Three-dimensional conformal radiation therapy in localized carcinoma of the prostate: interim report of a phase 1 dose-escalation study

Methodological Development of Combination Drug and Radiotherapy in Basic and Clinical Research

Newer technical improvements in radiation oncology have been rapidly implemented in recent decades, allowing an improved therapeutic ratio. The development of strategies using local and systemic treatments concurrently, mainly targeted therapies, has however plateaued. Targeted molecular compounds and immunotherapy are increasingly being incorporated as the new standard of care for a wide array of cancers. A better understanding of possible prior methodology issues is therefore required and should be integrated into upcoming early clinical trials including individualized radiotherapy-drug combinations. The outcome of clinical trials is influenced by the validity of the preclinical proofs of concept, the impact on normal tissue, the robustness of biomarkers and the quality of the delivery of radiation. Herein, key methodological aspects are discussed with the aim of optimizing the design and implementation of future precision drug-radiotherapy trials.

Low-dose rate brachytherapy for men with localized prostate cancer

BACKGROUND

Localized prostate cancer is a slow growing tumor for many years for the majority of affected men. Low-dose rate brachytherapy (LDR-BT) is short-distance radiotherapy using low-energy radioactive sources. LDR-BT has been recommended for men with low risk localized prostate cancer.

OBJECTIVES

To assess the benefit and harm of LDR-BT compared to radical prostatectomy (RP), external beam radiotherapy (EBRT), and no primary therapy (NPT) in men with localized prostatic cancer.

SEARCH STRATEGY

The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (from 1950), and EMBASE (from 1980) were searched in June 2010 as well as online trials registers and reference lists of reviews.

SELECTION CRITERIA

Randomized, controlled trials comparing LDR-BT versus RP, EBRT, and NPT in men with clinically localized prostate cancer.

DATA COLLECTION AND ANALYSIS

Data on study methods, participants, treatment regimens, observation period and outcomes were recorded by two reviewers independently.

MAIN RESULTS

We identified only one RCT (N = 200; mean follow up 68 months). This trial compared LDR-BT and RP. The risk of bias was deemed high. Primary outcomes (overall survival, cause-specific mortality, or metastatic-free survival) were not reported. Biochemical recurrence-free survival at 5 years follow up was not significantly different between LDR-BT (78/85 (91.8%)) and RP (81/89 (91.0%)); P = 0.875; relative risk 0.92 (95% CI: 0.35 to 2.42).For severe adverse events reported at 6 months follow up, results favored LDR-BT for urinary incontinence (LDR-BT 0/85 (0.0%) versus RP 16/89 (18.0%); P < 0.001; relative risk 0) and favored RP for urinary irritation (LDR-BT 68/85 (80.0%) versus RP 4/89 (4.5%); P < 0.001; relative risk 17.80, 95% CI 6.79 to 46.66). The occurrence of urinary stricture did not significantly differ between the treatment groups (LDR-BT 2/85 (2.4%) versus RP 6/89 (6.7%); P = 0.221; relative risk 0.35, 95% CI: 0.07 to 1.68). Long-term information was not available.We did not identify significant differences of mean scores between treatment groups for patient-reported outcomes function and bother as well as generic health-related quality of life.

AUTHORS' CONCLUSIONS

Low-dose rate brachytherapy did not reduce biochemical recurrence-free survival versus radical prostatectomy at 5 years. For short-term severe adverse events, low-dose rate brachytherapy was significantly more favorable for urinary incontinence, but radical prostatectomy was significantly more favorable for urinary irritation. Evidence is based on one RCT with high risk of bias.

A systematic methodology review of phase I radiation dose escalation trials

BACKGROUND AND PURPOSE

The purpose of this review is to evaluate the methodology used in published phase I radiotherapy (RT) dose escalation trials. A specific emphasis was placed on the frequency of reporting late complications as endpoint.

MATERIALS AND METHODS

We performed a systematic literature review using a predefined search strategy to identify all phase I trials reporting on external radiotherapy dose escalation in cancer patients.

RESULTS

Fifty-three trials (phase I: n = 36, phase I-II: n = 17) fulfilled the inclusion criteria. Of these, 20 used a modified Fibonacci design for the RT dose escalation, but 32 did not specify a design. Late toxicity was variously defined as > 3 months (n = 43) or > 6 months (n = 3) after RT, or not defined (n = 7). In only nine studies the maximum tolerated dose (MTD) was related to late toxicity, while only half the studies reported the minimum follow-up period for dose escalation (n = 26).

CONCLUSION

In phase I RT trials, late complications are often not taken into account and there is currently no consensus on the methodology used for radiation dose escalation studies. We therefore propose a decision-tree algorithm which depends on the endpoint selected and whether a validated early surrogate endpoint is available, in order to choose the most appropriate study design.

The Translational Research Working Group developmental pathway for interventive devices

The interventive device pathway refers to one of six pathways developed by the Translational Research Working Group (TRWG) that, together, describe the core domains of early translational cancer research. This pathway focuses on the development of devices (as classified by the Food and Drug Administration), designed for local ablation of cancer or precancerous lesions (e.g., radiation therapy, microwave, radiofrequency ablation, and high-intensity focused ultrasound systems). This article describes the distinctive features of the pathway and issues that are encountered in the real-world development of interventive devices for the treatment of cancer. The interventive device pathway is envisioned to be a general guideline of the steps required for effective development, optimization, testing, and validation of developing devices, to be dynamic and adaptable, and to form a framework for discussions focused on improving the efficiency and effectiveness of new device development.

Localized Prostate Cancer Treated with Intensity-Modulated Radiotherapy

Aims and background

The development and use of new radiotherapy techniques, especially 3D conformal radiotherapy or intensity-modulated radiotherapy, has allowed the safe application of high doses of external beam radiotherapy without increasing toxicity. The aim of this analysis was to describe the acute and when possible late toxicity and the feasibility on using intensity-modulated radiotherapy into our routine work.

Patients and methods

From June 2003 to December 2004, 60 patients with prostate cancer underwent high dose (80 Gy) radiotherapy treatment with intensity-modulated radiotherapy at the University of Florence. In the current analysis, we included patients without clinical or radiographic evidence of distant disease at the time of the first evaluation in the radiotherapy unit.

Results

Intensity-modulated radiotherapy treatments were delivered successfully without any interruption or technical problem. High-dose intensity-modulated radiotherapy was well tolerated acutely. Four patients (10%) developed grade 1 late rectal toxicity after completion of intensity-modulated radiotherapy and 8 patients (20%) developed grade 1 late urinary symptoms.

Conclusions

Intensity-modulated radiotherapy is the approach of choice for high-dose radiotherapy delivery. No patient had severe toxicity (grade 3) despite the high dose delivered. From a cost-benefit point of view, our experience shows that delivery of intensity-modulated radiotherapy requires only minor corrections to the ordinary activity schedule.

Radiation therapy in the management of locally advanced prostate cancer

Locally advanced prostate cancer generally refers to those patients with clinical stages T3-4 disease. Patients with locally advanced cancer frequently are included in clinical trials that examine treatment for patients at high risk for relapse based on presenting prostate-specific antigen, high Gleason score, or advanced clinical stage. There is a growing body of evidence that suggests that men with localized prostate cancer benefit from high-dose radiation therapy delivered with three-dimensional conformal radiation therapy, intensity-modulated radiation therapy, or proton beam therapy. Most importantly, neoadjuvant and adjuvant androgen-deprivation therapy have significantly improved outcomes in men with locally advanced or high-risk prostate cancer. Although questions remain regarding the optimal timing and duration of adjuvant hormonal therapy, a combination of long-term androgen deprivation started before radiation therapy and continued for 2 years represents a North American standard of care for this patient population.

Evaluation of image-guided radiation therapy (IGRT) technologies and their impact on the outcomes of hypofractionated prostate cancer treatments: A radiobiologic analysis

PURPOSE

To quantify the mitigation of geometric uncertainties achieved with the application of various patient setup techniques during the delivery of hypofractionated prostate cancer treatments, using tumor control probability (TCP) and normal tissue complication probability.

METHODS AND MATERIALS

Five prostate cancer patients with approximately 16 treatment CT studies, taken during the course of their radiation therapy (77 total), were analyzed. All patients were planned twice with an 18 MV six-field conformal technique, with 10- and 5-mm margin sizes, with various hypofractionation schedules (5 to 35 fractions). Subsequently, four clinically relevant patient setup techniques (laser guided and image guided) were simulated to deliver such schedules.

RESULTS

As hypothesized, the impact of geometric uncertainties on clinical outcomes increased with more hypofractionated schedules. However, the absolute gain in TCP due to hypofractionation (up to 21.8% increase) was significantly higher compared with the losses due to geometric uncertainties (up to 8.6% decrease).

CONCLUSIONS

The results of this study suggest that, although the impact of geometric uncertainties on the treatment outcomes increases as the number of fractions decrease, the reduction in TCP due to the uncertainties does not significantly offset the expected theoretical gain in TCP by hypofractionation.

