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

Dosimetry and preliminary acute toxicity in the first 100 men treated for prostate cancer on a randomized hypofractionation dose escalation trial

PURPOSE

The alpha/beta ratio for prostate cancer is postulated to be between 1 and 3, giving rise to the hypothesis that there may be a therapeutic advantage to hypofractionation. The dosimetry and acute toxicity are described in the first 100 men enrolled in a randomized trial.

PATIENTS AND METHODS

The trial compares 76 Gy in 38 fractions (Arm I) to 70.2 Gy in 26 fractions (Arm II) using intensity modulated radiotherapy. The planning target volume (PTV) margins in Arms I and II were 5 mm and 3 mm posteriorly and 8 mm and 7 mm in all other dimensions. The PTV D95% was at least the prescription dose.

RESULTS

The mean PTV doses for Arms I and II were 81.1 and 73.8 Gy. There were no differences in overall maximum acute gastrointestinal (GI) or genitourinary (GU) toxicity acutely. However, there was a slight but significant increase in Arm II GI toxicity during Weeks 2, 3, and 4. In multivariate analyses, only the combined rectal DVH parameter of V65 Gy/V50 Gy was significant for GI toxicity and the bladder volume for GU toxicity.

CONCLUSION

Hypofractionation at 2.7 Gy per fraction to 70.2 Gy was well tolerated acutely using the planning conditions described.

Biologically effective dose values for prostate brachytherapy: Effects on PSA failure and posttreatment biopsy results

PURPOSE

To analyze the effect of biologically effective dose (BED) values on prostate-specific antigen (PSA) failure and posttreatment biopsy.

METHODS AND MATERIALS

From 1990 to 2003, 1,377 patients had prostate brachytherapy alone (I-125 or Pd-103) (571), hormonal and brachytherapy (371), and trimodality therapy (hormonal, implant, and external beam) (435). Dose was defined as the D90 (dose delivered to 90% of the gland from the dose-volume histogram).

RESULTS

Freedom from PSA failure (FFPF) at 10 years was 87%. The 10-year FFPF for BED<100, >100-120, >120-140, >140-160, <160-180, >180-200, and >200 were 46%, 68%, 81%, 85.5%, 90%, 90%, and 92%, respectively (p<0.0001). BED and Gleason score had the greatest effect, with p values of p<0.0001 in multivariate analysis. Posttreatment positive biopsy rate was 7% (31/446). The positive biopsy rates for BED<or=100, >100-120, >120-140, >140-160, >160-180, >180-200, and >200 were 24% (8/33), 15% (3/20), 6% (2/33), 6% (3/52), 7% (6/82), 1% (1/72), and 3% (4/131), respectively (p<0.0001). BED was the most significant predictor of biopsy outcome in multivariate analysis (p=0.006).

CONCLUSIONS

Biologically effective dose equations provide a method of comparing different isotopes and combined therapies in the brachytherapy management of prostate cancer. The effects of BED on FFPF and posttreatment biopsy demonstrate a strong dose-response relationship.

Estimating the risk of long-term erectile, urinary and bowel symptoms resulting from prostate cancer treatment

Reports on long-term complications resulting from treatment for localized prostate cancer are very inconsistent. In order to estimate the risks of long-term erectile dysfunction, urine symptoms and bowel symptoms following prostatectomy (RP), external conventional or conformal beam radiation (ERT or CRT) and brachytherapy (BRT), 98 papers from the PubMed and Cochrane Clinical Trial databases were selected, reviewed and critically evaluated. The majority of papers were institution-based retrospective and prospective follow-up studies; only two of these studies measured the risk of developing more than one treatment complication. Due to differences in study designs and populations, it is difficult to directly compare studies and not meaningful to calculate summary estimates. In addition to focusing on randomized clinical trials and well-designed population based studies, future research should adopt standardized methodologies and should measure the risk of developing more than one treatment complication.

Radical radiotherapy for invasive bladder cancer: What dose and fractionation schedule to choose?

PURPOSE

To establish the alpha/beta ratio of bladder cancer from different radiotherapy schedules reported in the literature and provide guidelines for the design of new treatment schemes.

METHODS AND MATERIALS

Ten external beam radiotherapy (EBRT) and five brachytherapy schedules were selected. The biologically effective dose (BED) of each schedule was calculated. Logistic modeling was used to describe the relationship between 3-year local control (LC3y) and BED.

RESULTS

The estimated alpha/beta ratio was 13 Gy (95% confidence interval [CI], 2.5-69 Gy) for EBRT and 24 Gy (95% CI, 1.3-460 Gy) for EBRT and brachytherapy combined. There is evidence for an overall dose-response relationship. After an increase in total dose of 10 Gy, the odds of LC3y increase by a factor of 1.44 (95% CI, 1.23-1.70) for EBRT and 1.47 (95% CI, 1.25-1.72) for the data sets of EBRT and brachytherapy combined.

CONCLUSION

With the clinical data currently available, a reliable estimation of the alpha/beta ratio for bladder cancer is not feasible. It seems reasonable to use a conventional alpha/beta ratio of 10-15 Gy. Dose escalation could significantly increase local control. There is no evidence to support short overall treatment times or large fraction sizes in radiotherapy for bladder cancer.

Late gastrointestinal toxicity after radiation for prostate cancer

BACKGROUND

The current study was designed to determine rates and predictors of late, lower gastrointestinal toxicity after radiation therapy in a population-based cohort of older men with prostate cancer.

METHODS

The study population consisted of men with localized or regional stage prostate cancer who were age > or =66 years and were diagnosed between 1992 and 1999 who were identified in the Surveillance, Epidemiology, and End Results (SEER)-Medicare database. Gastrointestinal diagnoses were ascertained through claims from 6 to 60 months after diagnosis. The relative rates of diagnoses in the radiation group versus the nonradiation group were used as a means of estimating toxicity from radiotherapy. Cox modeling was used to determine factors associated with gastrointestinal diagnoses.

RESULTS

A total of 57,955 men were included, 24,130 of whom were treated with radiation therapy. Among patients with 5 years of follow-up, the rates of gastrointestinal diagnoses were 19.4% higher in irradiated patients than among patients who did not have local therapy. Hemorrhage was the most common diagnosis, and was increased by 18.9% among patients treated with radiation (39.6% of irradiated patients vs. comparison rates of 18.2% in patients treated with radical prostatectomy and 20.7% in patients with no local therapy). Diagnostic lower endoscopies were performed in an additional 20.9% of men (32.4% of men treated with radiation vs. 12.7% of men who underwent prostatectomy). In all, 4.4% of irradiated men were hospitalized with a gastrointestinal diagnosis versus comparison rates of 3.2% among men with no local therapy. In multivariate models, increasing patient age, hormonal therapy, comorbidity, diabetes, peripheral vascular disease, and hemorrhoids were all associated with gastrointestinal diagnoses consistent with toxicity, whereas tumor stage and grade were not predictors.

CONCLUSIONS

Lower gastrointestinal toxicity after radiation therapy for prostate cancer continues for at least 5 years and may be more common than previously reported.

Prostate-specific antigen recurrence and mortality after conventional dose radiation therapy in select men with low-risk prostate cancer

BACKGROUND

Prostate-specific antigen (PSA) recurrence, prostate cancer-specific mortality (PCSM), and all-cause mortality (ACM) were evaluated for men age >70 years receiving conventional dose external beam radiation therapy (RT).

METHODS

Between January 1, 1989, and December 1, 2002, 358 men were treated with RT for localized prostate cancer at a Harvard Medical School Affiliate in Fall River, MA. Median age was 71.2 (range, 43.2-83.5) years and patients were followed for a median of 4.0 (range, 0.2-13.5) years.

RESULTS

Univariable analysis demonstrated that increasing pretreatment PSA velocity was significantly associated with increasing pretreatment PSA (P < .0001), Gleason score (P = .0002), and shorter post-RT PSA doubling time (P = .0007) but not with clinical T-category (P = .09) or percent positive biopsies (P = .08). For the select cohort of men age >70 years with low-risk disease and a pretreatment PSA velocity < or =1.0 ng/mL per year, all deaths observed to date have been from nonprostate cancer etiologies. Whereas PSA recurrence in this group reached 43.3% by 7 years, due to the advanced age of the cohort and less aggressive biology, competing causes of mortality predominated as the cause of death despite PSA failure.

CONCLUSIONS

In men age >70 years with low-risk prostate cancer and pretreatment PSA velocity < or =1.0 ng/mL/year, prostate cancer death was not observed despite a modest PSA recurrence rate.

Lifestyle and health-related quality of life of men with prostate cancer managed with active surveillance

OBJECTIVES

To assess the impact of lifestyle on health-related quality of life (HR-QOL), perceived stress, and self-reported sexual function in men with early-stage prostate cancer electing active surveillance.

METHODS

A total of 44 intervention and 49 usual-care control participants were enrolled in a randomized clinical trial examining the effects of lifestyle changes on prostate cancer progression. The intervention consisted of a low-fat, vegan diet, exercise, and stress management. Participants completed the Medical Outcomes Study Short Form-36 Health Status Survey (a measure of mental and physical HR-QOL), the Perceived Stress Scale, the Sexual Function subscale of the University of California, Los Angeles, Prostate Cancer Index, and measures of lifestyle behaviors (to yield an overall lifestyle index) at baseline and 12 months. The data were analyzed using analysis of variance for repeated measures. The relationship between lifestyle and QOL was also analyzed using multiple linear regression analyses.

RESULTS

Intervention participants had significantly improved their lifestyle compared with controls at 12 months. The quality-of-life scores were high across groups and time points. However, a healthier lifestyle was related to better QOL at baseline. Participants in both groups who reported a healthier lifestyle also reported better mental and physical HR-QOL and sexual function. Furthermore, participants whose lifestyle improved over time showed enhanced physical HR-QOL and decreased perceived stress.

CONCLUSIONS

Men who choose active surveillance for early-stage prostate cancer are able to make comprehensive lifestyle changes. Although the average QOL was already high in this sample, individuals who improved their lifestyle enhanced their QOL further.

