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

Long-term results of the M. D. Anderson randomized dose-escalation trial for prostate cancer

PURPOSE

To report the long-term results of a randomized radiotherapy dose escalation trial for prostate cancer.

METHODS AND MATERIALS

From 1993 to 1998, a total of 301 patients with stage T1b to T3 prostate cancer were accrued to a randomized external beam dose escalation trial using 70 Gy versus 78 Gy. The median follow-up is now 8.7 years. Kaplan-Meier analysis was used to compute rates of prostate-specific antigen (PSA) failure (nadir + 2), clinical failure, distant metastasis, disease-specific, and overall survival as well as complication rates at 8 years post-treatment.

RESULTS

For all patients, freedom from biochemical or clinical failure (FFF) was superior for the 78-Gy arm, 78%, as compared with 59% for the 70-Gy arm (p = 0.004, and an even greater benefit was seen in patients with initial PSA >10 ng/ml (78% vs. 39%, p = 0.001). The clinical failure rate was significantly reduced in the 78-Gy arm as well (7% vs. 15%, p = 0.014). Twice as many patients either died of prostate cancer or are currently alive with cancer in the 70-Gy arm. Gastrointestinal toxicity of grade 2 or greater occurred twice as often in the high dose patients (26% vs. 13%), although genitourinary toxicity of grade 2 or greater was less (13% vs. 8%) and not statistically significantly different. Dose-volume histogram analysis showed that the complication rate could be significantly decreased by reducing the amount of treated rectum.

CONCLUSIONS

Modest escalation in radiotherapy dose improved freedom from biochemical and clinical progression with the largest benefit in prostate cancer patients with PSA >10 ng/ml.

[Current treatment in high risk and locally advanced prostate cancer]

Treatment of locally advanced prostate cancer remains controversial. Treatment options include radical prostatectomy (PR), radiotherapy (RT) and hormonotherapy (HT). A Medline database search with key words "prostate cancer", "locally advanced", "high risk" and "treatment" in articles published during the last 15 years was done. Fifty one out of 329 papers were selected and reviewed. Selection criteria were a minimum of scientific evidence level of IIa, except for some specific level IV reference. Numerous randomized studies show that patients may benefit of a combined therapy with RT and HT. RP has shown its usefulness in selected cases of locally advanced prostate cancer. Results of long follow-up series are similar to those obtained with RT and HT. Furthermore, the possibility of clinical over staging is an argument in favour of RP. We perform an updated revision of every possible choice available in the treatment of these tumours.

Late radiotherapy-induced lower intestinal toxicity (RILIT) of intensity-modulated radiotherapy for prostate cancer: the need for adapting toxicity scales and the appearance of the sigmoid colon as co-responsible organ for lower intestinal toxicity

PURPOSE

To report on: 1. Late radiotherapy-induced lower intestinal toxicity (RILIT) after intensity-modulated radiotherapy (IMRT) for prostate cancer. 2. The correlation between late RILIT and volume parameters of the rectum, sigmoid colon and small bowel.

MATERIALS AND METHODS

We included 241 patients with a follow-up of >or=18 months for this analysis. Late RILIT consisted of 8 different symptoms, comprising the 5 symptoms from the RTOG toxicity score supplemented with urgency, fecal incontinence and anal pain. Late RILIT and late RTOG toxicity were scored prospectively and correlated with: 1. Different rectum, sigmoid colon and small bowel volume parameters. 2. Patient-related morbidity. We calculated the median, quartile and percentiles for the different volume parameters and correlated them with grade 1-3 late RILIT.

RESULTS

Median follow-up was 42 months. Three patients developed grade 3 red blood loss. We registered grade 2 RILIT and RTOG toxicity in 13% and 10%, respectively, the most frequent grade 1 symptom being fecal urgency. The intermediate rectal volume parameters were significantly correlated with late RILIT. We were able to calculate cut-off dose-volume histograms (DVHs) that predict for grade 0-2 RILIT.

CONCLUSIONS

After IMRT for prostate cancer, the overall incidence of grade >or=2 RILIT is low. Cut-off DVHs can be used for patient counseling.

Antisense-MDM2 sensitizes LNCaP prostate cancer cells to androgen deprivation, radiation, and the combination in vivo

PURPOSE

To test the effects of antisense (AS)-MDM2 alone and with androgen deprivation (AD), radiotherapy (RT), and AD + RT on wild-type LNCaP cells in an orthotopic in vivo model.

METHODS

Androgen-sensitive LNCaP cells were grown in the prostates of nude mice. Magnetic resonance imaging-based tumor volume and serum prostate-specific antigen (PSA) measurements were used to assess effects on tumor response. Tumor response was measured by biochemical and tumor volume failure definitions and doubling time estimates from fitted PSA and tumor volume growth curves. Expression of MDM2, p53, p21, and Ki-67 was quantified using immunohistochemical staining and image analysis of formalin-fixed tissue, analogous to methods used clinically.

RESULTS

Antisense-MDM2 significantly inhibited the growth of LNCaP tumors over the mismatch controls. The most significant increase in tumor growth delay and tumor doubling time was from AS-MDM2 + AD + RT, although the effect of AS-MDM2 + AD was substantial. Expression of MDM2 was significantly reduced by AS-MDM2 in the setting of RT.

CONCLUSIONS

This is the first in vivo investigation of the effects of AS-MDM2 in an orthotopic model and the first to demonstrate incremental sensitization when added to AD and AD + RT. The results with AD underscore the potential to affect micrometastatic disease, which is probably responsible for treatment failure in 30-40% of men with high-risk disease.

Radiosensitization of prostate cancer by priming the wild-type p53-dependent cellular senescence pathway

A dramatic stage-migration in diagnosis of prostate cancer has led to earlier detection of clinically localized carcinoma and an increased use of radiation therapy. The p53 protein responds to irradiation-induced DNA damage by removing critically damaged cells from the proliferative pool. This review will focus on the dominant role that p53-dependent cellular senescence, rather than cell death, plays in determining the radiosensitivity of human prostate cancer cells in vitro. The finding that senescence is a primary mechanism of tumor regression indicates that p53 activators or downstream effectors may prove effective in radiosensitizing some carcinoma of the prostate.

Magnetic resonance-based treatment planning for prostate intensity-modulated radiotherapy: creation of digitally reconstructed radiographs

PURPOSE

To develop a technique to create magnetic resonance (MR)-based digitally reconstructed radiographs (DRR) for initial patient setup for routine clinical applications of MR-based treatment planning for prostate intensity-modulated radiotherapy.

METHODS AND MATERIALS

Twenty prostate cancer patients' computed tomography (CT) and MR images were used for the study. Computed tomography and MR images were fused. The pelvic bony structures, including femoral heads, pubic rami, ischium, and ischial tuberosity, that are relevant for routine clinical patient setup were manually contoured on axial MR images. The contoured bony structures were then assigned a bulk density of 2.0 g/cm(3). The MR-based DRRs were generated. The accuracy of the MR-based DDRs was quantitatively evaluated by comparing MR-based DRRs with CT-based DRRs for these patients. For each patient, eight measuring points on both coronal and sagittal DRRs were used for quantitative evaluation.

RESULTS

The maximum difference in the mean values of these measurement points was 1.3 +/- 1.6 mm, and the maximum difference in absolute positions was within 3 mm for the 20 patients investigated.

CONCLUSIONS

Magnetic resonance-based DRRs are comparable to CT-based DRRs for prostate intensity-modulated radiotherapy and can be used for patient treatment setup when MR-based treatment planning is applied clinically.

Computed Tomography-Based High-Dose-Rate Intracavitary Brachytherapy for Uterine Cervical Cancer: Preliminary Demonstration of Correlation Between Dose–Volume Parameters and Rectal Mucosal Changes Observed by Flexible Sigmoidoscopy

PURPOSE

To compare the dose-volume histogram (DVH) parameters obtained by three-dimensional gynecologic brachytherapy planning with the rectosigmoid mucosal changes observed by flexible sigmoidoscopy.

