Clinical evaluation of intensity-modulated radiotherapy for locally advanced pancreatic cancer

Yoko Goto, Akira Nakamura, Ryo Ashida, Katsuyuki Sakanaka, Satoshi Itasaka, Keiko Shibuya, Shigemi Matsumoto, Masashi Kanai, Hiroyoshi Isoda, Toshihiko Masui, Yuzo Kodama, Kyoichi Takaori, Masahiro Hiraoka, Takashi Mizowaki

The purpose was to retrospectively evaluate the effect of intensity-modulated radiotherapy (IMRT) on gastrointestinal (GI) toxicities and outcomes compared to three-dimensional conformal radiotherapy (3DCRT) for locally advanced pancreatic cancer (LAPC). We included 107 consecutive patients who underwent CRT for LAPC from September 2001 to March 2015; 80 patients underwent 3DCRT and 27 patients underwent IMRT. They were compared for GI toxicities, locoregional progression free survival (LRPFS), distant metastasis free survival (DMS), and overall survival (OS). Median radiation dose and fractions for 3DCRT and IMRT were 54 Gy/30 fr. and 48 Gy/15 fr. The regimens of CRT consisted of weekly gemcitabine 250 mg/m2 (for 3DCRT) or 1000 mg/m2 (for IMRT). Acute GI toxicity ≥grade 2 occurred in 32 patients (40%) treated with 3DCRT compared with five patients (19%) treated with IMRT. Late GI toxicity of grade 3 occurred in 10 patients (12%) treated with 3DCRT and one patient (4%) treated with IMRT. Patients who underwent IMRT had superior 1-year LRPFS (73.1% vs. 63.2%, p = 0.035) and 1-year OS (92.3% vs. 68.2%, p = 0.037) as compared with those treated with 3DCRT. Multivariate analysis showed that in IMRT patients, higher dose (≥45 Gy) was an independent factor for better LRPFS and OS. LAPC patients treated with hypofractionated full-dose gemcitabine IMRT had improved OS and LRPFS without increased GI toxicities when compared to those of patients treated with conventionally fractionated low dose gemcitabine 3DCRT. In IMRT patients, higher dose was an independent favorable prognostic factor for better LRPFS and OS, which suggests that dose escalation with IMRT for LAPC is a promising strategy.