Percentage of Tumor Invasion at Pretreatment High-Resolution Magnetic Resonance Imaging: Associating With Aggressive and Tumor Response in Chinese T3 Rectal Cancer-Preliminary Results

Abstract

Purpose: The purpose of the study was to assess the ability of percentage of tumor invasion (PTI) of T3 rectal cancer on pretreatment MRI as an imaging biomarker to reflect aggressiveness and to predict tumor response after neoadjuvant chemoradiation (NCRT) in Chinese population.

Methods: A total of 107 Chinese rectal cancer patients who underwent pretreatment MRI staging as T3 were included. The extramural depth of tumor invasion (EMD), the distance between outer border of muscularis propria (MP) and mesorectal fascia (MRF) we called "thickness of the mesorectum (TM)") at the same slice and direction were measured at pretreatment MRI, and PTI was equal to EMD/TM, was calculated. The EMD and PTI of subgroups based on pretreatment CEA, CA19-9 levels; N category and pathological complete response (pCR) were compared. The parameters, which described tumor invasion, were compared between pCR and non-pCR group. Student t-tests and logistic analysis were applied.

Results: The pretreatment PTI was higher in CEA ≥5.2 ng/ml patients (58.52% ± 27.68%) than in CEA <5.2 ng/ml patients (47.27% ± 24.15%) (p = 0.034). The pretreatment EMD in non-pCR group (7.21 ± 2.85 mm) was higher than in pCR group (6.14 ± 3.56 mm) (p = 0.049). The pretreatment PTI in non-pCR group (57.4% ± 26.4%) was higher than in pCR group (47.3% ± 29.1%) (p = 0.041). Compared with patients with PTI ≥50%, MRF (+), more patients with PTI <50%, MRF (-) showed pCR (OR = 8.44, p = 0.005; OR = 6.32, p = 0.024).

Conclusion: The PTI obtained at pretreatment MRI may serve as an imaging biomarker to reflect tumor aggressiveness and predict which T3 rectal cancer patients may benefit from NCRT in Chinese population.

Keywords: chemoradiotherapy; feasibility studies; magnetic resonance imaging; neoplasm staging; rectal neoplasms.

Figure 1

Flowchart of the study population.

Figure 2

The EMD was measured and recorded using the calipers of workstation, and the TM from the outer edge of the MP to the MRF according to the same path of EMD and the PTI which was equal to EMD/TM were calculated.

Figure 3

Sixty-three-year-old woman with an mr-T3N0 rectal adenocarcinoma 5 cm from the anal verge. Pretreatment rectal MRI (A, B) before NCRT. The EMD was 6.1 mm (A), TM was 10.5 mm (B), and the calculated PTI was 58.1%. The rectal cancer had slightly regressed after NCRT. The postoperative staging confirmed by pathology was T3N0, and the tumor response was non-pCR.

Figure 4

Sixty-seven-year-old man with an mr-T3N0 rectal adenocarcinoma 9.5 cm from the anal verge. Pretreatment rectal MRI (A, B) before NCRT. The EMD was 9.7 mm (A), the TM was 21.7 mm (B), and the calculated PTI was 44.7%. The rectal cancer had regressed after NCRT. The postoperative staging confirmed by pathology was T0N0, and the tumor response was pCR.