The efficiency of 18F-FDG-PET/CT in the assessment of tumor response to preoperative chemoradiation therapy for locally recurrent rectal cancer

Mamoru Uemura,Rio Handa,Masataka Ikeda,Hirofumi Yamamoto,Ichiro Takemasa,Taishi Hata,Mitsugu Sekimoto,Yuichiro Doki,Tsunekazu Mizushima,Hidetoshi Eguchi,Katsuki Danno,Junichi Nishimura

doi:10.1186/s12885-021-08873-7

Abstract

BackgroundLocally recurrent rectal cancer (LRRC) remains a major problem after curative resection of primary rectal cancer. A noninvasive, prognostic biomarker with which to accurately evaluate disease status and assess the treatment response is critically needed to optimize treatment plans. This study assesses the effectiveness of PET/CT evaluation of preoperative chemoradiation therapy (CRT) in patients with LRRC.MethodsSince 2004, we have been performing preoperative CRT to improve local tumor control and survival. Between 2004 and 2013, 40 patients with LRRC underwent preoperative CRT (radiation: 50 Gy/25 fractions; chemotherapy: irinotecan plus UFT [tegafur and uracil]/leucovorin) and radical surgery, and underwent 18F-FDG-PET/CT before and 3 weeks after the completion of CRT. The maximum standardized uptake values (SUVmax) of the pre-CRT scan (Pre-SUV) and the post-CRT scan (Post-SUV) were measured. The predictive value of the 18F-FDG-PET and CT/MRI response assessments was evaluated.ResultsThe mean Pre-SUV was significantly higher than the Post-SUV (8.2 ± 6.1, vs. 3.8 ± 4.0; P < 0.0001). Following CRT, 17/40 patients (42.5%) were classified as responders according to the Mandard tumor regression grade (TRG1–2). The mean Post-SUV was significantly lower in responders than in nonresponders (2.0 ± 1.7 vs. 5.1 ± 3.9; P = 0.0038). Pathological response was not correlated with the response as evaluated by CT (P > 0.9999) or MRI (P > 0.9999). Multivariate regression analysis identified Post-SUV as an independent predictor of local re-recurrence-free survival (P = 0.0383) and for overall survival (P = 0.0195).ConclusionsPET/CT is useful in assessing tumor response to preoperative CRT for LRRC and predicting prognosis after surgery.

Highlights

Recurrent rectal cancer (LRRC) remains a major problem after curative resection of primary rectal cancer
According to Mandard’s criteria [11], 17 of the 40 patients were classified as responders (TRG1-TRG2) and 23 patients were classified as nonresponders (TRG3-TRG5)
We observed that Post-standardized uptake value (SUV) was especially useful in the assessment of Locally recurrent rectal cancer (LRRC) survival, whereas computed tomography (CT) and magnetic resonance imaging (MRI) less accurately reflected the pathological tumor response

Summary

Introduction

Recurrent rectal cancer (LRRC) remains a major problem after curative resection of primary rectal cancer. This study assesses the effectiveness of PET/CT evaluation of preoperative chemoradiation therapy (CRT) in patients with LRRC. Recurrent rectal cancer (LRRC) remains a major problem after curative resection of primary advanced rectal cancer [1]. Since 20 to 50% of these patients have local recurrence in the absence of distant metastasis, surgical intervention is one of the best curative treatment choices [3, 4]. Local re-recurrence and distant metastasis after resection of LRRC are relatively frequent [5]. We have been performing preoperative chemoradiation therapy (CRT) aiming to achieve local control and survival benefit [6]. Assessment of the tumor response is clinically important, but evaluation of the extent of LRRC by abdominopelvic computed tomography (CT) and pelvic magnetic resonance imaging (MRI) is sometimes difficult due to the main characteristics of LRRC, such as infiltrating growth, tissue scarring, and fibrosis [5]

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