Prostate cancer radiation dose response: results of the M. D. Anderson phase III randomized trial

Dose–Volume Comparison of Proton Therapy and Intensity-Modulated Radiotherapy for Prostate Cancer

PURPOSE

The contrast in dose distribution between proton radiotherapy (RT) and intensity-modulated RT (IMRT) is unclear, particularly in regard to critical structures such as the rectum and bladder.

METHODS AND MATERIALS

Between August and November 2006, the first 10 consecutive patients treated in our Phase II low-risk prostate proton protocol (University of Florida Proton Therapy Institute protocol 0001) were reviewed. The double-scatter proton beam plans used in treatment were analyzed for various dosimetric endpoints. For all plans, each beam dose distribution, angle, smearing, and aperture margin were optimized. IMRT plans were created for all patients and simultaneously analyzed. The IMRT plans were optimized through multiple volume objectives, beam weighting, and individual leaf movement. The patients were treated to 78 Gray-equivalents (GE) in 2-GE fractions with a biologically equivalent dose of 1.1.

RESULTS

All rectal and rectal wall volumes treated to 10-80 GE (percentage of volume receiving 10-80 GE [V(10)-V(80)]) were significantly lower with proton therapy (p < 0.05). The rectal V(50) was reduced from 31.3% +/- 4.1% with IMRT to 14.6% +/- 3.0% with proton therapy for a relative improvement of 53.4% and an absolute benefit of 16.7% (p < 0.001). The mean rectal dose decreased 59% with proton therapy (p < 0.001). For the bladder and bladder wall, proton therapy produced significantly smaller volumes treated to doses of 10-35 GE (p < 0.05) with a nonsignificant advantage demonstrated for the volume receiving < or =60 GE. The bladder V(30) was reduced with proton therapy for a relative improvement of 35.3% and an absolute benefit of 15.1% (p = 0.02). The mean bladder dose decreased 35% with proton therapy (p = 0.002).

CONCLUSION

Compared with IMRT, proton therapy reduced the dose to the dose-limiting normal structures while maintaining excellent planning target volume coverage.

p53 protein expression status and recurrence in men treated with radiation and androgen suppression therapy for higher-risk prostate cancer: a prospective phase II Cancer and Leukemia Group B Study (CALGB 9682)

OBJECTIVES

It has been hypothesized that abnormal p53 protein expression is associated with a worse prognosis after radiation (RT) and androgen suppression therapy (AST). This hypothesis was prospectively tested.

METHODS

Between May 1997 and April 2001, 180 men with clinical stage T1c-T3cN0M0 adenocarcinoma of the prostate were registered on a study evaluating whether the endorectal magnetic resonance imaging (eMRI)-defined change in tumor volume (TV) during neoadjuvant (n) AST was associated with prostate-specific antigen (PSA) outcome. Of these, 141 had sufficient tissue to perform immunohistochemical detection of the p53 protein expression status and 113 had complete eMRI information. Multivariable Cox regression analysis was used to assess whether p53 protein expression status predicted time to PSA failure adjusting for known prognostic factors.

RESULTS

After a median follow-up of 6.9 years and adjusting for PSA level, Gleason score, clinical stage, and eMRI-defined TV change during nAST, men with abnormal compared with normal p53 expression were at increased risk of PSA failure (hazard ratio [HR]: 2.8; 95% confidence interval [CI]: 1.3-5.9; P = 0.008 for the 141; HR: 2.4; 95% CI: 1.1-5.4; P = 0.03 for the 113). Adjusted estimates of PSA failure were significantly higher (P = 0.03) in men with abnormal compared with normal p53 expression. At 5 years, these respective estimates were 33% and 18%.

CONCLUSIONS

Maximizing local control and randomized trials evaluating the impact on survival of adding novel agents to maximal local therapy are warranted in men whose prostate cancer demonstrates abnormal p53 expression.

Does transurethral resection of prostate (TURP) affect outcome in patients who subsequently develop prostate cancer?

OBJECTIVES

Pretreatment prostate specific antigen (PSA) is a strong predictor of prostate cancer outcome after radiotherapy and is a key parameter in pretreatment risk assessment. Because PSA is secreted from both benign and malignant tissue, a prior transurethral resection of prostate (TURP) may lower pretreatment PSA levels out of proportion to the extent of cancer. The purpose of this study was to determine whether a history of TURP is associated with increased biochemical failure (BF) after definitive radiotherapy for prostate cancer.

METHODS

From April 1989 to October 2001, 1135 men with low to intermediate risk T1c-2NX/0M0 (2002 AJCC) prostate cancer with a pretreatment PSA less than 20 ng/mL received three-dimensional conformal radiotherapy (median dose, 76 Gy) without androgen deprivation. The median pretreatment PSA was 7.4 ng/mL (range, 0.4 to 19.9). There were 126 men with a prior history of TURP. The Cox proportional hazards model was used for univariate and multivariate analyses for BF (nadir + 2 ng/mL definition).

RESULTS

On multivariable analysis, Gleason score (GS), PSA, and T-stage were significant predictors of BF in a model containing TURP and dose. A history of TURP was not a significant independent predictor of BF on subgroup analysis. There was a trend toward significance for the subgroup of GS less than 7 (P = 0.12).

CONCLUSIONS

A history of prior TURP does not affect outcome after RT for prostate cancer in low to intermediate risk patients.

Pelvic lymph node irradiation for prostate cancer: who, why, and when?

Prostate cancers are best characterized by their clinical (TNM) stage, Gleason score, and serum prostate-specific antigen (PSA) level. These 3 factors are known to influence the risk of pelvic nodal involvement. By combining these prognostic factors, nomograms and equations have been developed and are widely used in clinical practice as an accurate way of predicting the probability of a given pathological stage. Patients who have a significant risk of pelvic nodal metastasis will likely have higher biochemical failure rates. Results from the multi-institutional prospective trials have shown that patients at an intermediate to high risk for pelvic nodal involvement experience disease progression-free survival benefits from the use of whole pelvic radiotherapy combined with hormone therapy. Yet, significant biological interactions between radiation treatment volumes and timing of hormone therapy have been shown. Further study of these issues is necessary to define the best treatment for patients at significant risk of pelvic lymph node involvement.