The efficacy of conventional external beam, three-dimensional conformal, intensity-modulated, particle beam radiation, and brachytherapy for localized prostate cancer

Technologic advances in radiation treatment planning and delivery have generated popular interest in the different radiation therapy techniques used in treating patients with localized prostate cancer. Throughout the past decade, high-energy (> 4 MV) linear accelerators have largely replaced Cobalt machines in external beam radiation therapy (EBRT) delivery. Conventional EBRT has been used to treat prostate cancer successfully since the 1950s. By switching to computed tomography-based planning, three-dimensional conformal radiation therapy provides better relative conformality of dose than does conventional EBRT. Intensity-modulated radiation therapy (IMRT) has further refined dose conformality by spreading the low-dose region to a larger volume. However, the potential long-term risks of larger volumes of normal tissues receiving low doses of radiation in IMRT are unknown. Particle-beam radiation therapy offers unique dose distributions and characteristics with higher relative biologic effect and linear energy transfer. Transperineal prostate brachytherapy offers the shortest treatment time with equivalent efficacy without significant risk of radiation exposure. The addition of hormonal therapy to radiation therapy has been shown to improve the outcome of radiation therapy.

Evidence-based review of three-dimensional conformal radiotherapy for localized prostate cancer: An ASTRO outcomes initiative

PURPOSE

To perform a systematic review of the evidence to determine the efficacy and effectiveness of three-dimensional conformal radiotherapy (3D-CRT) for localized prostate cancer; provide a clear presentation of the key clinical outcome questions related to the use of 3D-CRT in the treatment of localized prostate cancer that may be answered by a formal literature review; and provide concise information on whether 3D-CRT improves the clinical outcomes in the treatment of localized prostate cancer compared with conventional RT.

METHODS AND MATERIALS

We performed a systematic review of the literature through a structured process developed by the American Society for Therapeutic Radiology and Oncology's Outcomes Committee that involved the creation of a multidisciplinary task force, development of clinical outcome questions, a formal literature review and data abstraction, data review, and outside peer review.

RESULTS

Seven key clinical questions were identified. The results and task force conclusions of the literature review for each question are reported.

CONCLUSION

The technological goals of reducing morbidity with 3D-CRT have been achieved. Randomized trials and follow-up of completed trials remain necessary to address these clinical outcomes specifically with regard to patient subsets and the use of hormonal therapy.

Acute and late complications after radiotherapy for prostate cancer: results of a multicenter randomized trial comparing 68 Gy to 78 Gy

PURPOSE

To compare acute and late gastrointestinal (GI) and genitourinary (GU) side effects in prostate cancer patients randomized to receive 68 Gy or 78 Gy.

METHODS AND MATERIALS

Between June 1997 and February 2003, 669 prostate cancer patients were randomized between radiotherapy with a dose of 68 Gy and 78 Gy, in 2 Gy per fraction and using three-dimensional conformal radiotherapy. All T stages with prostate-specific antigen (PSA) <60 ng/mL were included, except any T1a and well-differentiated T1b-c tumors with PSA < or =4 ng/mL. Stratification was done for four dose-volume groups (according to the risk of seminal vesicles [SV] involvement), age, hormonal treatment (HT), and hospital. The clinical target volume (CTV) consisted of the prostate with or without the SV, depending on the estimated risk of SV invasion. The CTV-planning target volume (PTV) margin was 1 cm for the first 68 Gy and was reduced to 0.5 cm (0 cm toward the rectum) for the last 10 Gy in the 78 Gy arm. Four Dutch hospitals participated in this Phase III trial. Evaluation of acute and late toxicity was based on 658 and 643 patients, respectively. For acute toxicity (<120 days), the Radiation Therapy Oncology Group (RTOG) scoring system was used and the maximum score was reported. Late toxicity (>120 days) was scored according to the slightly adapted RTOG/European Organization for Research and Treatment of Cancer (EORTC) criteria.

RESULTS

The median follow-up time was 31 months. For acute toxicity no significant differences were seen between the two randomization arms. GI toxicity Grade 2 and 3 was reported as the maximum acute toxicity in 44% and 5% of the patients, respectively. For acute GU toxicity, these figures were 41% and 13%. No significant differences between both randomization arms were seen for late GI and GU toxicity, except for rectal bleeding requiring laser treatment or transfusion (p = 0.007) and nocturia (p = 0.05). The 3-year cumulative risk of late RTOG/EORTC GI toxicity grade > or =2 was 23.2% for 68 Gy, and 26.5% for 78 Gy (p = 0.3). The 3-year risks of late RTOG/EORTC GU toxicity grade > or =2 were 28.5% and 30.2% for 68 Gy and 78 Gy, respectively (p = 0.3). Factors related to acute GI toxicity were HT (p < 0.001), a higher dose-volume group (p = 0.01), and pretreatment GI symptoms (p = 0.04). For acute GU toxicity, prognostic factors were: pretreatment GU symptoms (p < 0.001), HT (p = 0.003), and prior transurethral resection of the prostate (TURP) (p = 0.02). A history of abdominal surgery (p < 0.001) and pretreatment GI symptoms (p = 0.001) were associated with a higher incidence of late GI grade > or =2 toxicity, whereas HT (p < 0.001), pretreatment GU symptoms (p < 0.001), and prior TURP (p = 0.006) were prognostic factors for late GU grade > or =2.

CONCLUSIONS

Raising the dose to the prostate from 68 Gy to 78 Gy resulted in higher incidences of acute and late GI and GU toxicity, but these differences were not significant, except for late rectal bleeding requiring treatment and late nocturia. Other factors than the studied dose levels appeared to be important in predicting toxicity after radiotherapy, especially previous surgical interventions (abdominal surgery or TURP), hormonal therapy, and the presence of pretreatment symptoms.

Treatment outcomes of three-dimensional conformal radiotherapy for localized prostate carcinoma

BACKGROUND

The current study documented the implementation of three-dimensional conformal radiotherapy and assessed the tumor control and toxicity of such treatment in a large, multisite community practice.

METHODS

The authors retrospectively reviewed their first 222 consecutive patients with clinically localized (N0) prostate carcinoma treated with a 6-field conformal technique from October 1993 through March 2000. Standardized target definitions, dose planning constraints, and gantry angles were utilized to develop the treatment plan. Patients were categorized by low, intermediate, and high risk. Low risk was defined as T1a-T2a disease, a Gleason score < 7, and prostate-specific antigen (PSA) level </= 10.0 ng/mL (n = 47 [21%]). Intermediate risk was defined as T2b disease, a Gleason score > 6, or PSA level > 10.01 ng/mL (n = 60 [27%]). High risk was defined as 2 of the above risk factors or as T3 disease, a Gleason score > 7, or a PSA level > 20 (n = 115 [52%]). Biochemical disease recurrence was defined in accordance with the American Society for Therapeutic Radiology and Oncology definition. Urinary and bowel toxicity were graded using the Radiation Therapy Oncology Group morbidity scoring system.

RESULTS

The median follow-up after radiotherapy for surviving patients was 47 months (range, 0-99 months). The 2 and 5-year actuarial biochemical control rates for all patients were 84% and 78%, respectively. Using logistic regression analysis, lower dose (< 75.6 gray [Gy] vs. 75.6 Gy; P = 0.006), higher risk group (P = 0.033), higher stage (P = 0.045), and higher PSA level (P = 0.001) were significantly associated with biochemical disease recurrence. Toxicity was not significantly correlated with a higher radiotherapy dose.

CONCLUSIONS

Dose escalation to 75.6 Gy using a 6-field conformal technique was feasible in the authors' community practice and resulted in acceptable toxicity and early biochemical outcomes.

Analysis of interaction between number of implant catheters and dose-volume histograms in prostate high- dose-rate brachytherapy using a computer model

PURPOSE

In prostate high-dose-rate brachytherapy, to determine before implant, using the standard geometric optimization algorithm, whether there is an optimal number of catheters.

MATERIALS AND METHODS

Transrectal ultrasound images of the prostate from 24 patients were transferred into the brachytherapy planning system. Urethra and prostate contours were digitized onto each axial slice of a CT scan, as well as hypothetical locations of the catheters (2/3 of the catheters along the prostate contour, 1/3 around the urethra). Each prostate was implanted with 9, 12, 15, 18, and 21 catheters. Dosimetry was optimized using a geometric optimization algorithm; prescription isodose was chosen so that 95% of planning target volume was covered by the 100% isodose.

RESULTS

A significant increase in mean volume of prostate receiving 150% of the dose (V150) when the number of catheters decreased (p < 0.0001). The 9-catheter group significantly differed from each of the other groups; no difference was seen in V150 among the 21-, 18-, and 15-catheter groups. Parallel results were observed for urethra V150 and homogeneity index; there was no difference in conformity index by catheter group.