Automatic prostate localization on cone-beam CT scans for high precision image-guided radiotherapy

PURPOSE

Previously, we developed an automatic three-dimensional gray-value registration (GR) method for fast prostate localization that could be used during online or offline image-guided radiotherapy. The method was tested on conventional computed tomography (CT) scans. In this study, the performance of the algorithm to localize the prostate on cone-beam CT (CBCT) scans acquired on the treatment machine was evaluated.

METHODS AND MATERIALS

Five to 17 CBCT scans of 32 prostate cancer patients (332 scans in total) were used. For 18 patients (190 CBCT scans), the CBCT scans were acquired with a collimated field of view (FOV) (craniocaudal). This procedure improved the image quality considerably. The prostate (i.e., prostate plus seminal vesicles) in each CBCT scan was registered to the prostate in the planning CT scan by automatic 3D gray-value registration (normal GR) starting from a registration on the bony anatomy. When these failed, registrations were repeated with a fixed rotation point locked at the prostate apex (fixed apex GR). Registrations were visually assessed in 3D by one observer with the help of an expansion (by 3.6 mm) of the delineated prostate contours of the planning CT scan. The percentage of successfully registered cases was determined from the combined normal and fixed apex GR assessment results. The error in gray-value registration for both registration methods was determined from the position of one clearly defined calcification in the prostate gland (9 patients, 71 successful registrations).

RESULTS

The percentage of successfully registered CBCT scans that were acquired with a collimated FOV was about 10% higher than for CBCT scans that were acquired with an uncollimated FOV. For CBCT scans that were acquired with a collimated FOV, the percentage of successfully registered cases improved from 65%, when only normal GR was applied, to 83% when the results of normal and fixed apex GR were combined. Gray-value registration mainly failed (or registrations were difficult to assess) because of streaks in the CBCT scans caused by moving gas pockets in the rectum during CBCT image acquisition (i.e., intrafraction motion). The error in gray-value registration along the left-right, craniocaudal, and anteroposterior axes was 1.0, 2.4, and 2.3 mm (1 SD) for normal GR, and 1.0, 2.0, and 1.7 mm (1 SD) for fixed apex GR. The systematic and random components of these SDs contributed approximately equally to these SDs, for both registration methods.

CONCLUSIONS

The feasibility of automatic prostate localization on CBCT scans acquired on the treatment machine using an adaptation of the previously developed three-dimensional gray-value registration algorithm, has been validated in this study. Collimating the FOV during CBCT image acquisition improved the CBCT image quality considerably. Artifacts in the CBCT images caused by large moving gas pockets during CBCT image acquisition were the main cause for unsuccessful registration. From this study, we can conclude that CBCT scans are suitable for online and offline position verification of the prostate, as long as the amount of nonstationary gas is limited.

Radiotherapeutic techniques for prostate cancer, dose escalation and brachytherapy

There is evidence to confirm a dose-response relationship in prostate cancer. The relative benefit is dependent on the clinical prognostic risk factors (T stage, Gleason score and presenting prostate-specific antigen [PSA]) being more favourable for intermediate-risk patients. Refinement of prognostic groups and clinical threshold parameters is ongoing. Escalation of dose in prostate radiotherapy using conventional techniques is limited by rectal tolerance. Substantial advances have been made in radiotherapy practice, such as the development of conformal radiotherapy (CFRT) and intensity-modulated radiotherapy (IMRT). Randomised data support the value of CFRT in reducing rectal toxicity. IMRT can permit higher-dose escalation while still respecting known rectal tolerance thresholds. Brachytherapy is a recognised alternative for low-risk prostate cancer subgroups. New radiotherapeutic strategies for prostate cancer include pelvic nodal irradiation, exploiting the presumed low alpha/beta ratio in prostate cancer for hypofractionation and combining external beam with high-dose-rate brachytherapy boosts. New image-guided methodologies will enhance the therapeutic ratio of any radiotherapy technique or dose escalation programme by enabling more reliable and accurate treatment delivery for improved patient outcomes.

Whole pelvic radiotherapy for prostate cancer using 3D conformal and intensity-modulated radiotherapy

PURPOSE

To investigate the correlations between observed clinical morbidity and dosimetric parameters for whole pelvic radiotherapy (WPRT) for prostate cancer using either three-dimensional conformal radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT).

METHODS AND MATERIALS

Between December 1996 and January 2002, 27 patients with prostate adenocarcinoma were treated with conformal WPRT as part of their definitive treatment. WPRT was delivered with 3D-CRT in 14 patients and with IMRT in 13 patients. For each of the patients treated with IMRT, optimized conventional two-dimensional (2D) and 3D-CRT plans were retrospectively generated for the whole pelvic phase of the treatment. Dose-volume histograms for the bowel, bladder, and rectum were compared for the three techniques. Acute toxicities were evaluated for all 27 patients, and late toxicities were evaluated for 25 patients with sufficient follow-up. Toxicities were scored according to the Radiation Therapy Oncology Group morbidity grading scales. Median follow-up was 30 months.

RESULTS

Three-dimensional-CRT resulted in a 40% relative reduction (p < 0.001) in the volume of bowel receiving 45 Gy compared with 2D, and IMRT provided a further 60% reduction relative to 3D-CRT (p < 0.001). Compared with either 2D or 3D-CRT, IMRT reduced the volume of rectum receiving 45 Gy by 90% (p < 0.001). Overall, 9 patients (33%) experienced acute Grade 2 gastrointestinal (GI) toxicity, and only 1 of these patients was treated with IMRT. Antidiarrhea medication was required for 6 patients (22%). However, 5 of these 6 patients also received chemotherapy, and none were treated with IMRT. No Grade 3 or higher acute or late GI toxicities were observed. No cases of late radiation enteritis were observed. Acute and late genitourinary toxicity did not appear significantly increased by the addition of conformal WPRT.

CONCLUSIONS

Compared to conventional 2D planning, conformal planning for WPRT resulted in significant reductions in the doses delivered to the bowel, rectum, and bladder. IMRT was superior to 3D-CRT in limiting the volume of bowel and rectum within high-dose regions. These dosimetric findings correlated with low rates of acute and late GI morbidity.

Short-term androgen deprivation and radiotherapy for locally advanced prostate cancer: results from the Trans-Tasman Radiation Oncology Group 96.01 randomised controlled trial

BACKGROUND

Androgen deprivation is an established treatment regimen for disseminated prostate cancer; however, its role in patients with localised cancer is less clear. We did a large randomised controlled trial to determine whether 3 months or 6 months of androgen deprivation given before and during radiotherapy improves outcomes for patients with locally advanced prostate cancer.

METHODS

818 men with locally advanced prostate cancer were randomly assigned to: no androgen deprivation (ie, radiotherapy alone: 66 Gy in 33 fractions of 2 Gy per day over 6.5-7.0 weeks to the prostate and seminal vesicles); 3 months' androgen deprivation with 3.6 mg goserelin given subcutaneously every month and 250 mg flutamide given orally three times a day starting 2 months before radiotherapy (same regimen as control group); or 6 months' androgen deprivation, with the same regimen, starting 5 months before radiotherapy (same regimen as control group). Primary endpoints were time to local failure and prostate-cancer-specific survival; secondary endpoints were distant failure, disease-free survival, and freedom from salvage treatment. Analyses were done by intention to treat.

FINDINGS

802 (98%) patients were eligible for analysis. Median follow-up was 5.9 years (range 0.1-8.5). Compared with patients assigned no androgen deprivation, those assigned 3 months' treatment had significantly improved local failure (hazard ratio [HR] 0.56 [95% CI 0.39-0.79], p=0.001), biochemical failure-free survival (0.70 [0.56-0.88], p=0.002), disease-free survival (0.65 [0.52-0.80], p=0.0001), and freedom from salvage treatment (0.73 [0.56-0.96], p=0.025). 6 months' androgen deprivation significantly improved local failure (0.42 [0.28-0.62], p<0.0001), biochemical failure-free survival (0.58 [0.46-0.74], p<0.0001), disease-free survival (0.56 [0.45-0.69], p<0.0001), freedom from salvage treatment (0.53 [0.40-0.71], p<0.0001), distant failure (0.67 [0.45-0.99], p=0.046) and prostate-cancer-specific survival (0.56 [0.32-0.98], p=0.04) compared with no androgen deprivation.

INTERPRETATION

6 months' androgen deprivation given before and during radiotherapy improves the outlook of patients with locally advanced prostate cancer. Further follow-up is needed to estimate precisely the size of survival benefits. Increased radiation doses and additional periods of androgen deprivation might lead to further benefit.

Phase II Feasibility Study of High-Dose Radiotherapy for Prostate Cancer Using Proton Boost Therapy: First Clinical Trial of Proton Beam Therapy for Prostate Cancer in Japan

OBJECTIVE

To assess the feasibility of high-dose radiotherapy for prostate cancer using proton boost therapy following photon radiotherapy.

METHODS

The primary endpoint was acute grade 3 or greater genitourinary (GU) and gastrointestinal (GI) toxicities. The study included patients with clinical stage T1-3N0M0 prostate cancer. Radiotherapy consisted of 50 Gy/25 fx photon irradiation to the prostate and the bilateral seminal vesicles followed by proton boost of 26 Gy(E)/13 fx to the prostate alone. Hormonal therapy was allowed before and during the radiation therapy.

RESULTS

Between January 2001 and January 2003, 30 patients were enrolled in this study. Acute grade 1/2 GU and GI toxicities were observed in 20/4 and 17/0 patients, respectively. With the median follow-up period of 30 months (range 20-45), late grade 1/2 GU and GI toxicities occurred in 2/3 and 8/3 patients, respectively. No grade 3 or greater acute or late toxicities were observed. All patients were alive, but six patients relapsed biochemically after 7-24 months.

CONCLUSIONS

Proton boost therapy following photon radiotherapy for prostate cancer is feasible. To evaluate the efficacy and safety of proton beam therapy, a multi-institutional phase II trial is in progress in Japan.

