Importance of high radiation doses (72 Gy or greater) in the treatment of stage T1-T3 adenocarcinoma of the prostate

Comparison of Moderate Hypofractionated Volumetric-Modulated Arc Therapy Plans With and Without Flattening Filter for Localized Prostate Cancer

Background/Aim The aim of this study was to compare volumetric-modulated arc therapy (VMAT) radiation plans between conventional VMAT with flattening filter (cFF-VMAT) and flattening filter-free VMAT (FFF-VMAT) for localized prostate cancer. Materials and methods Ten patients with localized prostate cancer who underwent cFF-VMAT at Yokosuka General Hospital Uwamachi, Yokosuka, Japan, from July 2020 to October 2020 were enrolled. Dose-volume histogram (DVH) parameters of the target volume, normal organs, monitor units (MU), and beam-on time (BOT) were compared between cFF-VMAT and FFF-VMAT plans. Results No significant difference was observed for DVH parameters for the target volume. No significant difference was observed in all parameters for the bladder and rectum between the cFF-VMAT and FFF-VMAT groups. The mean values of MU were 686 ± 52 and 784 ± 80 in cFF-VMAT and FFF-VMAT, respectively (p < 0.001). The mean BOT was 97.0 ± 6.6 s and 72.9 ± 1.4 s for cFF-VMAT and FFF-VMAT, respectively (p < 0.001). Conclusion DVH parameters of the target volume and normal organs were not significantly different between the cFF-VMAT and FFF-VMAT plans. In FFF-VMAT, MU was significantly higher, and the BOT was significantly shorter than those in cFF-VMAT.

Conversion and validation of rectal constraints for prostate carcinoma receiving hypofractionated carbon-ion radiotherapy with a local effect model

Background

The study objective was to establish the local effect model (LEM) rectum constraints for 12-, 8-, and 4-fraction carbon-ion radiotherapy (CIRT) in patients with localized prostate carcinoma (PCA) using microdosimetric kinetic model (MKM)-defined and LEM-defined constraints for 16-fraction CIRT.

Methods

We analyzed 40 patients with PCA who received 16- or 12-fraction CIRT at our center. Linear-quadratic (LQ) and RBE-conversion models were employed to convert the constraints into various fractionations and biophysical models. Based on them, the MKM LQ strategy converted MKM rectum constraints for 16-fraction CIRT to 12-, 8-, and 4-fraction CIRT using the LQ model. Then, MKM constraints were converted to LEM using the RBE-conversion model. Meanwhile the LEM LQ strategy converted MKM rectum constraints for 16-fraction CIRT to LEM using the RBE-conversion model. Then, LEM constraints were converted from 16-fraction constraints to the rectum constraints for 12-, 8-, and 4-fraction CIRT using the LQ model. The LEM constraints for 16- and 12-fraction CIRT were evaluated using rectum doses and clinical follow-up. To adapt them for the MKM LQ strategy, CNAO LEM constraints were first converted to MKM constraints using the RBE-conversion model.

Results

The NIRS (i.e. D_MKM|v, V-20%, 10%, 5%, and 0%) and CNAO rectum constraints (i.e. D_LEM|v, V-10 cc, 5 cc, and 1 cc) were converted for 12-fraction CIRT using the MKM LQ strategy to LEM 37.60, 49.74, 55.27, and 58.01 Gy (RBE), and 45.97, 51.70, and 55.97 Gy (RBE), and using the LEM LQ strategy to 39.55, 53.08, 58.91, and 61.73 Gy (RBE), and 49.14, 55.30, and 59.69 Gy (RBE). We also established LEM constraints for 8- and 4-fraction CIRT. The 10-patient RBE-conversion model was comparable to 30-patient model. Eight patients who received 16-fraction CIRT exceeded the corresponding rectum constraints; the others were within the constraints. After a median follow-up of 10.8 months (7.1–20.8), No ≥ G1 late rectum toxicities were observed.

Conclusions

The LEM rectum constraints from the MKM LQ strategy were more conservative and might serve as the reference for hypofractionated CIRT. However, Long-term follow-up plus additional patients is necessary.

Survival Outcomes of Radical Prostatectomy + Extended Pelvic Lymph Node Dissection and Radiotherapy in Prostate Cancer Patients With a Risk of Lymph Node Invasion Over 5%: A Population-Based Analysis

Purpose

We aimed to compare the efficacy of radical prostatectomy (RP) + extended pelvic lymph node dissection (ePLND) and radiotherapy (RT) in localized prostate cancer (PCa) patients with a risk of lymph node invasion (LNI) over 5%.

Methods

The Surveillance, Epidemiology, and End Results (SEER) databases were used to identify patients with PCa from 2010 to 2014. Propensity score matching (PSM) was performed to balance baseline characteristics between patients in different treatment groups. Kaplan-Meier curves and Cox regression were used to assess the effects of treatments on cancer-specific survival (CSS) and overall survival (OS).

Results

Overall 20584 patients were included in this study, with 4,057 and 16,527 patients receiving RP + ePLND and RT, respectively. After PSM, patients with RP + ePLND had similar CSS (5-year CSS rate: 97.8% vs. 97.2%, P=0.310) but longer OS (5-year OS rate: 96.0% vs. 90.8%, P<0.001) compared to those receiving RT. When separating RT cohort into external beam radiotherapy (EBRT) group and EBRT+ brachytherapy (BT) group, treatments with RP + ePLND and EBRT+ BT achieved equivalent OS and were both superior to EBRT alone (5-year OS rate: 96.0% vs. 94.4% vs. 90.0%, P<0.001). Subgroup analyses and multivariate analyses further confirmed the superiority of RP + ePLND and EBRT+ BT.

Conclusion

RP + ePLND and EBRT + BT were associated with better survival outcomes compared to EBRT alone in PCa patients with a probability of LNI over 5%. However, no survival difference was observed between RP + ePLND and EBRT + BT.

Preliminary result of carbon-ion radiotherapy using the spot scanning method for prostate cancer

BACKGROUND

Carbon-ion radiotherapy (CIRT) for prostate cancer was initiated at Kanagawa Cancer Center in 2015. The present study analyzed the preliminary clinical outcomes of CIRT for prostate cancer.

METHODS

The clinical outcomes of 253 patients with prostate cancer who were treated with CIRT delivered using the spot scanning method between December 2015 and December 2017 were retrospectively analyzed. The irradiation dose was set at 51.6 Gy (relative biological effectiveness) delivered in 12 fractions over 3 weeks. Biochemical relapse was defined using the Phoenix definition. Toxicities were assessed according to CTCAE version 4.0.

RESULTS

The median patient age was 70 (47-86) years. The median follow-up duration was 35.3 (4.1-52.9) months. According to the D'Amico classification system, 8, 88, and 157 patients were classified as having low, intermediate, and high risks, respectively. Androgen deprivation therapy was administered in 244 patients. The biochemical relapse-free rate in the low-, intermediate-, and high-risk groups at 3 years was 87.5, 88.0, and 97.5%, respectively (P = 0.036). Grade 2 acute urinary toxicity was observed in 12 (4.7%) patients. Grade 2 acute rectal toxicity was not observed. Grade 2 late urinary toxicity and grade 2 late rectal toxicity were observed in 17 (6.7%) and 3 patients (1.2%), respectively. Previous transurethral resection of the prostate was significantly associated with late grade 2 toxicity in univariate analysis. The predictive factor for late rectal toxicity was not detected.

CONCLUSION

The present study demonstrated that CIRT using the spot scanning method for prostate cancer produces favorable outcomes.