METHODS AND MATERIALS

Between January 2004 and July 2005, 71 patients with International Federation of Gynecology and Obstetrics Stage IB-IIIB uterine cervical cancer underwent computed tomography-based high-dose-rate intracavitary brachytherapy. The total dose (external beam radiotherapy [RT] plus intracavitary brachytherapy) to the International Commission of Radiation Units and Measurements rectal point (ICRU(RP)) and DVH parameters for rectosigmoid colon were calculated using the equivalent dose in 2-Gy fractions (alpha/beta = 3 Gy). Sigmoidoscopy was performed every 6 months after RT, with the 6-scale scoring system used to determine mucosal changes.

RESULTS

The mean values of the DVH parameters and ICRU(RP) were significantly greater in patients with a score of > or =2 than in those with a score <2 at 12 months after RT (ICRU(RP), 71 Gy(alpha/beta3) vs. 66 Gy(alpha/beta3), p = 0.02; D(0.1cc), 93 Gy(alpha/beta3) vs. 85 Gy(alpha/beta3), p = 0.04; D(1cc), 80 Gy(alpha/beta3) vs. 73 Gy(alpha/beta3), p = 0.02; D(2cc), 75 Gy(alpha/beta3) vs. 69 Gy(alpha/beta3), p = 0.02). The probability of a score of > or =2 showed a significant relationship with the DVH parameters and ICRU(RP) (ICRU(RP), p = 0.03; D(0.1cc), p = 0.05; D(1cc), p = 0.02; D(2cc), p = 0.02).

CONCLUSION

Our preliminary data have shown that DVH values of the rectosigmoid colon obtained by computed tomography-based three-dimensional brachytherapy planning are reliable and predictive of score > or =2 rectosigmoid mucosal changes.

Set-up errors due to endorectal balloon positioning in intensity modulated radiation therapy for prostate cancer

PURPOSE

To investigate the set-up errors and deformation associated with daily placement of endorectal balloons in prostate radiotherapy.

MATERIALS AND METHODS

Endorectal balloons were placed daily in 20 prostate cancer patients undergoing radiotherapy. Electronic portal images (EPIs) were collected weekly from anterior-posterior (AP) and lateral views. The EPIs were compared with digitally reconstructed radiographs from computed tomography scans obtained during pretreatment period to estimate displacements. The interfraction deformation of balloon was estimated with variations in diameter in three orthogonal directions throughout the treatment course.

RESULTS

A total of 154 EPIs were evaluated. The mean displacements of balloon relative to bony landmark were 1.8mm in superior-inferior (SI), 1.3mm in AP, and 0.1mm in left-right (LR) directions. The systematic errors in SI, AP, and LR directions were 3.3mm, 4.9 mm, and 4.0mm, respectively. The random (interfraction) displacements, relative to either bony landmarks or treatment isocenter, were larger in SI direction (4.5mm and 4.5mm), than in AP (3.9 mm and 4.4mm) and LR directions (3.0mm and 3.0mm). The random errors of treatment isocenter to bony landmark were 2.3mm, 3.2mm, and 2.6mm in SI, AP, and LR directions, respectively. Over the treatment course, balloon deformations of 2.8mm, 2.5mm, and 2.6mm occurred in SI, AP, and LR directions, respectively. The coefficient of variance of deformation was 7.9%, 4.9%, and 4.9% in these directions.

CONCLUSIONS

Larger interfractional displacement and the most prominent interfractional deformation of endorectal balloon were both in SI direction.

Evidence-based radiation oncology: Definitive, adjuvant and salvage radiotherapy for non-metastatic prostate cancer

The standard treatment options based on the risk category (stage, Gleason score, PSA) for localized prostate cancer include surgery, radiotherapy and watchful waiting. The literature does not provide clear-cut evidence for the superiority of surgery over radiotherapy, whereas both approaches differ in their side effects. The definitive external beam irradiation is frequently employed in stage T1b-T1c, T2 and T3 tumors. There is a pretty strong evidence that intermediate- and high-risk patients benefit from dose escalation. The latter requires reduction of the irradiated normal tissue (using 3-dimensional conformal approach, intensity modulated radiotherapy, image-guided radiotherapy, etc.). Recent data suggest that prostate cancer may benefit from hypofractionation due to relatively low alpha/beta ratio; these findings warrant confirmation though. The role of whole pelvis irradiation is still controversial. Numerous randomized trials demonstrated a clinical benefit in terms of biochemical control, local and distant control, and overall survival from the addition of androgen suppression to external beam radiotherapy in intermediate- and high-risk patients. These studies typically included locally advanced (T3-T4) and poor-prognosis (Gleason score >7 and/or PSA >20 ng/mL) tumors and employed neoadjuvant/concomitant/adjuvant androgen suppression rather than only adjuvant setting. The ongoing trials will hopefully further define the role of endocrine treatment in more favorable risk patients and in the setting of the dose escalated radiotherapy. Brachytherapy (BRT) with permanent implants may be offered to low-risk patients (cT1-T2a, Gleason score <7, or 3+4, PSA <or=10 ng/mL), with prostate volume of <or=50 ml, no previous transurethral prostate resection and a good urinary function. Some recent data suggest a benefit from combining external beam irradiation and BRT for intermediate-risk patients. EBRT after radical prostatectomy improves disease-free survival and biochemical and local control rates in patients with positive surgical margins or pT3 tumors. Salvage radiotherapy may be considered at the time of biochemical failure in previously non-irradiated patients.

High dose rate brachytherapy in combination with external beam radiotherapy in the radical treatment of prostate cancer: initial results of a randomised phase three trial

BACKGROUND AND PURPOSE

A randomised phase III trial has compared external beam radiotherapy alone with a dose escalated schedule using high dose rate brachytherapy. Patients with histologically confirmed prostate cancer, no evidence of metastases, a PSA <50, no previous TURP and fit for general anaesthetic were included.

METHODS

Patients were randomised to receive either standard radiotherapy 55 Gy in 20 fractions treating Monday to Friday over 4 weeks or a combined schedule comprising external beam treatment delivering 35.75 Gy in 13 fractions treating daily Monday to Friday over 2.5 weeks followed by a temporary high dose rate afterloading implant delivering 17 Gy in two fractions over 24h.

RESULTS

A total of 220 patients were randomised, balanced for important prognostic parameters including tumour stage, presenting PSA, Gleason score and use of adjuvant anti-androgens. With a median follow up of 30 months (range 3-91) a significant improvement in actuarial biochemical relapse-free survival is seen in favour of the combined brachytherapy schedule (p=0.03). A lower incidence of acute rectal discharge was seen in the brachytherapy group (p=0.025) and other acute and late toxicities were equivalent. Patients randomised to brachytherapy had a significantly better FACT-P score at 12 weeks (p=0.02).

CONCLUSIONS

The use of high dose rate brachytherapy in combination with external beam radiotherapy resulted in an improved biochemical relapse-free survival compared to external beam radiotherapy alone with less acute rectal toxicity and improved quality of life in this randomised trial.

Tomotherapy for prostate adenocarcinoma: A report on acute toxicity

BACKGROUND AND PURPOSE

To analyze the impact of Tomotherapy (TOMO) intensity modulated radiotherapy (IMRT) on acute gastrointestinal (GI) and genitourinary (GU) toxicity in prostate cancer.

MATERIALS AND METHODS

The records of 55 consecutively treated TOMO patients were reviewed. Additionally a well-matched group of 43 patients treated with LINAC-based step and shoot IMRT (LINAC) was identified. Acute toxicity was scored according to Radiation Therapy Oncology Group acute toxicity criterion.

