Recurrence patterns of pancreatic cancer treated with adjuvant intensity modulated radiotherapy

The aim of this study was to investigate the recurrence patterns in pancreatic cancer patients treated with adjuvant intensity modulated radiotherapy (IMRT) and to correlate the sites of locoregional recurrence with radiotherapy target volumes.

Thirty-eight patients who had undergone resection and adjuvant chemoradiation for pancreatic cancer were evaluated. Radiotherapy (RT) was started after 1-3 cycles of adjuvant chemotherapy (CHT). Clinical target volume (CTV) was contoured according to the RTOG guideline. All patients were treated with IMRT with a dose of 45-50.4 Gy. Computerized tomography (CT) images at the time of recurrence were correlated with radiotherapy plans. Locoregional recurrences were classified as in-field, out-field and marginal.

Median overall survival (OS) was 19 months. One- and 2-year OS rates were 73.6% and 37.1%, respectively. Locoregional recurrence and distant metastases were observed in 11 (28.9%) and 23 (60.5%) patients, respectively. For the 11 locoregional recurrences, 7 were in-field, 1 was marginal, and 3 were out-of-field. One patient had isolated local, 2 patients had isolated regional and 15 (57.6%) patients had only distant failures. The first presentations of failures were mostly distant (58%). On multivariate analysis, tumor size ≥ 3 cm (p = 0.011) and positive vascular invasion (p = 0.014) predicted for worse OS rate.

The majority of locoregional recurrences were in the radiation field among pancreatic cancer patients treated with postoperative IMRT. However, failures were predominantly distant, and improvement of systemic control may be of particular interest.