EFFICACY OF 18FDG-PET/CT IN PREDICTING RESPONSE AFTER NEOADJUVANT CHEMORADIATION IN RECTAL CANCER

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

Abstract

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

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Published
2023-08-15
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: 04 oct. 2024.