Brachytherapy for prostate cancer

Locally recurrent prostate cancer after high-dose-rate brachytherapy: the value of diffusion-weighted imaging, dynamic contrast-enhanced MRI, and T2-weighted imaging in localizing tumors

OBJECTIVE

The purpose of this article is to retrospectively evaluate the utility of prostate MRI for detecting locally recurrent prostate cancer after high-dose-rate (HDR) brachytherapy.

MATERIALS AND METHODS

Sixteen men with biochemical failure after HDR brachytherapy for prostate cancer underwent prostate MRI, including T2-weighted imaging, dynamic contrast-enhanced MRI (DCE-MRI), and diffusion-weighted imaging (DWI), using a 1.5-T MRI unit before 12-core-specimen biopsy. Two radiologists in consensus assessed the presence of tumor on each sequence within eight regions of the prostate (six from the peripheral zone [PZ] and two from the transition zone [TZ]) on the basis of biopsy.

RESULTS

Biopsy revealed locally recurrent prostate cancer in 22 (17 in PZ and five in TZ) of 128 regions (17.2%). The sensitivity, specificity, and accuracy of each MRI method in the detection of recurrent tumor were 27%, 99%, and 87%, respectively, for T2-weighted imaging; 50%, 98%, and 90%, respectively, for DCE-MRI; and 68%, 95%, and 91%, respectively, for DWI. The sensitivity of DWI in detecting recurrent tumor was significantly higher than that of T2-weighted imaging (p = 0.004). Multiparametric MRI achieved the highest sensitivity (77%) but with slightly decreased specificity (92%).

CONCLUSION

These results indicate that a multiparametric MRI protocol that includes DWI provides a sensitive method to detect local recurrence after HDR brachytherapy.

Unification of a common biochemical failure definition for prostate cancer treated with brachytherapy or external beam radiotherapy with or without androgen deprivation

PURPOSE

Minimal data are available regarding selection of an optimal biochemical failure (BF) definition for patients treated with brachytherapy, external beam radiotherapy (EBRT), and combinations of these treatments with or without androgen deprivation (AD). We retrospectively analyzed our institution's experience treating localized prostate cancer in an attempt to determine a BF definition that could be applied for these various treatment modalities.

METHODS AND MATERIALS

A total of 2376 patients with clinical stage T1-T3 N0 M0 prostate cancer were treated with conventional dose (median, 66.6 Gy) EBRT (n = 1201), high-dose (median, 75.6 Gy) adaptive radiation therapy (n = 465), EBRT + high-dose-rate brachytherapy boost (n = 416), or brachytherapy alone (n = 294) between 1987 and 2003. A total of 496 patients (21%) received neoadjuvant AD with radiation therapy. There were 21924 posttreatment prostate-specific antigen (PSA) measurements. Multiple BF definitions were tested for their sensitivity, specificity, positive predictive value (+PV), and negative PV (-PV) in predicting subsequent clinical failure (CF) (any local failure or distant metastasis), overall survival (OS), and cause-specific survival (CSS). Median follow-up was 4.5 years. The date of BF was the date BF criteria were met (e.g., date of third rise).

RESULTS

A total of 290 patients (12%) experienced CF at a median interval of 3.6 years (range, 0.2-15.2 years). The 5- and 10-year CF rates were 12% and 26%, respectively. Three consecutive rises yielded a 46% sensitivity and 84% specificity for predicting CF. The 10-year CF for those 475 patients who experienced three rises (BF) was 37% vs. 17% for those patients who did not meet these criteria (biochemically controlled [BC]). For all patients, the following definitions were superior to three rises for predicting CF for both +PV, and -PV: n + 1 (> or =1 ng/mL above nadir), n + 2, n + 3, threshold 2 (any PSA > or =2.0 ng/mL at or after nadir), threshold 3, threshold 4, and threshold 5. For the subset of patients treated with EBRT alone, the n + k definitions and threshold k definitions maintained superior predictive capacity. However, the threshold k definitions seemed to maintain a slightly greater separation in 10-year CF rates (43% for BF vs. 13% for BC = 30% difference for threshold 3). Surprisingly, all definitions generally had better predictive capacity for those patients who received brachytherapy or neoadjuvant AD vs. EBRT alone. The endpoints appeared similar for n + 1 vs. threshold 3 and n + 2 vs. threshold 4 in EBRT alone patients, but for brachytherapy or neoadjuvant AD patients, there were similarities for n + 2 vs. threshold 3 and n + 3 vs. threshold 4. This may be a reflection of the lower nadir levels in patients receiving AD (median <0.1 ng/mL vs. 0.2 ng/mL for brachytherapy vs. 0.8 ng/mL for EBRT alone, p < 0.01). When examining CF correlation for the various classes of BF definitions, the threshold k definitions clearly demonstrated the greatest area under the receiver operating characteristic curve, followed by the n + k definitions. For OS, the threshold k definitions again demonstrated the greatest area under the curve, followed by definitions based on specific nadir cutoffs (nadir > or =k ng/mL).

CONCLUSIONS

Biochemical failure definitions applying a PSA threshold at or after the nadir (e.g., threshold 3) demonstrated the highest association with CF, OS, and CSS for all assessed treatment modalities. Definitions incorporating a PSA increase above the nadir value (e.g., nadir + 2 ng/mL) were also superior for all modalities. In general, BF definitions have greater predictive capacity for clinical outcome with brachytherapy or neoadjuvant AD than EBRT alone, possibly because of less "noise" from production of background PSA.

The Role of Imaging in the Surveillance of Urologic Malignancies

Urologic malignancies are common, accounting for approximately 25% of all new cancer cases in the United States. Patients with urologic malignancies require long-term surveillance to detect progression or recurrence as early as possible. The urologist is faced with the task of balancing patient safety and cost-effectiveness, while finding the most practical follow-up regimen. For each urologic malignancy, this article reviews the commonly used radiologic techniques for surveillance and offers recommended follow-up schedules.