Dosimetric comparison of doses to organs at risk using 3-D conformal radiotherapy versus intensity modulated radiotherapy in postoperative radiotherapy of periampullary cancers: implications for radiation dose escalation

Adjuvant chemoradiation in pancreatic cancer: impact of radiotherapy dose on survival

BACKGROUND

To evaluate the impact of radiation dose on overall survival (OS) in patients treated with adjuvant chemoradiation (CRT) for pancreatic ductal adenocarcinoma (PDAC).

METHODS

A multicenter retrospective analysis on 514 patients with PDAC (T1-4; N0-1; M0) treated with surgical resection with macroscopically negative margins (R0-1) followed by adjuvant CRT was performed. Patients were stratified into 4 groups based on radiotherapy doses (group 1: < 45 Gy, group 2: ≥ 45 and < 50 Gy, group 3: ≥ 50 and < 55 Gy, group 4: ≥ 55 Gy). Adjuvant chemotherapy was prescribed to 141 patients. Survival functions were plotted using the Kaplan-Meier method and compared through the log-rank test.

RESULTS

Median follow-up was 35 months (range: 3-120 months). At univariate analysis, a worse OS was recorded in patients with higher preoperative Ca 19.9 levels (≥ 90 U/ml; p < 0.001), higher tumor grade (G3-4, p = 0.004), R1 resection (p = 0.004), higher pT stage (pT3-4, p = 0.002) and positive nodes (p < 0.001). Furthermore, patients receiving increasing doses of CRT showed a significantly improved OS. In groups 1, 2, 3, and 4, median OS was 13.0 months, 21.0 months, 22.0 months, and 28.0 months, respectively (p = 0.004). The significant impact of higher dose was confirmed by multivariate analysis.

CONCLUSIONS

Increasing doses of CRT seems to favorably impact on OS in adjuvant setting. The conflicting results of randomized trials on adjuvant CRT in PDAC could be due to < 45 Gy dose generally used.

Impact of radiation dose in postoperative radiotherapy after R1 resection for extrahepatic bile duct cancer: long term results from a single institution

Purpose

This study was conducted to evaluate the impact of radiation dose after margin involved resection in patients with extrahepatic bile duct cancer.

Methods

Among the 251 patients who underwent curative resection followed by adjuvant chemoradiotherapy, 86 patients had either invasive carcinoma (n = 63) or carcinoma in situ (n = 23) at the resected margin. Among them, 54 patients received conventional radiation dose (40-50.4 Gy) and 32 patients received escalated radiation dose (54-56 Gy).

Results

Escalated radiation dose was associated with improved locoregional control (5yr rate, 73.8% vs. 47.1%, p = 0.069), but not disease-free survival (5yr rate, 43.4% vs. 32.6%, p = 0.490) and overall survival (5yr rate, 40.6% vs. 29.6%, p = 0.348). In multivariate analysis for locoregional control, invasive carcinoma at the margin (HR 2.957, p = 0.032) and escalated radiation dose (HR 0.394, p = 0.047) were independent prognostic factors. No additional gastrointestinal toxicity was observed in escalated dose group.

Conclusions

Delivery of radiation dose ≥ 54 Gy was well tolerated and associated with improved locoregional control, but not with overall survival after margin involved resection. Further validation study is warranted.

The impact of positron emission tomography on primary tumour delineation and dosimetric outcome in intensity modulated radiotherapy of early T-stage nasopharyngeal carcinoma

Background

In intensity modulated radiotherapy (IMRT) of nasopharyngeal carcinoma (NPC), accurate delineation of the gross tumour volume (GTV) is important. Image registration of CT and MRI has been routinely used in treatment planning. With recent development of positron emission tomography (PET), the aims of this study were to evaluate the impact of PET on GTV delineation and dosimetric outcome in IMRT of early stage NPC patients.

Methods

Twenty NPC patients with T1 or T2 disease treated by IMRT were recruited. For each patient, 2 sets of NP GTVs were delineated separately, in which one set was performed using CT and MRI registration only (GTV_CM), while the other set was carried out using PET, CT and MRI information (GTV_CMP). A 9-field IMRT plan was computed based on the target volumes generated from CT and MRI (PTV_CM). To assess the geometric difference between the GTV_CM and GTV_CMP, GTV volumes and DICE similarity coefficient (DSC), which measured the geometrical similarity between the two GTVs, were recorded. To evaluate the dosimetric impact, the D_max, D_min, D_mean and D₉₅ of PTVs were obtained from their dose volume histograms generated by the treatment planning system.

Results

The overall mean volume of GTV_CMP was greater than GTV_CM by 4.4 %, in which GTV_CMP was slightly greater in the T1 group but lower in the T2 group. The mean DSC of the whole group was 0.79 ± 0.05. Similar mean DSC values were also obtained from the T1 and T2 groups separately. The dosimetric parameters of PTV_CM fulfilled the planning requirements. When applying this plan to the PTV_CMP, the average D_min (56.9 Gy) and D₉₅ (68.6 Gy) of PTV_CMP failed to meet the dose requirements and demonstrated significant differences from the PTV_CM (p = 0.001 and 0.016 respectively), whereas the doses to GTV_CMP did not show significant difference with the GTV_CM.

Conclusion

In IMRT of early stage NPC, PET was an important imaging modality in radiotherapy planning so as to avoid underdosing the PTV, although its effect on GTV delineation was not significant. It was recommended that PET images should be included in the treatment planning of NPC patients.