CONCLUSION

V150 increased when fewer catheters were used. There was no significant difference among the 21-, 18-, and 15-catheter groups: the geometric optimization routine probably compensated for the larger distance between dwell positions. Based on the technique described in our study, we conclude that 15 to 21 catheters seem to cover the prostate adequately without creating excess hot spots.

Primary radiation therapy for localized prostate cancer

Prostate cancer in men is similar to breast cancer in women; both cancers rank first, respectively, in incidence and are normally responsive to radiation therapy. In addition, advances in mammography help detect earlier breast cancers, and the development and refinement of prostatic specific antigen (PSA) has resulted in early detection of low-stage localized prostate cancers. This has generated debate over the proper management of localized prostate cancer. While there have not been any controlled, prospective, randomized trials of sufficient power to compare the various local therapies, based on the current available data, the three commonly used local modalities, surgery, and external beam radiation therapy and brachytherapy (radioactive seed implant), have similar efficacy controlling the disease up to 10 years in many patients. Technological advances in treatment delivery and planning have improved the treatment of prostate cancer with external-beam radiotherapy using three-dimensional conformal radiotherapy (3DCRT), ultrasound-guided transperineal implant, or intensity-modulated radiotherapy (IMRT), as well as proton or neutron beam based therapies.

The use of conformal radiotherapy and the selection of radiation dose in T1 or T2 low or intermediate risk prostate cancer – a systematic review

BACKGROUND AND PURPOSE

The purpose was to develop a systematic review that would address the following questions: (a) when single-modality treatment external-beam radiotherapy is selected as the modality of choice, what is the role of three-dimensional (3D) conformal radiotherapy in treating clinically localized (T1, T2/NO, NX/MO) prostate cancer? The outcomes of interest are biochemical freedom from failure (bNED) rates, clinical recurrence-free survival, disease-specific survival and acute and late toxicity; (b) what is the appropriate dose and fractionation prescription in this clinical setting?

MATERIALS AND METHODS

A systematic review of the English published literature was undertaken to provide evidence relevant to the above outcomes.

RESULTS

One randomized controlled trial comparing conventional radiotherapy to conformal therapy with dose escalation reported bNED rates. Three additional randomized controlled trials reported acute or chronic late outcome assessments. Additionally, phase II studies of dose escalation in sequential patient cohorts and non-randomized comparative assessments of dose-response and bNED rates in controlled analyses were reviewed. There is convincing evidence from randomized trials that the use of conformal therapy reduces acute and late treatment-related morbidity. There is preliminary evidence suggesting that when external-beam therapy alone is used to treat patients, conformal therapy with dose-escalation is more efficacious than doses of 70Gy. The increased efficacy appears to be predominantly seen in the subset of patients with intermediate-risk disease (PSA 10-20). There is conflicting evidence of the efficacy of dose-escalation in patients with low initial PSA (<10) and in patients with initial PSA greater than 20. Conformal radiotherapy at a dose of 78Gy appears to be relatively safe with no increase in acute or late effects compared with conventional treatment (up to 70Gy) so long as appropriate technological principles are considered.

CONCLUSIONS

Patients who have external-beam radiotherapy should be treated using a 3D conformal technique. Patients with intermediate-risk disease (PSA 10-20) who are treated with external-beam radiotherapy alone should be offered doses of 75-78Gy in 180-200cGy fractions.

Analysis of intraprostatic failures in patients treated with hormonal therapy and radiotherapy: implications for conformal therapy planning

PURPOSE

Conformal therapy of prostate cancer is based on high-dose irradiation to the entire prostate gland. The aim of this study was to analyze the pattern of intraprostatic recurrence in patients undergoing external beam radiotherapy (EBRT) at a dose of 65-70 Gy to evaluate whether conventional radiotherapy doses are adequate to control microscopic disease outside the primary tumor and therefore whether high-dose irradiation can be exclusively focused on the macroscopic disease.

METHODS AND MATERIALS

The clinical and radiologic reports of 118 patients with prostate cancer undergoing EBRT (64.8-70.2 Gy) combined with hormonal therapy were evaluated. In all patients, before and after therapy, the size and site of the primary neoplasm within the prostate were assessed by clinical examination and imaging studies.

RESULTS

With a median follow-up of 45 months (range 14-119), the 5-year actuarial local control rate was 83.9%. Twelve patients had an intraprostatic recurrence, with the appearance of a new nodule (in 5 patients with a complete response after therapy) or increased nodular size compared with the minimal size (in the 7 other patients). In all patients, on the basis of a semiquantitative evaluation of the site of recurrence, this was shown to originate within the initial tumor volume.

CONCLUSION

The results of this analysis seem to confirm some histologic findings observed in patients undergoing prostatectomy for local recurrence after radiotherapy that suggest that local recurrence usually originates in the primary tumor rather than in focal prostatic intraepithelial neoplasia. This observation might justify the application of conformal therapy procedures aimed at identifying the gross tumor volume, in the phase of boost, exclusively with the primary tumor.

Neoadjuvant androgen withdrawal prior to external radiotherapy for locally advanced adenocarcinoma of the prostate

BACKGROUND

It is unclear whether positive interactions between radiation and androgen withdrawal for patients with locally advanced prostate cancer is synergistic or additive. The present study aimed to clarify the significance of neoadjuvant androgen ablation prior to external radiotherapy in a human prostate LNCaP tumor model and in patients with locally advanced prostate cancer.

METHODS

Comparisons were made between the effect of castration prior to radiation on the growth of subcutaneous LNCaP tumors implanted into male nude mice and their serum prostate-specific antigen (PSA) levels, and the results of castration or radiation alone. Twenty-nine patients with histologically proven and locally advanced adenocarcinoma of the prostate were treated with luteinizing hormone-releasing hormone analog at least 3 months before, during, and after external radiation therapy with a total dose of 70 Gy. The toxicity and response to this therapy were evaluated.

RESULTS

Treatment combining castration and radiation resulted in synergistic inhibition of LNCaP tumor growth and a significant delay in the emergence of androgen-independent recurrence as opposed to either treatment alone. The external radiotherapy was completed in 28 patients (96.6%), resulting in a reduction of serum PSA levels in all 28 patients to below 1.0 ng/mL. All patients were alive after a mean follow-up period of 34 months (range 11-53) with a 3-year PSA relapse-free survival rate of 83.7%. Among several factors examined, only the Gleason score was significantly associated with PSA relapse-free survival in univariate analysis, but not in multivariate analysis. Thirteen of 28 patients (46%) and 7 of 28 (25%) also showed at least one form of gastrointestinal or genitourinary toxicity, respectively. Of these patients, 8 with gastrointestinal toxicities, and 1 with genitourinary toxicity, experienced acute complications higher than grade 3.

CONCLUSION

The experimental findings objectively suggested the use of neoadjuvant androgen withdrawal prior to radiation therapy. Although our clinical experience is preliminary, combined androgen ablation and radiation therapy may also be effective in controlling locally advanced prostate cancer, with tolerable side-effects.

[Conformal radiotherapy in prostate cancer: for whom and how?]

External radiotherapy is one of the modalities used to cure localized prostate carcinoma. Most of localized prostate carcinomas, specially those of the intermediate prognostic group, may benefit from escalated dose above 70 Gy at least as regard biochemical and clinical relapse free survival. 3D-CRT allows a reduction of the dose received by organs at risk and an increase of prostate dose over 70 Gy. It is on the way to become a standard. Intensity modulated radiation therapy increases dose homogeneity and reduces rectal dose. These methods necessitate rigorous procedures in reproducibility, delineation of volumes, dosimetry, daily treatment. They need also technological and human means. It is clear that localized prostate cancer is a good example for evaluation of these new radiotherapy modalities.

Intensity-modulated arc therapy simplified

PURPOSE

We present a treatment planning strategy for intensity-modulated radiation therapy using gantry arcs with dynamic multileaf collimator, previously termed intensity-modulated arc therapy (IMAT).

METHODS AND MATERIALS

The planning strategy is an extension of the photon bar arc and asymmetric arc techniques and is classified into three levels of complexity, with increasing number of gantry arcs. This principle allows us to generalize the analysis of the number of arcs required for intensity modulation for a given treatment site. Using a phantom, we illustrate how the current technique is more flexible than the photon bar arc technique. We then compare plans from our strategy with conventional three-dimensional conformal treatment plans for three sites: prostate (prostate plus seminal vesicles), posterior pharyngeal wall, and chest wall.

RESULTS

Our strategy generates superior IMAT treatment plans compared to conventional three-dimensional conformal plans. The IMAT plans spare critical organs well, and the trade-off for simplicity is that the dose uniformity in the target volume may not rival that of true inverse treatment plans.

CONCLUSIONS

The analyses presented in this paper give a better understanding of IMAT plans. Our strategy is easier to understand and more efficient in generating plans than inverse planning systems; our plans are also simpler to modify, and quality assurance is more intuitive.