Target localization for post-prostatectomy patients using CT and ultrasound image guidance

We conducted a study comparing B‐mode acquisition and targeting (BAT) ultrasound alignments based on CT data in the postoperative setting. CT scans were obtained with a Primatom CT‐on‐rails on nine patients. Two CT scans were obtained each week, while setup error was minimized by BAT ultrasounds. For the first three patients, a direct comparison was performed. For the next six patients, a template based on the shifts from the week 1 CT during treatment was used for subsequent setup. Comparison of isocenter shifts between the BAT ultrasound and CT was made by the difference, absolute difference, and improvement (using CT alignments as the reference technique). A total of 90 image comparisons were made. The average interfraction motion was 3.2 mm in the lateral, 3.0 mm in the longitudinal, and 5.1 mm in the AP direction. The results suggest that the CT‐based ultrasound templates can improve the localization of the prostate bed when the initial displacements are greater than 4 mm. For initial displacements smaller than 4 mm, the technique neither improved nor worsened target localization. However, ultrasound alignments performed without the use of a template deteriorated patient positioning for two out of three patients, demonstrating that the use of a CT template was beneficial even at small initial displacements.

PACS numbers: 87.53.‐j, 87.53.Kn, 87.53.Xd

Rectal wall sparing effect of three different endorectal balloons in 3D conformal and IMRT prostate radiotherapy

PURPOSE

To investigate the dosimetric consequences and rectal wall (Rwall) sparing effect of three different endorectal balloons (ERBs) for three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) for prostate cancer.

METHODS AND MATERIALS

In 20 patients, 4 planning computed tomography scans were made: 1 without ERB and 3 with ERB1, ERB2, or ERB3 inserted. Two different planning target volumes were defined: prostate only, and prostate plus seminal vesicles. The 3D-CRT and IMRT planning techniques were used, and the prescription dose was 78 Gy. In 284 treatment plans, the Rwall mean dose, the Rwall normal tissue complication probability, and the absolute Rwall volumes exposed to > or =50 Gy (V(50)) and > or =70 Gy (V(70)) were calculated. For spatial dose distribution analysis, inner rectal wall dose maps and dose surface histograms were generated.

RESULTS

Each ERB was tolerated well. In the case of 3D-CRT, each ERB showed a statistically significant reduction of all the measured parameters. ERB2 and ERB3 performed better than ERB1. In IMRT, a statistically significant reduction in the Rwall dose parameters could not be demonstrated for any of the ERBs. For 3D-CRT and IMRT, as a result of the rectal dilation, ranging from 8 to 20 cm in circumference, the ERBs resulted in a reduction of the relative inner Rwall surface exposed to intermediate and high doses.

CONCLUSIONS

In 3D-CRT, any ERB showed a significant rectal wall sparing effect. ERB2 and ERB3 were superior to ERB1. For both 3D-CRT and IMRT, a reduction of the relative inner Rwall surface exposed to intermediate and high doses was found, which may lead to reduced late rectal toxicity. Development of user- and patient-friendly ERBs is warranted to increase their acceptability.

Radiotherapy in the Management of Clinically Localized Prostate Cancer: Evolving Standards, Consensus, Controversies and New Directions

Major advances have been made in the definitive use of various forms of radiotherapy (RT) in the management of clinically localized prostate cancer (PCa). Despite tremendous gains, the radiation oncology community continues to struggle with several key questions. In general, the areas of controversy pertain to how to improve the therapeutic ratio of RT. Specifically, key issues include dose escalation; the relative benefit of alternative forms of RT (ie, brachytherapy and protons); target localization; the use, timing, and duration of androgen deprivation; and the need for pelvic nodal irradiation. Multiple efforts have been made to address each of these issues; however, there is no consensus on how to resolve them. This review is an evidence-based critique of the available treatment approaches considered for the optimal use of radiotherapy as definitive management of clinically localized PCa.

Long-term outcomes of 60 Gy conventional radiotherapy combined with androgen deprivation for localized or locally advanced prostate cancer

BACKGROUND

Until 1998 in Japan, very few institutions were treating prostate cancer solely with radiotherapy (RT) >70 Gy and most were using < or =65 Gy in combination with hormone therapy. The present study reports the long-term results of RT combined with hormone therapy for localized and locally advanced prostate cancer.

METHODS

We investigated 57 patients who were treated by external beam RT plus hormone therapy (median age 79 years, median prostate-specific antigen concentration 15.0 ng/ml) between 1992 and 1998. Patients received 40 Gy of radiation to the pelvis and an additional 20 Gy as a prostatic boost. Hormone therapy was begun on the first day of irradiation and continued thereafter.

RESULTS

The median follow-up was 93.3 months and the 5 and 10 year actual overall survival rates were 67.8 and 32.6%, respectively, with 5 and 10 year cause-specific survival rates of 97.9 and 95.0%, respectively. The expected survival rate was 66.2% at 5 years, and overall survival was above expected survival. Only one patient developed severe proctitis (Grade 3). The 5 year occurrence of Grade 1/2 genitourinary toxicity was 23.2%.

CONCLUSIONS

Combined RT and hormone therapy has a good long-term outcome without severe adverse events. The overall survival rate compares well with the expected survival rate.

Prostate position relative to pelvic bony anatomy based on intraprostatic gold markers and electronic portal imaging

PURPOSE

To describe the relative positions and motions of the prostate, pelvic bony anatomy, and intraprostatic gold fiducial markers during daily electronic portal localization of the prostate.

METHODS AND MATERIALS

Twenty prostate cancer patients were treated supine with definitive external radiotherapy according to an on-line target localization protocol using three or four intraprostatic gold fiducial markers and an electronic portal imaging device. Daily pretherapy and through-treatment electronic portal images (EPIs) were obtained for each of four treatment fields. The patients' pelvic bony anatomy, intraprostatic gold markers, and a best visual match to the target (i.e., prostate) were identified on simulation digitally reconstructed radiographs and during daily treatment setup and delivery. These data provided quantitative inter- and intrafractional analysis of prostate motion, its position relative to the bony anatomy, and the individual intraprostatic fiducial markers. Treatment planning margins, with and without on-line localization, were subsequently compared.

RESULTS

A total of 22,266 data points were obtained from daily pretherapy and through-treatment EPIs. The pretherapy three-dimensional (3D) average displacement of the fiducial markers, as a surrogate for the prostate, was 5.6 mm, which improved to 2.8 mm after use of the localization protocol. The bony anatomy 3D average displacement was 4.4 mm both before and after localization to the prostate (p = 0.46). Along the superior-inferior (SI), anterior-posterior (AP), and right-left (RL) axes, the average prostate displacement improved from 2.5, 3.7, and 1.9 mm, respectively, before localization to 1.4, 1.6, and 1.1 mm after (all p < 0.001). The pretherapy to through-treatment position of the bony landmarks worsened from 1.7 to 2.5 mm (p < 0.001) in the SI axis, remained statistically unchanged at 2.8 mm (p = 0.39) in the AP axis, and improved from 2.0 to 1.2 mm in the RL axis (p < 0.001). There was no significant intrafractional displacement of prostate position or bony anatomic landmarks. An intermarker distance was identified for all fiducial markers, and 96 were followed daily. Seventy-nine percent had a standard deviation of <1 mm, and 96% were <1.5 mm. Margins were 5.1, 7.3, and 5.0 mm in the SI, AP, and RL axes, respectively, before localization and 2.7, 2.9, and 2.8 mm after localization.

CONCLUSIONS

Significant interfractional motion exists for patients' prostate and pelvic bony anatomy. However, these move independently, so the pelvic bony anatomy should not be used as a surrogate for prostate motion. Fiducial markers are stable within the prostate and allow significant margin reduction when used for on-line localization of the prostate.

Long-term androgen deprivation therapy improves survival in prostate cancer patients presenting with prostate-specific antigen levels >20 ng/mL

PURPOSE

To assess the benefit of androgen deprivation (AD) and its optimal duration in patients with prostate cancer treated with external beam radiotherapy, who present with prostate-specific antigen levels > 20 ng/mL.

METHODS AND MATERIALS

A total of 307 patients treated with external beam radiotherapy, AD, and presenting with a PSA level > 20 ng/mL were identified from the Prostate Cancer Outcomes Initiative database of the British Columbia Cancer Agency. Androgen deprivation was defined as short term (ST-AD, < 12 months) or long term (LT-AD, > or = 12 months). The endpoints analyzed were biochemical control (no evidence of disease) (bNED), overall survival, and cause-specific survival. Statistical analysis was conducted with Kaplan-Meier estimates, log-rank tests, and multivariate analyses with logistic and Cox regression models.

RESULTS

There were 151 patients in the ST-AD group and 156 in the LT-AD group. The distributions of Gleason score and stage were comparable in the two cohorts. Median follow-up times were 48 months for patients treated with ST-AD and 45 months for patients treated with LT-AD. The median durations of AD were 6 and 25.6 months for the ST-AD and LT-AD groups, respectively. The bNED rate was 37% for the ST-AD group and 62.5% for the LT-AD group (p < 0.0001). The 5-year overall survival rate was 75% in the ST-AD group vs. 87.5% for the LT-AD group (p = 0.0091). The 5-year cause-specific survival rate was 82% for the ST-AD group vs. 94% for the LT-AD group (p = 0.0072).

CONCLUSIONS

Several randomized trials have demonstrated the benefit of LT-AD in high-risk patients with prostate cancer. In some reports, the survival advantage seems to be restricted to patients with high Gleason score. The present analysis supports the hypothesis that LT-AD improves bNED and survival rates in patients presenting with a PSA level > 20, irrespective of Gleason score or T stage.

Systematic review of the effect of radiation dose on tumor control and morbidity in the treatment of prostate cancer by 3D-CRT

PURPOSE

A higher radiation dose is believed to result in a larger probability of tumor control and a higher risk of side effects. To make an evidence-based choice of dose, the relation between dose and outcome needs to be known. This study focuses on the dose-response relation for prostate cancer.

