888, 547 and 383 (P < 0.001) with TCA; and 7290, 6950 and 5170 (P < 0.01) with tiopronin.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcription of N-myc and proliferation-related genes is linked in human neuroblastoma

A definite association between the transcription of N-myc oncogene and proliferation-related genes, histone H3, c-myc and p53, was found in a set of 12 primary untreated neuroblastomas and a metastasis of one of these at relapse. Molecular analysis allowed us to discriminate between actually proliferating and non-proliferating tumors, and suggested a link between N-myc and proliferation. Flow cytometric analysis of DNA distribution was less reliable for assessing tumor proliferative activity. Our data also seem to indicate a down-regulation of c-myc by N-myc in human neuroblastoma.