Risk group dependence of dose-response for biopsy outcome after three-dimensional conformal radiation therapy of prostate cancer

BACKGROUND AND PURPOSE

We fit phenomenological tumor control probability (TCP) models to biopsy outcome after three-dimensional conformal radiation therapy (3D-CRT) of prostate cancer patients to quantify the local dose-response of prostate cancer.

MATERIALS AND METHODS

We analyzed the outcome after photon beam 3D-CRT of 103 patients with stage T1c-T3 prostate cancer treated at Memorial Sloan-Kettering Cancer Center (MSKCC) (prescribed target doses between 64.8 and 81Gy) who had a prostate biopsy performed >or=2.5 years after end of treatment. A univariate logistic regression model based on D(mean) (mean dose in the planning target volume of each patient) was fit to the whole data set and separately to subgroups characterized by low and high values of tumor-related prognostic factors T-stage (<T2c vs. >or=T2c), Gleason score (<or=6 vs. >6), and pre-treatment prostate-specific antigen (PSA) (<or=10 ng/ml vs. >10 ng/ml). In addition, we evaluated five different classifications of the patients into three risk groups, based on all possible combinations of two or three prognostic factors, and fit bivariate logistic regression models with D(mean) and the risk group category to all patients. Dose-response curves were characterized by TCD(50), the dose to control 50% of the tumors, and gamma(50), the normalized slope of the dose-response curve at TCD(50).

RESULTS

D(mean) correlates significantly with biopsy outcome in all patient subgroups and larger values of TCD(50) are observed for patients with unfavorable compared to favorable prognostic factors. For example, TCD(50) for high T-stage patients is 7Gy higher than for low T-stage patients. For all evaluated risk group definitions, D(mean) and the risk group category are independent predictors of biopsy outcome in bivariate analysis. The fit values of TCD(50) show a clear separation of 9-10.6Gy between low and high risk patients. The corresponding dose-response curves are steeper (gamma(50)=3.4-5.2) than those obtained when all patients are analyzed together (gamma(50)=2.9).

CONCLUSIONS

Dose-response of prostate cancer, quantified by TCD(50) and gamma(50), varies by prognostic subgroup. Our observations are consistent with the hypothesis that the shallow nature of clinically observed dose-response curves for local control result from a patient population that is a heterogeneous mixture of sub-populations with steeper dose-response curves and varying values of TCD(50). Such results may eventually help to identify patients, based on their individual pre-treatment prognostic factors, that would benefit most from dose-escalation, and to guide dose prescription.

Evolution of toxicity after conformal radiotherapy for prostate cancer

The limiting factor for radiation (RT) dose-escalation is normal tissue toxicity. In dose-escalation studies, it is important to determine the factors associated with toxicity and the length of follow-up period after which a particular RT dose is considered safe. We analyzed 449 prostate cancer patients treated with RT at our institution and followed for a median of 27 months. Genitourinary (GU) and gastrointerological (GI) complications were graded and analyzed using three different statistical models. Univariate and multivariate analyses were conducted for factors associated with toxicity. There was no RTOG grade 4 or 5 toxicity. Only 23 patients (5%) experienced grade 3 toxicity. After treatment, there was an initial rapid decline in the risk of toxicity following treatment, followed by an increase or stabilization of the toxicity with time of follow-up. The breakpoints between the two periods were 2 y (any toxicity) and 1 y (high toxicity) for GU and 9 months (any toxicity, high toxicity) for GI. Age, dose, fraction size, duration of treatment and hospital of treatment emerge as important factors in the probability of developing toxicity. Our study shows that delivering conventional doses using conformal techniques is associated with minimal high-grade toxicity. However, even within a narrow dose range and fraction size used, differences do emerge which should lead one to be cautious in extending the results of dose escalation study to the community practice without a sufficient follow-up.

Fitting tumor control probability models to biopsy outcome after three-dimensional conformal radiation therapy of prostate cancer: pitfalls in deducing radiobiologic parameters for tumors from clinical data

PURPOSE

The goal of tumor control probability (TCP) models is to predict local control for inhomogeneous dose distributions. All existing fits of TCP models to clinical data have utilized summaries of dose distributions (e.g., prescription dose). Ideally, model fits should be based on dose distributions in the tumor, but usually only dose-volume histograms (DVH) of the planning target volume (PTV) are available. We fit TCP models to biopsy outcome after three-dimensional conformal radiation therapy of prostate cancer using either a dose distribution summary or the full DVH in the PTV. We discuss differences in the radiobiologic parameters and dose-response curves and demonstrate pitfalls in interpreting the results.

METHODS AND MATERIAL

Two mechanistic TCP models were fit with a maximum likelihood technique to biopsy outcome from 103 prostate patients treated at Memorial Sloan-Kettering Cancer Center. Fits were performed separately for different patient subgroups defined by tumor-related prognostic factors. Fits were based both on full DVHs, denoted TCP(DVH(calc)), and, alternatively, assuming a homogeneous PTV dose given by the mean dose (Dmean) of each DVH, denoted TCP(Dmean(calc)). Dose distributions for these patients were very homogeneous with any cold spots located on the periphery of the PTV. These cold spots were uncorrelated with biopsy outcome, likely because the low-dose regions may not contain tumor cells. Therefore, fits of TCP models that are potentially sensitive to cold spots (e.g., TCP(DVH(calc))) likely give biologic parameters that diminish this sensitivity. In light of this, we examined differences in fitted clonogenic cell number, N(C), or density, rho(C), surviving fraction after 2 Gy, SF(2), or radiosensitivity, alpha, and their standard deviations in the population, sigma(SF(2)) and sigma(alpha), resulting from fits based on TCP(DVH(calc)) and TCP(Dmean(calc)). Dose-response curves for homogeneous irradiation (characterized by TCD(50), the dose for a TCP of 50%) and differences in TCP predictions calculated from the DVH using alternatively derived parameters were evaluated.

RESULTS

Fits of TCP(Dmean(calc)) are better (i.e., have larger likelihood) than fits of TCP(DVH(calc)). For TCP(Dmean(calc)) fits, matching values of SF(2) and sigma(SF(2)) (or alpha and sigma(alpha)) exist for all N(C) (rho(C)) above a threshold that give fits of equal quality, with no maximum in likelihood. In contrast, TCP(DVH(calc)) fits have maximum likelihood for high SF(2) (low alpha) values that minimize effects of cold spots. Consequently, small N(C) (rho(C)) values are obtained to match the observed control rate. For example, for patients in low-, intermediate-, and high-risk groups, optimum values of SF(2) and N(C) are 0.771 and 3.3 x 10(3), 0.736 and 2.2 x 10(4), and 0.776 and 1.0 x 10(4), respectively. The TCD(50) of dose-response curves for intermediate-risk patients is 2.6 Gy lower using TCP(DVH(calc)) parameters (TCD(50) = 67.8 Gy) than for TCP(Dmean(calc)) parameters (TCD(50) = 70.4 Gy). TCP predictions calculated from the DVH using risk group-dependent TCP(Dmean(calc)) parameters are up to 53% lower than corresponding calculations with TCP(DVH(calc)) parameters.

CONCLUSION

For our data, TCP parameters derived from DVHs likely do not reflect true radiobiologic parameters in the tumor, but are a consequence of the reduced importance of low-dose regions at the periphery of the PTV. Deriving radiobiologic parameters from TCP(Dmean(calc)) fits is not possible unless one parameter is already known. TCP predictions using TCP(DVH(calc)) and TCP(Dmean(calc)) parameters may differ substantially, requiring consistency in the derivation and application of model parameters. The proper derivation of radiobiologic parameters from clinical data requires both substantial dose inhomogeneities and understanding of how these coincide with tumor location.

Three dimensional conformal radiotherapy in patients with T2a-b, N0, M0 prostatic carcinoma

The current study was undertaken to evaluate the Prostate Specific Antigen (PSA) relapse free survival and the prognostic factors in a total of 38 patients with stages of T2a-b, N0, M0 prostate carcinoma treated with three-dimensional conformal radiotherapy (3D-CRT). Mean 69.63 Gy was given with 3D-CRT, the mean follow up time was 13.89 months, and the mean prebiopsied PSA level was 25.12 ng/ml. The 2-year PSA relapse free survival was 47.37% for the entire group. The 2-year PSA relapse free survival rates were 100% and 44.74% for the patients with Gleason score < or = 7 and greater than 7 (p < or = 0.05). Patients with prebiopsied PSA level < or = 10 ng/ml and the stages of T2a or T2b did not show any significant differences (p > or = 0.05). Although the few case number and short term follow up, in this study 3D-CRT was a new effective technique to prostate cancer for our institutes and the Gleason score was important predictor of PSA relapse free survival.