RESULTS

The grade 2-3 acute GU toxicity rates for the TOMO vs. LINAC groups were 51% vs. 28% (p=0.001). Acute grade 2 GI toxicity was 25% vs. 40% (p=0.024), with no grade 3 GI toxicity in either group. In univariate analysis, androgen deprivation, prostate volume, pre-treatment urinary toxicity, and prostate dose homogeneity correlated with acute GI and GU toxicity. With multivariate analysis use of Tomotherapy, median bladder dose and bladder dose homogeneity remained significantly correlated with GU toxicity.

CONCLUSIONS

Acute GI toxicity for prostate cancer is improved with Tomotherapy at a cost of increased acute GU toxicity possibly due to differences in bladder and prostate dose distribution.

Effect of low dose-rate prostate brachytherapy on the sexual health of men with optimal sexual function before treatment: analysis at ≥ 7 years of follow-up

OBJECTIVE

To evaluate the effect of low-dose rate prostate brachytherapy on the sexual health of men with > or = 7 years of prospective evaluation and optimum sexual function before treatment.

PATIENTS AND METHODS

In all, 223 patients with T1b to T3a prostate cancer and a median (range) age of 66 (50-82) years were treated with permanent seed implantation from November 1990 to March 1998. They were followed for a median (range) of 8.2 (7-14.1) years using prospective quality-of-life measures. Erectile function (EF) was assessed using a physician-assigned score and beginning in June 2000; the validated International Index of EF (IIEF-5) was used as a complementary method to quantify late EF. No adjustment was made to differentiate sexual function with or with no pharmacological intervention for EF. Pearson's chi-square test and Student's t-test were used to compare the groups.

RESULTS

Of the 223 men, 131 (59%) had optimal EF before their brachytherapy; of these, 51 (40%) at the last follow-up evaluation were using either a phosphodiesterase type 5 inhibitor (44, 86%), yohimbine (two, 4%) or alprostadil (five, 10%). The age at implantation was highly predictive of current EF; 23 of 25 (92%) men aged 50-59 years had a current EF of > or = 2; those aged 60-69 and 70-78 years had an EF of > or =2 in 48/75 (64%) and 18/31 (58%) (P = 0.01). A current IIEF-5 score of > or = 16 also correlated highly with age at implant, i.e. 50-59, 16/25 (64%); 60-69, 20/75 (27%) and 70-78 years, 6/31 (19%) (P < 0.001).

CONCLUSION

Patients aged <60 years and with optimal EF before low-dose rate prostate brachytherapy have a very high probability of long-term EF.

Timing of biochemical failure and distant metastatic disease for low-, intermediate-, and high-risk prostate cancer after radiotherapy

BACKGROUND

The relation of prostate cancer risk-group stratification and the timing of biochemical failure (BF) and distant metastasis (DM) is not well defined. The authors hypothesized that early failures due to subclinical micrometastasis at presentation could be differentiated from late failures due to local persistence.

METHODS

A total of 1833 men with clinically localized prostate cancer treated with 3D-conformal radiotherapy with or without short-term androgen deprivation were retrospectively analyzed. By using American Society for Therapeutic Radiology and Oncology (ASTRO) and Phoenix (Nadir+2) definitions (developed at the ASTRO-RTOG [Radiation Therapy Oncology Group] consensus meeting, Phoenix, Arizona, January 21, 2005), the interval hazard rates of BF and DM were determined for men with low-risk, intermediate-risk, and high-risk disease.

RESULTS

Median follow-up was 67 months. Multivariate analysis showed that increasing risk group was independently associated with higher ASTRO BF (P < .0001) and Nadir+2 BF (P < .0001). The preponderance (87%) of ASTRO BF occurred 4 years. The hazard of Nadir+2 BF persisted in Years 8-12 in all risk groups. The interval hazard function for DM appeared to be biphasic (early peak followed by a drop and late increase) for intermediate-risk and high-risk patients, but no distinct early wave was evident for low-risk patients.

CONCLUSIONS

Because of backdating, ASTRO BF underestimates late BF. Local persistence of disease is suggested by delayed Nadir+2 BF and subsequent late DM in every risk group. The paucity of early DM among those with low-risk tumors supports the hypothesis that occult micrometastases contributed to the early wave.

Patient-Assessed Late Toxicity Rates and Principal Component Analysis After Image-Guided Radiation Therapy for Prostate Cancer

PURPOSE

The aims of this study were to determine the incidence of patient-assessed late toxicity after high-dose, image-guided radiation therapy in a cohort of men with prostate cancer; and to correlate toxicity with conventional dosimetric parameters and rectal and bladder dose-volume histograms (DVH) reduced using principal component analysis.

METHODS AND MATERIALS

Toxicity questionnaires were sent to 690 men treated for localized prostate cancer to 75.6 Gy or 79.8 Gy using three-dimensional conformal radiation therapy (3DCRT) or intensity-modulated radiation therapy (IMRT) between 1997 and 2003 at the Princess Margaret Hospital. Toxicity was graded according to the modified Radiation Therapy Oncology Group (RTOG)-late effects normal tissue (LENT) scoring system. Late rectal and bladder toxicity scores were dichotomized as < Grade 2 and > or = Grade 2, and correlated with dosimetric parameters and with the first three principal components of rectal and bladder DVHs.

RESULTS

In all, 63% of the patients completed the questionnaire. At a median follow-up of 37 months, the incidence of late rectal toxicity RTOG Grades 1, 2, and 3 was 25.2%, 2.5%, and 0.7% respectively. The incidence of late urinary toxicity RTOG Grade 1, 2, and 3 was 16.5%, 8.8%, and 0.9% respectively. Maintenance of erectile function sufficient for intercourse was reported in 68%. No dosimetric parameter analyzed, including principal component analysis reduction of DVHs, correlated with late toxicity.

CONCLUSIONS

Postal questionnaire was effective for collection of patient-assessed late toxicity data. The incidence of late toxicity was low, with a lack of correlation to dosimetric parameters. We attribute this to the use of conformal techniques and daily image guidance.

High-Dose-Rate Brachytherapy Plus External Beam Radiotherapy for T1 to T3 Prostate Cancer: An Experience in Taiwan

OBJECTIVES

To report outcomes for localized prostate cancer patients treated with the combination of high-dose-rate (HDR) brachytherapy and external beam radiotherapy (EBRT).

METHODS

Eighty-five Stage T1c to T3b prostate cancer patients treated with HDR brachytherapy plus EBRT were included. An HDR dose of 16.5 Gy in 3 fractions over 24 hours was given 2 weeks before EBRT. An EBRT dose of 50.4 Gy was administered to the prostate and seminal vesicles. Younger patients (aged less than 75 years) with greater than 15% risk of nodal metastasis received whole-pelvis RT (45 Gy in 25 fractions) as part of EBRT.

RESULTS

Fifty percent of patients belonged to the high-risk (T3a or Gleason score 8-10 or prostate-specific antigen greater than 20 ng/mL) or very-high-risk (T3b) groups. After a median follow-up of 49 months (range, 24 to 70 months), 4-year biochemical control survival (less than nadir + 2) was 86% (100%, 91%, and 81% for patients in the low, intermediate, and high-risk groups, respectively. Three of four T3b patients experienced early biochemical failure. Four patients (5%) had grade 3 implant-related urinary retention. Chronic gastrointestinal toxicities were limited, but four grade 3 chronic genitourinary toxicities (5%) were noted in relation to urethral stricture and severe hematuria. Whole-pelvis EBRT was a major contributing factor to acute but not to chronic gastrointestinal toxicities. Among 60 patients with pretreatment sexual potency, 17 (26%) retained capability after 4 years. Six patients (10%) lost potency merely as a result of salvage hormone therapy.

CONCLUSIONS

High-dose-rate brachytherapy plus EBRT can achieve satisfactory biochemical control with acceptable complications for T1c to T3a prostate cancer patients.

