[¹⁸F]Fluoromisonidazole PET in rectal cancer

Area of Science:

• Oncology
• Radiotherapy
• Medical Imaging

Background:

• Increasing interest in predictive biomarkers for personalized radiotherapy in rectal cancer.
• Evaluating [18F]fluoromisonidazole ([18F]FMISO) positron emission tomography (PET) for predicting response to neoadjuvant chemoradiotherapy (CRT).

Purpose of the Study:

• To explore the utility of [18F]FMISO PET scans in predicting clinical response in rectal cancer patients undergoing neoadjuvant CRT.
• To identify potential biomarkers of tissue hypoxia for personalized treatment strategies.

Main Methods:

• [18F]FMISO PET scans were performed at baseline and after 8-10 fractions of CRT in rectal cancer patients.
• Analysis included tumour-to-muscle (T:M) and tumour-to-blood (T:B) SUVmax, and dynamic PET scans for hypoxia and perfusion.
• Comparison of imaging data with pathological tumour regression grade (AJCC 7.0).

Main Results:

• Tumour perfusion changes showed a trend with clinical outcome: decreasing in non-responders and increasing in responders.
• Median T:M SUVmax decreased from 2.14 to 1.30, and median T:B SUVmax decreased from 2.46 to 1.61 post-CRT.
• No clear trends were observed for other PET parameters concerning clinical outcome.

Conclusions:

• Significant challenges exist in the delivery and interpretation of [18F]FMISO PET scans for rectal cancer.
• Spill-in from rectal and bladder contents is a principal problem affecting data quality.
• Fundamental difficulties limit the clinical applicability of [18F]FMISO PET in this patient group.