Image segmentation in treatment planning for prostate cancer using the region growing technique

The purpose of this study was to evaluate the performance of a region growing technique for segmenting prostate, bladder and rectum in CT images of prostate cancer patients. Prostate, bladder and rectum were segmented in all CT images of 10 patients using the region growing technique and manual tracing. Volumes of the above organs computed with the region growing technique were compared with those from manually traced images on a slice-by-slice basis. Measurement reproducibility of both segmentation techniques was evaluated using the data obtained from four independent observers. The region growing technique was 1.5 times faster than manual tracing. There was no statistical difference between the slice volumes of prostate, bladder and rectum obtained by the two segmentation techniques (p > 0.05, paired Student's t-test). Correlation between slice volumes of all organs of interest provided both by region growing and by manual tracing was very good (prostate r2 = 0.84; bladder r2 = 0.93; rectum r2 = 0.85). An overall reasonable agreement was found between the two segmentation techniques. The intraobserver and interobserver variations for prostate, bladder and rectum volume segmentation were found to be lower with the region growing technique than with manual tracing. The suggested semi-automatic technique allows the possibility of generating accurate and reproducible segmentation of prostate, bladder and rectum from CT data with great saving in labour.

Equivalent racial outcome after conformal radiotherapy for prostate cancer: a single departmental experience

PURPOSE

African-American (AA) men with prostate cancer present with advanced disease, relative to white (W) men. This report summarizes our clinical and biochemical control (bNED) rates after conformal radiotherapy (RT). In particular, we aim to characterize any race-based outcome differences seen after comparable treatment.

PATIENTS AND METHODS

We reviewed 893 patients (418 AA and 475 W) with clinically localized prostate cancer treated between 1988 and 1997. Neoadjuvant hormonal blockade was used in 22.5% of cases, and all patients received conformal RT to a median dose of 68 Gy (range, 60 to 74.8 Gy). Biochemical failure was defined according to the American Society of Therapeutic Radiology and Oncology consensus definition. Median follow-up was 24 months (range, 1 to 114 months).

RESULTS

The 5-year actuarial survival, disease-free survival, and bNED rates for the entire population were 80.5%, 70.0%, and 57.6%, respectively. When classified by prognostic risk category, the 5-year actuarial bNED rates were 78.7% for favorable, 57.7% for intermediate, and 39.8% for unfavorable category patients. AA men presented at younger ages and with more advanced disease. Controlled for prognostic risk category, AA and W men had similar 5-year actuarial bNED rates in favorable (78% v 79%, P: = .91), intermediate (52% v 62%, P: =.44), and unfavorable categories (36% v 45%, P: = .09). Race was not an independent prognostic factor (P: = .36).

CONCLUSION

Conformal RT is equally effective for AA and W patients. More research is needed in order to understand and correct the advanced presentations in AA men. These data suggest a need for early screening in AA populations.

Salvage radiotherapy for prostate cancer recurrence after cryosurgical ablation

OBJECTIVES

To retrospectively determine the outcome of patients treated with salvage three-dimensional conformal radiotherapy (RT) for prostate cancer recurrence after cryosurgical ablation of the prostate (CSAP). Biochemical control rates and morbidity were analyzed.

METHODS

Between January 1990 and November 1999, a total of 49 patients initially treated with CSAP were later irradiated because of a rising prostate-specific antigen (PSA) level and/or a positive biopsy at Allegheny General Hospital. The clinical stage before cryosurgery was T1c in 7 patients; T2a in 7 patients; T2b in 10 patients; T3 in 17 patients; and T4 and/or N1 in 8 patients. The Gleason score was 6 or lower in 29 patients, 7 in 11 patients, and 8 or higher in 9 patients. The mean pre-CSAP PSA level was 15.7 ng/mL (range 2.4 to 45). One patient had a PSA level less than 4 ng/mL, 16 had a PSA level of 4 to 10 ng/mL, 21 had a PSA level of 10 to 20 ng/mL, and 11 had a PSA level greater than 20 ng/mL. Before the start of RT, a complete restaging workup was performed and was negative for distant metastatic disease in all 49 patients. The mean interval to recurrence after CSAP was 19 months (range 3 to 78). The mean RT dose to the planning target volume was 62.9 Gy (range 50.4 to 68.4).

RESULTS

The mean pre-RT PSA level was 2.4 ng/mL (range 0.1 to 7.4). After RT, the mean nadir PSA level was 0.4 ng/mL (range 0 to 4.2). The mean time to PSA nadir was 5.8 months (range 1 to 15). In 42 patients, the PSA nadir was less than 1.0 ng/mL, in 5 patients the PSA nadir was greater than 1 ng/mL, and in 2 patients the PSA level remained stable. With a median follow-up time of 32 months (range 12 to 85), the overall biochemical control rate was 61%. The mean time to biochemical failure was 14.5 months (range 1 to 47). Of 30 patients with a pre-RT PSA level of 2.5 ng/mL or less, the disease of 22 (73%) was controlled compared with only 8 (42%) of 19 with a pre-RT PSA level greater than 2.5 ng/mL (P = 0.040). Biochemical control occurred in 18 (69%) of 26 patients with a dose of 64 Gy or greater compared with only 12 (52%) of 23 patients with a dose of less than 64 Gy (P = 0.024). The disease of 20 (70%) of 29 patients with a Gleason score of 6 or lower was controlled versus 10 (50%) of 20 patients with a Gleason score of 7 or greater (P = 0.064). Only 2 patients developed subacute morbidity (proctitis and a urethral stricture). All complications resolved with conservative measures.

CONCLUSIONS

Salvage RT for prostate cancer recurrence after CSAP appears feasible. Our preliminary experience revealed that post-CSAP RT in patients with prostate cancer appears to effectively diminish the post-RT PSA level to a nadir of 1.0 ng/mL or less in most patients. The pre-RT PSA level and radiation dose may be important predictors of biochemical control in the salvage setting. RT as described was associated with minimal toxicity to the gastrointestinal/genitourinary systems. Additional prospective randomized studies are necessary to better assess the role of RT in the treatment of these patients.

The external radiotherapy with three-dimensional conformal boost after the neoadjuvant androgen suppression for patients with locally advanced prostatic carcinoma

PURPOSE

To analyze the results in patients with locally advanced prostatic carcinoma treated by hormonal therapy followed by external radiotherapy using three-dimensional conformal radiation therapy (3D-CRT) boost.

METHODS AND MATERIALS

From 1987 to 1995, 46 patients with histologically proven locally advanced adenocarcinoma of the prostate were treated with 3D-CRT at the National Cancer Center Hospital, Tokyo. The neoadjuvant androgen suppression started immediately after the diagnosis followed by radical radiation therapy, according to the prospective protocol. They were treated with photons of 6-14 MV for wide fields and the boost, of which a multiple-leaf collimator of 2-cm width was available. The boosted dose was delivered with the rotational 3D-CRT, after the delivery of whole pelvis 4-field box from a dose of 40-46 Gy up to 66 Gy. The planning target volume encompassed 1 cm outside throughout the clinical target volume, and the prostate and the seminal vesicles were included in the boost field.

RESULTS

The 3D-CRT boost treatment completed as planned in all 46 patients. The median follow-up for all the patients was 60 months (range, 5-120 months). Nineteen of 46 patients died. Of these, 11 patients died of the intercurrent diseases. For all 46 patients, the 5- and 8-year overall survival rates were 61.3% and 42.4%, and the 5- and 8-year cause-specific survival rates were 82.4% and 64.4%, respectively. The prostate-specific antigen (PSA) relapse-free rates for 5- and 8-year were 64.6% and 52.5%, and the clinical local control rates for 5 and 8 years were 75.3% and 69.9%, respectively. The preradiation therapy PSA and the Gleason score were the factors that significantly associated with PSA relapse-free survival. Sixteen of 46 patients (35%) showed at least one form of late toxicities. Of these, 3 patients experienced late complications of Grade 3 (urinary, 2, proctitis, 1).

CONCLUSION

The treatment results were fairly good and were consistent with those in Western countries, indicating that this study shows the preliminary status of 3D-CRT for the locally advanced prostate cancer in Japan. Preradiation therapy PSA seems to be a significant predictor of PSA relapse-free survival (p = 0.004) after neoadjuvant androgen suppression.

Analysis of biopsy outcome after three-dimensional conformal radiation therapy of prostate cancer using dose-distribution variables and tumor control probability models

PURPOSE

To investigate tumor control following three-dimensional conformal radiation therapy (3D-CRT) of prostate cancer and to identify dose-distribution variables that correlate with local control assessed through posttreatment prostate biopsies.

METHODS AND MATERIAL

Data from 132 patients, treated at Memorial Sloan-Kettering Cancer Center (MSKCC), who had a prostate biopsy 2.5 years or more after 3D-CRT for T1c-T3 prostate cancer with prescription doses of 64.8-81 Gy were analyzed. Variables derived from the dose distribution in the PTV included: minimum dose (Dmin), maximum dose (Dmax), mean dose (Dmean), dose to n% of the PTV (Dn), where n = 1%,...,99%. The concept of the equivalent uniform dose (EUD) was evaluated for different values of the surviving fraction at 2 Gy (SF(2)). Four tumor control probability (TCP) models (one phenomenologic model using a logistic function and three Poisson cell kill models) were investigated using two sets of input parameters, one for low and one for high T-stage tumors. Application of both sets to all patients was also investigated. In addition, several tumor-related prognostic variables were examined (including T-stage, Gleason score). Univariate and multivariate logistic regression analyses were performed. The ability of the logistic regression models (univariate and multivariate) to predict the biopsy result correctly was tested by performing cross-validation analyses and evaluating the results in terms of receiver operating characteristic (ROC) curves.