Particle therapy for prostate cancer: The past, present and future

Although prostate cancer control using radiotherapy is dose‐dependent, dose–volume effects on late toxicities in organs at risk, such as the rectum and bladder, have been observed. Both protons and carbon ions offer advantageous physical properties for radiotherapy, and create favorable dose distributions using fewer portals compared with photon‐based radiotherapy. Thus, particle beam therapy using protons and carbon ions theoretically seems suitable for dose escalation and reduced risk of toxicity. However, it is difficult to evaluate the superiority of particle beam radiotherapy over photon beam radiotherapy for prostate cancer, as no clinical trials have directly compared the outcomes between the two types of therapy due to the limited number of facilities using particle beam therapy. The Japanese Society for Radiation Oncology organized a joint effort among research groups to establish standardized treatment policies and indications for particle beam therapy according to disease, and multicenter prospective studies have been planned for several common cancers. Clinical trials of proton beam therapy for intermediate‐risk prostate cancer and carbon‐ion therapy for high‐risk prostate cancer have already begun. As particle beam therapy for prostate cancer is covered by the Japanese national health insurance system as of April 2018, and the number of facilities practicing particle beam therapy has increased recently, the number of prostate cancer patients treated with particle beam therapy in Japan is expected to increase drastically. Here, we review the results from studies of particle beam therapy for prostate cancer and discuss future developments in this field.

Long-term outcome of hypofractionated intensity-modulated radiotherapy using TomoTherapy for localized prostate cancer: A retrospective study

BACKGROUND

Recently, the clinical outcome of prostate cancer treated by hypofractionated radiation therapy has been reported. However, there are few reports from Japan. In Hidaka Hospital, hypofractionated intensity-modulated radiotherapy (HIMRT) for prostate cancer was initiated in 2007. The purpose of this study is to analyze the long-term outcome.

METHODS

Ninety-two patients with localized prostate cancer treated with HIMRT at Hidaka Hospital between 2007 and 2009 were retrospectively analyzed. HIMRT was delivered using TomoTherapy. The prescription dose was 66 Gy at 95% of the PTV in 22 fractions performed 3 days a week over 7 weeks in all patients. The overall survival rate, biochemical relapse-free rate, and acute and late toxicities were evaluated.

RESULTS

The median follow-up duration was 78 (range 14-100) months. The median age at the start of the HIMRT was 72 (range 46-84) years. The disease characteristics were as follows: stage T1c, 45; T2a, 20; T2b, 5; T2c, 1; T3a, 13; T3b, 6; T4, 2; Gleason score 6, 13; 7, 44; 8, 20; 9, 15; 10, 0; pretreatment PSA ≤10 ng/mL, 42; 10 to ≤20, 27; and >20, 23. According to the D'Amico classification system, 10, 37, and 45 patients were classified as low-risk, intermediate-risk, and high-risk. The overall survival rate, the cause-specific survival rate, and the biochemical relapse-free rate at 5 years was 94.7%, 100% and 98.9%, respectively. Severe acute toxicity (grade 3 or more) was not observed. The late urinary toxicity was 52.2% in grade 0, 28.3% in grade 1, 19.6% in grade 2, and 2.2% in grade 3. The late rectal toxicity was 78.3% in grade 0, 7.6% in grade 1, 9.8% in grade 2, and 4.3% in grade 3.

CONCLUSIONS

The present study demonstrated that HIMRT using TomoTherapy for prostate cancer has a favorable outcome with tolerable toxicity.

Brachytherapy improves outcomes in young men (≤60 years) with prostate cancer: A SEER analysis

PURPOSE

The aim of the study was to compare prostate cancer-specific mortality (PCSM) in young men with clinically localized prostate cancer treated by either external beam radiation (EBRT) alone or brachytherapy with or without external beam radiation.

METHODS AND MATERIALS

Utilizing the Surveillance, Epidemiology and End Results database, 15,505 patients ≤60 years of age diagnosed with prostate cancer between 2004 and 2009 and treated with radiation therapy alone were identified. Incidence of PCSM was determined for both groups and compared using competing risk models.

RESULTS

The overall 8-year PCSM for the study population was 1.9% (95% confidence interval [CI]: 1.6-2.2). For patients treated with EBRT or brachytherapy with or without external beam, the 8-year PCSM was found to be 2.8% (CI: 2.2-3.4) and 1.2% (CI: 0.9-1.6), respectively (p < 0.001). Univariable analysis demonstrated that brachytherapy was associated with lower PCSM risk (hazard ratio = 0.40; CI: 0.30-0.54; p < 0.001). High Gleason risk category, black race, higher Tumor (T) stage, and higher grade were all associated with greater mortality risk (p < 0.01). On multivariable analysis, brachytherapy continued to be associated with a significantly lower mortality risk (hazard ratio = 0.65; CI: 0.47-0.89; p = 0.008). Subgroup analyses found that among those with Gleason score ≥8, younger patients had increased risk of PCSM (p = 0.001).

CONCLUSIONS

In men ≤60 years of age with prostate cancer, radiation therapy continues to offer excellent outcomes. After adjusting for relevant variables, the use of brachytherapy was associated with reduced PCSM compared to treatment with EBRT alone.

Localized prostate cancer treated with external beam radiation therapy: Long-term outcomes at a European comprehensive cancer centre

AIMS AND BACKGROUND

To present survival and toxicity outcomes in patients with clinically localized, non-metastatic prostate cancer (PCa) treated with external beam radiotherapy (EBRT) combined with androgen deprivation therapy (ADT).

MATERIALS AND METHODS

Retrospective study of 849 PCa patients (pts) treated from 1996 to 2005. Until August 2000, all patients (281) were treated with conventional dose EBRT (<76 Gy); subsequent pts received ≥76 Gy (565 pts). Median age was 70 years (range, 39-82). Most pts were intermediate (353; 42.8%) or high-risk (344; 41.7%). Mean PSA was 10.1 ng/ml. Median dose to the prostate was 75 Gy. Complete ADT was administered to 525 pts (61.8%).

RESULTS

Median follow-up was 109.6 months (range, 68.3-193.4). Overall survival (OS) was 92.5% and 81.1% at 5 and 10 years; by risk group (low, intermediate, high), 5- and 10-year OS rates were 94.3% and 85.9%, 92.3% and 79.2%, and 91.9% and 80.2% (p = 0.728). Five- and 10-year BRFS was 94.1% and 80.6% (low risk), 86.4% and 70.9% (intermediate), and 85.2% and 71.4% (high) (p = 0.0666). Toxicity included rectitis: grade 1 (G1) (277 pts; 32.6%), G2 (108; 12.7%), and G3 (20; 2.6%) and urethritis: G1 (294; 34.6%); G2 (223; 26.2%), and G3 (11; 1.3%). By dose rate (<76 Gy vs. ≥76 Gy), 5 and 10-year BRFS rates were 83.1% and 68.3% vs. 88.4% and 74.8% (p = 0.038).

CONCLUSIONS

Our results are comparable to other published series in terms of disease control and toxicity. These findings confirm the need for dose escalation to achieve better biochemical control and the benefits of ADT in high-risk PCa patients.

Parametrized rectal dose and associations with late toxicity in prostate cancer radiotherapy

OBJECTIVE

We investigated possible associations between planned dose-volume parameters and rectal late toxicity in 170 patients having radical prostate cancer radiotherapy.

METHODS

For each patient, the rectum was outlined from anorectal junction to sigmoid colon, and rectal dose was parametrized using dose-volume (DVH), dose-surface (DSH) and dose-line (DLH) histograms. Generation of DLHs differed from previous studies in that the rectal dose was parametrized without first unwrapping onto 2-dimensional dose-surface maps. Patient-reported outcomes were collected using a validated Later Effects in Normal Tissues Subjective, Objective, Management and Analytic questionnaire. Associations between dose and toxicity were assessed using a one-sided Mann-Whitney U test.

RESULTS

Associations (p < 0.05) were found between equieffective dose (EQD23) and late toxicity as follows: overall toxicity with DVH and DSH at 13-24 Gy; proctitis with DVH and DSH at 25-36 Gy and with DVH, DSH and DLH at 61-67 Gy; bowel urgency with DVH and DSH at 10-20 Gy. None of these associations met statistical significance following the application of a Bonferroni correction.

CONCLUSION

Independently confirmed associations between rectal dose and late toxicity remain elusive. Future work to increase the accuracy of the knowledge of the rectal dose, either by accounting for interfraction and intrafraction rectal motion or via stabilization of the rectum during treatment, may be necessary to allow for improved dose-toxicity comparisons.

ADVANCES IN KNOWLEDGE

This study is the first to use parametrized DLHs to study associations with patient-reported toxicity for prostate radiotherapy showing that it is feasible to model rectal dose mapping in three dimensions.