Long-term results of conformal radiotherapy for prostate cancer: impact of dose escalation on biochemical tumor control and distant metastases-free survival outcomes

PURPOSE

To report prostate-specific antigen (PSA) relapse-free survival and distant metastases-free survival (DMFS) outcomes for patients with clinically localized prostate cancer treated with high-dose conformal radiotherapy.

METHODS AND MATERIALS

Between 1988 and 2004, a total of 2,047 patients with clinically localized prostate cancer were treated with three-dimensional conformal radiotherapy or intensity-modulated radiotherapy. Prescribed dose levels ranged from 66-86.4 Gy. Median follow-up was 6.6 years (range, 3-18 years).

RESULTS

Although no differences were noted among low-risk patients for the various dose groups, significant improvements were observed with higher doses for patients with intermediate- and high-risk features. In patients with intermediate-risk features, multivariate analysis showed that radiation dose was an important predictor for improved PSA relapse-free survival (p < 0.0001) and improved DMFS (p = 0.04). In patients with high-risk features, multivariate analysis showed that the following variables predict for improved PSA relapse-free survival: dose (p < 0.0001); age (p = 0.0005), and neoadjuvant-concurrent androgen deprivation therapy (ADT; p = 0.01). In this risk group, only higher radiation dose was an important predictor for improved DMFS (p = 0.04).

CONCLUSIONS

High radiation dose levels were associated with improved biochemical tumor control and decreased risk of distant metastases. For high-risk patients, despite the delivery of high radiation dose levels, the use of ADT conferred an additional benefit for improved tumor control outcomes. We observed a benefit for ADT in high-risk patients who received higher doses.

Reducing biochemical recurrence rates in EBRT-treated prostate cancer patients: the influence of dose and dose per fraction

In the last 15-20 years, technological improvements in radiation treatment planning and delivery have allowed radiation oncologists to increase the total dose to the prostate gland. The results of four randomized trials using conventional daily doses (1.8-2 Gy) demonstrate that higher total doses lead to lower rates of biochemical recurrence, but with a modest increase in late toxicity. Preclinical data suggest that treatment schedules relying on fewer, larger daily fractions of radiotherapy (hypofractionation) may increase the therapeutic ratio. Early results from several uncontrolled trials indicate that schedules that rely on larger daily doses are associated with low toxicity, provided some form of daily target localization and sophisticated treatment delivery are used. The results of several randomized trials that compare hypofractionated regimens to conventionally fractionated regimens will be available in the next 5-10 years.

Permanent prostate seed brachytherapy: a current perspective on the evolution of the technique and its application

This Review highlights current areas of controversy and development in the field of transperineal permanent prostate seed implantation brachytherapy (PPI), in particular the technological evolution of PPI treatment planning that has led to intra-operative treatment planning and execution, the use of MRI spectroscopy and ultrasonography to target intraprostatic tumor foci, and the introduction of (131)Cs as a new PPI isotope. Here we present a comprehensive review of mature data for PPI monotherapy and PPI combined with supplemental external beam radiation therapy, and a critical discussion of issues pertinent to supplemental EBRT. We also present our current policies in the treatment of prostate cancer at the University of California, San Francisco.

A Phase II study of high-dose-rate afterloading brachytherapy as monotherapy for the treatment of localized prostate cancer

PURPOSE

A Phase II dose escalation study has been undertaken to evaluate high-dose-rate brachytherapy (HDRBT) monotherapy for prostate cancer.

METHODS AND MATERIALS

A total of 110 patients have been entered, all with locally advanced cancer. Three dose levels have been used; 34 Gy in four fractions, 36 Gy in four fractions, and 31.5 Gy in three fractions. These equate to 226Gy(1.5), 252Gy(1.5), and 252Gy(1.5), respectively. Thirty patients have received 34 Gy, 25 received 36 Gy, and 55 patients received 31.5 Gy. Acute and late toxicity was analyzed using the International Prostate Symptom Score, and urologic and rectal events were scored using the Radiation Therapy Oncology Group/Common Terminology Criteria scoring systems.

RESULTS

Seven patients required urethral catheterization at 2 weeks; 3 receiving 34 Gy, 1 receiving 36 Gy, and 3 receiving 31.5 Gy. Only 3 patients remained catheterized at 12 weeks. Radiation Therapy Oncology Group 1 and 2 gastrointestinal toxicity at 2 weeks was seen in 61%, 68%, and 77%, respectively. Grade 3 bladder toxicity was seen in 2 patients at 6 months, 1 each from the 36 Gy and 31.5 Gy arms. One patient from the 31.5-Gy cohort reported Grade 2 bowel toxicity at 6 months. Prostate-specific antigen (PSA), stratified for androgen deprivation therapy (ADT) and no-ADT patients ranged from 16.1-22.9 microg/L and 11.1-12.5 microg/L, respectively. This fell at 12 months to 0.2-0.6 microg/L and 0.5-1.4 microg/L, respectively. No PSA relapses have yet been seen with a median follow-up of 30 months (34 Gy), 18 months (36 Gy), and 11.8 months (31.5 Gy).

CONCLUSIONS

Early results suggest an excellent biochemical response with no differences seen in acute and late toxicity between doses of 34 Gy/four fractions, 36 Gy/four fractions, or 31.5 Gy/three fractions.

Short-Term Neoadjuvant Androgen Deprivation Therapy and External-Beam Radiotherapy for Locally Advanced Prostate Cancer: Long-Term Results of RTOG 8610

Purpose

Radiation Therapy Oncology Group (RTOG) 8610 was the first phase III randomized trial to evaluate neoadjuvant androgen deprivation therapy (ADT) in combination with external-beam radiotherapy (EBRT) in men with locally advanced prostate cancer. This report summarizes long-term follow-up results.

Materials and Methods

Between 1987 and 1991, 456 assessable patients (median age, 70 years) were enrolled. Eligible patients had bulky (5 × 5 cm) tumors (T2-4) with or without pelvic lymph node involvement according to the 1988 American Joint Committee on Cancer TNM staging system. Patients received combined ADT that consisted of goserelin 3.6 mg every 4 weeks and flutamide 250 mg tid for 2 months before and concurrent with EBRT, or they received EBRT alone. Study end points included overall survival (OS), disease-specific mortality (DSM), distant metastasis (DM), disease-free survival (DFS), and biochemical failure (BF).