Late toxicity and biochemical recurrence after external-beam radiotherapy combined with permanent-source prostate brachytherapy: analysis of Radiation Therapy Oncology Group study 0019

BACKGROUND

The combination of external-beam radiotherapy and brachytherapy is used commonly to treat men with prostate cancer. In this analysis, the authors examined the rate of biochemical recurrence (BR) and late grade > or =3 genitourinary (GU) and gastrointestinal (GI) toxicity after treatment with external-beam radiotherapy and brachytherapy in a multiinstitutional, cooperative group setting.

METHODS

All eligible patients received external-beam radiotherapy (45 Gray [Gy] in 25 fractions) followed 2 to 6 weeks later by an interstitial implant using iodine-125 to deliver an additional 108 Gy. BR was defined in 2 ways: according to the American Society for Therapeutic Radiology and Oncology (ASTRO) Consensus Definition (ACD) and according to the Phoenix definition (PD) (prostate-specific antigen nadir +2 ng/mL). The Radiation Therapy Oncology Group(RTOG)/European Organization for Research and Treatment of Cancer late radiation morbidity scoring system was used to grade all toxicity.

RESULTS

One hundred thirty-eight patients were enrolled, and 130 were eligible for the current analysis. The median follow-up for surviving patients was 49 months (range, 20-60 months). The 48-month estimate of late grade > or =3 GU/GI toxicity was 15% (95% confidence interval [95% CI], 8-21%), and the 48-month estimate of BR was 19% (95% CI, 12-26%) and 14% (95% CI, 8-20%) according to the ACD and PD, respectively.

CONCLUSIONS

The morbidity observed in this multiinstitutional, cooperative group study was slightly higher than that reported in recent RTOG studies using brachytherapy alone or high-dose external-beam radiotherapy. The BR rate observed in this report was similar to that observed with high-dose external-beam radiotherapy alone in similar patients.

Particle therapy in prostate cancer: a review

While dose escalation is proving important to achieve satisfactory long-term outcomes in prostate cancer, the optimal radiation modality to deliver the treatment is still a topic of debate. Charged particle beams can offer improved dose distributions to the target volume as compared to conventional 3D-conformal radiotherapy, with better sparing of surrounding healthy tissues. Exquisite dose distributions, with the fulfillment of dose-volume constraints to normal tissues, however, can also be achieved with photon-based intensity-modulated techniques. This review summarizes the literature on the use of particle therapy in prostate cancer and attempts to put in perspective its relative merits compared to current photon-based radiotherapy.

Optimizing decisions about treatment in locally advanced prostate cancer

The decision-making process for the management of locally advanced prostate cancer is very complex for both patients and health-care professionals. The Vitality Index can be used to help tailor therapy approaches to match the individual lifestyle needs of patients.

Physical models and simpler dosimetric descriptors of radiation late toxicity

Predicting radiation damage to specific organs is becoming ever more challenging with the use of intensity-modulated beams, nonuniform dose distributions, partial organ irradiation, and interpatient and even intraorgan variations in radiation sensitivity. Data-based physical models can be of use in summarizing complicated dose-volume data to help describe clinical outcomes and ultimately aid in the prediction of clinical toxicity. This article attempts to provide a brief overview of the use of normal tissue complication probability (NTCP) models and other simple dose/volume metrics to describe a few clinically significant complications (either frequent or serious) associated with radiation therapy of the head and neck, thorax, and abdominal-pelvic regions. Specifically, it reviews the application of these methods for late toxicities of the parotid, lung, heart, spinal cord, liver, and rectum. It focuses on organ-specific NTCP parameters as well as simple dosimetric descriptors that might be used to help treatment plan evaluation in clinical practice.

Escalated-dose versus standard-dose conformal radiotherapy in prostate cancer: first results from the MRC RT01 randomised controlled trial

BACKGROUND

In men with localised prostate cancer, conformal radiotherapy (CFRT) could deliver higher doses of radiation than does standard-dose conventional radical external-beam radiotherapy, and could improve long-term efficacy, potentially at the cost of increased toxicity. We aimed to present the first analyses of effectiveness from the MRC RT01 randomised controlled trial.

METHODS

The MRC RT01 trial included 843 men with localised prostate cancer who were randomly assigned to standard-dose CFRT or escalated-dose CFRT, both administered with neoadjuvant androgen suppression. Primary endpoints were biochemical-progression-free survival (bPFS), freedom from local progression, metastases-free survival, overall survival, and late toxicity scores. The toxicity scores were measured with questionnaires for physicians and patients that included the Radiation Therapy Oncology Group (RTOG), the Late Effects on Normal Tissue: Subjective/Objective/Management (LENT/SOM) scales, and the University of California, Los Angeles Prostate Cancer Index (UCLA PCI) scales. Analysis was done by intention to treat. This trial is registered at the Current Controlled Trials website http://www.controlled-trials.com/ISRCTN47772397.

FINDINGS

Between January, 1998, and December, 2002, 843 men were randomly assigned to escalated-dose CFRT (n=422) or standard-dose CFRT (n=421). In the escalated group, the hazard ratio (HR) for bPFS was 0.67 (95% CI 0.53-0.85, p=0.0007). We noted 71% bPFS (108 cumulative events) and 60% bPFS (149 cumulative events) by 5 years in the escalated and standard groups, respectively. HR for clinical progression-free survival was 0.69 (0.47-1.02; p=0.064); local control was 0.65 (0.36-1.18; p=0.16); freedom from salvage androgen suppression was 0.78 (0.57-1.07; p=0.12); and metastases-free survival was 0.74 (0.47-1.18; p=0.21). HR for late bowel toxicity in the escalated group was 1.47 (1.12-1.92) according to the RTOG (grade >/=2) scale; 1.44 (1.16-1.80) according to the LENT/SOM (grade >/=2) scales; and 1.28 (1.03-1.60) according to the UCLA PCI (score >/=30) scale. 33% of the escalated and 24% of the standard group reported late bowel toxicity within 5 years of starting treatment. HR for late bladder toxicity according to the RTOG (grade >/=2) scale was 1.36 (0.90-2.06), but this finding was not supported by the LENT/SOM (grade >/=2) scales (HR 1.07 [0.90-1.29]), nor the UCLA PCI (score >/=30) scale (HR 1.05 [0.81-1.36]).

INTERPRETATION

Escalated-dose CFRT with neoadjuvant androgen suppression seems clinically worthwhile in terms of bPFS, progression-free survival, and decreased use of salvage androgen suppression. This additional efficacy is offset by an increased incidence of longer term adverse events.

Is the α/β Value for Prostate Tumours Low Enough to be Safely Used in Clinical Trials?

There has been an intense debate over the past several years on the relevant alpha/beta value that could be used to describe the fractionation response of prostate tumours. Previously it has been assumed that prostate tumours have high alpha/beta values, similar to most other tumours and the early reacting normal tissues. However, the proliferation behaviour of the prostate tumours is more like that of the late reacting tissues, with slow doubling times and low alpha/beta values. The analyses of clinical results carried out in the past few years have indeed suggested that the alpha/beta value that characterises the fractionation response of the prostate is low, possibly even below the 3 Gy commonly assumed for most late complications, and hence that hypofractionation of the radiation treatment might improve the therapeutic ratio (better control at the same or lower complication rate). However, hypofractionation might also increase the complication rates in the surrounding late responding tissues and if their alpha/beta value is not larger that of prostate tumours it could even lead to a decrease in the therapeutic ratio. Therefore, the important question is whether the alpha/beta value for the prostate is lower than the alpha/beta values of the surrounding late responding tissues at risk. This paper reviews the clinical and experimental data regarding the radiobiological differential that might exist between prostate tumours and the late normal tissues around them. Several prospective hypofractionated trials that have been initiated recently in order to determine the alpha/beta value or the range of values that describe the fractionation response of prostate tumours are also reviewed. In spite of several confounding factors that interfere with the derivation of a precise value, it seems that most data support a trend towards lower alpha/beta values for prostate tumours than for rectum or bladder.

