The effect of dose on local control of prostate cancer

External beam radiotherapy dose response of prostate cancer

PURPOSE

To determine the external beam radiotherapy dose response of palpable Stage T1-T4, mostly Nx, patients with adenocarcinoma of the prostate.

METHODS AND MATERIALS

There were 938 men consecutively treated between 1987 and 1995 who had pretreatment prostate specific antigen (PSA) levels. Posttreatment failure was defined as disease recurrence and/or two elevations in PSA on consecutive follow-up visits. The radiotherapy technique consisted of a four-field box with a small four-field reduction after 46 Gy in 844 patients (total dose of 60-70 Gy) or with a six-field conformal boost after 46 Gy in 94 patients (total dose of 74-78 Gy). Neoadjuvant or adjuvant androgen ablation was not used in any patient. Median follow-up was 40 months.

RESULTS

The mean and median radiotherapy doses for the entire group were 67.8 +/- 13.3 Gy (+/-SEM) and 66 Gy. The mean radiotherapy dose was higher in those who had Stage T3/T4 disease, Gleason scores of 8-10, or pretreatment PSAs of > 4 ng/ml. In general, patients with more aggressive pretreatment prognostic features were treated to higher doses; yet, those that relapsed or had a rising PSA were treated to significantly lower doses. Actuarial analyses were facilitated by dividing patients into three dose groups: < or = 67, > 67-77, and > 77 Gy. The actuarial freedom from failure rates at 3 years were 61, 74, and 96% for the low, intermediate, and high dose groups. Stratification of the patients by pretreatment PSA revealed that dose was a significant correlate of freedom from relapse or a rising PSA for those with PSAs > 4-10, > 10-20, and > 20 ng/ml. The only patients in which an improvement in outcome was not related to higher doses were those with a pretreatment PSA < or = 4 ng/ml. Dose was significantly associated with freedom from failure for Stage T1/T2 and Stage T3/T4 patients, as well as for those stratified by Gleason score. Multivariate analysis using Cox proportional hazards models showed that dose was an independent and highly significant predictor of relapse or a rising PSA.

CONCLUSION

This retrospective review strongly indicates that radiotherapy dose to the prostate is critical to the cure of prostate cancer, even for favorable patients with pretreatment PSAs of > 4-10 ng/ml, Stages T1/T2, or Gleason scores of 2-6. Final confirmation awaits the results of our randomized trial.

Planning, delivery, and quality assurance of intensity-modulated radiotherapy using dynamic multileaf collimator: a strategy for large-scale implementation for the treatment of carcinoma of the prostate

PURPOSE

To improve the local control of patients with adenocarcinoma of the prostate we have implemented intensity modulated radiation therapy (IMRT) to deliver a prescribed dose of 81 Gy. This method is based on inverse planning and the use of dynamic multileaf collimators (DMLC). Because IMRT is a new modality, a major emphasis was on the quality assurance of each component of the process and on patient safety. In this article we describe in detail our procedures and quality assurance program.

METHODS AND MATERIALS

Using an inverse algorithm, we have developed a treatment plan consisting five intensity-modulated (IM) photon fields that are delivered with DMLC. In the planning stage, the planner specifies the number of beams and their directions, and the desired doses for the target, the normal organs and the "overlap" regions. Then, the inverse algorithm designs intensity profiles that best meet the specified criteria. A second algorithm determines the leaf motion that would produce the designed intensity pattern and produces a DMLC file as input to the MLC control computer. Our quality assurance program for the planning and treatment delivery process includes the following components: 1) verification of the DMLC field boundary on localization port film, 2) verification that the leaf motion of the DMLC file produces the planned dose distribution (with an independent calculation), 3) comparison of dose distribution produced by DMLC in a flat phantom with that calculated by the treatment planning computer for the same experimental condition, 4) comparison of the planned leaf motions with that implemented for the treatment (as recorded on the MLC log files), 5) confirmation of the initial and final positions of the MLC for each field by a record-and-verify system, and 6) in vivo dose measurements.

