Is PET/CT useful in the staging of anal cancer?

Abstract

422 Background: The use of 18flurodeoxyglucose PET or PET/CT in staging of anal cancer is becoming increasingly fashionable. However, evidence endorsing it as a definitive staging modality it is still emerging. The largest published series to date from the UK found sensitivity of PET to be superior for detection of regional nodal metastases and overall PET changed stage in 23% and management in 16% of cases [de Winton E et al. The impact of 18-fluorodeoxyglucose positron emission tomography on the staging, management and outcome of anal cancer. BJR 2009; 100: 693-700]. We initially performed a retrospective pilot feasibility study for the period 2009-2010 and found that PET/CT altered staging in 42% of the 43 patients included, predominantly upstaging nodal status. We continue our analysis and report this prospective series - to assess the usefulness of PET/CT in the staging of anal cancer. Methods: 47 patients were treated radically for anal cancer at Mount Vernon Cancer Centre (UK) between January 2010 and July 2011, of which 27 had PET/CT scans. Staging was compared following conventional modalities and PET/CT. The TNM clinical staging system was used. Results: In 9 patients the PET/CT stage differed from MRI staging. In total, there were 4 ‘T stage’ changes and 8 ‘N stage’ changes. Of these, 1 case showed a difference in ‘T’ staging alone 5 showed a change in ‘N’ staging alone and 3 showed a change in ‘T’ and ‘N’ staging. PET/CT altered staging in 33% of patients. Conclusions: We conclude that PET/CT alters staging in a significant number of cases correlating with the literature and our own retrospective analysis. Furthermore there is agreement that PET/CT shows greater sensitivity for detection of lymph nodes. Although PET/CT cannot replace CT/MRI as the optimal modality for planning, it can reveal useful information regarding tumour extent, nodal involvement and distal metastases. PET/CT can account for greater definition of dose delivery, and more accurately ascertain the need to include/exclude pelvic lymph nodes. With more precise staging, acute and late toxicity profiles will be greatly influenced, especially with more advanced radiotherapy techniques such as Intensity Modulated Radiotherapy (IMRT), whilst maintaining satisfactory outcomes.