Health-related quality of life in patients with locally advanced prostate cancer after 76 Gy intensity-modulated radiotherapy vs. 70 Gy conformal radiotherapy in a prospective and longitudinal study

PURPOSE

To compare quality of life (QoL) after 70 Gy conformal radiotherapy with QoL after 76 Gy intensity-modulated radiotherapy (IMRT) in patients with locally advanced prostate carcinoma.

METHODS AND MATERIALS

Seventy-eight patients with locally advanced prostate cancer were treated with 70 Gy three-field conformal radiotherapy, and 92 patients received 76 Gy IMRT with fiducial markers for position verification. Quality of life was measured by RAND-36, the European Organization for Research and Treatment of Cancer core questionnaire (EORTC QLQ-C30(+3)), and the prostate-specific EORTC QLQ-PR25, before radiotherapy (baseline) and 1 month and 6 months after treatment. Quality of life changes in time (baseline vs. 1 month and baseline vs. 6 months) of > or =10 points were considered clinically relevant.

RESULTS

Differences between the treatment groups for QoL changes over time occurred in several QoL domains. The 76-Gy group revealed no significant deterioration in QoL compared with the 70-Gy group. The IMRT 76-Gy group even demonstrated a significantly better change in QoL from baseline to 1 month in several domains. The conformal 70-Gy group revealed temporary deterioration in pain, role functioning, and urinary symptoms; for the IMRT 76-Gy group a better QoL in terms of change in health existed after 1 month, which persisted after 6 months. For both treatment groups temporary deterioration in physical role restriction occurred after 1 month, and an improvement in emotional role restriction occurred after 6 months. Sexual activity was reduced after treatment for both groups and remained decreased after 6 months.

CONCLUSIONS

Intensity-modulated radiotherapy and accurate position verification seem to provide a possibility to increase the radiation dose for prostate cancer without deterioration in QoL.

Increased expression of cyclooxygenase-2 correlates with resistance to radiation in human prostate adenocarcinoma cells

PURPOSE

Cyclooxygenase-2 functions as a survival factor by protecting cells from apoptosis. We analyzed cyclooxygenase-2 expression in LNCaP-COX-2 and LNCaP-Neo cell lines treated with irradiation.

MATERIALS AND METHODS

LNCaP-COX-2 and LNCaP-Neo cells were treated with 0 to 500 microM celecoxib and a dose response curve was generated. A clonogenic assay was performed in which cells were subjected to irradiation (0 to 6 Gy) with or without celecoxib. Cyclooxygenase-2 protein and other relevant proteins were measured by immunohistochemistry Western blot analysis after irradiation and celecoxib treatment.

RESULTS

The 2 studied cell lines experienced cytotoxic effects of celecoxib in a dose related manner. Clonogenic assays demonstrated that LNCaP-COX-2 cells were significantly more resistant to radiation therapy than LNCaP-Neo cells. Furthermore, the addition of celecoxib sensitized LNCaP-Neo and LNCaP-COX-2 cells to the cytocidal effects of radiation. Moreover, cyclooxygenase-2 over expression was associated with the over expression of pAkt and carbonic anhydrase. In this cell line irradiation alone was associated with increased expression of cyclooxygenase-2 and carbonic anhydrase. Combination therapy with irradiation and celecoxib down-regulated cyclooxygenase-2, pAKT and carbonic anhydrase. LNCaP-Neo cells expressed carbonic anhydrase and pAkt. Irradiation of these cells increased carbonic anhydrase and pAkt expression. Combination therapy with irradiation and celecoxib down-regulated carbonic anhydrase and pAkt.

CONCLUSIONS

Cyclooxygenase-2 expression is also associated with pAkt and carbonic anhydrase expression. Down-regulation of cyclooxygenase-2 by celecoxib is associated with decreased expression of cyclooxygenase-2, pAkt and carbonic anhydrase, and eventual radiation sensitization, which is a phenomenon that may have clinical usefulness.

Biochemical disease-free survival rates following definitive low-dose-rate prostate brachytherapy with dose escalation to biologic target volumes identified with SPECT/CT capromab pendetide

PURPOSE

To report biochemical disease-free survival (bDFS) after conformal brachytherapy with dose escalation to biological target volumes (BTVs) identified by Capromab Pendetide with single photon emission computed tomography and computed tomography image fusion (SPECT/CT).

METHODS AND MATERIALS

Two hundred thirty-nine (T1c-T3b NxM0) consecutive patients were evaluated by SPECT/CT before treatment. Intraprostatic SPECT/CT BTVs were identified and targeted for 150% dose escalation during brachytherapy seed implant (SI). Patients received either SI alone (n = 150) or external beam radiation therapy (EBRT) plus SI boost (EBRT+SI) (n = 89), with (n = 50) and without (n = 189) neoadjuvant hormone ablation therapy. Risk factors (RF) (prostate-specific antigen [PSA] >10 ng/mL, Stage > or = T2b, and Gleason grade > or = 7) defined risk group (RG) categories [none, 1, and > or = 2 RF define low, intermediate, and high RG] for bDFS calculations using four failure criteria: American Society for Therapeutic Radiology and Oncology (ASTRO) consensus definition, PSA >1.0 ng/mL (PSA >1), PSA >0.5 ng/mL after nadir (PSA >0.5), and PSA nadir+2 ng/mL rise in PSA clinical nadir (CN+2). Median followup was 47.2 months (range, 24.8-96.1).

RESULTS

Seven-year actuarial bDFS rates were 88.0%, 82.1%, 80.4%, and 79.9% using the ASTRO, PSA >1, PSA >0.5, and CN+2 failure criteria, respectively. ASTRO-defined bDFS rates were 96.0%, 87.0%, and 72.5% for low, intermediate, and high RG's.

CONCLUSION

The data presented here demonstrate the feasibility of performing SPECT/CT BTV dose escalation in a mature series.

[Prevention of local recurrence using adjuvant radiotherapy after radical prostatectomy. Indications, results, and side effects]

Depending on the tumor stage, 15-60% of patients develop a rise in PSA from levels around zero following radical prostatectomy. It is unclear whether this involves a local, systemic, or a mixed form of local/systemic progression. In addition to a multitude of retrospective studies, the results of three randomized trials are available that have already been published in full or in abstract form. For pT3 prostate cancer with extraprostatic extension, data are available from three randomized trials that consistently evidence an absolute decrease in biochemical progression rate of 20% after 4-5 years. These findings confirm the results of numerous retrospective studies. The large majority of authors employ total radiation doses of 60 Gy with single doses of 2 Gy. One randomized trial has shown that an increased local control rate is the basis for prolonged biochemical progression-free survival. The rate of acute and late radiation sequelae after three-dimensionally planned prostatic fossa radiotherapy (RT) with 60 Gy is very low; the rate of more severe late sequelae is <2%. Data on the status of pT2 prostate cancer with positive surgical margins are worse. The current findings are controversial and require further investigations. Basically, however, adjuvant RT is also possible for pT2 cancers with positive surgical margins. The efficacy of adjuvant RT for patients with positive surgical margins of pT3 carcinomas, whether or not they achieve PSA levels around zero, has been substantiated. A prolongation of survival time has, however, not yet been established because the follow-up period is too short. Randomized trials are still needed for cases of organ-confined prostate cancer (pT2 R1). It is unclear whether adjuvant RT is superior to RT when PSA levels increase beyond zero after radical prostatectomy. Randomized trials addressing this issue are still lacking.

