High Dose Rate Monotherapy for Prostate Cancer

Multicenter Trial of Stereotactic Body Radiation Therapy for Low- and Intermediate-Risk Prostate Cancer: Survival and Toxicity Endpoints

PURPOSE

The radiobiology of prostate cancer may favor the extreme hypofractionation inherent in stereotactic body radiation therapy (SBRT); however, data from a large multicenter study are lacking. We therefore examined the hypothesis that dose-escalated SBRT can be safely administered across multiple institutions, with favorable 5-year disease-free survival (DFS) rates compared with historical controls.

METHODS AND MATERIALS

Twenty-one centers enrolled 309 patients with prostate adenocarcinoma: 172 with low-risk (LR) and 137 with intermediate-risk (IR) disease. All were treated with a non-coplanar robotic SBRT platform using real-time tracking of implanted fiducials. The prostate was prescribed 40 Gy in 5 fractions of 8 Gy. We assessed toxicities using Common Terminology Criteria for Adverse Events (CTCAE) version 3 and biochemical failure using the "nadir + 2" definition. The study population yielded 90% power to identify excessive (>10%) rates of grade ≥3 genitourinary (GU) or gastrointestinal toxicities and, in the LR group, 80% power to show superiority in DFS over a 93% historical comparison rate.

RESULTS

At a median follow-up of 61 months, 2 LR patients (1.2%) and 2 IR patients (1.5%) experienced grade 3 GU toxicities, far below the 10% toxicity rate deemed excessive (upper limits of 95% confidence interval, 3.5% and 4.3%, respectively). No grade 4 or 5 toxicities occurred. All grade 3 toxicities were GU, occurring 11 to 51 months after treatment. For the entire group, the actuarial 5-year overall survival rate was 95.6% and the DFS rate was 97.1%. The 5-year DFS rate was 97.3% for LR patients (superior to the 93% DFS rate for historical controls; P = .0008; lower limit of 95% confidence interval, 94.6%) and 97.1% for IR patients.

CONCLUSIONS

Dose-escalated prostate SBRT was administered with minimal toxicity in this multi-institutional study. Relapse rates compared favorably with historical controls. SBRT is a suitable option for LR and IR prostate cancer.

Toxicity and quality of life after high-dose-rate brachytherapy as monotherapy for low- and intermediate-risk prostate cancer

BACKGROUND AND PURPOSE

The use of HDR brachytherapy (HDR-BT) as monotherapy for prostate cancer (PC) is increasing worldwide with good tumour control rates and acceptable toxicity. We report our results on toxicity and quality of life (QoL) after HDR-BT monotherapy for PC patients.

MATERIALS AND METHODS

166 low- and intermediate-risk localized PC patients were treated with HDR-BT to a total dose of 38Gy in four fractions. Genitourinary (GU) and gastrointestinal (GI) toxicities were prospectively assessed using EORTC-RTOG questionnaires and physicians charts. QoL was evaluated using EORTC QLQ-PR25 questionnaires.

RESULTS

Three months after treatment, acute GU and GI toxicities were reported in 10.8% and 7.2%. Acute toxicity resolved within two months in the majority of patients (61%). Late grade ⩾ 2 GU and GI toxicity were reported in 19.7% and 3.3% of patients 12 months after HDR-BT. Mean QLQ-PR25 scores showed clinically relevant changes from baseline for urinary symptoms and sexual functioning. With a mean follow-up of 35 months, biochemical failure was observed in 2.4%. Overall survival at 60 months was 93.6% and cancer-specific survival was 100%.

CONCLUSIONS

HDR-BT monotherapy for localized PC showed excellent clinical outcome and acceptable acute and late toxicity. Urinary symptoms and sexual function QoL decreased after treatment.

Dose-Escalated Robotic SBRT for Stage I-II Prostate Cancer

Stereotactic body radiotherapy (SBRT) is the precise external delivery of very high-dose radiotherapy to targets in the body, with treatment completed in one to five fractions. SBRT should be an ideal approach for organ-confined prostate cancer because (I) dose-escalation should yield improved rates of cancer control; (II) the unique radiobiology of prostate cancer favors hypofractionation; and (III) the conformal nature of SBRT minimizes high-dose radiation delivery to immediately adjacent organs, potentially reducing complications. This approach is also more convenient for patients, and is cheaper than intensity-modulated radiotherapy (IMRT). Several external beam platforms are capable of delivering SBRT for early-stage prostate cancer, although most of the mature reported series have employed a robotic non-coplanar platform (i.e., CyberKnife). Several large studies report 5-year biochemical relapse rates which compare favorably to IMRT. Rates of late GU toxicity are similar to those seen with IMRT, and rates of late rectal toxicity may be less than with IMRT and low-dose rate brachytherapy. Patient-reported quality of life (QOL) outcomes appear similar to IMRT in the urinary domain. Bowel QOL may be less adversely affected by SBRT than with other radiation modalities. After 5 years of follow-up, SBRT delivered on a robotic platform is yielding outcomes at least as favorable as IMRT, and may be considered appropriate therapy for stage I–II prostate cancer.

Stereotactic body radiotherapy: an emerging treatment approach for localized prostate cancer

Here we report results from the first cohort of over 100 patients treated with hypofractionated, stereotactic body radiotherapy (SBRT) for early stage prostate cancer. Between February 2005 and December 2006, 112 patients with localized, biopsy-proven adenocarcinoma of the prostate (clinical stage T1cN0M0 to T2cN0M0) were treated in Naples, FL on a CyberKnife system (Accuray Incorporated, Sunnyvale, CA). Eighty-one patients had a Gleason score of 3+3. Mean initial PSA was 6.0, and mean initial prostate volume was 46.3cc. Implanted gold fiducials were used for image-guided targeting and tracking. Patients received 35-36 Gy administered in 5 consecutive fractions to the prostate and the proximal seminal vesicles, as identified on CT and MRI scans. At a median follow-up of 24 months, the mean PSA value was 0.78 ng/ml. Two patients have developed biopsy-confirmed local relapse; one developed distant metastases. Acute side effects were generally mild and resolved shortly after treatment. A single Grade 3 rectal complication was reported (bleeding). Eighty-two percent of patients who were sexually potent before treatment maintained erectile function post-treatment. Additional follow-up is required to better evaluate potential late toxicity and long-term PSA outcomes.