Prostate Cancer: Role of Pretreatment MR in Predicting Outcome after External-Beam Radiation Therapy—Initial Experience

Abstract

Purpose-To retrospectively determine if pretreatment endorectal magnetic resonance (MR) imaging findings are predictive of outcome in patients who undergo external-beam radiation therapy for prostate cancer.Materials and Methods-Committee on Human Research approval, with waiver of the requirement for informed consent, was obtained for this HIPAA-compliant study. Eighty men with biopsy-proved prostate cancer (mean age, 59 years; range, 47-75 years) who underwent endorectal MR imaging of the prostate prior to external-beam radiation therapy were retrospectively identified; details of baseline tumor characteristics, treatment, and outcome were recorded. Two experienced readers independently reviewed all MR imaging studies and recorded tumor T stage and the radial diameter of extracapsular extension (if present). Univariate and multivariate stepwise Cox regression analyses were used to investigate the relationship between baseline imaging and clinical predictive variables and the end point of metastatic failure.Results-At MR imaging, readers 1 and 2, respectively, considered 50 and 60 patients to have T1 or T2 disease (ie, organ-confined disease) and 30 and 20 patients to have T3 disease. After a mean follow-up of 43 months, four patients developed metastases. Univariate Cox analysis revealed that baseline serum prostate-specific antigen level, presence of extracapsular extension at MR imaging (according to either reader), and degree of extracapsular extension (according to either reader) were all significantly (P < .05) related to the development of metastases. Multivariate Cox analysis revealed that the sole independent predictive variable was mean diameter of extracapsular extension (relative hazard ratio, 2.06; 95% confidence interval: 1.22, 3.48; P = .007). In particular, three of five patients with extracapsular extension of more than 5 mm at pretreatment MR imaging developed metastases 24, 43, and 63 months after therapy. Conclusion-The presence and degree of extracapsular extension at MR imaging prior to external-beam radiation therapy are important predictors of posttreatment metastatic recurrence.

Prostate Cancer: Prediction of Biochemical Failure after External-Beam Radiation Therapy—Kattan Nomogram and Endorectal MR Imaging Estimation of Tumor Volume

“…In concordance with data in prior studies ( 27,29,31 ), we found that extracapsular extension was an independent predictor of treatment failure, but seminal vesicle invasion was not predictive of treatment response (28)(29)(30). This was a surprising fi nding, as seminal vesicle invasion is widely believed to be associated with larger tumors with a poorer prognosis; our study is small and may have been underpowered to…”

“…Researchers in some studies have investigated the use of these techniques for prediction of patients' outcome following radiation therapy (27)(28)(29)31,46 ). The results of these studies have suggested that imaging fi ndings can be used to predict treatment response.…”

“…Westphalen et al radiation therapy ( 27,28,30,31 ). These latter four studies demonstrated that MR imaging fi ndings, more specifi cally the amount of extracapsular extension, the presence of seminal vesicle invasion, and the volume of metabolic abnormality at MR spectroscopy, are independent predictors of treatment failure after radiation therapy.…”

“…Endorectal magnetic resonance (MR) imaging has emerged as an accurate method of evaluating the aggressiveness and extent of prostate cancer (18)(19)(20)(21)(22)(23)(24)(25)(26). Previous publications have demonstrated that MR imaging and/or MR spectroscopic imaging fi ndings are predictive of radiation treatment outcome, particularly in intermediate and high-risk groups (27)(28)(29)(30)(31). Wang et al ( 32,33 ) have shown that the addition of endorectal MR imaging and MR spectroscopic imaging to staging nomograms results in added value in predicting organconfi ned prostate cancer in patients before radical prostatectomy .…”

Incremental value of magnetic resonance imaging in the advanced management of prostate cancer

“…In a multivariate analysis of 67 patients, SVI on MRI and MRSI prior to external-beam radiation therapy predicted a worse prognosis [87] . The group demonstrated that the presence and degree of ECE on MRI significantly predicted post-treatment metastatic recurrence [88] . A study of 36 consecutive patients demonstrated a significantly greater area under the ROC curve (Az) for combined T2WI and DWI (Az = 0.879, P < 0.01) as compared to T2WI (Az = 0.612).…”