Results

Ten-year OS estimates (43% v 34%) and median survival times (8.7 v 7.3 years) favored ADT and EBRT, respectively; however, these differences did not reach statistical significance (P = .12). There was a statistically significant improvement in 10-year DSM (23% v 36%; P = .01), DM (35% v 47%; P = .006), DFS (11% v 3%; P < .0001), and BF (65% v 80%; P < .0001) with the addition of ADT, but no differences were observed in the risk of fatal cardiac events.

Conclusion

The addition of 4 months of ADT to EBRT appears to have a dramatic impact on clinically meaningful end points in men with locally advanced disease with no statistically significant impact on the risk of fatal cardiac events.

Radiotherapy after prostatectomy: is the evidence for dose escalation out there?

PURPOSE

To study the effective doses of radiotherapy (RT) after prostatectomy in search for evidence of a dose-response.

METHODS AND MATERIALS

Original and available data from published studies of adjuvant and salvage RT after prostatectomy were analyzed in the context of biochemical tumor control probability (TCP) dose-response curves. Comparisons were made with dose-escalation studies of radical RT for localized disease. Arguments based on a microscopic vs. macroscopic disease dose-response relationships were used to interpret the clinical data.

RESULTS

The tumor control rates after salvage RT were consistent with the TCP dose-response curve of radical RT, suggesting the presence of macroscopic-equivalent disease among salvage patients. For radical RT, the dose to achieve 50% biochemical tumor control was 65.9 Gy (95% confidence interval [CI], 64.8-66.8) and the Slope(50) was 2.6%/Gy (95% CI, 2.3-3.0). For salvage RT, the corresponding values were 66.8 Gy (95% CI, 65.1-68.4) and 3.8%/Gy (95% CI, 2.5-7.6). For a comparable TCP, the dose for adjuvant RT was approximately 6 Gy lower, consistent with one-tenth the burden of local disease. The present doses for adjuvant or salvage RT in the range of 60-70 Gy appear to be still on the steep part of the TCP dose-response curve.

CONCLUSIONS

The effective doses and dose-response relation observed with RT after prostatectomy are consistent with the presence of macroscopic-equivalent disease for salvage patients and about a tenth of the residual disease for adjuvant patients. Greater doses would potentially achieve significantly greater disease-free control rates. A randomized trial with 250 patients comparing 64 vs. 70 Gy for salvage RT or 60 vs. 66 Gy for adjuvant RT would be capable of addressing this issue.

Late rectal and urinary toxicity from conformal, dose-escalated radiation therapy for prostate cancer: a prospective study of 402 patients

This study investigates the rate of late rectal and urinary toxicity from three-dimensional conformal radiation therapy (3DCRT) for localized prostate cancer. The influence of neoadjuvant androgen deprivation (AD) on toxicity rates was also examined. A total of 402 men at Liverpool and Westmead hospitals received radical 3DCRT for localized prostate cancer between 1999 and 2003. Patients received either 70 Gy or 74 Gy, according to their prognostic risk grouping and or date of commencing radiation therapy (RT). Late rectal and urinary toxicity data were collected prospectively using Radiation Therapy Oncology Group/European Organisation for Research and Treatment of Cancer criteria. The median follow up of this cohort was 43.5 months. At 36 months, the cumulative incidence of >or=grade 2 rectal and urinary toxicities was 6.7 and 17.5%, respectively. Peak prevalence of late urinary toxicity occurred at 36 months (9.5%), although late rectal toxicity was highest at 12 months (2.9%) from completion of 3DCRT. The use of AD did not cause additional late toxicities. Patients receiving 74 Gy did not experience significantly worse toxicities than the group receiving 70 Gy.

A comparison of acute and chronic toxicity for men with low-risk prostate cancer treated with intensity-modulated radiation therapy or (125)I permanent implant

PURPOSE

To compare the toxicity and biochemical outcomes of intensity-modulated radiation therapy (IMRT) and (125)I transperineal permanent prostate seed implant ((125)I) for patients with low-risk prostate cancer.

METHODS AND MATERIALS

Between 1998 and 2004, a total of 374 low-risk patients (prostate-specific antigen < 10 ng/ml, T1c-T2b, Gleason score of 6 or less, and no neoadjuvant hormones) were treated at Fox Chase Cancer Center (216 IMRT and 158 (125)I patients). Median follow-up was 43 months for IMRT and 48 months for (125)I. The IMRT prescription dose ranged from 74-78 Gy, and (125)I prescription was 145 Gy. Acute and late gastrointestinal (GI) and genitourinary (GU) toxicity was recorded by using a modified Radiation Therapy Oncology Group scale. Freedom from biochemical failure was defined by using the Phoenix definition (prostate-specific antigen nadir + 2.0 ng/ml).

RESULTS

Patients treated by using IMRT were more likely to be older and have a higher baseline American Urological Association symptom index score, history of previous transurethral resection of the prostate, and larger prostate volumes. On multivariate analysis, IMRT was an independent predictor of lower acute and late Grade 2 or higher GU toxicity and late Grade 2 or higher GI toxicity. Three-year actuarial estimates of late Grade 2 or higher toxicity were 2.4% for GI and 3.5% for GU by using IMRT compared with 7.7% for GI and 19.2% for GU for (125)I, respectively. Four-year actuarial estimates of freedom from biochemical failure were 99.5% for IMRT and 93.5% for (125)I (p = 0.09).

CONCLUSIONS

The IMRT and (125)I produce similar outcomes, although IMRT appears to have less acute and late toxicity.

Improved outcomes with higher doses for salvage radiotherapy after prostatectomy

PURPOSE

To evaluate relapse-free survival with higher doses for patients receiving salvage radiotherapy (RT) after radical prostatectomy (RP).

PATIENTS AND METHODS

A total of 122 patients with pathologically negative lymph nodes received salvage RT after RP from 1984 to 2004. Median prostate bed dose was 60 Gy for 38 patients and 70 Gy for 84 patients. Four months of total androgen suppression and whole-pelvic RT were given concurrently to 68 and 72 patients, respectively. The median follow-up was >5 years. Kaplan-Meier and Cox proportional hazards multivariable analyses were performed for all clinical, pathologic, and treatment factors predicting for biochemical relapse-free survival (bRFS).