RESULTS

Using a five-field IMRT plan we have customized dose distribution to conform to and deliver 81 Gy to the PTV. In addition, in the overlap regions between the PTV and the rectum, and between the PTV and the bladder, the dose is kept within the tolerance of the respective organs. Our QA checks show acceptable agreement between the planned and the implemented leaf motions. Correspondingly, film and TLD dosimetry indicates that doses delivered agrees with the planned dose to within 2%. As of September 15, 1996, we have treated eight patients to 81 Gy with IMRT.

CONCLUSION

For complex planning problems where the surrounding normal tissues place severe constraints on the prescription dose, IMRT provides a powerful and efficient solution. Given a comprehensive and rigorous quality-assurance program, the intensity-modulated fields can be efficaciously and accurately delivered using DMLC. IMRT treatment is now ready for routine implementation on a large scale in our clinic.

Gold seed implantation in prostate brachytherapy

Interstitial brachytherapy for treatment of prostate cancer with radioactive gold--initially with liquid gold and later with seed technique--is based on an experience of more than four decades. With biopsy results approaching a 80% negative rate, and, at 5 years, a cancer specific survival of 100% for Stages A and B1, 90% for Stage B2, and 76% for Stage C, this form of treatment offers an effective and well-tolerated alternative mode of therapy for patients with localized prostate cancer.

Irradiation of localized prostatic carcinoma with a combination of high dose rate iridium-192 brachytherapy and external beam radiotherapy with three target definitions and dose levels inside the prostate gland

PURPOSE

Localized prostate cancer was treated with combined external beam radiotherapy and high dose rate Ir-192 brachytherapy with the purpose of a high dose. The technical aspects of a modified treatment are described.

METHODS

The brachytherapy was given in two sessions preceded and succeeded by external beam radiation. The radioactive source was temporarily implanted by a remote afterloading device through six to 15 needles inserted transperineally guided by transrectal ultrasound. The entire prostate gland was included in the clinical target volume. The urethra and the tumour volume could be defined and irradiated to different dose levels in more than 90% of the patients.

RESULTS

Fifty-four patients were treated. The total dose to the prostate was approximately 70 Gy and to the tumour volume 80 Gy. By calculating the corresponding dose given by 2.0 Gy fractions, considering the radiobiology by using the LQ formula and assuming an alpha/beta value for prostate tissue of 10, the dose to the prostate was approximately 84 Gy and to the tumour volume 112 Gy. For the late effects to the urethra an alpha/beta value of 3 was used, which corresponds to 85 Gy. The brachytherapy could be given with accuracy except when the dorsal border of the prostate was concave. The dose distribution then tended to be less satisfactory. Post-treatment calculations showed that the maximum dose to the rectum was 67 Gy (radiobiologically corrected to 88 Gy), given in a small volume. The early side effects from the brachytherapy were minimal. The treatment could not be performed as intended in four patients; three patients had a narrow pelvis and in one patient the prostate was unusually resilient, preventing the needles from being positioned properly.

CONCLUSIONS

This modification of a previously reported brachytherapy technique for prostate carcinoma permits a high radiation dose to the tumour and to the prostate gland, which ultimately may improve local control.

Combined treatment with temporary short-term high dose rate iridium-192 brachytherapy and external beam radiotherapy for irradiation of localized prostatic carcinoma

PURPOSE

To evaluate the treatment outcome after radical radiotherapy of localized prostate cancer in 50 patients (38 patients with stage T1-2 and 12 patients with stage T3) after a median follow-up time of 45 months (range 18-92 months).

METHODS

The treatment was given by combination of external beam radiotherapy (50 Gy) and brachytherapy (2 x 10 Gy). The brachytherapy was given using TRUS-guided percutaneously inserted temporary needles with a high dose rate remote afterloading technique with Ir-192 as the radionuclide source. Three target definitions and dose levels inside the prostate gland were used. Local control was evaluated by digital rectal examination, TRUS-guided biopsies and serum PSA evaluations.

RESULTS

Clinical and biopsy verified local control was achieved in 48 of the 50 (96%) patients; for stage T1-2 in 37 of 38 (97%) patients and for stage T3 in 11 of 12 (92%) patients. A posttreatment serum PSA level < or =1.0 ng/ml was seen in 42 (84%) patients, values from >1.0 to < or =2.0 ng/ml were seen in four (8%) patients and values exceeding 2.0 were seen in four (8%) patients. The late toxicity was minimal.

