• Narendra Pandit MS, MCh, Surgical gastroenterology Division, department of Surgery, BPKIHS, Dharan
  • B R Mittal
  • Nandita Kakkar
  • G R Verma


Introduction: Neoadjuvant chemoradiation (NACRT) may result in significant response in rectal cancer.  Conventional imaging may not be accurate. 18FDG-PET/CT scan has shown promising results for monitoring the response to NACRT. The aim of this study is to evaluate the role of 18FDG-PET/CT scan in predicting pathological response after NACRT in carcinoma rectum.
Methods: Thirty-two consecutive patients with locally advanced rectal cancer were enrolled. Patients underwent NACRT comprising of external beam radiotherapy and concomitant infusional 5-FU based chemotherapy. It was followed 6 weeks later by total mesorectal excision. All patients underwent FDG-PET/CT before and minimum 6 weeks after the completion of NACRT. Maximum standardized uptake (SUVmax) value was calculated. The tumor regression grade (TRG) in resected specimen was scored according to the Mandard criteria. TRG 1-2 was considered as responders and TRG 3-5, non-responders. The SUVmax within the tumor was correlated to differentiate pathological responders from non-responders.
Results: Fourteen of 30 patients were excluded due to protocol deviation.  Following NACRT, 7 (50%) patients were classified as responders (TRG 1-2) and 7 (50%) non-responders (TRG 3-5). There were no significant differences in pre NACRT SUVmax between responders (12.05±2.81) and non-responders (17.65±7.20) (p=0.079). The mean post-NACRT SUVmax was significantly lower in responders than non-responders (6.4 vs 10.8; p=0.024). To compare the response using ROC curve analysis (AUC=0.83), and considering a cut-off post SUVmax as 7.0, the sensitivity was 57.14%, specificity 71.43%, positive predictive value (PPV) 66.67%, negative predictive value (NPV) 62.50%, and the overall accuracy  was 64.28%  to differentiate pathological responders from non-responders.
Conclusion: These preliminary results suggest that 18FDG-PET/CT could be a potentially useful tool in predicting response after NACRT in locally advanced rectal cancer.  Post SUVmax  of 7.0  appears to be the best predictor tumor response following NACRT.

Author Biographies

B R Mittal
Department of Nuclear Medicine, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
Nandita Kakkar
Department of Histopathology, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
G R Verma
Department of Surgical Gastroenterology, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India


1. Sauer R, Becker H, Hohenberger W, et al. Preoperative versus postoperative chemoradiotherapy for rectal cancer. N Engl J Med 2004;351(17):1731–40.
2. Folkesson J, Birgisson H, Pahlman L, et al. Swedish rectal cancer trial: long lasting benefits from radiotherapy on survival and local recurrence rate. J Clin Oncol 2005;23(24):5644–50.
3. Tjandra JJ, Kilkenny JW, Buie WD, et al. Practice parameters for the management of rectal cancer (revised). Dis Colon Rectum 2005;48(3):411–23.
4. Schaffizin DM, Wong WD. Endorectal ultrasound in the preoperative evaluation of rectal cancer. Clin Colorectal Cancer 2004;4(2):124-132.
5. Habr-Gama A, Perez RO, Nadalin W, et al. Operative versus nonoperative treatment for stage O distal rectal cancer following chemoradiation therapy: long-term results. Ann Surg 2004;240(4):711-7.
6. Zerhouni EA, Rutter C, Hamiton SR, et al. CT and MR imaging in the staging of colorectal carcinoma: report of the Radiology Diagnostic Oncology Group II. Radiology 1996;200(2):443-451.
7. Capirci C, Rampin L, Erba PA, et al. Sequential FDG-PET/CT reliably predicts response of locally advanced rectal cancer to neo-adjuvant chemo-radiation therapy. Eur J Nucl Med Mol Imaging 2007;34:1583–1593.
8. Rau B, Hunerbein M, Barth C, et al. Accuracy of endorectal ultrasound after preoperative radiochemotherapy in locally advanced rectal cancer. Surg Endosc. 1999;13:980–4.
9. Guillem JG, Puig-La Calle Jr J, Akhurst T, Tickoo S, Ruo L, Minsky BD, et al. Prospective assessment of primary rectal cancer response to preoperative radiation and chemotherapy using 18- fluorodeoxyglucose positron emission tomography. Dis Colon Rectum. 2000;43:18–24.
10. Richard L, Heather J, Lodge Martin et al. From RECIST to PERCIST : Evolving consideration for PET response criteria in solid tumors. J Nucl Med. 2009;50: 122S-150S
11. Mandard AM, Dalibard F, Madard JC, Marnay J, Henry-Amar M, Petiot JF, et al. Pathologic assessment of tumor regression after preoperative chemoradiation therapy of esophageal carcinoma. Clinicopathologic correlations. Cancer. 1994;73:2680–6.
12. Cascini GL, Avallone A, Delrio P, et al. 18F-FDG PET is an early predictor of pathologic tumor response to preoperative radiochemotherapy in locally advanced rectal cancer. J Nucl Med 2006;47:1241–1248.
13. Chongjial Li, Xiaoli Lan, Hui Yuan, et al. 18FDG PET predicts pathological response to preoperative chemoradiotherapy in patients with primary rectal cancer: a meta-analysis. Ann Nucl Med 2014;28:436-446.
14. Capirici C, Rubello D, Pasini F, et al. The role of Dual-time combined 18Fluorodeoxyglucose positron emission tomorgaphy and computed tomography in the staging and restaging workup of locally advanced rectal cancer, treated with preoperative chemoradiation therapy and radical surgery. Int J radiation Oncology Biol Phys 2009;74(5):1461-1469.
15. Caruso R, Vicente E, Quijano Y, Duran H, Fabra I, Diaz E, Malave L, Agresott R, Cañamaque LG, Ielpo B, Ferri V. Role of 18F-PET-CT to predict pathological response after neoadjuvant treatment of rectal cancer. Discov Oncol. 2021 May 18;12(1):16.
16. Di Fabio F, Pinto C, Ceccarelli C, et al. Correlation between FDG-PET and pathological response in patients with rectal cancer treated with neo-adjuvant chemoradiotherapy: First results of the Bologna Project. ASCO 2005;Abs. n. 3623.
17. Kristiansen C, Loft A, Berthelsen AK, Graff J, et al. PET/CT and histopathologic response to preoperative chemoradiation therapy in locally advanced rectal cancer Dis Colon Rectum 2008;51:21-25.
18. Janssen MH, Ollers MC, Riedl RG, et al. Accurate prediction of pathological rectal tumor response after weeks of preoperative radiochemotherapy using 18Fluorodeoxyglucose-positron emission tomography-computed tomography imaging. Int J Radiat Oncol Biol Phys 2010;77:392-399.
How to Cite
PANDIT, Narendra et al. EFFICACY OF 18FDG-PET/CT IN PREDICTING RESPONSE AFTER NEOADJUVANT CHEMORADIATION IN RECTAL CANCER. J Soc Surg Nep, [S.l.], v. 26, n. 1, p. 22-28, aug. 2023. ISSN 2392-4772. Available at: <https://jssn.org.np/index.php?journal=jssn&page=article&op=view&path%5B%5D=545>. Date accessed: 22 sep. 2023.