Hypofractionated helical tomotherapy (75 Gy at 2.5 Gy per fraction) for localized prostate cancer: long-term analysis of gastrointestinal and genitourinary toxicity

Background

This study is a report on the long-term analysis of acute and late toxicities for patients with localized prostate cancer treated with hypofractionated helical tomotherapy.

Methods

From January 2008 through August 2013, 70 patients with localized prostate cancer were treated definitively with hypofractionated helical tomotherapy. The helical tomotherapy was designed to deliver 75 Gy in 2.5 Gy per fraction to the prostate gland, 63 Gy in 2.1 Gy per fraction to the seminal vesicles, and 54 Gy in 1.8 Gy per fraction to the pelvic lymph nodes. Incidence rates and predictive factors for radiation toxicities were analyzed retrospectively.

Results

The incidences of grades 0, 1, and 2 acute gastrointestinal (GI) toxicity were 51.4%, 42.9%, and 5.7%, and those of acute genitourinary (GU) toxicity were 7.1%, 64.3%, and 28.6%, respectively. The maximum dose of rectum and bladder V40 and V50 were significant predictive factors for acute GI and GU toxicity. The cutoff value of rectum maximum dose and bladder V40 and V50 by receiver-operating characteristic curves analysis were 76.5 Gy, 17.3%, and 10.2%, respectively. The incidences of grades 0, 1, and 2 late GI toxicity were 82.0%, 14.0%, and 4.0%, and those of late GU toxicity were 18.0%, 56.0%, and 26.0%, respectively. Rectum V70 and bladder V70 and V75 were significant predictive factors for late GI and GU toxicity. The cutoff value of rectum V70 and bladder V70 and V75 by receiver-operating characteristic curves analysis was 2.8%, 2.8%, and 1.0%, respectively.

Conclusion

Hypofractionated helical tomotherapy using a schedule of 75 Gy at 2.5 Gy per fraction had favorable acute and late toxicity rates and no serious complication, such as grade 3 or worse toxicity. To minimize radiation toxicities, constraining the rectum maximum dose to less than 76.5 Gy, rectum V70 to less than 2.8%, bladder V40 to less than 17.3%, bladder V50 to less than 10.2%, bladder V70 to less than 2.8%, and bladder V75 to less than 1.0% would be necessary.

Optimal Local Control and Tolerability of Three-Dimensional Conformal Radiation Therapy in Prostate Cancer: A Single Institutional Experience of Dose Escalation in 125 Patients

Aims

To evaluate long-term late side effects, clinical and biochemical relapse in non-metastatic prostate cancer patients treated with dose escalation, from 74 to 78 Gy, by means of three dimensional conformal radiation therapy.

Materials and Methods

Clinical data of 125 patients with prostate cancer who underwent three-dimensional conformal radiation therapy were retrospectively evaluated. All patients were stratified, according to the NCCN classification, in low, intermediate and high risk, and all of them showed histologically proven adenocarcinoma stage T1–T3 with at least 2 years of follow-up. Late toxicity was analyzed using a modified Radiation Therapy Oncology Group toxicity scale.

Results

With a median of follow-up of 48 months, grade ≥2 late genitourinary toxicity was reported in 18% and grade ≥2 gastrointestinal toxicity was detected in 12%. The PSA relapse rate was 20% in the high-risk group, 7% in the intermediate-risk group, and 3% in the low-risk group.

Conclusions

Late side effects and tumor control in patients with non-metastatic prostate cancer in dose escalation from 74 to 78 Gy was acceptable. Three-dimensional conformal radiation therapy still represents a valid therapeutic option for departments where intensity-modulated radiation therapy or image-guided radiation therapy is still not available.

Optimal planning target volume margins for elective pelvic lymphatic radiotherapy in high-risk prostate cancer patients

Purpose. High-risk prostate cancer patients often receive radiotherapy (RT) to pelvic lymphatics (PLs). The aim of this study was to determine the safety margin around clinical target volume for PL (PL-CTV) to construct planning target volume for PL (PL-PTV) and for planning elective PL irradiation. Methods and Materials. Six patients who received RT to PL as part of prostate cancer treatment were identified. To determine average daily shifts of PL, the right and left IVs were contoured at 3 predetermined slices on the daily MV scans and their daily shifts were measured at these 3 levels using a measuring tool. Results. A total of 1,932 observations were made. Daily shifts of IV were random in distribution, and the largest observed shift was 13.6 mm in lateral and 15.4 mm in AP directions. The mean lateral and AP shifts of IV were 2.1 mm (±2.2) and 3.5 mm (±2.7), respectively. The data suggest that AP and lateral margins of 8.9 mm and 6.5 mm are necessary. Conclusions. With daily alignment to the prostate, we recommend an additional PL-CTV to PL-PTV conversion margin of 9 mm (AP) and 7 mm (lateral) to account for daily displacement of PL relative to the prostate.

Hypofractionated helical intensity-modulated radiotherapy (75 Gy at 2.5 Gy/fraction) for intermediate- and high-risk prostate cancer: Assessment of toxicity

Purpose: To evaluate the toxicity of hypofractionated helical intensity-modulated radiotherapy (IMRT) for men with intermediate- and high-risk prostate cancer.

Methods and Materials: A retrospective toxicity analysis was performed in 22 patients treated definitively with hypofractionated helical IMRT. The helical IMRT were designed to deliver 75 Gy in 2.5 Gy/fraction to the prostate gland, 63 Gy in 2.1 Gy/fraction to seminal vesicle, and 54 Gy in 1.8 Gy/fraction to pelvic lymph nodes. No patient received hormonal therapy. Toxicity was graded by the Radiation Therapy Oncology Group (RTOG) scales.

Results: All patients tolerated the treatment well without treatment interruption, and there was no Grade 3 or more acute toxicity. With a median follow-up of 24.5 months, there was no Grade 3 or more late toxicity. The late Grade 2 gastrointestinal (GI) and genitourinary (GU) toxicity for total 22 patients were 9.1% and 18.2%, respectively, and the late Grade 1 GI and GU toxicity were 18.2% and 50%, respectively. Late GU toxicity was associated with greater bladder volume irradiated ≥70 Gy. Late GI toxicity did not correlate with any of the dosimetric parameters.

Conclusions: This study demonstrate that hypofractionated helical IMRT with high biologic effective dose (BED) is well tolerated with favourable toxicity rate. If longer follow-up periods and larger cohorts confirm the favourable biochemical control rate and our favourable toxicity assessment results, the hypofractionated IMRT (total 75 Gy, 2.5 Gy/fraction) might be implemented in clinical field for treatment of prostate cancer.

An evaluation of the Clarity 3D ultrasound system for prostate localization

The purpose of this study is to evaluate the accuracy and precision of the Clarity 3D ultrasound system to track prostate gland positional variations due to setup error and organ motion. Seventeen patients (n = 17) undergoing radical external beam radiation therapy for localized prostate cancer were studied. Subsequent to initial reference ultrasound and planning CT scans, each patient underwent seven repeat weekly tracking CT and ultrasound (US) scans during the course of treatment. Variations in the location of the prostate between reference and tracking scans were measured. Differences reported by CT and ultrasound scans are compared. Ultrasound tracking was initially performed clinically by a group of trained general users. Retrospective prostate localization was then performed by a trained dedicated user upon the original raw data set and also a reduced data set derived from the original by an expert user from Resonant Medical. Correlation accuracy between ultrasound and CT shifts acquired and delineated by a pool of trained general users was deemed unacceptable for radiotherapy purposes. A mean discrepancy between CT and US localizations of greater than 10 mm, with a 5 mm or greater discrepancy rate of nearly 90%, was observed. Retrospective analysis by a dedicated user of both the original and Resonant Medical reduced data sets yielded mean CT-Us discrepancies of 8.7 mm and 7.4 mm, respectively. Unfortunately, the 5 mm or greater CT-US discord rate for these retrospective analyses failed to drop below 80%. The greatest disparity between CT and ultrasound was consistently observed in the superior-inferior direction, while greatest agreement was achieved in the lateral dimension. Despite an expert reanalysis of the original data, the Clarity ultrasound system failed to deliver an acceptable level of geometric accuracy required for modern radiotherapy purposes.