METHODS AND MATERIALS

A systematic review was carried out on the literature from 1990 to 2003. From the selected studies, the radiation dose, the associated 5-year survival, 5-year bNED (biochemical no evidence of disease), acute and late gastrointestinal (GI) and genitourinary (GU) morbidity Grade 2 or more, and sexual dysfunction were extracted. With logistic regression models, the relation between dose and outcome was described.

RESULTS

Thirty-eight studies met our criteria, describing 87 subgroups and involving up to 3000 patients per outcome measure. Between the (equivalent) dose of 70 and 80 Gy, various models estimated an increase in 5-year survival (ranging from 10% to 11%), 5-year bNED for low-risk patients (5-7%), late GI complications (12-16%), late GU complications (8-10%), and erectile dysfunction (19-24%). Only for the overall 5-year bNED, results were inconclusive (range, 0-18%).

CONCLUSIONS

The data suggest a relationship between dose and outcome measures, including survival. However, the strength of these conclusions is limited by the sometimes small number of studies, the incompleteness of the data, and above all, the correlational nature of the data. Unambiguous proof for the dose-response relationships can, therefore, only be obtained by conducting randomized trials.

Adenoviral-E2F-1 radiosensitizes p53wild-type and p53null human prostate cancer cells

PURPOSE

E2F-1 is a transcription factor that enhances the radiosensitivity of various cell lines by inducing apoptosis. However, there are conflicting data concerning whether this enhancement is mediated via p53 dependent pathways. Additionally, the role of E2F-1 in the response of human prostate cancer to radiation has not been well characterized. In this study, we investigated the effect of Adenoviral-E2F-1 (Ad-E2F-1) on the radiosensitivity of p53wild-type (LNCaP) and p53null (PC3) prostate cancer cell lines.

METHODS AND MATERIALS

LNCaP and PC3 cells were transduced with Ad-E2F-1, Adenoviral-Luciferase (Ad-Luc) control vector, or Adenoviral-p53 (Ad-p53). Expression of E2F-1 and p53 was examined by Western blot analysis. Annexin V and caspase 3 + 7 assays were performed to estimate the levels of apoptosis. Clonogenic survival assays were used to determine overall cell death. Statistical significance was determined by analysis of variance, using the Bonferroni method to correct for multiple comparisons.

RESULTS

Western blot analysis confirmed the efficacy of transductions with Ad-E2F-1 and Ad-p53. Ad-E2F-1 transduction significantly enhanced apoptosis and decreased clonogenic survival in both cell lines. These effects were compounded by the addition of RT. Although E2F-1-mediated radiosensitization was independent of p53 status, this effect was more pronounced in p53wild-type LNCaP cells. When PC3 cells were treated with Ad-p53 in combination with RT and Ad-E2F-1, there was at least an additive reduction in clonogenic survival.

CONCLUSIONS

Our results suggest that Ad-E2F-1 significantly enhances the response of p53wild-type and p53null prostate cancer cells to radiation therapy, although radiosensitization is more pronounced in the presence of p53. Ad-E2F-1 may be a useful adjunct to radiation therapy in the treatment of prostate cancer.

Acute genitourinary toxicity after high dose rate (HDR) brachytherapy combined with hypofractionated external-beam radiation therapy for localized prostate cancer: Second analysis to determine the correlation between the urethral dose in HDR brachytherapy and the severity of acute genitourinary toxicity

PURPOSE

We have been treating localized prostate cancer with high-dose-rate (HDR) brachytherapy combined with hypofractionated external beam radiation therapy (EBRT) at our institution. We recently reported the existence of a correlation between the severity of acute genitourinary (GU) toxicity and the urethral radiation dose in HDR brachytherapy by using different fractionation schema. The purpose of this study was to evaluate the role of the urethral dose in the development of acute GU toxicity more closely than in previous studies. For this purpose, we conducted an analysis of patients who had undergone HDR brachytherapy with a fixed fractionation schema combined with hypofractionated EBRT.

METHODS AND MATERIALS

Among the patients with localized prostate cancer who were treated by 192-iridium HDR brachytherapy combined with hypofractionated EBRT at Gunma University Hospital between August 2000 and November 2004, we analyzed 67 patients who were treated by HDR brachytherapy with the fractionation schema of 9 Gy x two times combined with hypofractionated EBRT. Hypofractionated EBRT was administered at a fraction dose of 3 Gy three times weekly, and a total dose of 51 Gy was delivered to the prostate gland and seminal vesicles using the four-field technique. No elective pelvic irradiation was performed. After the completion of EBRT, all the patients additionally received transrectal ultrasonography-guided HDR brachytherapy. The planning target volume was defined as the prostate gland with a 5-mm margin all around, and the planning was conducted based on computed tomography images. The tumor stage was T1c in 13 patients, T2 in 31 patients, and T3 in 23 patients. The Gleason score was 2-6 in 12 patients, 7 in 34 patients, and 8-10 in 21 patients. Androgen ablation was performed in all the patients. The median follow-up duration was 11 months (range 3-24 months). The toxicities were graded based on the Radiation Therapy Oncology Group and the European Organization for Research and Treatment of Cancer toxicity criteria.

RESULTS

The main symptoms of acute GU toxicity were dysuria and increase in the urinary frequency or nocturia. The grade distribution of acute GU toxicity in the patients was as follows: Grade 0-1, 42 patients (63%); Grade 2-3, 25 patients (37%). The urethral dose in HDR brachytherapy was determined using the following dose-volume histogram (DVH) parameters: V30 (percentage of the urethral volume receiving 30% of the prescribed radiation dose), V80, V90, V100, V110, V120, V130, and V150. In addition, the D5 (dose covering 5% of the urethral volume), D10, D20, and D50 of the urethra were also estimated. The V30-V150 values in the patients with Grade 2-3 acute GU toxicity were significantly higher than those in patients with Grade 0-1 toxicity. The D10 and D20, but not D5 and D50, values were also significantly higher in the patients with Grade 2-3 acute GU toxicity than in those with Grade 0-1 toxicity. Regarding the influence of the number of needles implanted, there was no correlation between the number of needles implanted and the severity of acute GU toxicity or the V30-V150 values and D5-D50 values.

CONCLUSIONS

It was concluded that HDR brachytherapy combined with hypofractionated EBRT is feasible for localized prostate cancer, when considered from the viewpoint of acute toxicity. However, because the urethral dose was closely associated with the grade of severity of the acute GU toxicity, the urethral dose in HDR brachytherapy must be kept low to reduce the severity of acute GU toxicity.

Acute genitourinary toxicity after high-dose-rate (HDR) brachytherapy combined with hypofractionated external-beam radiation therapy for localized prostate cancer: Correlation between the urethral dose in HDR brachytherapy and the severity of acute genitourinary toxicity

PURPOSE

Several investigations have revealed that the alpha/beta ratio for prostate cancer is atypically low, and that hypofractionation or high-dose-rate (HDR) brachytherapy regimens using appropriate radiation doses may be expected to yield tumor control and late sequelae rates that are better or at least as favorable as those achieved with conventional radiation therapy. In this setting, we attempted treating localized prostate cancer patients with HDR brachytherapy combined with hypofractionated external beam radiation therapy (EBRT). The purpose of this study was to evaluate the feasibility of using this approach, with special emphasis on the relationship between the severity of acute genitourinary (GU) toxicity and the urethral dose calculated from the dose-volume histogram (DVH) of HDR brachytherapy.

METHODS AND MATERIALS

Between September 2000 and December 2003, 70 patients with localized prostate cancer were treated by iridium-192 HDR brachytherapy combined with hypofractionated EBRT at the Gunma University Hospital. Hypofractionated EBRT was administered in fraction doses of 3 Gy, three times per week; a total dose of 51 Gy was delivered to the prostate gland and the seminal vesicles using the four-field technique. No elective pelvic irradiation was performed. After the completion of EBRT, all the patients additionally received transrectal ultrasonography (TRUS)-guided HDR brachytherapy. The fraction size and the number of fractions in HDR brachytherapy were prospectively changed, whereas the total radiation dose for EBRT was fixed at 51 Gy. The fractionation in HDR brachytherapy was as follows: 5 Gy x 5, 7 Gy x 3, 9 Gy x 2, administered twice per day, although the biologic effective dose (BED) for HDR brachytherapy combined with EBRT, assuming that the alpha/beta ratio is 3, was almost equal to 138 in each fractionation group. The planning target volume was defined as the prostate gland with 5-mm margin all around, and the planning was conducted based on computed tomography images. The number of patients in each fractionation group was as follows: 13 in the 5-Gy group; 19 in the 7-Gy group, and 38 in the 9-Gy group. The tumor stage was T1 in 10 patients, T2 in 36 patients, and T3 in 24 patients. The Gleason score was 2-6 in 11 patients, 7 in 34 patients, and 8-10 in 25 patients. Androgen ablation was performed in all the patients. The median follow-up duration was 14 months (range 3-42 months). The toxicities were graded based on the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer toxicity criteria.

RESULTS

The main symptoms of acute GU toxicity were dysuria and increase in urinary frequency or nocturia. The grade distribution of acute GU toxicity in the patients was as follows: Grade 0-1, 39 patients (56%), and Grade 2-4, 31 patients (44%). One patient who developed acute urinary obstruction was classified as having Grade 4 toxicity. Comparison of the distribution of the grade of acute GU toxicity among the different fractionation groups revealed no statistically significant differences among the groups. The urethral dose in HDR brachytherapy was evaluated using the following DVH parameters: V30 (percentage of the urethral volume receiving 30% of the prescribed radiation dose), V80, V90, V100, V110, V120, V130, and V150. The V30-110 values in the patients with Grade 2-4 acute GU toxicity were significantly higher than those in patients with Grade 0-1 toxicity. On the other hand, there were no significant differences in the V120-150 values between patients with Grade 0-1 and Grade 2-4 toxicity. Regarding the influence of the number of needles implanted for the radiation therapy, patients with 11 needles or less showed a significantly higher incidence of Grade 2-4 acute GU toxicity compared with those with 12 needles or more (p < 0.05).