CONCLUSION

The local control results and the minimal toxicity after the combined radiotherapy treatment are promising. However, long term results are necessary before general use.

Dose-volume histograms for bladder and rectum

PURPOSE

A careful examination of the foundation upon which the concept of the Dose-Volume Histogram (DVH) is built, and the implications of this set of parameters on the clinical application and interpretation of the DVH concept has not been conducted since the introduction of DVHs as a tool for the quantitative evaluation of treatment plans. The purpose of the work presented herein is to illustrate problems with current methods of implementing and interpreting DVHs when applied to hollow anatomic structures such as the bladder and rectum.

METHODS AND MATERIALS

A typical treatment plan for external beam irradiation of a patient with prostate cancer was chosen to provide a data set from which DVH curves for both the bladder and rectum were calculated. The two organs share the property of being shells with contents that are of no clinical importance. DVHs for both organs were computed using a solid model and using a shell model. Typical treatment plans for prostate cancer were used to generate DVH curves for both models. The Normal Tissue Complication Probability (NTCP) for these organs is discussed in this context.

RESULTS

For an eight-field conformal treatment plan of the prostate, a bladder DVH curve generated using the shell model is higher than the corresponding curve generated using the solid model. The shell model also has a higher NTCP. A six-field conformal treatment plan also results in a higher DVH curve for the shell model. A treatment plan consisting of bilateral 120-degree arcs, results in a higher DVH curve for the shell model, as well as a higher NTCP.

CONCLUSION

The DVH concept currently used in evaluation of treatment plans is problematic because current practices of defining exactly what constitutes "bladder" and "rectum." Commonly used methods of tracing the bladder and rectum imply use of a solid structure model for DVHs. In reality, these organs are shells and the critical structure associated with NTCP is obviously and indisputably the shell, as opposed to its contents. Treatment planning algorithms for DVH computation should thus be modified to utilize the shell model for these organs.

Low acute gastrointestinal and genitourinary toxicities in whole pelvic irradiation of prostate cancer

PURPOSE

This retrospective study was done to determine the frequency and severity of acute gastrointestinal (GI) and genitourinary (GU) toxicity associated with whole pelvic radiotherapy of localized prostate cancer.

METHODS AND MATERIALS

Between 1989 and 1994, we treated 156 patients with localized prostate cancer, ranging in age from 54 to 86 (median 71), of which 86 were older than 70 years of age. No attempt at selection was made, and many were from the Veteran's Administration Hospital where they had been precluded from their surgical program because of comorbidities and/or advanced age. Of 156 patients, 45 (28.8%) underwent pretreatment laparoscopic lymphadenectomy (LAP); 40 had negative findings. Four-field box technique was used for all patients. We treated the whole pelvis to 45 Gy, followed by a cone-down and a final boost to a total dose of 72 Gy. The cone-down to the lower pelvis and boost to the prostate were based on computed tomography and/or magnetic resonance imaging findings for volume reconstruction with field size of approximately 8 x 8 and 6 x 6 cm, respectively. Diet instructions were given before treatment and emphasized weekly. Toxicities were evaluated weekly by physicians and nurses independently using Cancer and Leukemia Group B (CALGB) grading criteria.

RESULTS

The acute GI and GU toxicities gradually increased from Week 2, peaked at Week 5, and then declined after that. During Week 5, acute Grade 1-3 GI morbidities were observed in 19 (12.2%), 2 (1.3%), and 1 (0.6%) patients, respectively. Genitourinary toxicity was similar, accounting for 17 (10.9%), 6 (3.8%), and 1 (0.6%), respectively. Overall Grade 2 toxicities occurred in 30 of 156 patients (19%). Comorbidity was associated with more GI toxicity. Patients over 70 years of age tended to reach the maximal GI and GU toxicity 1-2 weeks earlier than did patients under the age of 70. Of the patients who did not follow the diet instruction, all experienced side effects.

CONCLUSIONS

Whole pelvic irradiation was very well tolerated in this group of patients. The frequency of acute Grade 2 GI and GU toxicity compared favorably with the reported results of conformal treatment. Diet restriction and psychosocial input may have had a positive impact. Late sequelae will be evaluated in long-term follow-up.