A retrospective study on accessibility of palliative radiation therapy in the management of prostate cancer in British Columbia

Timely administration of palliative radiation therapy (PRT) to manage symptoms derived from advanced prostate cancer is necessary to help alleviate discomfort and improve quality of life. Despite PRT being an effective treatment, analyzing utilization rates in British Columbia (BC), Canada for palliative purposes implies it is an under-utilized medical resource. Access to and utilization of radiation therapy (RT) is lower in remote geographical regions and higher in urban regions where a cancer care facility is close in proximity suggesting the presence of geographical barrier affecting access to health care and services. Equitable access to PRT can be achieved by reducing barriers such as geographical distance. This retrospective cohort study describes accessibility of PRT in the management of prostate cancer and the impact of an additional facility on improving access to PRT.

CyberKnife stereotactic radiotherapy as monotherapy for low- to intermediate-stage prostate cancer: early experience, feasibility, and tolerance

PURPOSE

The CyberKnife (CK), a linear accelerator mounted on a robotic device, enables excellent dose conformation to the target and minimizes dose to surrounding normal tissue. It is a very suitable device for performing hypofractionated stereotactic body radiotherapy as monotherapy for low- to intermediate-risk prostate cancer patients. We report our early experience using this technique.

MATERIALS AND METHODS

Between June 2008 and June 2009, 10 patients underwent CK monotherapy as treatment for their prostate cancer (stage <or=T2b, Gleason score (GS) <or=7, initial PSA <or=15 microg/L). The prescribed dose was 38 Gy in four daily fractions of 9.5 Gy. The International Prostate Symptom Score and Radiation Therapy Oncology Group symptom scale were prospectively administered before and at 0.5, 1, 2, 3, 6, and 12 months.

RESULTS

Median age of the patients was 71 years (range, 66-76). Three patients had stage T2a and 7a T1c disease, one patient had GS of 7, and all others had GS of 6. Median follow-up was 5.1 months. Median initial PSA was 8.3 ng/mL (range, 1.3-13.6 ng/mL). Median planning target volume delineated on computed tomography after matching with the magnetic resonance imaging scan was 107 cc (range, 42-158 cc). The median V100 of the prostate was 95.8% (range, 94.8-97.2). The D95 of the prostate was 38.3 Gy (range, 38.1-38.8 Gy). The constraints for the bladder, rectum, and urethra were well met. The International Prostate Symptom Scores after 3 months were stable compared with the pretreatment scores. Urinary and bowel Radiation Therapy Oncology Group symptoms were mild and within the expected levels.

CONCLUSIONS

This regimen of stereotactic CK monotherapy for low- to intermediate-risk prostate cancer with excellent dose coverage of the prostate was well tolerated. Data collection is ongoing for further assessment of toxicity and PSA response.

Radiobiological impact of reduced margins and treatment technique for prostate cancer in terms of tumor control probability (TCP) and normal tissue complication probability (NTCP)

Dose escalation in prostate radiotherapy is limited by normal tissue toxicities. The aim of this study was to assess the impact of margin size on tumor control and side effects for intensity-modulated radiation therapy (IMRT) and 3D conformal radiotherapy (3DCRT) treatment plans with increased dose. Eighteen patients with localized prostate cancer were enrolled. 3DCRT and IMRT plans were compared for a variety of margin sizes. A marker detectable on daily portal images was presupposed for narrow margins. Prescribed dose was 82 Gy within 41 fractions to the prostate clinical target volume (CTV). Tumor control probability (TCP) calculations based on the Poisson model including the linear quadratic approach were performed. Normal tissue complication probability (NTCP) was calculated for bladder, rectum and femoral heads according to the Lyman-Kutcher-Burman method. All plan types presented essentially identical TCP values and very low NTCP for bladder and femoral heads. Mean doses for these critical structures reached a minimum for IMRT with reduced margins. Two endpoints for rectal complications were analyzed. A marked decrease in NTCP for IMRT plans with narrow margins was seen for mild RTOG grade 2/3 as well as for proctitis/necrosis/stenosis/fistula, for which NTCP <7% was obtained. For equivalent TCP values, sparing of normal tissue was demonstrated with the narrow margin approach. The effect was more pronounced for IMRT than 3DCRT, with respect to NTCP for mild, as well as severe, rectal complications.

A new method for synthesizing radiation dose-response data from multiple trials applied to prostate cancer

PURPOSE

A new method is presented for synthesizing dose-response data for biochemical control of prostate cancer according to study design (randomized vs. nonrandomized) and risk group (low vs. intermediate-high).

METHODS AND MATERIALS

Nine published prostate cancer dose escalation studies including 6,539 patients were identified in the MEDLINE and CINAHL databases and reviewed to assess the relationship between dose and biochemical control. A novel method of analysis is presented in which the normalized dose-response gradient, gamma(50), is estimated for each study and subsequently synthesized across studies. Our method does not assume that biochemical control rates are directly comparable between studies.

RESULTS

Nonrandomized studies produced a statistically significantly higher gamma(50) than randomized studies for intermediate- to high-risk patients (gamma(50) = 1.63 vs. gamma(50) = 0.93, p = 0.03) and a borderline significantly higher (gamma(50) = 1.78 vs. gamma(50) = 0.56, p = 0.08) for low-risk patients. No statistically significant difference in gamma(50) was found between low- and intermediate- to high-risk patients (p = 0.31). From the pooled data of low and intermediate- to high-risk patients in randomized trials, we obtain the overall best estimate of gamma(50) = 0.84 with 95% confidence interval 0.54-1.15.

CONCLUSIONS

Nonrandomized studies overestimate the steepness of the dose-response curve as compared with randomized trials. This is probably the result of stage migration, improved treatment techniques, and a shorter follow-up in higher dose patients that were typically entered more recently. This overestimation leads to inflated expectations regarding the benefit from dose-escalation and could lead to underpowered clinical trials. There is no evidence of a steeper dose response for intermediate- to high-risk compared with low-risk patients.

A prediction study on radiation-induced second malignancies for IMRT treatment delivery

Low-level peripheral organ dose and its effect on second malignancies for patients undergoing radiation therapy have been reported in the literature. However, a comprehensive database outlining the treatment modalities, the tumor location, and a quantification of the overall relative risk of second malignancies is rather limited. In this work, we quantify the relative risks or percent likelihood of second malignancies for patients undergoing IMRT and conventional radiotherapy for four different tumor sites: breast, head and neck, lung, and prostate. We utilize Monte Carlo methods based on actual patient plans to compute the whole body effective dose equivalent for each plan and then deduce the percent likelihood of the occurrence of second malignancy. Based on an evaluation of over 30 actual patient plans and Monte Carlo simulations using 6, 10, and 18MV photon beam energies, we observed that the IMRT patients treated for head and neck cancer showed a 40% increase in risk for developing a second malignancy compared to those treated with conventional radiotherapy. The increase in risk for prostrate patients was 30% while the IMRT lung patients gave the highest relative risk almost tripling that observed in their conventionally treated counterparts. There was negligible difference in risk between breast patients undergoing IMRT treatment versus conventional therapy. The overall relative risk of radiation induced malignancy observed was below 6% in all treatment plans considered.