CONCLUSIONS

It was concluded that HDR brachytherapy combined with hypofractionated EBRT is feasible for localized prostate cancer when considered from the viewpoint of acute toxicity. Increase in the fraction dose or reduction in the number of fractions in HDR brachytherapy did not affect the severity of acute GU toxicity, and the volume of urethra receiving an equal or lower radiation dose than the prescribed dose was more closely associated with the grade severity of acute GU toxicity than that receiving a higher than the prescribed dose.

Dose-volume analysis of predictors for chronic rectal toxicity after treatment of prostate cancer with adaptive image-guided radiotherapy

PURPOSE

We analyzed our experience treating localized prostate cancer with image-guided off-line correction with adaptive high-dose radiotherapy (ART) in our Phase II dose escalation study to identify factors predictive of chronic rectal toxicity.

MATERIALS AND METHODS

From 1999-2002, 331 patients with clinical stage T1-T3N0M0 prostate cancer were prospectively treated in our Phase II 3D conformal dose escalation ART study to a median dose of 75.6 Gy (range, 63.0-79.2 Gy), minimum dose to confidence limited-planning target volume (cl-PTV) in 1.8 Gy fractions (median isocenter dose = 79.7 Gy). Seventy-four patients (22%) also received neoadjuvant/adjuvant androgen deprivation therapy. A patient-specific cl-PTV was constructed using 5 computed tomography scans and 4 sets of electronic portal images by applying an adaptive process to assure target accuracy and minimize PTV margin. For each case, the rectum (rectal solid) was contoured from the sacroiliac joints or rectosigmoid junction (whichever was higher) to the anal verge or ischial tuberosities (whichever was lower), with a median volume of 81.2 cc. The rectal wall was defined using the rectal solid with an individualized 3-mm wall thickness (median volume = 29.8 cc). Rectal wall dose-volume histogram was used to determine the prescribed dose. Toxicity was quantified using the National Cancer Institute Common Toxicity Criteria 2.0. Multiple dose-volume endpoints were evaluated for their association with chronic rectal toxicity.

RESULTS

Median follow-up was 1.6 years. Thirty-four patients (crude rate = 10.3%) experienced Grade 2 chronic rectal toxicity at a median interval of 1.1 years. Nine patients (crude rate = 2.7%) experienced Grade > or =3 chronic rectal toxicity (1 was Grade 4) at a median interval of 1.2 years. The 3-year rates of Grade > or =2 and Grade > or =3 chronic rectal toxicity were 20% and 4%, respectively. Acute toxicity predicted for chronic: Acute Grade 2-3 rectal toxicity (p < 0.001) including any acute rectal Grade 2-3 tenesmus (p = 0.02) and pain (p = 0.008) were significant predictors of chronic Grade > or =2 rectal toxicity. Any acute rectal toxicity (p = 0.001), any acute tenesmus (p = 0.03), and any acute diarrhea (p < 0.001) were also found to be predictive for chronic toxicity, as continuous variables. Dose-volume histogram predicted for chronic toxicity: Rectal wall absolute and relative V50, V60, V66.6, V70, and V72 and rectal solid relative V60-V72 were significantly associated with chronic Grade > or =2 rectal toxicity both as categorical and continuous variables (t test, linear regression) and when divided into subgroups (chi-square table). The chronic rectal toxicity Grade > or =2 risk was 9%, 18%, and 25% for the rectal wall relative V70 <15%, 25%-40%, and >40% respectively. The volume of rectum or rectal wall radiated to > or =50 Gy was a strong predictor for chronic rectal toxicity. Nonpredictive factors: Rectal solid/wall absolute or relative volumes irradiated to < or =40 Gy, dose level, and use of androgen deprivation were not found predictive.

CONCLUSIONS

In our ART dose escalation study, rectal wall or rectum relative > or =V50 are closely predictive for chronic rectal toxicity. If rectal dose-volume histogram constraints are used to select the dose level, the risk of chronic rectal toxicity will reflect the risk of toxicity of the selected constraint rather than the dose selected as found in our study using an adaptive process. To select the prescribed dose, different dose-volume histogram constraints may be used including the rectal wall V70. Patients experiencing acute rectal toxicity are more likely to experience chronic toxicity.

Risk-Adapted Androgen Deprivation and Escalated Three-Dimensional Conformal Radiotherapy for Prostate Cancer: Does Radiation Dose Influence Outcome of Patients Treated With Adjuvant Androgen Deprivation? A GICOR Study

Purpose

Multicenter study conducted to determine the impact on biochemical control and survival of risk-adapted androgen deprivation (AD) combined with high-dose three-dimensional conformal radiotherapy (3DCRT) for prostate cancer. Results of biochemical control are reported.

Patients and Methods

Between October 1999 and October 2001, 416 eligible patients with prostate cancer were assigned to one of three treatment groups according to their risk factors: 181 low-risk patients were treated with 3DCRT alone; 75 intermediate-risk patients were allocated to receive neoadjuvant AD (NAD) 4-6 months before and during 3DCRT; and 160 high-risk patients received NAD and adjuvant AD (AAD) 2 years after 3DCRT. Stratification was performed for treatment/risk group and total radiation dose.

Results

After a median follow-up of 36 months (range, 18 to 63 months), the actuarial biochemical disease-free survival (bDFS) at 5 years for all patients was 74%. The corresponding figures for low-risk, intermediate-risk, and high-risk disease were 80%, 73%, and 79%, respectively (P = .847). Univariate analysis showed that higher radiation dose was the only significant factor associated with bDFS for all patients (P = .0004). When stratified for treatment group, this benefit was evident for low-risk patients (P = .009) and, more interestingly, for high-risk patients treated with AAD. The 5-year bDFS for high-risk patients treated with AAD was 63% for radiation doses less than 72 Gy and 84% for those ≥ 72 Gy (P = .003).

Conclusion

The results of combined AAD plus high-dose 3DCRT are encouraging. To our knowledge, this is the first study showing an additional benefit of high-dose 3DCRT when combined with long-term AD for unfavorable disease.

The emerging role of high-dose-rate brachytherapy for prostate cancer

By placing radioactive sources directly into the cancer, brachytherapy allows delivery of a highly conformal radiation dose to the prostate. Permanent seed brachytherapy is most commonly used for low-risk cancer, whereas high-dose-rate (HDR) brachytherapy is combined with external-beam radiotherapy to treat higher risk disease. The high rate of dose delivery and the large fraction size may be a radiobiological advantage for tumours with high sensitivity to radiation fraction size. The ability to optimise dose delivery allows for exquisite shaping of dose around the prostate and sparing of normal tissues. HDR brachytherapy is most commonly delivered in two or more fractions of 810 Gy combined with 40-50 Gy external beam. Published studies are almost entirely limited to single-institution case series. Most of the patients treated have relatively unfavourable localised disease, with a reported disease-free survival of 68-93%, and a local control rate of over 90%. Treatment is well tolerated, with urethral stricture the most common late effect (risk around 8%). Early results using HDR monotherapy in low-risk disease seem promising. Patients most likely to benefit from a combined HDR/external-beam approach have bulky local disease (stage T2b-T3) or intermediate to high-grade cancers. Prospective multicentre studies of HDR brachytherapy have begun in this patient group in Canada and the USA, which hopefully will allow future comparisons with high-dose conformal external-beam techniques.

Hypofractionated intensity-modulated radiotherapy (70 gy at 2.5 Gy per fraction) for localized prostate cancer: long-term outcomes

PURPOSE

To analyze the long-term relapse-free survival and toxicity rates in patients treated with hypofractionated intensity-modulated radiotherapy.

METHODS AND MATERIALS

The study sample includes the first 100 consecutive localized prostate cancer patients treated to 70.0 Gy at 2.5 Gy per fraction. The median follow-up was 66 months (range, 3 to 75 months). Biochemical failure was the study endpoint, using both the ASTRO definition (A-bRFS) and the alternate "nadir + 2 ng/mL" definition (N-bRFS). RTOG scores were used to assess toxicity.

RESULTS

The 5-year A-bRFS and N-bRFS rates were 85% (95%CI, 78-93%) and 88% (95%CI, 82-95%) for all cases, respectively. For low, intermediate and high-risk disease, the 5-year A-bRFS rates were 97%, 88%, and 70%. The corresponding 5-year N-bRFS rates were 97%, 93%, and 75%, respectively. The acute rectal toxicity scores were 0 in 20, 1 in 61, and 2 in 19 patients. The acute urinary toxicity scores were 0 in 9, 1 in 76, and 2 in 15 patients. The late rectal toxicity scores were 0 in 71, 1 in 19, 2 in 7, and 3 in 3 patients. The actuarial late Grade 3 rectal toxicity rate at 5 years was 3%. A number of the toxicities observed either resolved spontaneously or were corrected. At last follow-up, the rate of combined Grades 2 and 3 late rectal toxicity at 5 years was only 5%. The late urinary toxicity scores were 0 in 75, 1 in 13, 2 in 11, and 3 in 1 patients. The actuarial late Grade 3 urinary toxicity rate at 5 years was 1%.

CONCLUSION

With a median follow-up of 66 months, the long-term results after high-dose hypofractionation are excellent. Late toxicity, urinary and rectal, has been limited. High-dose hypofractionation is an alternative dose escalation method in the treatment of localized prostate cancer.

Phase II dose escalation study of image-guided adaptive radiotherapy for prostate cancer: Use of dose–volume constraints to achieve rectal isotoxicity

PURPOSE

In our Phase II prostate cancer Adaptive Radiation Therapy (ART) study, the highest possible dose was selected on the basis of normal tissue tolerance constraints. We analyzed rectal toxicity rates in different dose levels and treatment groups to determine whether equivalent toxicity rates were achieved as hypothesized when the protocol was started.

