Diagnostic and Clinical Impact of 18F-FDG PET/CT in Staging and Restaging Soft-Tissue Sarcomas of the Extremities and Trunk: Mono-Institutional Retrospective Study of a Sarcoma Referral Center.

BACKGROUND: Soft-tissue sarcomas (STS) represent a wide heterogeneous class of rare tumors. The exact role 18F-fluorodeoxyglucose positron emission/computed tomography (18F-FDG PET/CT) in the evaluation of STS is not well established. The aim of the present study was to evaluate how the use of 18F-FDG PET/CT in STS could influence patient therapy planning, looking for a possible added value over computed tomography and magnetic resonance imaging-the most used modalities in the study of STS. Differences in SUVmax according to histologic subtype and tumor grade were also considered. METHODS: a total of 345 consecutive 18F-FDG PET/CT scans performed for initial staging (n = 171) or for suspected disease relapse (n = 174) in 282 patients with STS extracted from the local Information System database were retrospectively reviewed. RESULTS: 18F-FDG PET/CT altered therapy planning in 80 cases (16.4% for staging and 29.9% in restaging), both for disease upstaging (58.8%) and downstaging (41.2%) Conclusions: 18F-FDG PET/CT could significantly influence management of patients with STS, particularly for restaging.

Relationships between rectal wall dose-volume constraints and radiobiologic indices of toxicity for patients with prostate cancer.

PURPOSE: The purpose of this article was to investigate how exceeding specified rectal wall dose-volume constraints impacts on the risk of late rectal bleeding by using radiobiologic calculations. METHODS AND MATERIALS: Dose-volume histograms (DVH) of the rectal wall of 250 patients with prostate cancer were analyzed. All patients were treated by three-dimensional conformal radiation therapy, receiving mean target doses of 80 Gy. To study the main features of the patient population, the average and the standard deviation of the distribution of DVHs were generated. The mean dose , generalized equivalent uniform dose formulation (gEUD), modified equivalent uniform dose formulation (mEUD)(0), and normal tissue complication probability (NTCP) distributions were also produced. The DVHs set was then binned into eight classes on the basis of the exceeding or the fulfilling of three dose-volume constraints: V(40) = 60%, V(50) = 50%, and V(70) = 25%. Comparisons were made between them by , gEUD, mEUD(0), and NTCP. RESULTS: The radiobiologic calculations suggest that late rectal toxicity is mostly influenced by V(70). The gEUD and mEUD(0) are risk factors of toxicity always concordant with NTCP, inside each DVH class. The mean dose, although a reliable index, may be misleading in critical situations. CONCLUSIONS: Both in three-dimensional conformal radiation therapy and particularly in intensity-modulated radiation therapy, it should be known what the relative importance of each specified dose-volume constraint is for each organ at risk. This requires a greater awareness of radiobiologic properties of tissues and radiobiologic indices may help to gradually become aware of this issue.

A study of the effect of setup errors and organ motion on prostate cancer treatment with IMRT.

PURPOSE: To assess the influence of setup errors and organ motion in terms of the probability of tumor control and normal-tissue complications by tumor control probability and normal-tissue complication probability. METHODS AND MATERIALS: Twelve patients were treated for prostate cancer with intensity-modulated radiation therapy. Two orthogonal portal images were taken daily. All patients underwent three computed tomography scans during the 8-week treatment time (i.e., baseline, intermediate, and final). The original treatment plans were re-evaluated, taking into account setup errors and organ motion. RESULTS: The mean shifts +/- standard deviation of the whole patient population in the lateral, anterior-posterior, and craniocaudal direction were 1.0 +/- 1.5 mm, 0.9 +/- 2.1 mm, and 1.9 +/- 2.1 mm, respectively. In most of the recalculated dose-volume histograms, the coverage of clinical target volume was granted despite organ motion, whereas the rectal wall histograms were often very different from the planned ones. CONCLUSION: We have studied the impact of prostate and rectum motion, as well as setup errors, on dose-volume histograms. The estimate of these effects may have implications for predictive indications when planning intensity-modulated radiation therapy treatments on prostate.

Modeling of alpha/beta for late rectal toxicity from a randomized phase II study: conventional versus hypofractionated scheme for localized prostate cancer.

BACKGROUND: Recently, the use of hypo-fractionated treatment schemes for the prostate cancer has been encouraged due to the fact that alpha/beta ratio for prostate cancer should be low. However a major concern on the use of hypofractionation is the late rectal toxicity, it is important to be able to predict the risk of toxicity for alternative treatment schemes, with the best accuracy. The main purpose of this study is to evaluate the response of rectum wall to changes in fractionation and to quantify the alpha/beta ratio for late rectal toxicity METHODS: 162 patients with localized prostate cancer, treated with conformal radiotherapy, were enrolled in a phase II randomized trial. The patients were randomly assigned to 80 Gy in 40 fractions over 8 weeks (arm A) or 62 Gy in 20 fractions over 5 weeks (arm B). The median follow-up was 30 months. The late rectal toxicity was evaluated using the Radiation Therapy Oncology Group (RTOG) scale. It was assumed >or= Grade 2 (G2) toxicity incidence as primary end point. Fit of toxicity incidence by the Lyman-Burman-Kutcher (LKB) model was performed. RESULTS: The crude incidence of late rectal toxicity >or= G2 was 14% and 12% for the standard arm and the hypofractionated arm, respectively. The crude incidence of late rectal toxicity >or= G2 was 14.0% and 12.3% for the arm A and B, respectively. For the arm A, volumes receiving >or= 50 Gy (V50) and 70 Gy (V70) were 38.3 +/- 7.5% and 23.4 +/- 5.5%; for arm B, V38 and V54 were 40.9 +/- 6.8% and 24.5 +/- 4.4%. An alpha/beta ratio for late rectal toxicity very close to 3 Gy was found. CONCLUSION: The >or= G2 late toxicities in both arms were comparable, indicating the feasibility of hypofractionated regimes in prostate cancer. An alpha/beta ratio for late rectal toxicity very close to 3 Gy was found.