Abstract 50P
Background
Neoadjuvant chemoradiotherapy (CCRT) is the current standards of care for locally advanced rectal cancer. Precise observation of tumor during CCRT with daily MRI can provide real-time treatment sensitivity and tumor biology, enabling patient-driven treatment decision at early phase.
Methods
Patients with cT3-4 and/or cN+ rectal adenocarcinoma undergoing preoperative CCRT with capecitabine on the pelvis up to 50 Gy in 25 fractions from 2018 to 2019 were consecutively included. Rectal tumor volume was measured by single physician (YKK) using daily 0.35T MRI of an MR-guided linear accelerator. Primary endpoint was to assess the pattern of tumor volume regression throughout the full course of CCRT using daily registration MRI. Secondary endpoint was to assess the effect of tumor regression velocity on disease-free survival (DFS). Tumor regression velocity (cc) per fraction of each patient was calculated using the simple regression analysis of tumor volumes from fractions 1 to 25.
Results
Twenty patients were included. Daily tumor volumetry demonstrated linear tumor regression during CCRT. Tumor regression velocity of 20 patients was 2.40 cc per fraction (R2 = 0.93; P < 0.001). Median tumor regression velocity was 1.52 cc per fraction. Rapid regressors had tumor regression velocity > 1.52 cc per fraction (N = 9). Slow regressors had tumor regression velocity < 1.52 cc per fraction (N = 11). Rapid regressors had significantly greater tumor regression velocity (4.58 cc per fraction) than slow regressors (0.78 cc per fraction; P < 0.001). Rapid regressors had numerically superior DFS rate compared to slow regressors. The 2-year DFS was 88.9% for rapid regressors and 72.7% for slow regressors, respectively (P = 0.400).
Conclusions
This study is the first observation of linear tumor regression in daily MRI during preoperative CCRT of locally advanced rectal cancer. Daily tumor regression velocity numerically discriminated DFS. Although this study is hypothesis-generating, the potential of CCRT from therapeutics to a newer level, the theranostics, has been sufficiently suggested. Further validation studies for the value of daily tumor volumetry on treatment decisions are warranted.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.
Resources from the same session
58P - Clinicopathologic profile and outcomes of rectal cancer (RC) in the young (<50 years old): A single institution experience
Presenter: Fatma Amina Hussin Ibrahim
Session: Poster viewing 02
59P - Platelet-derived growth factor (PDGF)-CC serum as clinical outcome predictor after six cycles of chemotherapy in colorectal cancer at RSMH Palembang
Presenter: Erty Sundarita
Session: Poster viewing 02
60P - Predictors of survival in stage III colorectal cancer patients treated with surgery and adjuvant chemotherapy: A single institution observational study
Presenter: Keng Man Chiang
Session: Poster viewing 02
61P - Can total neoadjuvant therapy in locally advanced rectal cancer replace standard treatment protocol?
Presenter: Ankita Mallick
Session: Poster viewing 02
62P - Chief complaints and baseline clinicopathological features of patients with colorectal cancer in a tertiary hospital in Yogyakarta Indonesia
Presenter: Yasjudan Putra
Session: Poster viewing 02
63P - Tumor sidedness and clinicopathological features of colorectal cancer in Medical Oncology Department, Yangon General Hospital: A retrospective review
Presenter: Thiri Tun
Session: Poster viewing 02
64P - Clinical profile and treatment outcome of patients with non-metastatic colon cancer: A single institutional study from India
Presenter: Sandip Ganguly
Session: Poster viewing 02
65P - Comparison of survival and recurrence pattern in Thai early stage colorectal cancer patients by tumor sidedness
Presenter: Chanchai Charonpongsuntorn
Session: Poster viewing 02
77P - Long-term outcomes of indocyanine green fluorescence imaging-guided laparoscopic lymphadenectomy for gastric cancer: The FUGES-012 randomized clinical trial
Presenter: Qing Zhong
Session: Poster viewing 02