METHODS AND MATERIALS

From 1999 to 2002, 331 patients with clinical stage T1 to T3, node-negative prostate cancer were prospectively treated with three-dimensional conformal adaptive RT. A patient-specific confidence-limited planning target volume was constructed on the basis of 5 CT scans and 4 sets of electronic portal images after the first 4 days of treatment. For each case, the rectum (rectal solid) was contoured in its entirety. The rectal wall was defined by use of a 3-mm wall thickness (median volume: 29.8 cc). The prescribed dose level was chosen using the following rectal wall dose constraints: (1) Less than 30% of the rectal wall volume can receive more than 75.6 Gy. (2) Less than 5% of the rectal wall can receive more than 82 Gy. Low-risk patients (PSA < 10, Stage < or = T2a, Gleason score < 7) were treated to the prostate alone (Group 1). All other patients, intermediate and high risk, where treated to the prostate and seminal vesicles (Group 2). The risk of chronic toxicity (NCI Common Toxicity Criteria 2.0) was assessed for the different dose levels prescribed. HIC approval was acquired for all patients. Median follow-up was 1.6 years.

RESULTS

Grade 2 chronic rectal toxicity was experienced by 34 patients (10%) (9% experienced rectal bleeding, 6% experienced proctitis, 3% experienced diarrhea, and 1% experienced rectal pain) at a median interval of 1.1 year. Nine patients (3%) experienced grade 3 or higher chronic rectal toxicity (1 Grade 4) at a median interval of 1.2 years. The 2-year rates of Grade 2 or higher and Grade 3 or higher chronic rectal toxicity were 17% and 3%, respectively. No significant difference by dose level was seen in the 2-year rate of Grade 2 or higher chronic rectal toxicity. These rates were 27%, 15%, 14%, 17%, and 24% for dose levels equal to or less than 72, 73.8, 75.6, 77.4, and 79.2 Gy, respectively (p = 0.3). Grade 2 or higher chronic rectal bleeding was significantly greater for Group 2 than for Group 1, 17% vs. 8% (p = 0.035).

CONCLUSIONS

High doses (79.2 Gy) were safely delivered in selected patients by our adaptive radiotherapy process. Under the rectal dose-volume histogram constraints for the dose level selection, the risk of chronic rectal toxicity is similar among patients treated to different dose levels. Therefore, rectal chronic toxicity rates reflect the dose-volume cutoff used and are independent of the actual dose levels. On the other hand, a larger PTV will increase the rectal wall dose and chronic rectal toxicity rates. PTV volume and dose constraints should be defined, considering their potential benefit.

Randomized Trial Comparing Two Fractionation Schedules for Patients With Localized Prostate Cancer

Purpose

The optimal radiation dose fractionation schedule for localized prostate cancer is unclear. This study was designed to compare two dose fractionation schemes (a shorter 4-week radiation schedule v a longer 6.5-week schedule).

Patients and Methods

Patients with early-stage (T1 or T2) prostate cancer were randomly assigned to 66 Gy in 33 fractions over 45 days (long arm) or 52.5 Gy in 20 fractions over 28 days (short arm). The study was designed as a noninferiority investigation with a predefined tolerance of −7.5%. The primary outcome was a composite of biochemical or clinical failure (BCF). Secondary outcomes included presence of tumor on prostate biopsy at 2 years, survival, and toxicity.

Results

From March 1995 to December 1998, 936 men were randomly assigned to treatment; 470 were assigned to the long arm, and 466 were assigned to the short arm. The median follow-up time was 5.7 years. At 5 years, the BCF probability was 52.95% in the long arm and 59.95% in the short arm (difference = −7.0%; 90% CI, −12.6% to −1.4%), favoring the long arm. No difference in 2-year postradiotherapy biopsy or in overall survival was detected between the arms. Acute toxicity was found to be slightly higher in the short arm (11.4%) compared with the long arm (7%; difference = −4.4%; 95% CI, −8.1% to −0.6%); however, late toxicity was similarly low in both arms (3.2%).

Conclusion

Given the results, we cannot exclude the possibility that the chosen hypofractionated radiation regimen may be inferior to the standard regimen. Further evaluation involving higher dose hypofractionated radiation regimens in contemporary radiation settings is necessary.

Increased risk of biochemical and local failure in patients with distended rectum on the planning CT for prostate cancer radiotherapy

PURPOSE

To retrospectively test the hypothesis that rectal distension on the planning computed tomography (CT) scan is associated with an increased risk of biochemical and local failure among patients irradiated for prostate carcinoma when a daily repositioning technique based on direct prostate-organ localization is not used.

METHODS AND MATERIALS

This study included 127 patients who received definitive three-dimensional conformal radiotherapy for prostate cancer to a total dose of 78 Gy at The University of Texas M. D. Anderson Cancer Center. Rectal distension was assessed by calculation of the average cross-sectional rectal area (CSA; defined as the rectal volume divided by length) and measuring three rectal diameters on the planning CT. The impact of rectal distension on biochemical control, 2-year prostate biopsy results, and incidence of Grade 2 or greater late rectal bleeding was assessed.

RESULTS

The incidence of biochemical failure was significantly higher among patients with distended rectums (CSA >11.2 cm(2)) on the planning CT scan (p = 0.0009, log-rank test). Multivariate analysis indicates that rectal distension and high-risk disease are independent risk factors for biochemical failure, with hazard ratios of 3.89 (95% C.I. 1.58 to 9.56, p = 0.003) and 2.45 (95% C.I. 1.18 to 5.08, p = 0.016), respectively. The probability of residual tumor without evidence of radiation treatment (as scored by the pathologist) increased significantly with rectal distension (p = 0.010, logistic analysis), and a lower incidence of Grade 2 or greater late rectal bleeding within 2 years was simultaneously observed with higher CSA values (p = 0.031, logistic analysis).

CONCLUSIONS

We found strong evidence that rectal distension on the treatment-planning CT scan decreased the probability of biochemical control, local control, and rectal toxicity in patients who were treated without daily image-guided prostate localization, presumably because of geographic misses. Therefore, an empty rectum is warranted at the time of simulation. These results also emphasize the need for image-guided radiotherapy to improve local control in irradiating prostate cancer.

Comparing measures of acute bowel toxicity in patients with prostate cancer treated with external beam radiation therapy

PURPOSE

This study strives to compare early measures of bowel toxicity in patients with prostate cancer receiving definitive or adjuvant 3D conformal external beam radiation therapy and concurrent daily endorectal application of amifostine.

METHODS

Eighteen patients were enrolled in the clinical study with a median follow-up of 12 months. Prescription doses ranged from 66 Gy to 76 Gy with a daily fractionation of 2 Gy. Acute bowel toxicity was measured at baseline, at Weeks 5 and 7 of radiotherapy, and at 1 and 3 months after the completion of therapy. Measures of acute bowel toxicity included the Radiation Therapy Oncology Group (RTOG) acute radiation morbidity scoring criteria, Expanded Prostate Cancer Index Composite (EPIC) self-assessment questionnaires, and proctoscopic examinations.

RESULTS

The mean EPIC bowel scores changed significantly through the course of therapy and follow-up (p < 0.0001), with a progressive decrease in scores at Weeks 5 and 7 of treatment, a partial recovery at 3 months, and a correlation to the gold standard RTOG grade (p = 0.004). Proctoscopic toxicity scores were low, did not vary over time, and did not correlate with either EPIC or RTOG scores.

CONCLUSION

The EPIC questionnaire measurements are most sensitive to changes in acute bowel toxicity through a course of radiotherapy and correlate with RTOG acute toxicity scores. Endoscopic examination of the rectal mucosa at the end and immediate follow-up of a course of therapy does not seem to be informative or reproducible between observers in the acute setting.

Intensity modulated radiotherapy for high risk prostate cancer based on sentinel node SPECT imaging for target volume definition

Background

The RTOG 94-13 trial has provided evidence that patients with high risk prostate cancer benefit from an additional radiotherapy to the pelvic nodes combined with concomitant hormonal ablation. Since lymphatic drainage of the prostate is highly variable, the optimal target volume definition for the pelvic lymph nodes is problematic. To overcome this limitation, we tested the feasibility of an intensity modulated radiation therapy (IMRT) protocol, taking under consideration the individual pelvic sentinel node drainage pattern by SPECT functional imaging.

Methods

Patients with high risk prostate cancer were included. Sentinel nodes (SN) were localised 1.5–3 hours after injection of 250 MBq ^99mTc-Nanocoll using a double-headed gamma camera with an integrated X-Ray device. All sentinel node localisations were included into the pelvic clinical target volume (CTV). Dose prescriptions were 50.4 Gy (5 × 1.8 Gy / week) to the pelvis and 70.0 Gy (5 × 2.0 Gy / week) to the prostate including the base of seminal vesicles or whole seminal vesicles. Patients were treated with IMRT. Furthermore a theoretical comparison between IMRT and a three-dimensional conformal technique was performed.

Results

Since 08/2003 6 patients were treated with this protocol. All patients had detectable sentinel lymph nodes (total 29). 4 of 6 patients showed sentinel node localisations (total 10), that would not have been treated adequately with CT-based planning ('geographical miss') only. The most common localisation for a probable geographical miss was the perirectal area. The comparison between dose-volume-histograms of IMRT- and conventional CT-planning demonstrated clear superiority of IMRT when all sentinel lymph nodes were included. IMRT allowed a significantly better sparing of normal tissue and reduced volumes of small bowel, large bowel and rectum irradiated with critical doses. No gastrointestinal or genitourinary acute toxicity Grade 3 or 4 (RTOG) occurred.

Conclusion

IMRT based on sentinel lymph node identification is feasible and reduces the probability of a geographical miss. Furthermore, IMRT allows a pronounced sparing of normal tissue irradiation. Thus, the chosen approach will help to increase the curative potential of radiotherapy in high risk prostate cancer patients.

A phase II study of localized prostate cancer treated to 75.6Gy with 3D conformal radiotherapy

BACKGROUND AND PURPOSE

To prospectively evaluate toxicity, biochemical failure-free survival (bFFS) and biopsy-proven local control for prostate cancer patients treated with 75.6 Gy in 42 fractions using 6-field conformal radiotherapy to prostate alone.

