M. Di Tommaso

Diffusion-weighted magnetic resonance for prediction of response after neoadjuvant chemoradiation therapy for locally advanced rectal cancer: preliminary results of a monoinstitutional prospective study.

PURPOSE To evaluate diffusion-weighted imaging (DWI) for assessment of treatment response in locally advanced rectal cancer (LARC) 8 weeks after neoadjuvant chemoradiotherapy (CRT). METHODS AND MATERIALS A total of 28 patients with LARC underwent magnetic resonance imaging (MRI) prior to and 8 weeks after CRT. Tumor volume (TV) was calculated on T2-weighted MRI scans as well as the apparent diffusion coefficient (ADC) was calculated using Echo-planar DWI-sequences. All data were correlated to surgical results and histopathologic tumor regression grade (TRG), according to Mandards classification. Post-treatment difference ADC (%ΔADC) and TV (%ΔTV) changes at 8 weeks were compared complete response (CR; TRG1) and non-complete response tumors (non-CR; TRG2-5). RESULTS The mean % ADC increase of CR group was significantly higher compared to non-CR group (77.2 ± 54.63% vs. 36.0 ± 29.44%; p = 0.05). Conversely, the mean % TV reduction did not significantly differ in CR group from non-CR group (73.7% vs. 63.77%; p = 0.21). Accordingly, the diagnostic accuracy of the mean % ADC increase to discriminate CR from non-CR group was significantly higher than that of the mean % TV reduction (0.913 vs. 0.658; p = 0.022). No correlation was found between mean % TV reduction and TRG (rho = 0.22; p = 0.3037), whereas a negative correlation between mean % ADC increase and TRG was recorded (r = -0.69; p = 0.006). CONCLUSION The mean % ADC increase appears to be a reliable tool to differentiate CR from non-CR after CRT in patients with LARC.

Interobserver variability of clinical target volume delineation in soft-tissue sarcomas

PURPOSE The present observational study reports the results of a multi-institutional dummy-run designed to estimate the consistency of interobserver variability in clinical target volume delineation in two different cases of soft-tissue sarcomas in which postoperative and preoperative radiotherapy were prescribed, respectively. The purpose of this work was to quantify interobserver variability in routine clinical practice. PATIENTS AND METHODS Two different cases of soft-tissues sarcomas were chosen: a case of postoperative and a case of preoperative radiation therapy. Participating centres were requested to delineate clinical target volumes according to their experience in both cases. Descriptive statistic was calculated for each variable (volume, diameters) separately for two cases. Box-whiskers plots were used for presentation of clinical target volume. A Shapiro-Wilks test was performed to evaluate the departures from normality distribution for each variable. The comparison between relative variations of diameters was evaluated using the Students t test. RESULTS Several variations affecting both volumes and diameters were observed. Main variations were observed in the craniocaudal and laterolateral diameters. Each case showed similar dispersion, indicating a lack of reproducibility in volumes definition. CONCLUSIONS This observational study highlighted that, in the absence of specific instructions or guidelines, the interobserver variability can be significant both in postoperative and preoperative radiotherapy of soft-tissue sarcomas.

Hippocampal sparing in stereotactic radiotherapy for brain metastases: To contour or not contour the hippocampus?

PURPOSE The aim of our study was to evaluate hippocampal irradiation in patients treated with fractionated stereotactic brain radiotherapy. PATIENTS AND METHODS Retrospective hippocampal dosimetric analysis performed on 22 patients with one to four brain metastases treated with fractionated stereotactic radiotherapy using volumetric intensity-modulated arc therapy. Original plans did not include hippocampus as avoidance structure in optimization criteria; hippocampus was retrospectively delineated on magnetic resonance coregistered with planning CT and using as reference the RTOG 0933 atlas. Hippocampus was defined both as a single and as pair organ. Constraints analysed were: Dmax<16Gy, D40%<7.3Gy, D100%=Dmin<9Gy. Assuming a α/β ratio of 2Gy, biologically equivalent dose in 2Gy fractions was calculated. Hippocampal-sparing plans were developed in cases where hippocampal constraints were not respected in the original plan. RESULTS Among constraints analysed Dmax and D40% have been exceeded in ten out of 22 cases. The constraints were not respected in patients with more than one metastatic lesion and in three patients with only one lesion. Considering all exceeded constraints values in non-hippocampal sparing plans, the 50% of them was respected after replanning. No significant differences were found among conformity and homogeneity index between non-hippocampal sparing and hippocampal sparing plans. CONCLUSION Volumetric intensity-modulated arc therapy hippocampal sparing plans significantly decreases dose to hippocampus assuring an equal target coverage and organs at risk avoiding.