RESULTS

There were 60 biochemical failures after salvage RT, with a median time to failure of 1.2 years. A dose response was observed, with a 5-year bRFS rate of 25% vs. 58% for prostate bed doses of 60 Gy vs. 70 Gy (p < 0.0001). For patients receiving RT alone the 5-year bRFS rate was 17% vs. 55% (p = 0.016), and for those receiving prostate-bed-only RT it was 23% vs. 66% (p = 0.037) for doses of 60 Gy vs. 70 Gy, respectively. On multivariate analysis a prostate bed dose of 70 Gy (p = 0.012, hazard ratio [HR] 0.48 [95% Confidence Interval (CI), 0.27-0.87]), pre-RT prostate-specific antigen value < or =1 ng/mL (p < 0.0001, HR 0.28 [95% CI, 0.16-0.48]), and lack of seminal vesicle involvement (p = 0.009, HR 0.44 [95% CI, 0.26-0.77]) remained independently significant.

CONCLUSIONS

A clinically significant dose response from 60 Gy to 70 Gy was observed in the setting of salvage RT after prostatectomy. A dose of 70 Gy to the prostate bed is recommended to achieve optimal disease-free survival.

Does intensity modulated radiation therapy (IMRT) prevent additional toxicity of treating the pelvic lymph nodes compared to treatment of the prostate only?

BACKGROUND

To evaluate the risk of rectal, bladder and small bowel toxicity in intensity modulated radiation therapy (IMRT) of the prostate only compared to additional irradiation of the pelvic lymphatic region.

METHODS

For ten patients with localized prostate cancer, IMRT plans with a simultaneous integrated boost (SIB) were generated for treatment of the prostate only (plan-PO) and for additional treatment of the pelvic lymph nodes (plan-WP). In plan-PO, doses of 60 Gy and 74 Gy (33 fractions) were prescribed to the seminal vesicles and to the prostate, respectively. Three plans-WP were generated with prescription doses of 46 Gy, 50.4 Gy and 54 Gy to the pelvic target volume; doses to the prostate and seminal vesicles were identical to plan-PO. The risk of rectal, bladder and small bowel toxicity was estimated based on NTCP calculations.

RESULTS

Doses to the prostate were not significantly different between plan-PO and plan-WP and doses to the pelvic lymph nodes were as planned. Plan-WP resulted in increased doses to the rectum in the low-dose region </= 30 Gy, only, no difference was observed in the mid and high-dose region. Normal tissue complication probability (NTCP) for late rectal toxicity ranged between 5% and 8% with no significant difference between plan-PO and plan-WP. NTCP for late bladder toxicity was less than 1% for both plan-PO and plan-WP. The risk of small bowel toxicity was moderately increased for plan-WP.

DISCUSSION

This retrospective planning study predicted similar risks of rectal, bladder and small bowel toxicity for IMRT treatment of the prostate only and for additional treatment of the pelvic lymph nodes.

Comparing two strategies of dynamic intensity modulated radiation therapy (dIMRT) with 3-dimensional conformal radiation therapy (3DCRT) in the hypofractionated treatment of high-risk prostate cancer

Background

To compare two strategies of dynamic intensity modulated radiation therapy (dIMRT) with 3-dimensional conformal radiation therapy (3DCRT) in the setting of hypofractionated high-risk prostate cancer treatment.

Methods

3DCRT and dIMRT/Helical Tomotherapy(HT) planning with 10 CT datasets was undertaken to deliver 68 Gy in 25 fractions (prostate) and simultaneously delivering 45 Gy in 25 fractions (pelvic lymph node targets) in a single phase. The paradigms of pelvic vessel targeting (iliac vessels with margin are used to target pelvic nodes) and conformal normal tissue avoidance (treated soft tissues of the pelvis while limiting dose to identified pelvic critical structures) were assessed compared to 3DCRT controls. Both dIMRT/HT and 3DCRT solutions were compared to each other using repeated measures ANOVA and post-hoc paired t-tests.

Results

When compared to conformal pelvic vessel targeting, conformal normal tissue avoidance delivered more homogenous PTV delivery (2/2 t-test comparisons; p < 0.001), similar nodal coverage (8/8 t-test comparisons; p = ns), higher and more homogenous pelvic tissue dose (6/6 t-test comparisons; p < 0.03), at the cost of slightly higher critical structure dose (D_dose, 1–3 Gy over 5/10 dose points; p < 0.03). The dIMRT/HT approaches were superior to 3DCRT in sparing organs at risk (22/24 t-test comparisons; p < 0.05).

Conclusion

dIMRT/HT nodal and pelvic targeting is superior to 3DCRT in dose delivery and critical structure sparing in the setting of hypofractionation for high-risk prostate cancer. The pelvic targeting paradigm is a potential solution to deliver highly conformal pelvic radiation treatment in the setting of nodal location uncertainty in prostate cancer and other pelvic malignancies.

On Voxel based Iso-Tumor Control Probabilty and Iso-Complication Maps for Selective Boosting and Selective Avoidance Intensity Modulated Radiotherapy

Voxel based iso-Tumor Control Probability (TCP) maps and iso-Complication maps are proposed as a plan-review tool especially for functional image-guided intensity-modulated radiotherapy (IMRT) strategies such as selective boosting (dose painting) and conformal avoidance IMRT. The maps employ voxel-based phenomenological biological dose-response models for target volumes and normal organs. Two IMRT strategies for prostate cancer, namely conventional uniform IMRT delivering an EUD = 84 Gy (equivalent uniform dose) to the entire PTV and selective boosting delivering an EUD = 82 Gy to the entire PTV, are investigated, to illustrate the advantages of this approach over iso-dose maps. Conventional uniform IMRT did yield a more uniform isodose map to the entire PTV while selective boosting did result in a nonuniform isodose map. However, when employing voxel based iso-TCP maps selective boosting exhibited a more uniform tumor control probability map compared to what could be achieved using conventional uniform IMRT, which showed TCP cold spots in high-risk tumor subvolumes despite delivering a higher EUD to the entire PTV. Voxel based iso-Complication maps are presented for rectum and bladder, and their utilization for selective avoidance IMRT strategies are discussed. We believe as the need for functional image guided treatment planning grows, voxel based iso-TCP and iso-Complication maps will become an important tool to assess the integrity of such treatment plans.

Adaptive Radiotherapy for Prostate Cancer Using Kilovoltage Cone-Beam Computed Tomography: First Clinical Results

PURPOSE

To evaluate the first clinical results of an off-line adaptive radiotherapy (ART) protocol for prostate cancer using kilovoltage cone-beam computed tomography (CBCT) in combination with a diet and mild laxatives.