RESULTS

In univariate analysis, prescription dose (Dprescr), Dmax, Dmean, dose to n% of the PTV with n of 70% or less correlate with outcome (p < 0.01). The area under the ROC curve for Dmean is 0.64. In contrast, Dmin (p = 0.6), D98 (p = 0.2) or D95 (p = 0.1) are not significantly correlated with outcome. The results for EUD depend on the input parameter SF(2): EUD correlates significantly with outcome for SF(2) of 0.4 or more, but not for lower SF(2) values. Using either of the two input parameters sets, all TCP models correlate with outcome (p < 0.05; ROC areas 0.60-0.62). Using T-stage dependent input parameters, the correlation is improved (logistic function: p < 0.01, ROC area 0.67, Poisson models: p < 0.01, ROC areas 0.64-0.66). In comparison, the ROC area is 0.68 for the combination of Dmean and T-stage. After multivariate analysis, a model based on TCP, D20 and Gleason score is the best overall model (ROC area 0.73). However, an alternative model based on Dmean, Gleason score, and T-stage is competitive (ROC area 0.70).

CONCLUSION

Biopsy outcome after 3D-CRT of prostate cancer at MSKCC is not correlated with Dmin in the PTV and appears to be insensitive to cold spots in the dose distribution. This observation likely reflects the fact that much of the PTV, especially at the periphery, may not contain viable tumor cells and that the treatment margins were sufficiently large. Therefore, the predictive power of all variables which are sensitive to cold spots, like TCPs with Poisson models and EUD for low SF(2), is limited because the low dose region may not coincide with the tumor location. Instead, for MSKCC prostate cancer patients with their standardized CTV definition, substantial target motion and small dose inhomogeneities, Dmean (or any variable that downplays the effect of cold spots) is a very good predictor of biopsy outcome. While our findings may indicate a general problem in the application of current TCP models to clinical data, these conclusions should not be extrapolated to other disease sites without careful analysis.

Three-dimensional conformal therapy or standard irradiation in localized carcinoma of prostate: preliminary results of a nonrandomized comparison

PURPOSE

We present preliminary results of a nonrandomized comparison of three-dimensional conformal radiation therapy (3D CRT) and standard radiation therapy (SRT) in localized carcinoma of the prostate in two groups of patients with comparable prognostic factors treated during the same period.

METHODS AND MATERIALS

Between January 1992 and December 1997, 146 patients were treated with 3D CRT and 131 with SRT alone for clinical stage T1c or T2 histologically confirmed carcinoma of the prostate. None of these patients received hormonal therapy. Mean follow-up for all patients is 3 years (range, 1-6 years). For 3D CRT, 7 intersecting fields were used (Cerrobend blocking or multileaf collimation) to deliver 68-73.8 Gy to the prostate; 3D dose distributions and dose-volume histograms (DVHs) of the planning target volume, bladder, and rectum were obtained. SRT consisted of bilateral 120 degrees rotational arcs, with portals with 2-cm margins around the prostate to deliver 68-70 Gy to the prostate. The criterion for chemical disease-free survival was a postirradiation prostate-specific antigen (PSA) (Tandem-R, Hybritech) value following the American Society for Therapeutic Radiology and Oncology guidelines. Symptoms during treatment were quantitated weekly, and late effects were assessed every 4-6 months.

RESULTS

DVHs showed a two-thirds reduction in normal bladder or rectum receiving 70 Gy or more with 3D CRT. Higher 5-year chemical disease-free survival was observed with 3D CRT (91% for T1c and 96% for T2 tumors) compared with SRT (53% and 58%, respectively). There was no statistically significant difference in chemical disease-free survival in patients with Gleason score of 4 or less (p = 0.83), but with Gleason score of 5-7, the 5-year survival rates were 96% with 3D CRT and 53% with SRT (p < or = 0.01). In 111 patients with pretreatment PSA of 10 ng/mL or less, treated with 3D CRT, the chemical disease-free rate was 96% vs. 65% in 94 patients treated with SRT (p < or = 0.01). In patients with PSA of 10. 1-20 ng/mL, the chemical disease-free survival rate for 26 patients treated with 3D CRT was 88% compared with 40% for 20 patients treated with SRT (p = 0.05). The corresponding values were 71% and 26%, respectively, for patients with PSA levels of greater than 20 ng/mL (p = 0.30). On multivariate analysis, the most important prognostic factors for chemical failure were pretreatment PSA (p = 0. 023), nadir PSA (p = 0.001), and 3D CRT technique (p = 0.033). Moderate dysuria and difficulty in urinating were reported by 2-5% of patients treated with 3D CRT in contrast to 6-9% of patients treated with SRT; moderate urinary frequency and nocturia were reported by 18-24% treated with 3D CRT and 18-27% of patients in the SRT group. The incidence of moderate loose stools/diarrhea, usually after the 4th week of treatment, was 3-5% in the 3D CRT patients and 8-19% in the SRT group. Late intestinal morbidity (proctitis, rectal bleeding) was very low (1.7%) in the 3D CRT group in contrast to the SRT patients (8%).

CONCLUSION

Three-dimensional CRT spares more normal tissues, yields higher chemical disease-free survival, and results in less treatment morbidity than SRT in treatment of Stage T1-T2 prostate cancer. Longer follow-up is needed to confirm these preliminary observations.

Cryosurgery for prostate cancer: new technology and indications

Patients diagnosed with prostate cancer who elect to pursue active treatment of their disease must choose among the many available treatment alternatives. Several treatment options now exist for similar-stage disease (clinical T1-3N0M0), including radical prostatectomy, external beam radiation, prostate brachytherapy (PB), and cryosurgical ablation of the prostate (CSAP). This article reviews the current role of CSAP in the treatment of clinically localized prostate cancer. CSAP has a role in the primary treatment of men with high-risk, clinically localized prostate cancer (defined as PSA >10, Gleason score >or=7, or clinical stage >or= cT2B). CSAP (occasionally followed by external beam radiotherapy) appears to offer improved rates of cancer control over other types of single or combination therapies for this high-risk prostate cancer, and it is associated with an acceptable side-effect profile. CSAP should also be the treatment of choice for men with recurrent local disease who have undergone external beam radiotherapy or PB.

Caution in interpreting biochemical control rates after treatment of prostate cancer: length of follow-up influences results

OBJECTIVES

Prostate-specific antigen (PSA) based end points are commonly used to report outcomes after treatment for prostate cancer. This study examines the influence of follow-up length on biochemical control (bNED) rates.

METHODS

We reviewed 437 patients with clinically localized prostate cancer treated with conformal radiotherapy without neoadjuvant androgen deprivation. Biochemical failure was defined as three consecutive PSA increases or an increase large enough to prompt androgen deprivation therapy. The failure date was projected back to the midpoint between the PSA nadir and the first PSA increase (or between the nadir and the initiation of androgen deprivation therapy). The analysis was performed by censoring patients with longer follow-up in a stepwise fashion, thus creating smaller subgroups with shorter follow-up intervals. Subgroup 1 (n = 191) and subgroup 2 (n = 273) were defined to include those patients monitored for up to 2 years and up to 3 years, respectively.

RESULTS

The median follow-up intervals for subgroup 1, subgroup 2, and the original study population were 1.1, 1.5, and 2.5 years. No significant differences were seen in pretreatment prognostic factors among the three groups. The 2-year bNED of subgroup 1, subgroup 2, and the original population was 86%, 77%, and 73%, respectively. Although subgroup 1 had a superior bNED compared with the original population (P = 0.04), no differences in clinical recurrence rates were seen among any of the three groups.

CONCLUSIONS

Because of projecting the biochemical failure dates back according to commonly used bNED definitions, control rates are highly dependent on the length of follow-up.

Comparison of MRI with CT for the radiotherapy planning of prostate cancer: a feasibility study

This feasibility study was performed to evaluate the suitability of MRI in defining appropriate pelvic radiotherapy treatment volumes, and to compare MRI sequences with CT for prostate cancer radiotherapy. Five patients with localized prostate cancer, imaged with four MRI sequences (spin echo (SE) T1, turbo SE (TSE) T2, high resolution TSE (HR) T2, and FLASH 3D (F3D)), compared with their corresponding CT planning scans. Segmentation ability of the following pelvic structures: prostatic apex (PA), prostate, rectum, bladder and seminal vesicles (SV), were evaluated by three independent observers. They used a five point grading scale based on the anatomical definition of the organ boundary, tissue contrast and multiplanar display. Results were averaged for the group and for each sequence. There was no significant interobserver variation in the assessed scores (p > 0.1). The average scores (+/- 1 SD) for all pelvic structures assessed by each imaging sequence were CT 1.3 +/- 0.6; SE T1 2.4 +/- 0.9; TSE T2 2.4 +/- 0.7; HR T2 2.2 +/- 0.7 and F3D 3.4 +/- 0.6. Compared with CT, the average MR score for each assessed pelvic structure was higher with a trend for all transaxial MR sequences to provide improved segmentation of the PA and rectum. The F3D sequence scored highest as it provided multiplanar views and avoided the problem of partial volume averaging. MRI, compared with CT, appears to provide improved definition of pelvic treatment volumes but further work is required to confirm this and to address the issues of MRI associated distortion and dosimetry before MRI can be used routinely for pelvic radiotherapy planning.

