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BackgroundAn observational multi-institutional study has been conducted aimed to evaluate the inter-observer variability in clinical target volume (CTV) delineation among different radiation oncologists in radiotherapy treatment of pancreatic cancer.MethodsA multi-institutional contouring dummy-run of two different cases of pancreatic cancer treated by postoperative and preoperative radiotherapy (RT) was performed. Clinical history, diagnostics, and planning CT imaging were available on AIRO website (http://www.radioterapiaitalia.it). Participants were requested to delineate CTVs according to their skills and knowledge. Aiming to quantify interobserver variability of CTVs delineations, the total volume, craniocaudal, laterolateral, and anteroposterior diameters were calculated. Descriptive statistic was calculated. The 95% Confidence Interval (95% CI) for coefficient of variation (CV) was estimated. The Dice Similarity Index (DSI) was used to evaluate the spatial overlap accuracy of the different CTVs compared with the CTVs of a national reference Centre considered as a benchmark. The mean DSI (mDSI) was calculated and reported.ResultsA total of 18 radiation oncologists from different Institutes submitted the targets. Less variability was observed for the Elective CTV rather than the Boost CTV, in both cases. The estimated CV were 28.8% (95% CI: 21.2 - 45.0%) and 20.0% (95% CI: 14.9 - 30.6%) for the Elective CTV, in adjuvant (Case 1) and neoadjuvant (Case 2) case, respectively. The mDSI value was 0.68 for the Elective CTVs in both cases (range 0.19 - 0.79 in postoperative vs range 0.35 - 0.79 in preoperative case). The mDSI was increased to 0.71 (Case 1) and 0.72 (Case 2) if the observers with a worse agreement have been excluded. On the other hand, a CV of 42.4% (95% CI: 30.1 - 72.4%) and 63.8% (95% CI: 43.9 - 119.2%) with a mDSI value of 0.44 and 0.52, were calculated for the Boost CTV in Case 1 and Case 2, respectively.ConclusionsThe CV and mDSI obtained values for Elective CTVs showed an acceptable agreement among participants either in postoperative as well in preoperative setting. Additional strategies to reduce the variability in Boost CTV delineation need to be found and promoted.

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n Abstract: We examined the effect of delaying radiation treatment after conservative surgery on the risk of breast cancer local recurrence (LR). From January 1997 to December 2001, 969 women with early-stage breast cancer were treated at the Radiation Oncology Department in Chieti. We analyzed 802 of them who underwent conservative surgery followed by whole-breast radiotherapy. The patients were divided into two groups: women who did not receive chemotherapy and women who received chemotherapy. The time intervals from surgery to breast irradiation used for the analysis were <16 or more weeks for no-chemotherapy-treated women, and <25 and 25 or more weeks for chemotherapy-treated women. The relationship between LR and factors such as age, tumor size, margin status, and surgery-radiotherapy time interval was evaluated. The 8-year LR risk was estimated using the Kaplan-Meier method. LR was observed in 33 (4.1%) of the 802 patients. The overall 8-year LR risk was 6.5% (±1.51). In the no-chemotherapy group, the risk of LR was associated with a younger age and a positive margin status. In the chemotherapy group LR was associated with a younger age and a tumor size >3 cm. Surgery-radiotherapy interval was not associated with LR in both groups of patients. Delay in the start of radiotherapy does not increase the risk of LR in patients with early breast cancer treated or not treated with chemotherapy. n

ΔADC at 2 weeks after the beginning of CRT is a reliable tool to early assess treatment response.