METHODS AND MATERIALS

Twenty-three patients began treatment with a planning target volume (PTV) margin of 10 mm. The CBCT scans acquired during the first six fractions were used to generate an average prostate clinical target volume (AV-CTV), and average rectum (AV-Rect). Using these structures, a new treatment plan was generated with a 7-mm PTV margin. Weekly CBCT scans were used to monitor the CTV coverage. A diet and mild laxatives were introduced to improve image quality and reduce prostate motion.

RESULTS

Twenty patients were treated with conform ART protocol. For these patients, 91% of the CBCT scans could be used to calculate the AV-CTV and AV-Rect. In 96% of the follow-up CBCT scans, the CTV was located within the average PTV. In the remaining 4%, the prostate extended the PTV by a maximum of 1 mm. Systematic and random errors for organ motion were reduced by a factor of two compared with historical data without diet and laxatives. An average PTV reduction of 29% was achieved. The volume of the AV-Rect that received >65 Gy was reduced by 19%. The mean dose to the anal wall was reduced on average by 4.8 Gy.

CONCLUSIONS

We safely reduced the high-dose region by 29%. The reduction in irradiated volume led to a significant reduction in the dose to the rectum. The diet and laxatives improved the image quality and tended to reduce prostate motion.

Intrarectal amifostine during external beam radiation therapy for prostate cancer produces significant improvements in Quality of Life measured by EPIC score

PURPOSE

To test whether intrarectal amifostine limits symptoms of radiation proctitis, measured by using the Radiation Therapy Oncology Group (RTOG) gastrointestinal (GI) toxicity score and the Expanded Prostate Cancer Index Composite (EPIC) score.

METHODS AND MATERIALS

Patients with localized prostate cancer received amifostine as a rectal suspension 30-45 minutes before daily three-dimensional conformal radiation therapy. The first 18 patients received 1 g of amifostine, and the next 12 patients received 2 g. Toxicity was assessed at baseline, during treatment, and at follow-up visits by using RTOG grading and the EPIC Quality of Life (QoL) 50-item questionnaire. The Bowel Function subset of the bowel domain (EPIC-BF), which targets symptom severity, and the Bowel Bother subset of the bowel domain (EPIC-BB), which assesses QoL, were evaluated and compared with the RTOG GI toxicity score.

RESULTS

Median follow-up was 30 months (range, 18-36 months). Overall, EPIC-BF and EPIC-BB scores both tracked closely with the RTOG GI toxicity score. Seven weeks after the start of radiation therapy, the incidence of RTOG Grade 2 toxicity was 33% in the 1-g group (6/18 patients) compared with 0% (0/12 patients) in the 2-g group and tended toward statistical significance (p = 0.06). A significant difference between amifostine groups was observed using the EPIC-BF score at 7 weeks (p = 0.04). A difference in EPIC-BB scores between dose groups was evident at 7 weeks (p = 0.07) and was significant at 12 months (p = 0.04).

CONCLUSIONS

Higher doses of amifostine produced significant improvements in acute and late bowel QoL (up to 1 year after therapy), measured using the EPIC score.

Radiothérapie robotisée des cancers de prostate par CyberKnife™

After 3D conformal radiation therapy without and with modulated intensity, image-guided radiation therapy represents a new technological step. Should prostate cancer treatment using radiotherapy with the CyberKnife robotic system be considered as a new treatment and then investigated through classical clinical research procedure rather than a technical improvement of an already validated treatment? After a general presentation of the CyberKnife , the authors focused on prostate cancer treatment assuming that, according to dosimetric and biological considerations, the treatment by robotic system appears comparable to high dose rate brachytherapy. For prostate cancer treatment are discussed: biological rational for hypofractionated treatment, high dose rate brachytherapy boost and interest of dose escalation. A comparison is presented between CyberKnife and other validated treatment for prostate cancer (radical prostatectomy, 3D conformal radiation therapy and low and high dose rate brachytherapy). In summary, CyberKnife treatment could be considered as a technical improvement of an already validated treatment in order to deliver a prostate boost after pelvic or peri-prostatic area irradiation. However, the clinical, biological and economical results must be precisely analyzed and could be assessed in the frame of a National Observatory based on shared therapeutic program.

Customized Dose Prescription for Permanent Prostate Brachytherapy: Insights From a Multicenter Analysis of Dosimetry Outcomes

PURPOSE

To investigate the biochemical control rate in patients undergoing permanent prostate brachytherapy as a function of the biologically effective dose (BED) and risk group.

METHODS AND MATERIALS

Six centers provided data on 3,928 permanent brachytherapy patients with postimplant dosimetry results. The mean prostate-specific antigen level was 8.9 ng/mL. (125)I was used in 2,293 (58%), (103)Pd in 1,635, and supplemental external beam radiotherapy in 882 (22.5%) patients. The patients were stratified into low- (n = 2,188), intermediate- (n = 1,188), and high- (n = 552) risk groups and into three BED groups of < 140 Gy (n = 524), 140-200 Gy (n = 2284), and >200 Gy (n = 1,115). Freedom from biochemical disease progression (biochemical freedom from failure [bFFF]) was determined using the American Society for Therapeutic Radiology Oncology and Phoenix definitions and calculated using the Kaplan-Meier method, with factors compared using the log-rank test.

RESULTS

The 10-year prostate-specific antigen bFFF rate for the American Society for Therapeutic Radiology Oncology and Phoenix definitions was 79.2% and 70%, respectively. The corresponding bFFF rates for the low-, intermediate-, and high-risk groups was 84.1% and 78.1%, 76.8% and 63.6%, and 64.4% and 58.2%, respectively (p < 0.0001). The corresponding bFFF rate for the three BED groups was 56.1% and 41.4%, 80% and 77.9%, and 91.1% and 82.9% (p < 0.0001). The corresponding bFFF rate for the low-risk patients by dose group was 69.8% and 49.8%, 86% and 85.2%, and 88.1% and 88.3% for the low-, intermediate, and high-dose group, respectively (p <0.0001). The corresponding bFFF rate for the intermediate-risk patients by dose group was 52.9% and 23.1%, 74.1% and 77.7%, and 94.3% and 88.8% for the low-, intermediate-, and high-dose group, respectively (p < 0.0001). The corresponding bFFF rate for high-risk patients by dose group was 19.2% and 41.7%, 61.8% and 53.2%, and 90% and 69.6% for the low-, intermediate-, and high-dose group, respectively (p < 0.0001).