Conventional treatments of localized prostate cancer

Established therapeutic approaches for clinically localized prostate cancer include watchful waiting (active surveillance), radical prostatectomy, and radiotherapy. The risk of progression during surveillance is related to the initial cancer stage and grade; reasonable evidence has supported the safety and feasibility, during a period of 5-10 years, of an active surveillance regimen for men with low-risk prostate cancer. The progression rates at >10 years have not yet been studied in modern trials. Patients with low-risk tumor characteristics can be actively monitored without sacrificing the possibility of cure and without being exposed to an undue risk of disease progression, although some patients will not accept the emotional burden of living with an untreated cancer. Focal ablation might be an attractive alternative to active surveillance for some patients with low-risk cancer, if it proves to have minimal adverse effects on their quality of life. Radical prostatectomy is an effective form of therapy for patients with clinically significant prostate cancer; however, outcomes are highly sensitive to variations in surgical technique. Because of the risks of perioperative complications and urinary and sexual dysfunction, which appear to be as great with robotic-assisted prostatectomy as with any other technique, patients with low-risk cancer, especially those >60 years, might be attracted to more conservative alternatives, including active surveillance, radiotherapy, and focal ablation. External beam radiotherapy is an effective, noninvasive form of therapy, but it carries the long-term risks of troublesome bowel and sexual and urinary dysfunction. It might be too aggressive for many low-risk cancers detected in screened populations. For more aggressive cancers, local recurrence after radiotherapy carries substantial morbidity and low rates of long-term cancer control. Brachytherapy, a convenient, effective form of radiotherapy, is targeted at selected patients with clinically confined cancer and a prostate size of <60 g without evidence of extraprostatic extension on imaging. However, excellent outcomes require meticulous technique; acute urinary symptoms are frequent; and the long-term risks of proctitis and erectile dysfunction are comparable to the risks associated with external beam radiotherapy. Androgen-deprivation therapy is not recommended for men with localized prostate cancer who would otherwise be candidates for surgery or radiotherapy, because, even with short-term use, the risk of side effects, including osteopenic fracture and major cardiovascular events, serious. For locally extensive cancer, androgen-deprivation therapy should be used alone only for the relief of local symptoms in men with a life expectancy of <5 years who are not eligible for more aggressive treatment.

Dynamic conformal arc radiotherapy with rectum hollow-out technique for localized prostate cancer

PURPOSE

To report the feasibility of dynamic conformal arc radiotherapy with rectum hollow-out technique (DCAT-HO) for localized prostate cancer.

METHODS AND MATERIALS

Between October 2000 and April 2007, 204 patients with clinically localized or locally advanced prostate cancer were treated with DCAT-HO. All patients were given neoadjuvant total androgen deprivation (AD) therapy (median 6 months, range 2-27 months). All patients with T3 or T4 stage received post-irradiation AD for 24 months. A total of 128 patients (63%) were treated with 70Gy, and 76 patients (37%) were treated with 74Gy. Acute and late toxicities were scored by the Radiation Therapy Oncology Group morbidity grading scales. PSA relapse was defined as three successive PSA elevations after a post-treatment nadir. The median follow-up was 37 months.

RESULTS

Both the acute Grade 2 rectal and urinary toxicities were 1.0%, and no patients experienced acute Grade 3 or higher symptoms. The 3-year rates of both late Grade 2 rectal and urinary toxicities were 3.4%. The 3-year PSA relapse-free survival for low, intermediate, and high-risk group patients treated with 70 Gy were 54%, 75%, and 87%, respectively.

CONCLUSIONS

These findings demonstrate the feasibility of DCAT-HO in a large number of patients with short follow-up. DCAT-HO reduced the volume of the rectum exposed to higher doses and this led to an overall reduction in late rectal toxicity.

Leuprorelin depot injection: patient considerations in the management of prostatic cancer

Hormone therapy is well established for treating patients with prostate cancer and remains the mainstay of the treatment of metastatic and locally advanced disease, this article reviews the rationale for its use, its different forms, and complications and controversies still surrounding some of its modalities. Availability of long-acting synthetic luteinizing hormone-releasing hormone (LHRH) agonists revolutionized the hormonal treatment of prostate cancer, and helped to avoid the emotional and psychological effects related to surgical castration. The depot formula has gained wide acceptance from both patients and physicians. This review emphasizes the newer, long-acting formula, leuprorelin (leuprolide acetate), especially the 6-month formula, its advantage over over shorter-acting depot products, and its potential to become a standard of care for patients eligible for androgen deprivation therapy.

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

PURPOSE

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

METHODS AND MATERIALS

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

RESULTS

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

CONCLUSIONS

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

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

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

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

PURPOSE

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

METHODS AND MATERIALS

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

RESULTS

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

CONCLUSION

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

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

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

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

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

PACS: 87.53.wz, 87.53.‐j

Quantification des mouvements prostatiques lors de l'irradiation prostatique

Decrease treatment uncertainties is one of the most important challenge in radiation oncology. Numerous techniques are available to quantify prostate motion and visualise prostate location day after day before each irradiation: CT-scan, cone-beam-CT-Scan, ultrason, prostatic markers... The knowledge of prostate motion is necessary to define the minimal margin around the target volume needed to avoid mispositioning during treatment session. Different kind of prostate movement have been studied and are reported in the present work: namely, those having a large amplitude extending through out the whole treatment period on one hand; and those with a shorter amplitude happening during treatment session one the other hand. The long lasting movement are mostly anterior-posterior (3 mm standard deviation), secondary in cranial-caudal (1-2 mm standard deviation) and lateral directions (0.5-1 mm standard deviation). They are mostly due to the rectal state of filling and mildly due to bladder filling or inferior limbs position. On the other hand, the shorter movement that occurs during the treatment session is mostly variation of position around a steady point represented by the apex. Ones again, the rectal filling state is the principle cause. This way, during the 20 minutes of a treatment session, including the positioning of the patient, a movement of less than 3 mm could be expected when the rectum is empty. Ideally, real time imaging tools should allow an accurate localisation of the prostate and the adaptation of the dosimetry before each treatment session in a time envelope not exceeding 20 minutes.

Long-term outcome of high dose intensity modulated radiation therapy for patients with clinically localized prostate cancer

PURPOSE

We report on the long-term results and late toxicity outcomes of high dose intensity modulated radiation therapy for patients with clinically localized prostate cancer.

MATERIALS AND METHODS

Between 1996 and 2000 a total of 561 patients with clinically localized prostate cancer were treated with intensity modulated radiation therapy. All patients were treated to a dose of 81 Gy prescribed to the planning target volume. Prostate specific antigen relapse was defined according to the American Society for Therapeutic Radiology and Oncology consensus and Houston definitions (absolute nadir plus 2 ng/ml dated at the call). Median followup was 7 years (range 5 to 9).

RESULTS

The 8-year actuarial PSA relapse-free survival rates for patients in favorable, intermediate and unfavorable risk groups according to the American Society for Therapeutic Radiology and Oncology definition were 85%, 76% and 72%, respectively (p <0.025). The 8-year actuarial prostate specific antigen relapse-free survival rates for patients in favorable, intermediate and unfavorable risk groups according to the Houston definition were 89%, 78% and 67%, respectively (p = 0.0004). The 8-year actuarial likelihood of grade 2 rectal bleeding was 1.6%. Three patients (0.1%) experienced grade 3 rectal toxicity requiring either 1 or more transfusions or a laser cauterization procedure. No grade 4 rectal complications have been observed. The 8-year likelihood of late grade 2 and 3 (urethral strictures) urinary toxicities were 9% and 3%, respectively. Among patients who were potent before intensity modulated radiation therapy, erectile dysfunction developed in 49%. The cause specific survival outcomes for favorable, intermediate and unfavorable risk cases were 100%, 96% and 84%, respectively.

CONCLUSIONS

These long-term results confirm our previous observations regarding the safety of high dose intensity modulated radiation therapy for clinically localized prostate cancer. Despite the application of high radiation doses, the incidence of rectal bleeding at 8 years was less than 2%. Despite the increased conformality of the dose distribution associated with intensity modulated radiation therapy, excellent long-term tumor control outcomes were achieved.

Use of different definitions of biochemical failure after external beam radiotherapy changes conclusions about relative treatment efficacy for localized prostate cancer

OBJECTIVES

To report biochemical relapse-free survival (bRFS) after radiotherapy (RT) for localized prostate cancer with two separate failure definitions and compare the results with those after radical prostatectomy (RP).

METHODS

The study sample comprised 2516 patients with a median follow-up of 78 months. Biochemical relapse after RT was defined as either the American Society for Therapeutic Radiology Oncology definition (definition A [DefA]) or a prostate-specific antigen elevation of more than 2 ng/mL greater than the nadir prostate-specific antigen level (definition N [DefN]). Failure after RP was defined as a prostate-specific antigen level greater than 0.2 ng/mL.