Indications for excluding the seminal vesicles when treating clinically localized prostatic adenocarcinoma with radiotherapy alone

PURPOSE

The indications for treating the seminal vesicles (SV) in patients with clinically localized carcinoma of the prostate are controversial. We sought to define subgroups of patients in whom coverage could be avoided, using pretreatment prostate specific antigen (PSA) values and the Gleason score. Because the rectum is the major dose-limiting structure, we also measured the extent of rectal sparing achieved by excluding the SV from external beam treatment fields.

METHODS AND MATERIALS

We retrospectively studied lateral x-ray simulation films of 43 patients treated with standard four-field radiotherapy and dose-volume histograms of eight patients treated with conformal radiotherapy. The rectal surface areas were measured and the volumes were calculated including and excluding the SV. The pathology reports of patients treated with radical prostatectomy alone between 1987 and 1993 were reviewed. Patients without preoperative PSA levels or biopsy Gleason scores, or who received neoadjuvant hormonal therapy were excluded. Of the 368 remaining patients, 66 (18%) had preoperative PSA levels < or = 4, 172 (47%) had PSA levels 4-10, and 130 (35%) had PSA levels > 10. The Gleason score was < or = 6 in 269 (73%), and 99 (27%) had a score > or = 7.

RESULTS

The reduction in the total irradiated rectal areas to full doses when the SV were excluded ranged from 5 to 67% in individual patients (median, 44%). The median reduction in the irradiated rectal volumes to 50% of the prescribed dose, as determined by dose-volume histograms, was 51% (range: 37-76%). The median reduction in bladder volumes was 9% (range: 6%-15%). The incidence of SV involvement was 19% (70 out of 368). Patients with normal PSA levels (< or = 4 ng/mL) had a 3% (2 out of 66) rate of SV involvement. Patients with PSA levels between 4-10 ng/mL had a 8% (10 out of 126) rate of SV involvement. All other cases had at least 20% rate of SV involvement, with a combined rate of 33%. Using a cutoff of 15%, two low risk groups were identified: all patients with PSA levels < or = 4, and patients with PSA 4-10 and Gleason score < or = 6. These constituted 52% (192 out of 368) of all patients. Overall, the low-risk patients had a 6% (12 out of 192) incidence of SV involvement vs. 33% (58 out of 176) for the high risk patients (p < or = .001).

CONCLUSIONS

Excluding the SV from the treatment field can significantly reduce (40%-50%) the volume of irradiated rectum. Our data confirm that pretreatment PSA levels and Gleason scores can be effectively used to define subgroups of patients in whom SV irradiation can be avoided. We propose excluding the SV in all patients with PSA levels < or = 4, and patients with PSA levels 4-10 and a Gleason score < or = 6.

Neoadjuvant androgen ablation prior to radiotherapy for prostate cancer: reducing the potential morbidity of therapy

OBJECTIVES

To determine the impact of neoadjuvant hormonal therapy (NHT) prior to conformal radiotherapy on the reduction of volume of normal tissue structures exposed to high doses of radiation therapy and to evaluate the overall late toxicity and response to treatment among patients treated with this approach.

METHODS

Among 214 patients treated with neoadjuvant leuprolide acetate and flutamide for 3 months prior to three-dimensional conformal radiotherapy (3D-CRT), 45 patients were prospectively evaluated with detailed dose-volume histogram (DVH) analyses to determine the extent of improvement of the geometry of the target volume after NHT. All patients underwent simulation and conformal treatment planning before and after NHT, and the pre- and posthormone DVH calculations for all normal tissue structures were compared for each patient. In addition, toxicity and response to therapy were evaluated in the 214 patients treated with this combined approach.

RESULTS

In the 45 patients evaluated, the median reduction of the rectal and bladder volumes receiving 95% of the prescription dose (D95) were 18% and 46%, respectively, while 91% showed a reduction of small bowel volume in a range of 27% to 100% of the prehormonal values. Among the entire group of 214 patients treated with NHT and 3D-CRT, no grade 3 or 4 toxicity was observed with a median follow-up of 15 months after 3D-CRT. The 3-year actuarial grade 2 late gastrointestinal and genitourinary toxicity rates were 6% and 18%, respectively.