Evaluating the effect of rectal distension and rectal movement on prostate gland position using cine MRI

PURPOSE

To evaluate the dynamic interrelationship between rectal distension and rectal movements, and to determine the effect of rectal movement on the position of the prostatic gland using cine magnetic resonance imaging (MRI).

METHODS AND MATERIALS

Fifty-five patients with biopsy-proven or suspected prostate cancer were examined in the axial plane using repeated spoiled gradient-echo sequences every 10 seconds for 7 minutes. Twenty-four patients received bowel relaxants before imaging. Images were analyzed for the degree of rectal distension, for the incidence, magnitude, and number of rectal and prostate movements.

RESULTS

Rectal movements were seen in 28 (51%) patients overall, in 10 (42%) of those receiving bowel relaxants and in 18 (58%) not receiving bowel relaxants. The incidence of rectal movements correlated with the degree of rectal distension (p = 0.0005), but the magnitude of rectal movements did not correlate with the degree of rectal distension. Eighty-six rectal movements resulting in 33 anterior-posterior (AP) prostate movements were seen. The magnitude of rectal movements correlated well with degree of prostate movements (p < 0.001). Prostate movements in the AP direction were seen in 16 (29%) patients, and in 9 (16%) patients the movement was greater than 5 mm. The median prostate AP displacement was anterior by 4.2 (-5 to +14 mm).

CONCLUSIONS

Cine MRI is able to demonstrate near real time rectal and associated prostate movements. Rectal movements are related to rectal distension and result in significant displacements of the prostate gland over a time period similar to that used for daily fractionated radiotherapy treatments. Delivery of radiotherapy needs to take into account these organ movements.

Conformal proton therapy for early-stage prostate cancer

OBJECTIVES

To assess the effect of proton radiation on clinical and biochemical outcomes for early prostate cancer.

METHODS

Three hundred nineteen patients with T1-T2b prostate cancer and initial prostate-specific antigen (PSA) levels 15.0 ng/mL or less received conformal radiation doses of 74 to 75 cobalt gray equivalent with protons alone or combined with photons. No patient had pre- or post-treatment hormonal therapy until disease progression was documented. Patients were evaluated for biochemical disease-free survival, PSA nadir, and toxicity; the mean and median follow-up period was 43 months.

RESULTS

Overall 5-year clinical and biochemical disease-free survival rates were 97% and 88%, respectively. Initial PSA level, stage, and post-treatment PSA nadir were independent prognostic variables for biochemical disease-free survival: a PSA nadir 0.5 ng/mL or less was associated with a 5-year biochemical disease-free survival rate of 98%, versus 88% and 42% for nadirs 0.51 to 1.0 and greater than 1.0 ng/mL, respectively. No severe treatment-related morbidity was seen.

CONCLUSIONS

It appears that patients treated with conformal protons have 5-year biochemical disease-free survival rates comparable to those who undergo radical prostatectomy, and display no significant toxicity. A Phase III randomized dose-escalation trial is underway to define the optimum radiation dose for early-stage prostate cancer.

Fractionated radiotherapy of rat prostatic adenocarcinoma (Dunning R3327-PAP) in nonanesthetized animals

BACKGROUND

The dose-response effect of fractionated external beam radiotherapy on nonanesthetized rats bearing the androgen-sensitive prostatic adenocarcinoma Dunning R3327-PAP was studied.

METHODS

The radiation was given with a photon beam from a 4-MeV linear accelerator in doses from 4 to 11 Gray per fraction during 5 consecutive days. When the tumors with low and intermediate radiation doses relapsed into regrowth, the rats were castrated. Tumor volumes and rat weights were followed, and at the end of the study a morphometric analysis of the tumors was done.

RESULTS

Fractionated irradiation induced a dose-dependent delay in tumor growth in hormonally intact rats. Castration stopped the tumor regrowth, showing that some of the tumor cells were still hormone-sensitive. The study was facilitated by the nonanesthesia procedure.

CONCLUSIONS

The Dunning R3327-PAP hormone-sensitive rat tumor is sensitive to radiotherapy in a dose-dependent way. Regrowing, irradiated tumors contain hormone-sensitive cells. This work provided basic knowledge for further experimental studies of the effects of radiation on prostatic adenocarcinoma.

The Role of Radiotherapy in the Treatment of Carcinoma of the Prostate: A Survey of Clinical Practices in Lombardy, Italy, by the Airo-Lombardia Cooperative Group

Aims and background

We report the results of a survey performed in 1994 by the AIRO-Lombardia Cooperative Group, on the clinical patterns of radiation treatment for prostatic carcinoma in Lombardy, Italy, involving all radiotherapy centers serving an overall local population of about 8,800,000 people.

Methods

A questionnaire was sent to all 13 radiotherapy centers throughout Lombardy, asking for demographic and treatment details concerning the local population of patients with a localized (T1-4, N0-1, M0) carcinoma of the prostate treated with radiotherapy; 12 centers responded, making the basis for the present report.

Results

Analysis of collected data showed that in Lombardy: a) approximately 400 patients per year are irradiated for a localized carcinoma of the prostate, accounting for less than 30% of the total expected number of patients with this disease presentation; b) a complete staging (with PSA, transrectal ultrasonography, abdomino-pelvic CT or MRI scan and total-body bone scan) is performed in over 95% of patients before initiating radiotherapy; c) significant differences exist between radiotherapy centers as regards treatment planning and delivery.

Conclusions

An urgent need exists for implementing procedures aimed at standardizing radiotherapy procedures within Lombardy.

Conformal proton therapy for prostate carcinoma

BACKGROUND

The role and optimum dose of radiation to eradicate prostate cancer continues to be evaluated. Protons offer an opportunity to increase the radiation dose to the prostate while minimizing treatment toxicity.

METHODS

Six hundred forty-three patients with localized prostate cancer were treated with protons, with or without photons. Treatments were planned with a 3D planning system; patients received 74-75 CGE (Cobalt Gray Equivalent) at 1.8-2.0 CGE per fraction. Patients were evaluated for response to therapy and treatment-related toxicity.

RESULTS

The overall clinical disease-free survival rate was 89% at 5 years. When post-treatment prostate-specific antigen (PSA) was used as an endpoint for disease control, the 4.5-year disease-free survival rate was 100% for patients with an initial PSA of < 4.0 ng/ml, and 89%, 72%, and 53% for patients with initial PSA levels of 4.1-10.0, 10.1-20.0, and > 20.0, respectively. Patients in whom the post-treatment PSA nadir was below 0.5 ng/ml did significantly better than those whose nadir values were between 0.51-1.0 or > 1.0 ng/ml: the corresponding 5-year disease-free survival rates were 91%, 79%, and 40%, respectively. Minimal radiation proctitis was seen in 21% of patients; toxicity of greater severity was seen in less than 1%.

CONCLUSION

Proton therapy to 74-75 CGE produced minimal treatment-related toxicity and excellent PSA normalization and disease-free survival in patients with low initial PSA levels. A prospective randomized dose-escalation trial is now underway to help define the optimum dose of radiation for patients with early stage prostate cancer.

High-precision conformal radiotherapy (HPCRT) of prostate cancer--a new technique for exact positioning of the prostate at the time of treatment

PURPOSE

Biopsies taken 2 years after radiotherapy of localized prostate cancer indicate residual tumor cells in 20-60% of cases, and the prognosis for these patients is unfavorable. More precise methods of localization of the prostate are desirable to increase the dose to the prostate tumor and minimize the volume of adjacent sensitive tissues that are currently included in the planning target volume. We have sought a method to more accurately locate the prostate at the time of treatment, allowing a reduction of the volume of rectum and bladder included in the high dose region during dose escalation.

METHODS AND RESULTS

We have developed a new technique using a special urethral catheter (patent pending), containing markers that can be visualized by the radiotherapy machine for accurate positioning of the prostate. The catheter is used throughout the treatment planning procedure and the isocenter is placed on one of the markers. On the treatment couch the markers are visualized on port-films and with portal imaging immediately before dose delivery. A beam-center-marker on the accelerator makes it possible to adjust the isocenter position to within 1 mm, giving very high precision, independent of external fixation. The technique involves a simple patient setup. The method has been tested in five patients with conventional dose level (70 Gy) and in 24 patients in the first Scandinavian dose escalation study with external beam radiotherapy. No increase in acute side-effects was observed.