RESULTS

Compared with DefA, DefN resulted in a 13% greater bRFS rate at 5 years and a 12% lower bRFS rate at 10 years. On multivariate analysis, the treatment modality (RP versus RT) was a significant predictor of bRFS using DefA in favor of RP (P <0.001), but was not with DefN (P = 0.87). Higher radiation doses were independently associated with a better outcome with either definition.

CONCLUSIONS

Compared with DefA, DefN resulted in better outcomes for up to 7 years after RT, but worse outcomes thereafter. The use of DefA versus DefN resulted in opposite conclusions about the relative efficacies of RT and RP, with DefN suggesting RT is equivalent to RP and DefA that it is worse than RP. Different definitions of biochemical failure after RT can result in differences in the conclusions about treatment efficacy in men with localized prostate cancer, thereby potentially affecting clinical decisions.

Update on Radiation Therapy in Prostate Cancer

Higher doses of radiation result in improved clinical control of prostate cancer,and the recent advances in prostate cancer radiotherapy are designed to escalate dose while minimizing toxicity. To achieve this goal, tighter treatment margins are needed, which require more accurate delineation of the prostate target and normal tissue at the time of treatment planning and before actual daily treatments. Modem radiation therapy techniques can deposit conformal dose virtually anywhere in the body; however, this precise therapy is of no value if it is not accurately hitting the target. Whether dose escalation is achieved by external beam techniques (eg, IMRT, protons) or brachytherapy, these ba-sic planning and delivery considerations are essentially the same. Future directions in prostate radiation therapy will use even higher radiation doses,alternative fractionation patterns, intraprostatic targets (eg, prostate tumor seen on MRI), and improved patient selection regarding which patients will benefit the most from these advanced techniques.

Radiothérapie conformationnelle du cancer de la prostate : technique et résultats

A number of retrospective and prospective studies have demonstrated that radiotherapy of prostate cancer must be actually conformal. Three-dimensional (3D) treatment planning consists in an as accurate as possible definition of target-volume, usually by CT-scan, and design of radiation fields shaped to this target-volume. Several steps are required, each step being important for the overall quality of the treatment. Conformal radiotherapy is better tolerated than conventional irradiation, with significantly less rectal toxicity. It allows dose-escalation up to 80 Gy. It is now possible to go beyond this dose with intensity-modulated radiotherapy. The benefit of these high doses was demonstrated by some large retrospective studies and some prospective dose-escalation trials. Several randomized trials are in progress, preliminary results of two of them have been published, both showing an improvement in disease control with the higher doses. The advantage of higher doses is clearly evident for patients in the intermediate prognostic group, but is still discussed for patients with a low risk tumour or treated in combination with hormone therapy. Late proctitis is the main toxicity of these high doses. Some volume constraints have been defined during the last years and will allow a decrease of the rate of rectal toxicity. Because of these technological improvements, results of radiation therapy are now similar to those of surgery: no direct comparison with a randomized trial is available, but large comparative studies show that long-term disease control are identical with both techniques. Radiation therapy must be proposed to all patients with a prostate carcinoma as an alternative to surgery.

A comparison of CT- and ultrasound-based imaging to localize the prostate for external beam radiotherapy

PURPOSE

This study assesses the accuracy of NOMOS B-mode acquisition and targeting system (BAT) compared with computed tomography (CT) in localizing the prostate.

METHODS AND MATERIALS

Twenty-six patients were CT scanned, and the prostate was localized by 3 observers using the BAT system. The BAT couch shift measurements were compared with the CT localization. Six of the patients had gold markers present in the prostate, and the prostate movement determined by BAT was compared with the movement determined by the gold markers.

RESULTS

Using the BAT system, the 3 observers determined the prostate position to be a mean of 1-5 mm over all directions with respect to the CT. The proportion of readings with a difference >3 mm between the observers was in the range of 25% to 44%. The prostate movement based on gold markers was an average of 3-5 mm different from that measured by BAT. The literature assessing the accuracy and reproducibility on BAT is summarized and compared with our findings.

CONCLUSIONS

We have found that there are systematic differences between the BAT-defined prostate position compared with that estimated on CT using gold grain marker seeds.

Clinicopathologic analysis of extracapsular extension in prostate cancer: Should the clinical target volume be expanded posterolaterally to account for microscopic extension?

PURPOSE

We performed a complete pathologic analysis examining extracapsular extension (ECE) and microscopic spread of malignant cells beyond the prostate capsule to determine whether and when clinical target volume (CTV) expansion should be performed.

METHODS AND MATERIALS

A detailed pathologic analysis was performed for 371 prostatectomy specimens. All slides from each case were reviewed by a single pathologist (N.S.G.). The ECE status and ECE distance, defined as the maximal linear radial distance of malignant cells beyond the capsule, were recorded.

RESULTS

A total of 121 patients (33%) were found to have ECE (68 unilateral, 53 bilateral). Median ECE distance=2.4 mm [range: 0.05-7.0 mm]. The 90th-percentile distance = 5.0 mm. Of the 121 cases with ECE, 55% had ECE distance>or=2 mm, 19%>or=4 mm, and 6%>or=6 mm. ECE occurred primarily posterolaterally along the neurovascular bundle in all cases. Pretreatment prostrate-specific antigen (PSA), biopsy Gleason, pathologic Gleason, clinical stage, bilateral involvement, positive margins, percentage of gland involved, and maximal tumor dimension were associated with presence of ECE. Both PSA and Gleason score were associated with ECE distance. In all 371 patients, for those with either pretreatment PSA>or=10 or biopsy Gleason score>or=7, 21% had ECE>or=2 mm and 5%>or=4 mm beyond the capsule. For patients with both of these risk factors, 49% had ECE>or=2 mm and 21%>or=4 mm.

CONCLUSIONS

For prostate cancer with ECE, the median linear distance of ECE was 2.4 mm and occurred primarily posterolaterally. Although only 5% of patients demonstrate ECE>4 to 5 mm beyond the capsule, this risk may exceed 20% in patients with PSA>or=10 ng/ml and biopsy Gleason score>or=7. As imaging techniques improve for prostate capsule delineation and as radiotherapy delivery techniques increase in accuracy, a posterolateral CTV expansion should be considered for patients at high risk.

Outcome analysis of 300 prostate cancer patients treated with neoadjuvant androgen deprivation and hypofractionated radiotherapy

PURPOSE

Neoadjuvant androgen deprivation and radical radiotherapy is an established treatment for localized prostate carcinoma. This study sought to analyze the outcomes of patients treated with relatively low-dose hypofractionated radiotherapy.

METHODS AND MATERIALS

Three hundred patients with T1-T3 prostate cancer were treated between 1996 and 2001. Patients were prescribed 3 months of neoadjuvant androgen deprivation before receiving 5250 cGy in 20 fractions. Patients' case notes and the oncology database were used to retrospectively assess outcomes. Median follow-up was 58 months.

RESULTS

Patients presented with prostate cancer with poorer prognostic indicators than that reported in other series. At 5 years, the actuarial cause-specific survival rate was 83.2% and the prostate-specific antigen (PSA) relapse rate was 57.3%. Metastatic disease had developed in 23.4% of patients. PSA relapse continued to occur 5 years from treatment in all prognostic groups. Independent prognostic factors for relapse included treatment near the start of the study period, neoadjuvant oral anti-androgen monotherapy rather than neoadjuvant luteinizing hormone releasing hormone therapy, and diagnosis through transurethral resection of the prostate rather than transrectal ultrasound.

CONCLUSION

This is the largest reported series of patients treated with neoadjuvant androgen deprivation and hypofractionated radiotherapy in the United Kingdom. Neoadjuvant hormonal therapy did not appear to adequately compensate for the relatively low effective radiation dose used.

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.

Dose-Response in Radiotherapy for Localized Prostate Cancer: Results of the Dutch Multicenter Randomized Phase III Trial Comparing 68 Gy of Radiotherapy With 78 Gy

Purpose

To determine whether a dose of 78 Gy improves outcome compared with a conventional dose of 68 Gy for prostate cancer patients treated with three-dimensional conformal radiotherapy.