CONCLUSIONS

These data suggest that permanent brachytherapy dose prescriptions can be customized to risk status. In low-risk patients, achieving a BED of >or=140 Gy might be adequate for prostate-specific antigen control. However, high-risk disease might require a BED dose of >or=200 Gy.

Effect of increasing radiation doses on local and distant failures in patients with localized prostate cancer

PURPOSE

To study the effect of radiation dose on local failure (LF) and distant metastasis (DM) in prostate cancer patients treated with external beam radiotherapy.

METHODS AND MATERIALS

The study sample consisted of 919 Stage T1-T3N0M0 patients treated with radiotherapy alone. Three separate dose groups were analyzed: <72 Gy (n = 552, median dose, 68.4 Gy), > or =72 but <82 Gy (n = 215, median dose, 78 Gy), and > or =82 Gy (n = 152, median dose, 83 Gy). The median follow-up period for all patients and those receiving <72 Gy, > or =72 but <82 Gy, and > or =82 Gy was 97, 112, 94, and 65 months, respectively.

RESULTS

For all patients, the LF rate at 10 and 15 years was 6% and 13%, respectively. The 7-year LF rate stratified by dose group (<72 Gy, > or =72 but <82 Gy, and > or =82 Gy) was 6%, 2%, and 2%, respectively (p = 0.012). For all patients, the DM rate at 10 and 15 years was 10% and 17%, respectively. The 7-year DM rate stratified by dose group (<72 Gy, > or =72 but <82 Gy, and > or =82 Gy) was 9%, 6%, and 1%, respectively (p = 0.008). Multivariate analysis revealed T stage (p < 0.001), pretreatment prostate-specific antigen level (p = 0.001), Gleason score (p < 0.001), and dose (p = 0.018) to be independent predictors of DM. For all 919 patients, multivariate analysis revealed only Gleason score (p = 0.009) and dose (p = 0.004) to be independent predictors of LF.

CONCLUSION

Although the effect of increasing radiation doses has been documented mostly for biochemical failure rates, the results of our study have shown a clear association between greater radiation doses and lower LF and DM rates.

A comparison of the use of bony anatomy and internal markers for offline verification and an evaluation of the potential benefit of online and offline verification protocols for prostate radiotherapy

PURPOSE

To evaluate the utility of intraprostatic markers in the treatment verification of prostate cancer radiotherapy. Specific aims were: to compare the effectiveness of offline correction protocols, either using gold markers or bony anatomy; to estimate the potential benefit of online correction protocol's using gold markers; to determine the presence and effect of intrafraction motion.

METHODS AND MATERIALS

Thirty patients with three gold markers inserted had pretreatment and posttreatment images acquired and were treated using an offline correction protocol and gold markers. Retrospectively, an offline protocol was applied using bony anatomy and an online protocol using gold markers.

RESULTS

The systematic errors were reduced from 1.3, 1.9, and 2.5 mm to 1.1, 1.1, and 1.5 mm in the right-left (RL), superoinferior (SI), and anteroposterior (AP) directions, respectively, using the offline correction protocol and gold markers instead of bony anatomy. The subsequent decrease in margins was 1.7, 3.3, and 4 mm in the RL, SI, and AP directions, respectively. An offline correction protocol combined with an online correction protocol in the first four fractions reduced random errors further to 0.9, 1.1, and 1.0 mm in the RL, SI, and AP directions, respectively. A daily online protocol reduced all errors to <1 mm. Intrafraction motion had greater impact on the effectiveness of the online protocol than the offline protocols.

CONCLUSIONS

An offline protocol using gold markers is effective in reducing the systematic error. The value of online protocols is reduced by intrafraction motion.

Practical issues in the implementation of image-guided radiotherapy for the treatment of prostate cancer within a UK department

AIMS

To study the feasibility of using implanted gold seeds in combination with a commercial software system for daily localisation of the prostate gland during conformal radiotherapy, and to assess the effect this may have on departmental workload.

MATERIALS AND METHODS

Six patients had three gold radio-opaque seeds implanted into the prostate gland before starting a course of radiotherapy. The seeds were identified on daily portal images and an automated online system provided immediate vector analysis of discrepancies between the planned and actual daily position of the intraprostatic seeds. In total, 138 interfractional displacements were analysed. The workload impact for the department was assessed using the basic treatment equivalence model, by comparing measurements of daily treatment session durations with a control group of patients receiving standard conformal radiotherapy, matched for treatment complexity.

RESULTS

No acute complications of seed insertion were observed. A number of developmental issues required solutions to be identified before clinical implementation was possible. The standard deviations of the set-up and organ motion systematic errors in the left-right, superior-inferior and anterior-posterior directions were 2.4, 3.0 and 2.5 mm, respectively. The standard deviations of the set-up and organ motion random errors calculated were 2.5, 2.9 and 3.7 mm. The mean treatment session duration with this daily prostate localisation system was increased by 3 min compared with matched controls using standard imaging practice. If all radical prostate patients in our department were to receive image-guided radiotherapy in this way, this would increase machine workload time by 2.2 h/day.

CONCLUSIONS

The implementation of this image-guided system is feasible. No additional linear accelerator modification is required and standard imaging devices can be used. It would be a useful addition to any department's image-guided radiotherapy developmental strategy.

Phase II Trial of Hypofractionated Image-Guided Intensity-Modulated Radiotherapy for Localized Prostate Adenocarcinoma

PURPOSE

To assess in a prospective trial the feasibility and late toxicity of hypofractionated radiotherapy (RT) for prostate cancer.

METHODS AND MATERIALS

Eligible patients had clinical stage T1c-2cNXM0 disease. They received 60 Gy in 20 fractions over 4 weeks with intensity-modulated radiotherapy including daily on-line image guidance with intraprostatic fiducial markers.

RESULTS

Between June 2001 and March 2004, 92 patients were treated with hypofractionated RT. The cohort had a median prostate-specific antigen value of 7.06 ng/mL. The majority had Gleason grade 5-6 (38%) or 7 (59%) disease, and 82 patients had T1c-T2a clinical staging. Overall, 29 patients had low-risk, 56 intermediate-risk, and 7 high-risk disease. Severe acute toxicity (Grade 3-4) was rare, occurring in only 1 patient. Median follow-up was 38 months. According to the Phoenix definition for biochemical failure, the rate of biochemical control at 14 months was 97%. According to the previous American Society for Therapeutic Radiology and Oncology definition, biochemical control at 3 years was 76%. The incidence of late toxicity was low, with no severe (Grade > or =3) toxicity at the most recent assessment.