CONCLUSION

With the new high precision conformal radiotherapy (HPCRT) technique we have developed a technique that allows us to increase the dose to the prostate without excessive side effects. The method reduces the uncertainties in prostate localization, is easy to handle, and feasible in routine treatment.

High-dose rate interstitial with external beam irradiation for localized prostate cancer--results of a prospective trial

PURPOSE

A prospective phase II trial was carried out to test the feasibility and effectiveness of a combined interstitial with external beam radiotherapy approach for localized prostate cancer.

MATERIALS AND METHODS

Between October 1992 and December 1994, 82 evaluable patients were treated. T2 and T3 tumours, according to the AJCC classification system of 1992, were found in 21 and 61 cases, respectively. The median follow-up was 24 months; three patients were lost during follow-up. All of the patients were pathologically proven to be node-negative by laparoscopic node dissection of the fossa obturatoria region. A dose of 9 Gy a week was prescribed during the first and second weeks of treatment (10 Gy each week from October 1992 to December 1993) interstitially with high-dose rate Iridium-192 brachytherapy to the prostate and tumour extension beyond the capsule. External beam four-field box irradiation was then given to the prostate to a dose of 45 Gy/25 fractions (40 Gy/20 fractions from October 1992 to December 1993).

RESULTS

Before starting treatment, a PSA value of > or =10 ng/ml was found in 64.6% (53/82) of patients with a median PSA of 14.0 ng/ml. The median PSA 3, 12 and 24 months after completion of therapy was 1.20, 0.78 and 0.70 ng/ml, respectively. The PSA value was < 1.0 ng/ ml in 52.9% of patients at 2 years. Negative punch biopsies 12 and 24 months after therapy were observed in 69.8% (44/63) and 73. 1% (38/ 52) of patients, respectively. A positive biopsy combined with a PSA value of > 1.0 ng/ml was considered as local failure. The local tumour control rate was 79.5% at 2 years. Acute side-effects were not increased relative to external beam irradiation alone. Severe side-effects were observed in three patients (two of the three patients had additional risk factors (colitis ulcerosa and diabetes mellitus)); they developed rectourethral fistulae requiring colostomy after biopsies from the anterior rectal wall.

CONCLUSION

The described method is feasible and well tolerable. The three complications observed were not caused by irradiation alone. Biopsies from the anterior rectal wall after definitive high-dose radiotherapy for prostate cancer have to be seen as obsolete. The rate of negative prostate biopsies of 73.1% after 24 months represents an encouraging result.

The relationship between biochemical failure and time to nadir in patients treated with external beam therapy for T1-T3 prostate carcinoma

PURPOSE AND BACKGROUND

To determine a prostatic-specific antigen (PSA) nadir value and time to nadir that predict a high probability of freedom from biochemical failure in men treated with external beam therapy for prostate cancer.

MATERIALS AND METHODS

Between January 1990 and March 1994, 228 men with T1-T3 adenocarcinoma of the prostate received a radical course of external beam irradiation with no prior or adjuvant hormonal therapy. All men had pre- and post-treatment serum PSA evaluations, and were followed up for at least 24 months, to ensure PSA nadir was reached. Biochemical failure was defined as three successive post-treatment rises in serum PSA, regardless of the magnitude of elevation.

RESULTS

Overall, 4-year biochemical disease-free survival (BDFS) was 42%. PSA nadir was predictive of subsequent BDFS. For those whose serum PSA nadir was < or =1 ng/ml, 4-year BDFS was 70%, versus 12% for those with serum PSA nadir > 1 ng/ml (P = < 0.001). The 4-year BDFS for patients with time to nadir < or =1 year, was 28%, versus 58% for those with time to nadir > 1 year (P < 0.001). For patients with PSA nadir < or =1 ng/ml, 4-year BDFS was 75% for those with time to nadir > 1 year, versus 61% for those with time to nadir < or =1 year (P < 0.021). In multivariate analysis, PSA nadir(< or =1 ng/ml versus >1 ng/ml, and time to nadir (< or =1 year versus > year) were independent predictors of BDFS alone with pre-treatment PSA and Gleason score.

CONCLUSION

Only those who achieved PSA nadir < or =1 ng/ml following external beam therapy have a favourable chance of lasting biochemical disease control, while those with nadir > 1 ng/ml have a high subsequent failure rate. The prognosis is better in patients with late time to nadir. In addition to PSA nadir, time to nadir, pretreatment PSA, and Gleason score were of independent prognostic significance.

Dose escalation with three-dimensional conformal radiation therapy affects the outcome in prostate cancer

PURPOSE

Three-dimensional conformal radiation therapy (3D-CRT) is a technique designed to deliver prescribed radiation doses to localized tumors with high precision, while effectively excluding the surrounding normal tissues. It facilitates tumor dose escalation which should overcome the relative resistance of tumor clonogens to conventional radiation dose levels. The present study was undertaken to test this hypothesis in patients with clinically localized prostate cancer.

METHODS AND MATERIALS

A total of 743 patients with clinically localized prostate cancer were treated with 3D-CRT. As part of a phase I study, the tumor target dose was increased from 64.8 to 81 Gy in increments of 5.4 Gy. Tumor response was evaluated by post-treatment decrease of serum prostate-specific antigen (PSA) to levels of < or = 1.0 ng/ml and by sextant prostate biopsies performed > or = 2.5 years after completion of 3D-CRT. PSA relapse-free survival was used to evaluate long-term outcome. The median follow-up was 3 years (range: 1-7.6 years).

RESULTS

Induction of an initial clinical response was dose-dependent, with 90% of patients receiving 75.6 or 81.0 Gy achieving a PSA nadir < or = 1.0 ng compared with 76% and 56% for those treated with 70.2 Gy and 64.8 Gy, respectively (p < 0.001). The 5-year actuarial PSA relapse-free survival for patients with favorable prognostic indicators (stage T1-2, pretreatment PSA < or = 10.0 ng/ml and Gleason score < or = 6) was 85%, compared to 65% for those with intermediate prognosis (one of the prognostic indicators with a higher value) and 35% for the group with unfavorable prognosis (two or more indicators with higher values) (p < 0.001). PSA relapse-free survival was significantly improved in patients with intermediate and unfavorable prognosis receiving > or = 75.6 Gy (p < 0.05). A positive biopsy at > or = 2.5 years after 3D-CRT was observed in only 1/15 (7%) of patients receiving 81.0 Gy, compared with 12/25 (48%) after 75.6 Gy, 19/42 (45%) after 70.2 Gy, and 13/23 (57%) after 64.8 Gy (p < 0.05).

CONCLUSIONS

The data provide evidence for a significant effect of dose escalation on the response of human prostate cancer to irradiation and defines new standards for curative radiotherapy in this disease.

The treatment of nonpalpable PSA-detected adenocarcinoma of the prostate with 3-dimensional conformal radiation therapy

PURPOSE

We reviewed our institution's experience treating patients with nonpalpable PSA-detected prostate cancer with three-dimensional conformal radiation therapy (3DCRT) to determine prognostic factors that predict for biochemical-free survival (bNED) control and present the bNED control rates.

METHODS AND MATERIALS

Between May 1, 1990 and November 30, 1994, 160 patients with nonpalpable PSA-detected prostate cancer received 3DCRT at Fox Chase Cancer Center (median total dose 73 Gy; range: 67-78 Gy). bNED failure was defined as three consecutive increases in posttreatment PSA after achieving a nadir. bNED failure was recorded as the time midway between the nadir and the first consecutive rising PSA. Five-year actuarial rates of bNED control were calculated for pretreatment PSA (0-9.9 vs. 10-19.9 vs. > or = 20 ng/ml), Gleason score (2-6 vs. 7-10), treatment field size (prostate vs. small pelvis), age (<65 vs. > or = 65), and dose (< or = 73 vs. >73 Gy) using Kaplan-Meier methods and compared using the Log rank test. The Cox model was used to multivariately establish independent predictors based on significant univariate factors. Median follow-up was 39 months (range: 2-84 months).

RESULTS

The 5-year actuarial rate of bNED control was 86% for the entire group of patients. The Cox Proportional Hazards model demonstrated that pretreatment PSA was an independent predictor of bNED control. Treatment field size was marginally predictive. There was no difference in bNED control when patients were stratified by the number of lobes positive for disease. Statistically different rates of bNED control were seen when the patients with nonpalpable disease were univariately compared to T2b and T2c patients. Three patients experienced Grade 3-4 genitourinary (GU) toxicity and 3 patients experienced Grade 3-4 gastrointestinal (GI) toxicity.

CONCLUSIONS

Patients with nonpalpable PSA-detected prostate cancer can be effectively treated with 3DCRT with minimal morbidity and high rates of bNED control at 5 years. Pretreatment PSA level is an independent predictor of bNED control.