Patients and Methods

Between June 1997 and February 2003, stage T1b-4 prostate cancer patients were enrolled onto a multicenter randomized trial comparing 68 Gy with 78 Gy. Patients were stratified by institution, age, (neo)adjuvant hormonal therapy (HT), and treatment group. Four treatment groups (with specific radiation volumes) were defined based on the probability of seminal vesicle involvement. The primary end point was freedom from failure (FFF). Failure was defined as clinical failure or biochemical failure, according to the American Society of Therapeutic Radiation Oncology definition. Other end points were freedom from clinical failure (FFCF), overall survival (OS), and toxicity.

Results

Median follow-up time was 51 months. Of the 669 enrolled patients, 664 were included in the analysis. HT was prescribed for 143 patients. FFF was significantly better in the 78-Gy arm compared with the 68-Gy arm (5-year FFF rate, 64% v 54%, respectively), with an adjusted hazard ratio of 0.74 (P = .02). No significant differences in FFCF or OS were seen between the treatment arms. There was no difference in late genitourinary toxicity of Radiation Therapy Oncology Group and European Organisation for Research and Treatment of Cancer grade 2 or more and a slightly higher nonsignificant incidence of late gastrointestinal toxicity of grade 2 or more.

Conclusion

This multicenter randomized trial shows a significantly improved FFF in prostate cancer patients treated with a higher dose of radiotherapy.

Cluster model analysis of late rectal bleeding after IMRT of prostate cancer: a case-control study

PURPOSE

Cluster models are newly developed normal-tissue complication probability models in which the spatial aspects of radiation-induced injury are taken into account by considering the size of spatially contiguous aggregates of damaged tissue units. The purpose of this study was to test the validity of a two-dimensional cluster model of late rectal toxicity based on maximum cluster size of damage to rectal surface.

METHODS AND MATERIALS

A paired case-control study was performed in which each of 9 patients experiencing Grade 2 or higher late rectal toxicity after intensity-modulated radiation therapy of localized prostate cancer was paired with a patient having a similar rectal dose-surface histogram but free of rectal toxicity. Numeric simulations were performed to determine the distribution of maximum cluster size on each rectal surface for each of many different choices of possible model parameters.

RESULTS

Model parameters were found for which patients with rectal toxicity were consistently more likely to have a significantly larger mean maximum cluster size than their matched controls. These parameter values correspond to a 50% probability of tissue-unit damage at doses near 30 Gy.

CONCLUSIONS

This study suggests that a cluster model based on maximum cluster size of damage to rectal surface successfully incorporates spatial information beyond that contained in the rectal dose-surface histogram and may therefore provide a useful new tool for predicting rectal normal-tissue complication probability after radiotherapy.

Radiotherapeutic techniques for prostate cancer, dose escalation and brachytherapy

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

Prostate gland motion assessed with cine-magnetic resonance imaging (cine-MRI)

PURPOSE

To quantify prostate motion during a radiation therapy treatment using cine-magnetic resonance imaging (cine-MRI) for time frames comparable to that expected in an image-guided radiation therapy treatment session (20-30 min).

MATERIALS AND METHODS

Six patients undergoing radiation therapy for prostate cancer were imaged on 3 days, over the course of therapy (Weeks 1, 3, and 5). Four hundred images were acquired during the 1-h MRI session in 3 sagittal planes through the prostate at 6-s intervals. Eleven anatomic points of interest (POIs) have been used to characterize prostate/bony pelvis/abdominal wall displacement. Motion traces and standard deviation for each of the 11 POIs have been determined. The probability of displacement over time has also been calculated.

RESULTS

Patients were divided into 2 groups according to rectal filling status: full vs. empty rectum. The displacement of POIs (standard deviation) ranged from 0.98 to 1.72 mm for the full-rectum group and from 0.68 to 1.04 mm for the empty-rectum group. The low standard deviations in position (2 mm or less) would suggest that these excursions have a low frequency of occurrence. The most sensitive prostate POI to rectal wall motion was the mid-posterior with a standard deviation of 1.72 mm in the full-rectum group vs. 0.79 mm in the empty-rectum group (p = 0.0001). This POI has a 10% probability of moving more than 3 mm in a time frame of approximately 1 min if the rectum is full vs. approximately 20 min if the rectum is empty.

CONCLUSION

Motion of the prostate and seminal vesicles during a time frame similar to a standard treatment session is reduced compared to that reported in interfraction studies. The most significant predictor for intrafraction prostate motion is the status of rectal filling. A prostate displacement of <3 mm (90%) can be expected for the 20 min after the moment of initial imaging for patients with an empty rectum. This is not the case for patients presenting with full rectum. The determination of appropriate intrafraction margins in radiation therapy to accommodate the time-dependent uncertainty in positional targeting is a topic of ongoing investigations for the on-line image guidance model.

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

PURPOSE

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

METHODS AND MATERIALS

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

RESULTS

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

CONCLUSIONS

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

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.

High Dose Rate (HDR) Brachytherapy with Conformal Radiation Therapy for Localized Prostate Cancer

OBJECTIVES

To evaluate the outcome of high dose rate (HDR) brachytherapy with iridium 192 (Ir(192)) and 3D conformal external beam radiotherapy in patients with localized prostate cancer.

METHODS

A total of 442 patients with localized prostate cancer underwent combined radiotherapy with interstitial brachytherapy with Ir(192) and 3D conformal external beam radiotherapy between December 1992 and March 2001. Patients underwent laparoscopic pelvic lymph node dissection to exclude patients with lymphatic involvement. Iridium 192 was delivered twice with a one-week interval in afterloading technique. 247 patients (56%) had clinical T3 disease and 128 patients (29%) had an initial PSA of more than 20 ng/ml. Progression was defined as biochemical failure according to ASTRO criteria. Patients were divided according to pretreatment variables that independently affected prostate-specific antigen (PSA) relapse-free survival in three risk groups. Low risk was defined as cT1c-cT2 and G1-G2 and PSA<10 ng/ml (n=94). Intermediate risk included patients with cT1c-cT2 and G1-G2 and PSA between 10 and 20 ng/ml (n=53). High risk group patients were cT3 or G3 or PSA>20 ng/ml (n=295).

RESULTS

Median follow-up was 5 years. Late grade 3-4 complications according to RTOG/EORTC criteria occurred in 50 patients (11%). The initial PSA value decreased from median 11.8 ng/ml to 0.98 ng/ml 12 months after treatment, to 0.3 ng/ml after 60 months and to 0.1 ng/ml 10 years after therapy. 53% of the patients (n=235) reached a PSA nadir of 0.5 ng/ml. 66 patients (15%) had a local recurrence, 54 (12%) developed systemic disease and 12 (3%) had both local and systemic failure. The progression free survival rate was 65% at 5-year follow-up. Five-year progression free survival was 81% in the low risk group, 65% in the intermediate risk group and 59% in the high risk group. Five-year overall survival was 87% and 5-year disease specific survival 94%. Initial PSA value, risk group and age were significantly related to progression free survival.

CONCLUSIONS

Combined HDR brachytherapy with Iridium 192 is an alternative treatment option for patients with localized prostate cancer. Initial PSA value, risk group, and age are important prognostic factors for progression free survival.

Dose–response characteristics of low- and intermediate-risk prostate cancer treated with external beam radiotherapy

PURPOSE

In this era of dose escalation, the benefit of higher radiation doses for low-risk prostate cancer remains controversial. For intermediate-risk patients, the data suggest a benefit from higher doses. However, the quantitative characterization of the benefit for these patients is scarce. We investigated the radiation dose-response relation of tumor control probability in low-risk and intermediate-risk prostate cancer patients treated with radiotherapy alone. We also investigated the differences in the dose-response characteristics using the American Society for Therapeutic Radiology and Oncology (ASTRO) definition vs. an alternative biochemical failure definition.