CONCLUSIONS

Hypofractionated RT using 60 Gy in 20 fractions over 4 weeks with image guidance is feasible and is associated with low rates of late bladder and rectal toxicity. At early follow-up, biochemical outcome is comparable to that reported for conventionally fractionated controls. The findings are being tested in an ongoing, multicenter, Phase III trial.

Radiothérapie guidée par l'image

Recent advances in radiation oncology are based on improvement in dose distribution thanks to IMRT and improvement in target definition through new diagnostic imaging such as spectroscopic or functional MRI or PET. However, anatomic variations may occur during treatment decreasing the benefit of such optimization. Image-guided radiotherapy reduces geometric uncertainties occurring during treatment and therefore should reduce dose delivered to healthy tissues and enable dose escalation to enhance tumour control. However, IGRT experience is still limited, while a wide panel of IGRT modalities is available. A strong quality control is required for safety and proper evaluation of the clinical benefit of IGRT combined or not with IMRT.

Residual set-up errors and margins in on-line image-guided prostate localization in radiotherapy

BACKGROUND AND PURPOSE

Image-guided on-line correction of the target position allows radiotherapy of prostate cancer with narrow set-up margins. The present study investigated the residual set-up error after on-line prostate localization and its impact on margins.

MATERIALS AND METHODS

Prostate localization based on two orthogonal X-ray images of gold markers implanted in the prostate was performed with an on-board imager at four treatment sessions for 90 patients. The set-up error in the sagittal plane residual after couch adjustment was evaluated on lateral verification portal images.

RESULTS

The set-up error was less than 3.0mm in 92% of the cases in the anterior-posterior (AP) direction and in 95% of the cases in the cranio-caudal (CC) direction. The set-up error was dominated by internal prostate motion taking place during the set-up procedure. Set-up margins were calculated using two formalisms: margins designed to ensure a minimum CTV dose of 95% for 90% of the patient population were 3.6mm (AP) and 3.5mm (CC). Patient-independent normal distributed set-up errors would result in margins of 4.3mm (AP) and 4.0mm (CC) to ensure complete CTV inclusion in the PTV with 90% probability.

CONCLUSION

Internal prostate motion during the set-up procedure was the main contributor to residual set-up errors.

Ultrasound-Guided Transrectal Implantation of Gold Markers for Prostate Localization During External Beam Radiotherapy: Complication Rate and Risk Factors

PURPOSE

To report the complication rate and risk factors of transrectally implanted gold markers, used for prostate position verification and correction procedures.

METHODS AND MATERIALS

In 209 consecutive men with localized prostate cancer, four gold markers (1 x 7 mm) were inserted under ultrasound guidance in an outpatient setting, and the toxicity was analyzed. All patients received a questionnaire regarding complications after marker implantation. The complications and risk factors were further evaluated by reviewing the medical charts.

RESULTS

Of the 209 men, 13 (6.2%) had a moderate complication, consisting of pain and fever that resolved after treatment with oral medication. In 1.9% of the men, minor voiding complaints were observed. Other minor transient complications, defined as hematuria lasting >3 days, hematospermia, and rectal bleeding, occurred in 3.8%, 18.5%, and 9.1% of the patients, respectively. These complications were seen more often in patients with advanced tumor stage, younger age, and shorter duration of hormonal therapy.

CONCLUSION

Transrectal gold marker implantation for high-precision prostate radiotherapy is a safe and well-tolerated procedure.

Intensity Modulated Radiation Therapy Reduces Gastrointestinal Toxicity in Patients Treated with Androgen Deprivation Therapy for Prostate Cancer

PURPOSE: Androgen deprivation therapy (AD) has been shown to increase late ≥ grade 2 rectal toxicity when used concurrently with three-dimensional conformal radiotherapy (3DCRT). Intensity modulated radiotherapy (IMRT) has the potential to reduce toxicity by limiting the radiation dose received by the bowel and bladder. This study compares both genitourinary (GU) and gastrointestinal (GI) toxicity in men treated with 3DCRT+AD versus IMRT+AD. METHODS AND MATERIALS: From July 1992 to July 2004, 293 men received 3DCRT (n=170) or IMRT (n=123) with concurrent AD (< 6 months, n=123; ≥ 6 months, n =170). Median RT doses were 76 Gy for 3DCRT (ICRU) and 76 Gy for IMRT (95% to the PTV). Toxicity was assessed by a patient symptom questionnaire assessing toxicity completed at each visit and recorded using a modified late effects normal tissue task force radiation morbidity scale (LENT). RESULTS: Mean follow-up was 86 months (SD=29.3) for the 3DCRT group and 40 months (SD=9.7) for the IMRT group. Acute GI toxicity (OR=4, 95% CI: 1.6-11.7, p=0.005) was significantly higher with 3DCRT than with IMRT and was independent of AD duration (i.e. <6 vs. ≥6 months). Time to development of late GI toxicity was significantly longer in the IMRT group. The 5-year Kaplan-Meier estimates for ≥ grade 2 GI toxicity were 20% for 3DCRT versus 8% for IMRT (p=0.01). On MVA, ≥ grade 2 late GI toxicity (HR=2.1, 95% CI: 1.1-4.3, p=0.04) was more prevalent in 3DCRT patients. CONCLUSIONS: Compared to 3DCRT, IMRT significantly decreased acute and late GI toxicity in patients treated with AD.

Simultaneous integrated boost of biopsy proven, MRI defined dominant intra-prostatic lesions to 95 Gray with IMRT: early results of a phase I NCI study

BACKGROUND

To assess the feasibility and early toxicity of selective, IMRT-based dose escalation (simultaneous integrated boost) to biopsy proven dominant intra-prostatic lesions visible on MRI.

METHODS

Patients with localized prostate cancer and an abnormality within the prostate on endorectal coil MRI were eligible. All patients underwent a MRI-guided transrectal biopsy at the location of the MRI abnormality. Gold fiducial markers were also placed. Several days later patients underwent another MRI scan for fusion with the treatment planning CT scan. This fused MRI scan was used to delineate the region of the biopsy proven intra-prostatic lesion. A 3 mm expansion was performed on the intra-prostatic lesions, defined as a separate volume within the prostate. The lesion + 3 mm and the remainder of the prostate + 7 mm received 94.5/75.6 Gray (Gy) respectively in 42 fractions. Daily seed position was verified to be within 3 mm.