CONCLUSIONS

Neoadjuvant hormonal therapy effectively reduces the volume of normal tissue exposed to high radiation doses in the majority of treated patients and decreases the potential morbidity of therapy.

[The conformal radiotherapy of localized prostatic carcinoma: acute tolerance and early efficacy]

AIM

In a prospective trial early effectiveness and acute toxicity of conformal 3D-planned radiotherapy for localized prostate cancer was quantified using dose-volume-histogramms and evaluated with respect of treatment technique.

PATIENTS AND METHOD

Thirty-two men (44 to 80 years old) with locally advanced carcinoma of the prostate (stage B2 or C) have been treated by 3D-planned conformal radiotherapy using high energy photons. In 28/32 men treatment technique was a monoaxial bisegmental rotation with irregular fields. With single doses of 2.0 Gy a mean total dose of 63.9 +/- 4.9 Gy according to ICRU was applied within 46 +/- 4 days. Maximum dose was in the mean 105.1% +/- 3.8%. 3D treatment volume was 274.1 +/- 113.4 cm3. Median follow-up is 1.8 years (15 to 34 months). Toxicity was evaluated according to RTOG-EORTC by patient interview and physical examination on a weekly basis during radiotherapy and by regular follow-up.

RESULTS

Eleven patients had none, 15 mild (RTOG grade 1) and 6 moderate symptoms (RTOG grade 2, mainly diarrhoea, dysuria and polyuria). Acute complications leading to treatment interruption did not occur. In 16 patients symptoms disappeared within 6 weeks after radiotherapy. Only 2 men had symptoms which lasted longer than 3 months and were endoscopically examined. Up to now no late complications were detected. Incidence and severity of toxicity was significantly (p < 0.05) related to the size of treatment volume. Acute toxicity was found to depend statistically significant (p < 0.05) on the proportional volume of bladder and rectum, irradiated with more than 35 Gy. In 81% of the patients with pretherapeutic elevated PSA levels normalisation of PSA was observed. Overall mean PSA levels of 15.7 +/- 22.6 micrograms/l at the beginning of radiotherapy fell to 2.1 +/- 3.7 micrograms/l 6 weeks after irradiation. Only 1 Patient relapsed locally 22 months after radiation therapy.

CONCLUSION

We conclude that due to modern 3D-planned conformal techniques with optimization of treatment dose and improved protection of critical organs such as urinary bladder and rectum, radiotherapy allows an effective and well tolerated therapy of localized prostatic carcinoma.

Number and orientations of beams in intensity-modulated radiation treatments

The fundamental question of how many equispaced coplanar intensity-modulated photon beams are required to obtain an optimum treatment plan is investigated in a dose escalation study for a typical prostate tumor. Furthermore, optimization of beam orientations to improve dose distributions is explored. A dose-based objective function and a fast gradient technique are employed for optimizing the intensity profiles (inverse planning). An exhaustive search and fast simulated annealing techniques (FSA) are used to optimize beam orientations. However, to keep computation times reasonable, the intensity profiles for each beam arrangement are still optimized using inverse planning. A pencil beam convolution algorithm is employed for dose calculation. All calculations are performed in three-dimensional (3D) geometry for 15 MV photons. DVHs, dose displays, TCP, NTCP, and biological score functions are used for evaluation of treatment plans. It is shown that for the prostate case presented here, the minimum required number of equiangular beams depends on the prescription dose level and ranges from three beams for 70 Gy plans to seven to nine beams for 81 Gy plans. For the highest dose level (81 Gy), beam orientations are optimized and compared to equiangular spaced arrangements. It is shown that (1) optimizing beam orientations is most valuable for a small numbers of beams (< or = 5) and the gain diminishes rapidly for higher numbers of beams; (2) if sensitive structures (for example rectum) are partially enclosed by the target volume, beams coming from their direction tend to be preferable, since they allow greater control over dose distributions; (3) while FSA and an exhaustive search lead to the same results, computation times using FSA are reduced by two orders of magnitude to clinically acceptable values. Moreover, characteristics of and demands on biology-based and dose-based objective functions for optimization of intensity-modulated treatments are discussed.