Phase I Trial of Replication-competent Adenovirus-mediated Suicide Gene Therapy Combined with IMRT for Prostate Cancer

Replication-competent adenovirus-mediated suicide gene therapy is an investigational cancer treatment in which an oncolytic adenovirus armed with chemo-radiosensitizing genes is used to destroy tumor cells. Previously, we evaluated the toxicity and efficacy of this approach in two clinical trials of prostate cancer using a first-generation adenovirus. Here, we report the toxicity and preliminary efficacy of this approach in combination with intensity-modulated radiotherapy (IMRT) in patients with newly diagnosed prostate cancer using an improved, second-generation adenovirus. The investigational therapy was associated with low toxicity, and there were no dose-limiting toxicities or treatment-related serious adverse events. Relative to a previous trial using a first-generation adenovirus, there was no increase in hematologic, hepatic, gastrointestinal (GI), or genitourinary (GU) toxicities. Post-treatment prostate biopsies yielded provocative preliminary results. When the results of two similar trials were combined, 22% of evaluable patients were positive for adenocarcinoma at their last biopsy, which is better than expected (>or=40%) for this cohort of patients (P=0.038). When the results were categorized by prognostic risk, most of the treatment effect was observed in the intermediate-risk group, with 0 of 12 patients (0%) being positive for cancer at their last biopsy (P<0.01). These results further demonstrate the safety of this investigational approach and raise the possibility that it may have the potential to improve the outcome of conformal radiotherapy in select patient groups.

Use of Individual Fraction Size Data from 3756 Patients to Directly Determine the α/β Ratio of Prostate Cancer

PURPOSE

To examine the effect of fraction size and total dose of radiation on recurrence of localized prostate cancer.

METHODS AND MATERIALS

A total of 3756 patients treated with radiation monotherapy at three institutions were analyzed, including 185 high-dose-rate brachytherapy (HDRB) boost patients. The 5th to 95th centiles of external beam radiotherapy (EBRT) fraction sizes and doses were 1.8 to 2.86 Gy, and 57.4 to 77.4 Gy, respectively, and HDRB fractional doses were between 5.5 and 12 Gy, totaling 147 unique fractionation schedules. Failure was defined by one biochemical (nadir + 2 ng/ml) and two advanced disease endpoints. The alpha/beta ratios were estimated via a proportional hazards model stratified by risk severity and institution.

RESULTS

The alpha/beta ratio using biochemical recurrence was 3.7 Gy (95% confidence interval [95% CI], 1.1, infinity Gy) for EBRT-only cases and 2.6 Gy (95% CI, 0.9, 4.8 Gy) after the addition of HDRB data. This estimate was highly dependent on an HDRB homogeneity correction factor (120% HDRB dose increase; alpha/beta ratio 4.5 Gy, 95% CI 1.6, 8.7 Gy). A 5-Gy increase in total dose reduced the hazard of failure by 16% (95% CI 11, 21%, p < 0.0001), and had more impact as follow-up matured (p < 0.0003). The clinically advanced endpoints concurred with the biochemical failure results, albeit with less precision.

CONCLUSIONS

This study supports the concept that the alpha/beta ratio of prostate cancer is low, although considerable uncertainty remains in the estimated value. Outcome data from EBRT studies using substantially higher doses per fraction are needed to show increased precision in these estimates.

Imaging prostate cancer: a multidisciplinary perspective

The major goal for prostate cancer imaging in the next decade is more accurate disease characterization through the synthesis of anatomic, functional, and molecular imaging information. No consensus exists regarding the use of imaging for evaluating primary prostate cancers. Ultrasonography is mainly used for biopsy guidance and brachytherapy seed placement. Endorectal magnetic resonance (MR) imaging is helpful for evaluating local tumor extent, and MR spectroscopic imaging can improve this evaluation while providing information about tumor aggressiveness. MR imaging with superparamagnetic nanoparticles has high sensitivity and specificity in depicting lymph node metastases, but guidelines have not yet been developed for its use, which remains restricted to the research setting. Computed tomography (CT) is reserved for the evaluation of advanced disease. The use of combined positron emission tomography/CT is limited in the assessment of primary disease but is gaining acceptance in prostate cancer treatment follow-up. Evidence-based guidelines for the use of imaging in assessing the risk of distant spread of prostate cancer are available. Radionuclide bone scanning and CT supplement clinical and biochemical evaluation (prostate-specific antigen [PSA], prostatic acid phosphate) for suspected metastasis to bones and lymph nodes. Guidelines for the use of bone scanning (in patients with PSA level > 10 ng/mL) and CT (in patients with PSA level > 20 ng/mL) have been published and are in clinical use. Nevertheless, changes in practice patterns have been slow. This review presents a multidisciplinary perspective on the optimal role of modern imaging in prostate cancer detection, staging, treatment planning, and follow-up.

Intensity-modulated radiotherapy using implanted fiducial markers with daily portal imaging: assessment of prostate organ motion

PURPOSE

To assess our single institutional experience with daily localization, using fiducials for prostate radiotherapy.

METHODS AND MATERIALS

From January 2004 to September 2005, 33 patients were treated with 1,097 intensity-modulated radiation treatments, using three implanted fiducials. Daily portal images were obtained before treatments. Shifts were made for deviations > or =3 mm in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) dimensions.

RESULTS

Of 1,097 treatments, 987 (90%) required shifts. Shifts were made in the LR, SI, and AP dimensions in 51%, 67%, and 58% of treatments, respectively. In the LR dimension, the median distance shifted was 5 mm. Of 739 shifts in the SI dimension, 73% were in the superior direction for a median distance of 6 mm, and 27% were shifted inferiorly for a median distance of 5 mm. The majority of shifts in the AP dimension were in the anterior direction (87%). Median distances shifted in the anterior and posterior directions were 5 mm and 4 mm, respectively. The median percentage of treatments requiring shifts per patient was 93% (range, 57-100%). Median deviations in the LR, SI, and AP dimensions were 3 mm, 4 mm, and 3 mm, respectively. Deviations in the SI and AP dimensions were more often in the superior rather than inferior (60% vs. 29%) and in the anterior rather than posterior (70% vs. 16%) directions.

CONCLUSIONS

Interfraction prostate motion is significant. Daily portal imaging with implanted fiducials improves localization of the prostate, and is necessary for the reduction of treatment margins.

Adjuvant Radiotherapy after Radical Prostatectomy: Indications, Results and Side Effects

BACKGROUND

Within 5 years following radical prostatectomy, between 15 and 60% of patients with pT3 prostate carcinomas show an increasing prostate-specific antigen (PSA) level as a sign of local and/or systemic tumor progression. Apart from a large number of retrospective investigations, available results are present only from three randomized studies which have either been completely published or are only in abstract form.

RESULTS

For pT3 prostate carcinomas the data from the three randomized studies agree, showing an around 20% reduced biochemical progression rate after 4-5 years. With these data the results of numerous retrospective studies have been confirmed. The majority of the authors use total doses of 60 Gy with single doses of 2 Gy. From one randomized study an increased local control rate is proposed as the basis for the extended freedom from biochemical progression. The rate of acute and late side effects after three-dimensional radiotherapy with 60 Gy is very small and the rate of severe side effects is below 2%. The data for pT2 prostate carcinomas with positive margins are worse. Here controversy exists, and further investigations are required. In principle, however, adjuvant radiotherapy seems reasonable also for pT2 carcinomas with positive margins (determined by bNED - no biochemical evidence of disease).

CONCLUSIONS

The effectiveness of adjuvant radiotherapy for patients with pT3 tumors and positive margins with and without detectable PSA levels is discussed. A survival advantage has not been demonstrated to date. For patients with positive margins in organ-limited prostate carcinomas (pT2 R1) randomized studies are recommended. It is unclear whether adjuvant radiotherapy is superior to radiotherapy for PSA levels increasing from the undetectable range after radical prostatectomy. To answer this question randomized studies are needed.

Prostate cancer gene therapy clinical trials

Despite recent advances in early detection and treatment, prostate cancer is still the second leading cause of cancer death in men in the United States, and approximately 27,000 men will die from it this year. Better treatments are needed for aggressive forms of localized disease and hormone-refractory metastatic disease. Recently, several gene therapy strategies have generated provocative results in early-stage clinical trials, raising the possibility that gene therapy may have the potential to affect both localized and metastatic disease. Much work lies ahead. Nevertheless, for the time being, these studies provide hope that gene therapy may someday earn a place in the management of prostate cancer.

