Endorectal MRI after radiation therapy: questioning the sextant analysis

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• The sextant approach is the standard for magnetic resonance imaging (MRI) and biopsy coregistration in prostate cancer.
• However, its limitations necessitate evaluating alternative methods for assessing locally recurrent prostate cancer after radiotherapy.

Purpose of the Study:

• To compare the diagnostic information gained from three MRI coregistration systems: sextant, hemi-prostate, and whole gland.
• To determine if one system is significantly superior, warranting routine preference over others.

Main Methods:

• Seventy patients treated with external beam radiotherapy for prostate cancer underwent 1.5 T endorectal MRI.
• A single reader assessed T2-weighted images for tumor presence.
• Receiver operating characteristic (ROC) curve analysis quantified the performance of each coregistration approach.

Main Results:

• Areas under the ROC curve (accuracy) were 0.63 for sextant, 0.68 for hemi-prostate, and 0.71 for whole gland.
• No statistically significant differences in accuracy were observed among the three MRI coregistration approaches.

Conclusions:

• Endorectal MRI using sextant, hemi-prostate, or whole gland approaches can reliably assess locally recurrent prostate cancer post-radiotherapy.
• The choice of coregistration method should be guided by the specific purpose of the procedure, not solely by imaging accuracy estimates.