PATIENTS AND METHODS

From 1997 to 1999, 140 patients with T1-2NxM0, Gleason score<or=8, and PSA<or=20 ng/ml prostate cancer were assessed using Radiation Therapy Oncology Group acute and late toxicity scores. bFFS was determined for 120 patients treated without hormones. Post-treatment prostate biopsies were performed at a median of 3 years and a late toxicity questionnaire was administered at a median of 5 years.

RESULTS

Clinically important acute toxicities were gastrointestinal (GI) grade 2: 22% and 3: 0%, and genitourinary (GU) grade 2: 24% and 3: 2%. Late physician-assessed toxicities were GI>or=grade 2: 2%, and GU>or=grade 2: 1%. The 3-year bFFS of patients failure-free before biopsy was 93% (95% CI: 83-100) from a negative biopsy and 22% (95% CI: 0-56) from a positive biopsy (P=0.001). Patients reported significantly more late toxicity than physicians (GI: P=0.003, GU: P<0.001). At 5.0 years median follow-up, cause-specific survival was 98% (95% CI: 96-100), overall survival was 91% (95% CI: 86-97), and bFFS was 55% (95% CI: 45-64).

CONCLUSIONS

75.6 Gy caused modest levels of acute and late toxicity. Three-year biopsies predicted subsequent biochemical outcome.

External beam radiotherapy as curative treatment of prostate cancer

External beam radiotherapy (RT) has been used as a curative treatment of prostate cancer for more than 5 decades, with the "modern" era emerging more than 3 decades ago. Its history is marked by gradual improvements punctuated by several quantum leaps that are increasingly driven by advancements in the computer and imaging sciences and by its integration with complementary forms of treatment. Consequently, the contemporary use of external beam RT barely resembles its earliest form, and this must be appreciated in the context of current patient care. The influence of predictive factors on the use and outcomes of external beam RT is presented, as is a selected review of the methods and outcomes of external beam RT as a single therapeutic intervention, in association with androgen suppression, or as a postoperative adjunct. Thus, the "state of the (radiotherapeutic) art" is presented to enhance the understanding of this treatment approach with the hope that this information will serve as a useful resource to physicians as they care for patients with prostate cancer.

Ultrasound-Based Localization

Ultrasound is a noninvasive, relatively easy, rapid, and real-time imaging technique for organ targeting for radiotherapy. Its application has been developed to a greater extent in prostate cancer than in other sites in which it has been shown to improve the accuracy of daily treatment delivery. With the move toward dose escalation and the need to maximally spare the adjacent critical structures through more conformal therapy and smaller field margins, an innovative technique for accurate and reproducible tumor targeting is mandatory. Basic ultrasound principles and organ location lend themselves well to the application of this modality in prostate cancer. Promising results using daily ultrasound-guided B-mode acquisition and targeting for patients with upper abdominal tumors suggest an area for additional trials and study. For breast cancer radiotherapy, ultrasound serves to define involved primary and nodal sites, especially in patients in whom surgical evaluation will not be the first therapeutic step.

Impact of hormone therapy on acute radiotherapy toxicity in the treatment of prostate cancer

PURPOSE

To analyze the impact of neoadjuvant hormone therapy (HT) on acute gastrointestinal (GI) and genitourinary (GU) toxicity from radiotherapy (RT).

SCOPE

The toxicity rates of 480 consecutive prostate cancer patients were reviewed and compared using the chi2 test. Ordered logit regression analyses were performed including the major demographic, disease, and treatment factors. Although no reduction in acute GI toxicity from HT use was observed (P=0.067), a lower rate of acute GU toxicity was observed (P=0.002). No factor reached statistical significance on regression analysis.

CONCLUSIONS

Observed toxicity rates were similar or lower in patients receiving HT. Thus, increased RT toxicity should not be a concern when deciding to add neoadjuvant HT to RT for prostate cancer.

Individualized planning target volumes for intrafraction motion during hypofractionated intensity-modulated radiotherapy boost for prostate cancer

PURPOSE

The objective of the study was to access toxicities of delivering a hypofractionated intensity-modulated radiotherapy (IMRT) boost with individualized intrafraction planning target volume (PTV) margins and daily online correction for prostate position.

METHODS AND MATERIALS

Phase I involved delivering 42 Gy in 21 fractions using three-dimensional conformal radiotherapy, followed by a Phase II IMRT boost of 30 Gy in 10 fractions. Digital fluoroscopy was used to measure respiratory-induced motion of implanted fiducial markers within the prostate. Electronic portal images were taken of fiducial marker positions before and after each fraction of radiotherapy during the first 9 days of treatment to calculate intrafraction motion. A uniform 10-mm PTV margin was used for the first phase of treatment. PTV margins for Phase II were patient-specific and were calculated from the respiratory and intrafraction motion data obtained from Phase I. The IMRT boost was delivered with daily online correction of fiducial marker position. Acute toxicity was measured using National Cancer Institute Common Toxicity Criteria, version 2.0.

RESULTS

In 33 patients who had completed treatment, the average PTV margin used during the hypofractionated IMRT boost was 3 mm in the lateral direction, 3 mm in the superior-inferior direction, and 4 mm in the anteroposterior direction. No patients developed acute Grade 3 rectal toxicity. Three patients developed acute Grade 3 urinary frequency and urgency.

CONCLUSIONS

PTV margins can be reduced significantly with daily online correction of prostate position. Delivering a hypofractionated boost with this high-precision IMRT technique resulted in acceptable acute toxicity.

Acute gastrointestinal, genitourinary, and dermatological toxicity during dose-escalated 3D-conformal radiation therapy (3DCRT) using an intrarectal balloon for prostate gland localization and immobilization

PURPOSE

We determined the acute gastrointestinal (GI), genitourinary (GU), and dermatologic (D) toxicity during dose-escalated three-dimensional conformal radiation therapy (3DCRT). A modified intrarectal balloon (Medrad) was used for prostate gland localization and immobilization.

METHODS

Forty-six men with clinical category T1c to T3a, and at least one high-risk feature (PSA >10, Gleason > or =7, or MRI evidence of extracapsular extension or seminal vesical invasion) comprised the study cohort. Treatment consisted of hormonal therapy and 4-field 3DCRT using an intrarectal balloon for the initial 15 of 40 treatments. Planning treatment volume dose was 72 Gy (95% normalization). A Mantel-Haenzel Chi-square test compared the distribution of GU, GI, and D symptoms at baseline and at end of treatment (EOT).

RESULTS

There was no significant difference between the 2 time points in the proportion of patients with bowel symptoms (p = 0.73), tenesmus (p = 0.27), nocturia (p = 1.00), or GU urgency (p = 0.40). However, there was a significant decrease in GU frequency (70% vs. 50%, p = 0.46) as a result of medical interventions and a significant increase in hemorrhoidal irritation (4% vs. 20%, p = 0.02) and anal cutaneous skin reaction (0% vs. 70%, p < 0.001). By 3 months after EOT compared to baseline, there was no significant difference in the proportion of patients experiencing hemorrhoidal bleeding (4% vs. 8%, p = 0.52), requiring intervention for hemorrhoidal symptoms (7% vs. 5%, p = 0.8), or experiencing persistent anal cutaneous skin reaction (0% vs. 3%, p = 0.31).

CONCLUSION

Dose-escalated 3DCRT using an intrarectal balloon for prostate localization and immobilization was well tolerated. Acute GU, GI, and D symptoms resolved with standard dietary or medical interventions by the EOT or shortly thereafter.

Lack of benefit of pelvic radiation in prostate cancer patients with a high risk of positive pelvic lymph nodes treated with high-dose radiation

PURPOSE

The use of pelvic radiation for patients with a high risk of lymph node (LN) metastasis (>15%) remains controversial. We reviewed the data at three institutions treating patients with a combination of external-beam radiation therapy and high-dose-rate brachytherapy to address the prognostic implications of the use of the Roach formula and the benefit of pelvic treatment.

METHODS AND MATERIALS

From 1986 to 2003, 1,491 patients were treated with external-beam radiation therapy and high-dose-rate brachytherapy. The Roach formula [2/3 prostate-specific antigen + (Gleason score -6) x 10] could be calculated for 1,357 patients. Group I consisted of patients having a risk of positive LN < or = 15% (n = 761), Group II had a risk >15% and < or = 30% (n = 422), and Group III had a risk of LN disease >30% (n = 174). A >15% risk of having positive LN was found in 596 patients and was used to determine the benefit of pelvic radiation. The pelvis was treated at two of the cancer centers (n = 312), whereas at the third center (n = 284) radiation therapy was delivered to the prostate and seminal vesicles alone. Average biologic effective dose was > or = 100 Gy (alphabeta = 1.2). Biochemical failure was as per the American Society for Therapeutic Radiology and Oncology definition. Statistics included the log-rank test as well as Cox univariate and multivariate analysis.

RESULTS

For all 596 patients with a positive LN risk >15%, median follow-up was 4.3 years, with a mean of 4.8 years. For all cases, median follow-up was 4 years and mean follow-up was 4.4 years. Five-year results for the three groups based on their risk of positive LN were significantly different in terms of biochemical failure (p < 0.001), clinical control (p < 0.001), disease-free survival excluding biochemical failure (p < 0.001), cause-specific survival (p < 0.001), and overall survival (p < 0.001). For all patients with a risk of positive LN >15% (n = 596), Group II (>15-30% risk), or Group III (>30% risk), no benefit was seen in the 5-year rates of clinical failure, cause-specific survival, or overall survival with pelvic radiation. In the Cox multivariate analysis for cause-specific survival, Gleason score (p = 0.009, hazard ratio [HR] 3.1), T stage (p = 0.03, HR 1.8), and year of treatment (p = 0.05, HR 1.1) were significant. A log-rank test for cause-specific survival for all patients (n = 577) by the use of pelvic radiation was not significant (p = 0.99) accounting for high-dose-rate brachytherapy dose, neoadjuvant hormones, Gleason score, prostate-specific antigen, T stage, and year of treatment as covariates.

CONCLUSIONS

The use of the Roach formula to stratify patients for clinical and biochemical outcomes is excellent. Pelvic radiation added to high prostate radiation doses did not show a clinical benefit for patients at a high risk of pelvic LN disease (>15%) selected using the Roach formula.