Accuracy of image-guided radiotherapy of prostate cancer based on the BeamCath® urethral catheter technique

BACKGROUND AND PURPOSE

To examine the accuracy of the BeamCath urethral catheter technique for prostate localization during radiotherapy.

MATERIALS AND METHODS

Sixty-four patients were CT scanned twice with the BeamCath catheter, and once without the catheter. The catheter contains radiopaque fiducial markers for prostate visualization on setup images. It is held in place by a balloon inflated with air in the bladder. The repeated CT scans were co-registered and the relative shifts of the BeamCath isocenter fiducial, the prostate center-of-mass, and external skin markers were evaluated. The displacement of the BeamCath isocenter fiducial relative to its position at the planning CT scan was also determined on setup films for 53 consecutive patients (222 setup films).

RESULTS

The standard deviation (SD) of the prostate movement relative to the BeamCath isocenter fiducial was 0.9 mm in the left-right (LR), 2.8 mm in the cranial-caudal (CC), and 1.6 mm in the anteroposterior (AP) directions, respectively. When the balloon radius differed more than 1mm between the CT scans (14 of 64 cases) the SD in the CC direction increased to 4.5 mm. The SD of the prostate movement relative to the pelvic bone was 0.6 mm (LR), 2.4 mm (CC), and 2.8 mm (AP), while the prostate movement relative to external skin markers was considerably larger. Removal of the catheter resulted in a mean cranial prostate movement of 1.5mm relative to the pelvic bone. Caudal catheter displacements of 7-30 mm were observed in 5% of the setup films. In these cases, recatherization was necessary to obtain reliable prostate localization.

CONCLUSIONS

The BeamCath catheter technique markedly improved prostate localization in all directions when compared with skin markers. In the AP direction, the BeamCath technique was also superior to the use of bony structures. However, in the CC direction the catheter position was very vulnerable to changes in the balloon volume.

Normal Tissue Tolerance Dose Metrics for Radiation Therapy of Major Organs

Late organ toxicity from therapeutic radiation is a function of many confounding variables. The total dose delivered to the organ and the volumes of organ exposed to a given dose of radiation are 2 important variables that can be used to predict the risk of late toxicity. Three-dimensional radiation planning enables accurate calculation of the volume of tissue exposed to a given dose of radiation, graphically depicted as a dose-volume histogram. Dose metrics obtained from this 3-dimensional dataset can be used as a quantitative measure to predict late toxicity. This review summarizes the published clinical data on the risk of late toxicity as a function of quantitative dose metrics and attempts to offer suggested dose constraints for radiation treatment planning.

Current status of radiotherapy with proton and light ion beams

Several model studies have shown potential clinical advantages with charged particles (protons and light ions) compared with 3D-conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) in many disease sites. The newly developed intensity-modulated proton therapy (IMPT) often yields superior dose distributions to photon IMRT, with the added advantage of a significant reduction in the volume of healthy normal tissues exposed to low-to-medium doses. Initially, the major emphasis in clinical research for proton and light ion therapy was dose escalation for inherently radioresistant tumors, or for lesions adjacent to critical normal structures that constrained the dose that could be safely delivered with conventional x-ray therapy. Since the advent of IMRT the interest in particle therapy has gradually shifted toward protocols aimed at morbidity reduction. Lately the emphasis has mostly been placed on the potential for reduced risk of radiation-induced carcinogenesis with protons. Compared with 3D-CRT, a 2-fold increase has been theoretically estimated with the use of IMRT due to the larger integral volumes. In the pediatric setting, due to a higher inherent susceptibility of tissues, the risk could be significant, and the benefits of protons have been strongly emphasized in the literature. There is a significant expansion of particle therapy facilities around the world. Increasing public awareness of the potential benefits of particle therapy and wider accessibility for patients require that treating physicians stay abreast of the clinical indications of this radiotherapy modality. The article reviews the available literature for various disease sites in which particle therapy has traditionally been considered to offer clinical advantages and to highlight current lines of clinical research. The issue of radiation-induced second malignancies is examined in the light of the controversial epidemiological evidence available. The cost-effectiveness of particle therapy is also discussed.

Three-Dimensional Conformal Radiotherapy in Localized Carcinoma of Prostate: Preliminary Reports of Toxicity in Dose-Escalation Treatment

Purpose

Many studies confirmed the evidence of a dose-response relationship in prostate cancer. Escalation of dose using conventional techniques is however limited by rectal tolerance. IMRT and 3D-CRT have been designed to allow dose escalation while not exceeding rectal tolerance. We evaluated the acute and early late tolerance to surrounding organs upon dose escalation from 70 to 78 Gy in 3D-CRT setting, in order to introduce the IMRT process as a routine practice in prostate cancer treatment.

Materials and Methods

We compared clinical data from 35 patients with localized adenocarcinoma of the prostate, who received 70 Gy within a traditional reconstructed three-dimensional treatment planning, and data from 72 patients who received 78 Gy within a three-dimensional conformal setting. In order to respect rectal tolerance in the higher dose group, limits were set for rectum doses, and simulation procedures were standardized. We evaluated radiation morbidity (acute and late gastrointestinal and genitourinary toxicity) using the Radiation Therapy Oncology Group scoring criteria (RTOG scale).

Results

Increasing doses from 70 Gy to 78 Gy resulted in no significant difference for acute and late effects.

Conclusion

A procedural standardization aiming at minimizing day-by-day variation, as well as a more consistent dose distribution to critical organs may significantly reduce the risk of increased toxicity in dose-escalation setting.

A prospective dose escalation trial of high-dose-rate brachytherapy boost for prostate cancer: Evidence of hypofractionation efficacy?

PURPOSE

The study aimed to evaluate mature outcomes of a Phase I/II high-dose-rate brachytherapy (HDRB) boost protocol.

METHODS AND MATERIALS

We analyzed data from 88 patients with T1a-T3a, N0, M0 prostate adenocarcinoma treated on a prospective Phase I/II HDRB boost protocol of 16 (n = 47) or 20 Gy (n = 41) in four fractions, without planned androgen deprivation therapy. HDRB was added to 46 Gy of external beam radiotherapy (EBRT). Outcomes were compared to a contemporaneous retrospective cohort of 104 patients receiving 66 Gy EBRT monotherapy. The primary endpoint was freedom from biochemical failure, defined as a 2 ng/mL rise above the lowest prostate-specific antigen (PSA) (FFbFn2), whereas the American Society of Therapeutic Radiology and Oncology consensus definition (ACD) was used for comparative purposes.

RESULTS

For the HDRB cohort, the overall actuarial 5-year FFbFn2 was 67.4% (95% CI: 58.2-75.5%). For the HDRB doses of 16 and 20 Gy, the 5-year FFbFn2 rates were 58.8% (95% CI: 41.9-72.5%) and 77.3% (95% CI: 64.4-88.3%), respectively (log-rank test p = 0.07). Compared to men treated with 66 Gy EBRT, using multivariate analysis, there was no significant benefit to using HDRB with the FFbFn2 outcome (p = 0.52), yet the ACD suggested a significant advantage (hazard ratio 0.50, 95% CI: 0.29-0.86, p = 0.011). There was a trend to better FFbFn2 outcomes with increasing biologically effective doses (p = 0.09), which was significant using the ACD (p = 0.0003).

CONCLUSIONS

The data support HDRB boost as a potential means of dose escalation in prostate cancer. Significant findings using the ACD need to be validated with contemporary biochemical failure definitions. Prospective trials to optimize fractionation and evaluate outcomes in comparison to contemporary EBRT techniques are warranted.

Analysis of biochemical control and prognostic factors in patients treated with either low-dose three-dimensional conformal radiation therapy or high-dose intensity-modulated radiotherapy for localized prostate cancer

PURPOSE

To identify prognostic factors and evaluate biochemical control rates for patients with localized prostate cancer treated with either high-dose intensity-modulated radiotherapy (IMRT) or conventional-dose three-dimensional conformal radiotherapy 3D-CRT.