RESULTS

Three patients were treated. Follow-up was 18, 6, and 3 months respectively. Two patients had a single intra-prostatic lesion. One patient had 2 intra-prostatic lesions. All four intra-prostatic lesions, with margin, were successfully targeted and treated to 94.5 Gy. Two patients experienced acute RTOG grade 2 genitourinary (GU) toxicity. One had grade 1 gastrointestinal (GI) toxicity. All symptoms completely resolved by 3 months. One patient had no acute toxicity.

CONCLUSION

These early results demonstrate the feasibility of using IMRT for simultaneous integrated boost to biopsy proven dominant intra-prostatic lesions visible on MRI. The treatment was well tolerated.

Vascular targeted photodynamic therapy with palladium-bacteriopheophorbide photosensitizer for recurrent prostate cancer following definitive radiation therapy: assessment of safety and treatment response

PURPOSE

Tookad is a novel intravascular photosensitizer. When activated by 763 nm light, it destroys tumors by damaging their blood supply. It then clears rapidly from the circulatory system. To our knowledge we report the first application of Tookad vascular targeted photodynamic therapy in humans. We assessed the safety, pharmacokinetics and preliminary treatment response as a salvage procedure after external beam radiation therapy.

MATERIALS AND METHODS

Patients received escalating drug doses of 0.1 to 2 mg/kg at a fixed light dose of 100 J/cm or escalated light doses of 230 and 360 J/cm at the 2 mg/kg dose. Four optical fibers were placed transperineally in the prostate, including 2 for light delivery and 2 for light dosimetry. Treatment response was assessed primarily by hypovascular lesion formation on contrast enhanced magnetic resonance imaging and transrectal ultrasound guided biopsies targeting areas of lesion formation and secondarily by serum prostate specific antigen changes.

RESULTS

Tookad vascular targeted photodynamic therapy was technically feasible. The plasma drug concentration was negligible by 2 hours after infusion. In the drug escalation arm 3 of 6 patients responded, as seen on magnetic resonance imaging, including 1 at 1 mg/kg and 2 at 2 mg/kg. The light dose escalation demonstrated an increasing volume of effect with 2 of 3 patients in the first light escalation cohort responding and all 6 responding at the highest light dose with lesions encompassing up to 70% of the peripheral zone. There were no serious adverse events, and continence and potency were maintained.

CONCLUSIONS

Tookad vascular targeted photodynamic therapy salvage therapy is safe and well tolerated. Lesion formation is strongly drug and light dose dependent. Early histological and magnetic resonance imaging responses highlight the clinical potential of Tookad vascular targeted photodynamic therapy to manage post-external beam radiation therapy recurrence.

Monte Carlo determination of radiation-induced cancer risks for prostate patients undergoing intensity- modulated radiation therapy

The application of intensity‐modulated radiation therapy (IMRT) has enabled the delivery of high doses to the target volume while sparing the surrounding normal tissues. The drawbacks of intensity modulation, as implemented using a computer‐controlled multileaf collimator (MLC), are the larger number of monitor units (MUs) and longer beam‐on time as compared with conventional radiotherapy. Additionally, IMRT uses more beam directions—typically 5 – 9 for prostate treatment—to achieve highly conformal dose and normal‐tissue sparing. In the present work, we study radiation‐induced cancer risks attributable to IMRT delivery using MLC for prostate patients.

Whole‐body computed tomography scans were used in our study to calculate (according to report no. 116 from the National Council on Radiation Protection and Measurements) the effective dose equivalent received by individual organs. We used EGS4 and MCSIM to compute the dose for IMRT and three‐dimensional conformal radiotherapy. The effects of collimator rotation, distance from the treatment field, and scatter and leakage contribution to the whole‐body dose were investigated. We calculated the whole‐body dose equivalent to estimate the increase in the risk of secondary malignancies.

Our results showed an overall doubling in the risk of secondary malignancies from the application of IMRT as compared with conventional radiotherapy. This increase in the risk of secondary malignancies is not necessarily related to a relative increase in MUs. The whole‐body dose equivalent was also affected by collimator rotation, field size, and the energy of the photon beam. Smaller field sizes of low‐energy photon beams (that is, 6 MV) with the MLC axis along the lateral axis of the patient resulted in the lowest whole‐body dose. Our results can be used to evaluate the risk of secondary malignancies for prostate IMRT patients.

PACS: 87.53.wz, 87.53.‐j

Salvage hypofractionated radiotherapy for biochemically recurrent prostate cancer after radical prostatectomy

PURPOSE

To evaluate whether hypofractionation is well tolerated and to preliminarily assess biochemical control of this regimen in a postprostatectomy, salvage setting.

METHODS AND MATERIALS

A retrospective analysis was performed in 50 patients treated between May 2003 and December 2005 with hypofractionated radiotherapy for biochemical recurrence after radical prostatectomy. Radiotherapy was prescribed to the prostatic fossa to 65-70 Gy in 26-28 fractions of 2.5 Gy each, using intensity-modulated radiotherapy with daily image localization. Toxicities were scored using a modified Radiation Therapy Oncology Group scale and the Fox Chase modification of Late Effects Normal Tissue scale. The median follow-up was 18.9 months (range, 5.3-35.9).

RESULTS

No Grade 3 or greater acute or late toxicities were observed. Grade 2 toxicities included four acute genitourinary, one acute gastrointestinal, two late genitourinary, and two late gastrointestinal toxicities. Of the 50 patients, 39 demonstrated a continuous biochemical response after salvage therapy, 3 had an initial response before prostate-specific antigen failure, and 7 had prostate-specific antigen progression, 1 of whom died of progressive metastatic disease. Finally, 1 patient discontinued therapy because of the diagnosis of a metachronous pancreatic cancer and died without additional prostate cancer follow-up. All remaining patients were alive at the last follow-up visit. A lower presalvage prostate-specific antigen level was the only significant prognostic factor for improved biochemical control. The estimated actuarial biochemical control rate at 2 years was 72.9%.

CONCLUSIONS

The toxicity and early biochemical response rates were consistent with expectations from conventional fractionation. Additional follow-up is required to better document the biochemical control, but these results suggest that hypofractionation is a well-tolerated approach for salvage radiotherapy.