Intensity-modulated radiation therapy: emerging cancer treatment technology

The use of intensity-modulated radiation therapy (IMRT) is rapidly advancing in the field of radiation oncology. Intensity-modulated radiation therapy allows for improved dose conformality, thereby affording the potential to decrease the spectrum of normal tissue toxicities associated with IMRT. Preliminary results with IMRT are quite promising; however, the clinical data is relatively immature and overall patient numbers remain small. High-quality IMRT requires intensive physics support and detailed knowledge of three-dimensional anatomy and patterns of tumour spread. This review focuses on basic principles, and highlights the clinical implementation of IMRT in head and neck and prostate cancer.

Long-term androgen deprivation increases Grade 2 and higher late morbidity in prostate cancer patients treated with three-dimensional conformal radiation therapy

PURPOSE

To determine whether the use of androgen deprivation (AD) increases late morbidity when combined with high-dose three-dimensional conformal radiation therapy (3D-CRT).

METHODS AND MATERIALS

Between May 1989 and November 1998, 1,204 patients were treated for prostate cancer with 3D-CRT to a median dose of 74 Gy. Patients were evaluated every 3-6 months. No AD was given to 945 patients, whereas 140 and 119 patients, respectively, received short-term AD (STAD; < or =6 months) and long-term AD (LTAD; > 6 months). Radiation morbidity was graded according to the Fox Chase modification of the Late Effects Normal Tissue Task Force late morbidity scale. Covariates in the multivariate analysis (MVA) included age, history of diabetes mellitus, prostate-specific antigen (PSA) level, Gleason score, T category, RT field size, total RT dose, use of rectal shielding, and AD status (no AD vs. STAD vs. LTAD).

RESULTS

The only independent predictor for Grade 2 or higher genitourinary (GU) morbidity in the MVA was the use of AD (p = 0.0065). The 5-year risk of Grade 2 or higher GU morbidity was 8% for no AD, 8% for STAD, and 14% for LTAD (p = 0.02). Independent predictors of Grade 2 or higher gastrointestinal (GI) morbidity in the MVA were the use of AD (p = 0.0079), higher total radiation dose (p < 0.0001), the lack of a rectal shield (p = 0.0003), and older age (p = 0.0009). The 5-year actuarial risk of Grade 2 or higher GI morbidity was 17% for no AD vs. 18% for STAD and 26% for LTAD (p = 0.017).

CONCLUSIONS

The use of LTAD seems to significantly increase the risk of both GU and GI morbidity for patients treated with 3D-CRT.

Dosimetric advantage and clinical implication of a micro-multileaf collimator in the treatment of prostate with intensity-modulated radiotherapy

This paper investigates the dosimetric benefits of a micro-multileaf (4-mm leaf width) collimator (mMLC) for intensity-modulated radiation therapy (IMRT) treatment planning of the prostate cancer and its potential application for dose escalation and hypofractionation. We compared treatment plans for IMRT delivery using 2 different multileaf collimator (MLC) leaf widths (4 vs. 10 mm) for 10 patients with prostate cancer. Treatment planning was performed on the XknifeRT2 treatment planning system. All beams and optimization parameters were identical for the mMLC and MLC plans. All of the plans were normalized to ensure that 95% of the planning target volume (PTV) received 100% of the prescribed dose (74 Gy). The differences in dose distribution between the 2 groups of plans using the mMLC and the MLC were assessed by dose-volume histogram (DVH) analysis of the target and critical organs. Significant reductions in the volume of rectum receiving medium to higher doses were achieved using the mMLC. The average decrease in the volume of the rectum receiving 40, 50, and 60 Gy using the mMLC plans was 40.2%, 33.4%, and 17.7%, respectively, with p-values less than 0.0001 for V40 and V50 and 0.012 for V60. The mean dose reductions for D17 and D35 for the rectum were 20.0% (p < 0.0001) and 18.3% (p < 0.0002), respectively, when compared to those with the MLC plans. There were consistent reductions in all dose indices studied for the bladder. The target dose inhomogeneity was improved in the mMLC plans by an average of 32%. In the high-dose range, there was no significant difference in the dose deposited in the "hottest" 1 cc of the rectum between the 2 MLC plans for all cases (p > 0.78). Because of the reduction of rectal volume receiving medium to higher doses, dose to the prostate target can be escalated by about 20 Gy to over 74 Gy, while keeping the rectal dose (either denoted by D17 or D35) the same as those with the use of the MLC. The maximum achievable dose, derived when the rectum is allowed to reach the tolerance level, was found to be in the range of 113-172 Gy (using the tolerance value of D17). We conclude that the use of the mMLC for IMRT of the prostate may facilitate dose hypofractionation due to its dosimetric advantage in significantly improving the DVH parameters of the prostate and critical organs. When used for conventional fractionation scheme, mMLC for IMRT of the prostate may reduce the toxicity to the critical organs.

Australia-wide comparison of intensity modulated radiation therapy prostate plans*

The aim of this study was to investigate the ability of Australian centres to produce high-dose intensity modulated radiation therapy (IMRT) prostate plans, and to compare the planning parameters and resultant dose distributions. Five Australian radiation therapy departments were invited to participate. Each centre received an identical 5 mm-slice CT data set complete with contours of the prostate, seminal vesicles, rectum, bladder, femoral heads and body outline. The planning team was asked to produce the best plan possible, using published Memorial Sloan-Kettering Cancer Centre prescription and dose constraints. Three centres submitted plans for evaluation. All plans covered the planning target volume adequately; however, only one plan met all the critical organ dose constraints. Although the planning parameters, beam arrangements and planning systems were different for each centre, the resulting plans were similar. In Australia, IMRT for prostate cancer is in the early stages of implementation, with routine use limited to a few centres.

Technological advances in radiotherapy for the treatment of localised prostate cancer

There is good evidence that radiation dose escalation in localised prostate cancer is associated with increased cell kill. The traditional two-dimensional (2D) technique of treatment planning and delivery is limited by normal tissue toxicity, such that the dose that can be safely delivered to the prostate by external beam radiotherapy is 65-70 Gy. Several technological advances over the last 20 years have enhanced the precision of external beam radiotherapy (EBRT), and have resulted in improved outcomes. The three-dimensional conformal radiotherapy (3D-CRT) approach reduces the dose-limiting late side-effect of proctitis and has allowed for dose escalation to the whole prostate to 78 Gy. More recently, intensity modulated radiotherapy (IMRT), an advanced form of conformal therapy, has resulted in reduced rectal toxicity when using doses greater than 80 Gy. In addition, IMRT can potentially escalate the dose to specific parts of the prostate where there are resistant subpopulations of tumour clonogens, or can be used to extend the high-dose region to pelvic lymph nodes. The addition of androgen deprivation to conventional radiotherapy has an impact on survival and local control. Initial hormone therapy causes cytoreduction of the prostate cancer allowing for a reduction in radiotherapy volume as well as an additive effect on cell kill. Long-term adjuvant androgen deprivation has been shown to improve overall survival in more advanced tumours. Prostate brachytherapy is now a recognised treatment for those with low-risk disease. It achieves similar long-term outcome to other treatment modalities. Brachytherapy can be used as monotherapy for localised disease, or as boost treatment following conventional EBRT for locally advanced disease. New techniques are available to improve the precision of both target definition and treatment verification. This so-called image-guided radiotherapy will help to enhance the accuracy of dose delivery by correcting both for inter-fraction positional variation and for intra-fraction movement of the prostate in real-time and will allow for tighter tumour margins and avoidance of normal tissues, thereby enhancing the safety of treatment.

70 Gy or more: which dose for which prostate cancer?

INTRODUCTION

Radical prostatectomy and radiotherapy are currently accepted treatment modalities for localized prostate cancer. Regarding radiotherapy, current evidence suggests that favorable treatment outcome critically depends on adequate radiation doses. However, the exact role of dose in relation to the individual risk profile is complex. In order to evaluate available data on radiation dose response relationships, in prostate cancer, a thorough and critical literature analysis was performed.

MATERIAL AND METHODS

Studies on dose response relationships from randomized trials, dose escalation trials, retrospective subgroup analyses and pooled data were identified by Pubmed and ISI web of sciences searches and were critically reviewed.

RESULTS AND CONCLUSION

All available data suggest a clear dose response relationship for radiotherapy for localized prostate cancer. In low risk cases, most studies suggest that doses of 70-72 Gy are adequate. Dose escalations up to 78-80 Gy seem to be beneficial for intermediate risk patients. Due to confounding variables, the dose response curves for high-risk patients are less steep. The integration of dose escalation into a more comprehensive treatment protocol is difficult, since trials on the relative impact of either hormonal ablation or inclusion of adjuvant nodal regions on dose escalation are missing.

Dosimetric evaluation of MRI-based treatment planning for prostate cancer

The purpose of this study is to evaluate the dosimetric accuracy of MRI-based treatment planning for prostate cancer using a commercial radiotherapy treatment planning system. Three-dimensional conformal plans for 15 prostate patients were generated using the AcQPlan system. For each patient, dose distributions were calculated using patient CT data with and without heterogeneity correction, and using patient MRI data without heterogeneity correction. MR images were post-processed using the gradient distortion correction (GDC) software. The distortion corrected MR images were fused to the corresponding CT for each patient for target and structure delineation. The femoral heads were delineated based on CT. Other anatomic structures relevant to the treatment (i.e., prostate, seminal vesicles, lymph notes, rectum and bladder) were delineated based on MRI. The external contours were drawn separately on CT and MRI. The same internal contours were used in the dose calculation using CT- and MRI-based geometries by directly transferring them between MRI and CT as needed. Treatment plans were evaluated based on maximum dose, isodose distributions and dose-volume histograms. The results confirm previous investigations that there is no clinically significant dose difference between CT-based prostate plans with and without heterogeneity correction. The difference in the target dose between CT- and MRI-based plans using homogeneous geometry was within 2.5%. Our results suggest that MRI-based treatment planning is suitable for radiotherapy of prostate cancer.