METHODS

Four hundred sixteen patients with a minimum follow-up of 3 years (median, 5 years) were included. Two hundred seventy-one patients received 3D-CRT with a median dose of 68.4 Gy (range, 66-71 Gy). The next 145 patients received IMRT with a median dose of 75.6 Gy (range, 70.2-77.4 Gy). Biochemical control rates were calculated according to both American Society for Therapeutic Radiology and Oncology (ASTRO) consensus definitions. Prognostic factors were identified using both univariate and multivariate analyses.

RESULTS

The 5-year biochemical control rate was 60.4% for 3D-CRT and 74.1% for IMRT (p < 0.0001, first ASTRO Consensus definition). Using the ASTRO Phoenix definition, the 5-year biochemical control rate was 74.4% and 84.6% with 3D-RT and IMRT, respectively (p = 0.0326). Univariate analyses determined that PSA level, T stage, Gleason score, perineural invasion, and radiation dose were predictive of biochemical control. On multivariate analysis, dose, Gleason score, and perineural invasion remained significant.

CONCLUSION

On the basis of both ASTRO definitions, dose, Gleason score, and perineural invasion were predictive of biochemical control. Intensity-modulated radiotherapy allowed delivery of higher doses of radiation with very low toxicity, resulting in improved biochemical control.

Perineural invasion is a marker for pathologically advanced disease in localized prostate cancer

PURPOSE

To determine if perineural invasion (PNI) should be included in addition to prostate-specific antigen (PSA), biopsy Gleason score, and clinical T-stage for risk-stratification of patients with localized prostate cancer.

METHODS AND MATERIALS

We analyzed prostatectomy findings for 1550 patients, from a prospectively collected institutional database, to determine whether PNI was a significant predictor for upgrading of Gleason score or pathologic T3 disease after patients were stratified into low-, intermediate-, and high-risk groups (on the basis of PSA, biopsy Gleason score, and clinical T-stage).

RESULTS

For the overall population, PNI was associated with a significantly increased frequency of upgrading and of pathologic T3 disease. After stratification, PNI was still associated with significantly increased odds of pathologic T3 disease within each risk group. In particular, for low-risk patients, there was a markedly increased risk of extraprostatic extension (23% vs. 7%), comparable to that of intermediate-risk patients. Among high-risk patients, PNI was associated with an increased risk of seminal vesicle invasion and lymph node involvement. Furthermore, over 80% of high-risk patients with PNI were noted to have an indication for postoperative radiation.

CONCLUSIONS

Perineural invasion may be useful for risk-stratification of prostate cancer. Our data suggest that low-risk patients with PNI on biopsy may benefit from treatment typically reserved for those with intermediate-risk disease. In addition, men with high-risk disease and PNI, who are contemplating surgery, should be informed of the high likelihood of having an indication for postoperative radiation therapy.

What dose of external-beam radiation is high enough for prostate cancer?

PURPOSE

To quantify the radiotherapy dose-response of prostate cancer, adjusted for prognostic factors in a mature cohort of men treated relatively uniformly at a single institution.

PATIENTS AND METHODS

The study cohort consisted of 1,530 men treated with three-dimensional conformal external-beam radiotherapy between 1989 and 2002. Patients were divided into four isocenter dose groups: <70 Gy (n = 43), 70-74.9 Gy (n = 552), 75-79.9 Gy (n = 568), and > or =80 Gy (n = 367). The primary endpoints were freedom from biochemical failure (FFBF), defined by American Society for Therapeutic Radiology and Oncology (ASTRO) and Phoenix (nadir + 2.0 ng/mL) criteria, and freedom from distant metastases (FFDM). Multivariate analyses were performed and adjusted Kaplan-Meier estimates were calculated. Logit regression dose-response functions were determined at 5 and 8 years for FFBF and at 5 and 10 years for FFDM.

RESULTS

Radiotherapy dose was significant in multivariate analyses for FFBF (ASTRO and Phoenix) and FFDM. Adjusted 5-year estimates of ASTRO FFBF for the four dose groups were 60%, 68%, 76%, and 84%. Adjusted 5-year Phoenix FFBFs for the four dose groups were 70%, 81%, 83%, and 89%. Adjusted 5-year and 10-year estimates of FFDM for the four dose groups were 96% and 93%, 97% and 93%, 99% and 95%, and 98% and 96%. Dose-response functions showed an increasing benefit for doses > or =80 Gy.

CONCLUSIONS

Doses of > or =80 Gy are recommended for most men with prostate cancer. The ASTRO definition of biochemical failure does not accurately estimate the effects of radiotherapy at 5 years because of backdating, compared to the Phoenix definition, which is less sensitive to follow-up and more reproducible over time.

Advances in image-guided radiation therapy

Imaging is central to radiation oncology practice, with advances in radiation oncology occurring in parallel to advances in imaging. Targets to be irradiated and normal tissues to be spared are delineated on computed tomography (CT) scans in the planning process. Computer-assisted design of the radiation dose distribution ensures that the objectives for target coverage and avoidance of healthy tissue are achieved. The radiation treatment units are now recognized as state-of-the-art robotics capable of three-dimensional soft tissue imaging immediately before, during, or after radiation delivery, improving the localization of the target at the time of radiation delivery, to ensure that radiation therapy is delivered as planned. Frequent imaging in the treatment room during a course of radiation therapy, with decisions made on the basis of imaging, is referred to as image-guided radiation therapy (IGRT). IGRT allows changes in tumor position, size, and shape to be measured during the course of therapy, with adjustments made to maximize the geometric accuracy and precision of radiation delivery, reducing the volume of healthy tissue irradiated and permitting dose escalation to the tumor. These geometric advantages increase the chance of tumor control, reduce the risk of toxicity after radiotherapy, and facilitate the development of shorter radiotherapy schedules. By reducing the variability in delivered doses across a population of patients, IGRT should also improve interpretation of future clinical trials.

Knock-down of Bcl-2 by antisense oligodeoxynucleotides induces radiosensitization and inhibition of angiogenesis in human PC-3 prostate tumor xenografts

Expression of the proto-oncogene Bcl-2 is associated with tumor progression. Bcl-2's broad expression in tumors, coupled with its role in resistance to chemotherapy and radiation therapy-induced apoptosis, makes it a rational target for anticancer therapy. Antisense Bcl-2 oligodeoxynucleotide (ODN) reagents have been shown to be effective in reducing Bcl-2 expression in a number of systems. We investigated whether treating human prostate cancer cells with antisense Bcl-2 ODN (G3139, oblimersen sodium, Genasense) before irradiation would render them more susceptible to radiation effects. Two prostate cancer cell lines expressing Bcl-2 at different levels (PC-3-Bcl-2 and PC-3-Neo) were subjected to antisense Bcl-2 ODN, reverse control (CTL), or mock treatment. Antisense Bcl-2 ODN alone produced no cytotoxic effects and was associated with G(1) cell cycle arrest. The combination of antisense Bcl-2 ODN with irradiation sensitized both cell lines to the killing effects of radiation. Both PC-3-Bcl-2 and PC-3-Neo xenografts in mice treated with the combination of antisense Bcl-2 ODN and irradiation were more than three times smaller by volume compared with xenografts in mice treated with reverse CTL alone, antisense Bcl-2 ODN alone, irradiation alone, or reverse CTL plus radiotherapy (P = 0.0001). Specifically, PC-3-Bcl-2 xenograft tumors treated with antisense Bcl-2 ODN and irradiation had increased rates of apoptosis and decreased rates of angiogenesis and proliferation. PC-3-Neo xenograft tumors had decreased proliferation only. This is the first study which shows that therapy directed at Bcl-2 affects tumor vasculature. Together, these findings warrant further study of this novel combination of Bcl-2 reduction and radiation therapy, as well as Bcl-2 reduction and angiogenic therapy.