METHODS AND MATERIALS

This study included 235 low-risk and 387 intermediate-risk prostate cancer patients treated with external beam radiotherapy without hormonal treatment between 1987 and 1998. The low-risk patients had 1992 American Joint Committee on Cancer Stage T2a or less disease as determined by digital rectal examination, prostate-specific antigen (PSA) levels of < or =10 ng/mL, and biopsy Gleason scores of < or =6. The intermediate-risk patients had one or more of the following: Stage T2b-c, PSA level of < or =20 ng/mL but >10 ng/mL, and/or Gleason score of 7, without any of the following high-risk features: Stage T3 or greater, PSA >20 ng/mL, or Gleason score > or =8. The logistic models were fitted to the data at varying points after treatment, and the dose-response parameters were estimated. We used two biochemical failure definitions. The ASTRO PSA failure was defined as three consecutive PSA rises, with the time to failure backdated to the mid-point between the nadir and the first rise. The second biochemical failure definition used was a PSA rise of > or =2 ng/mL above the current PSA nadir (CN + 2). The failure date was defined as the time at which the event occurred. Local, nodal, and distant relapses and the use of salvage hormonal therapy were also failures.

RESULTS

On the basis of the ASTRO definition, at 5 years after radiotherapy, the dose required for 50% tumor control (TCD(50)) for low-risk patients was 57.3 Gy (95% confidence interval [CI], 47.6-67.0). The gamma50 was 1.4 (95% CI, -0.1 to 2.9) around 57 Gy. A statistically significant dose-response relation was found using the ASTRO definition. However, no dose-response relation was noted using the CN + 2 definition for these low-risk patients. For the intermediate-risk patients, using the ASTRO definition, the TCD(50) was 67.5 Gy (95% CI, 65.5-69.5) Gy and the gamma50 was 2.2 (95% CI, 1.1-3.2) around TCD(50). Using the CN + 2 definition, the TCD(50) was 57.8 Gy (95% CI, 49.8-65.9) and the gamma50 was 1.4 (95% CI, 0.2-2.5). Recursive partitioning analysis identified two subgroups within the low-risk group, as well as the intermediate-risk group: PSA level <7.5 vs. > or =7.5 ng/mL. Most of the benefit from the higher doses for the low- and intermediate-risk group was derived from the patients with the higher PSA values. For the low-risk group, the dose-response curves essentially plateaued at 78 Gy.

CONCLUSION

A dose-response relation was found using the ASTRO definition for low-risk prostate cancer. However, we found only marginal or no dose-response relation when the CN + 2 definition was used. Most of the benefit from the higher doses derived from low-risk patients with higher PSA levels. In all cases, little projected gain appears to exist at doses >78 Gy for these patients. A dose-response relation was noted for the intermediate-risk patients using either the CN + 2 or ASTRO definition. Most of the benefit from the higher doses also derived from the intermediate-risk patients with higher PSA levels. Some room for improvement appears to exist with additional dose increases in this group.

Randomized Trial Comparing Iridium Implant Plus External-Beam Radiation Therapy With External-Beam Radiation Therapy Alone in Node-Negative Locally Advanced Cancer of the Prostate

Purpose

To determine if iridium implant (IM) and external-beam radiation therapy (EBRT) is better than standard EBRT in locally advanced prostate cancer.

Methods

Patients with T2 and T3 prostate cancer with no evidence of metastatic disease were randomly assigned to EBRT of 66 Gy in 33 fractions during 6.5 weeks or to IM of 35 Gy delivered to the prostate during 48 hours plus EBRT of 40 Gy in 20 fractions during 4 weeks. The primary outcome consisted of biochemical or clinical failure (BCF). BCF was defined by biochemical failure, clinical failure, or death as a result of prostate cancer. Secondary outcomes included 2-year postradiation biopsy positivity, toxicity, and survival.

Results

Between 1992 and 1997, 51 patients were randomly assigned to receive IM plus EBRT, and 53 patients were randomly assigned to receive EBRT alone. The median follow-up was 8.2 years. In the IM plus EBRT arm, 17 patients (29%) experienced BCF compared with 33 patients (61%) in the EBRT arm (hazard ratio, 0.42; P = .0024). Eighty-seven patients (84%) had a postradiation biopsy; 10 (24%) of 42 in the IM plus EBRT arm had biopsy positivity compared with 23 (51%) of 45 in the EBRT arm (odds ratio, 0.30; P = .015). Overall survival was 94% in the IM plus EBRT arm versus 92% in the EBRT arm.

Conclusion

The combination of IM plus EBRT was superior to EBRT alone for BCF and postradiation biopsy. This trial provides evidence that higher doses of radiation delivered in a shorter duration result in better local as well as biochemical control in locally advanced prostrate cancer.

Improved biochemical relapse-free survival with increased external radiation doses in patients with localized prostate cancer: The combined experience of nine institutions in patients treated in 1994 and 1995

PURPOSE

To study the radiation dose-response as determined by Kaplan-Meier prostate-specific antigen (PSA) disease-free survival (PSA-DFS) estimates in patients with stage T1-T2 prostate cancer treated within a 2-year period (1994-1995).

METHODS

Nine institutions combined data on 4839 patients with stage T1 and T2 adenocarcinoma of the prostate who received > or =60 Gy external beam radiation therapy (RT) as sole treatment. No patient received neoadjuvant androgen deprivation or planned adjuvant androgen deprivation. Of the 4839 patients, 1325 were treated in 1994 and 1995; 1061 were treated with <72 Gy and 264 with > or =72 Gy. The median RT doses for the <72 Gy and the > or =72 Gy groups were 68.4 Gy and 75.6 Gy, respectively. The median follow-up for the <72 Gy and the > or =72 Gy groups were 5.8 and 5.7 years, respectively. Risk groups, defined on the basis of T stage, pretherapy PSA level, and biopsy Gleason score (GS), were as follows: low risk--T1b, T1c, T2a, GS < or =6 and PSA < or =10 ng/mL; intermediate risk--T1b, T1c, T2a, GS < or =6 and PSA >10 ng/mL but < or =20 ng/mL or T2b, GS < or =6 and PSA < or =20 ng/mL or GS 7 and PSA < or =20 ng/mL; high risk--GS 8-10 or PSA >20 ng/mL. The endpoint for outcome analysis was PSA-DFS at 5 years after therapy using the American Society for Therapeutic Radiology and Oncology failure definition.

RESULTS

Patients receiving > or =72 Gy had significantly more advanced cancers. The proportion of stage T2b/T2c cancers in the > or =72 Gy group was 42% compared with 32% in the <72 Gy group (p = 0.027). The mean pretherapy PSA was 11.4 ng/mL in the > or =72 Gy group compared with 10.7 ng/mL in the <72 Gy group (p = 0.001). The proportion of GS > or =8 cancers in the > or =72 Gy group was 9% compared with 7% in the <72 Gy group (p = 0.309). Overall, 15% of patients receiving <72 Gy had high-risk disease, compared with 22% of patients receiving > or =72 Gy (p = 0.034). The > or =72 Gy group had a greater number of follow-up PSA levels (mean 10.6/patient) compared with the <72 Gy group (mean 9.6/patient) (p = 0.007). For all 1325 patients, the 5- and 8-year PSA-DFS estimates were 64% and 62%, respectively. The 5-year PSA-DFS estimates for <72 Gy vs. > or =72 Gy were 63% vs. 69%, respectively (p = 0.046). Multivariate analysis for factors affecting PSA-DFS was performed for all cases using the following variables: pretherapy PSA (continuous), biopsy GS (continuous), stage (T1 vs. T2), radiation dose (continuous), and radiation technique (three-dimensional conformal vs. conventional). Pretreatment PSA (p < 0.001, chi-square 112.2), GS (p < 0.001, chi-square 12.8), radiation dose (p < 0.001, chi-square 13.5), and stage (p = 0.007, chi-square 7.2) were independent predictors of outcome. Radiotherapy technique was not (p = 0.50).

CONCLUSION

Differences in PSA-DFS estimates observed in multiple retrospective series have been attributed to differences in follow-up duration between patients treated to conventional doses (longer follow-up intervals) and those treated to higher doses (shorter follow-up intervals). In this report, the median follow-up duration in the > or =72 Gy group was essentially identical to the <72 Gy group, because the study included a large number of patients treated consecutively during a narrow time range (1994-1995). With similar follow-up duration, higher than conventional radiotherapy doses were associated with improved PSA-DFS when controlled for the influence of pretreatment PSA levels, biopsy GS, and clinical T stage.