Combined proton and photon conformal radiation therapy for locally advanced carcinoma of the prostate: preliminary results of a phase I/II study

PURPOSE

A study was developed to evaluate the use of combined photons and protons for the treatment of locally advanced carcinoma of the prostate. This report is a preliminary assessment of treatment-related morbidity and tumor response.

METHODS AND MATERIALS

One hundred and six patients in stages T2b (B2), T2c (B2), and T3 (C) were treated with 45 Gy photon-beam irradiation to the pelvis and an additional 30 Cobalt Gray Equivalent (CGE) to the prostate with 250-MeV protons, yielding a total prostate dose of 75 CGE in 40 fractions. Median follow-up time was 20.2 months (range: 10-30 months). Toxicity was scored according to the Radiation Therapy Oncology Group (RTOG) grading system; local control was evaluated by serial digital rectal examination (DRE) and prostate specific antigen (PSA) measurements.

RESULTS

Morbidity evaluation was available on 104 patients. The actuarial 2-year rate of Grade 1 or 2 late morbidity was 12% (8% rectal, 4% urinary). No patients demonstrated Grade 3 or 4 late morbidity. Treatment response was evaluated on 100 patients with elevated pretreatment serum PSA levels. The actuarial 2-year rate of PSA normalization was 96%, 97%, and 63% for pretreatment PSAs of > 4-10, > 10-20, and > 20, respectively. The 13 patients with rising PSA demonstrated local recurrence (3 patients), distant metastasis (8 patients), or no evidence of disease except increasing PSA (2 patients).

CONCLUSIONS

The low incidence of side effects, despite the tumor dose of 75 CGE, demonstrates that conformal protons can deliver higher doses of radiation to target tissues without increasing complications to surrounding normal tissues. The initial tumor response, as assessed by the high actuarial rate of normalization with pretreatment PSA < or = 20, and the low rate of recurrences within the treatment field (2.8%), are encouraging.

Should brachytherapy be considered a therapeutic option in localized prostate cancer?

Contemporary prostate brachytherapy incorporates advances in computer analysis, imaging technology, and delivery apparatus, allowing exacting and reproducible results compared with historical approaches. The advances permit brachytherapy to be performed on a cost-effective, outpatient basis with low morbidity in the appropriately selected patient. Although unsettled questions remain regarding dosimetric issues, long-term outcomes, and morbidity, the weight of evidence to date appears to support the use of brachytherapy in selected patients. Brachytherapy may be considered a therapeutic option: as monotherapy for early-stage disease and also a boost following moderate doses of external beam irradiation for locally advanced disease.

Ultrasound image fusion for external beam radiotherapy for prostate cancer

PURPOSE

To determine whether real-time ultrasound imaging and targeting system for the treatment of prostate cancer was feasible. The initial phase of this project included a study to develop and determine (a) software for the fusion of ultrasound images to standard x-rays obtained during simulation, and (b) the potential reduction in field size with real-time imaging.

METHODS AND MATERIALS

During 13 patient simulations a transrectal ultrasound image was obtained. Orthogonal x-ray films were acquired with the rectal probe in place. Both the x-ray and ultrasound images were digitized and a fusion image was created of the prostate position in relation to the probe, bladder, and rectum. The two-dimensional area of the rectum, bladder, and prostate was determined in the lateral projection. Potential conformal blocks were designed for the lateral portals in a four-field treatment technique.

RESULTS

The transrectal ultrasound probe enabled real-time prostate imaging. The lateral field size can be reduced to 6.08 x 5.68 cm2 +/- 0.62 x 0.48 cm2 from the standard 8 x 8 cm2 field. The posterior rectal wall was physically displaced out of the lateral field. The area of the rectum included in the lateral field is 1.75 cm2 +/- 0.85 cm2.

CONCLUSION

The prostate position can be determined with certainty on a regular basis with transrectal ultrasonography. The amount of normal tissue in the high dose volume can be reduced. This approach may reduce acute and chronic morbidity and allow further dose escalation.

Conformal technique dose escalation for prostate cancer: biochemical evidence of improved cancer control with higher doses in patients with pretreatment prostate-specific antigen > or = 10 NG/ML

PURPOSE

Conformal radiation technology results in fewer late complications and allows testing of the value of higher doses in prostate cancer.

METHODS AND MATERIALS

We report the biochemical freedom from disease (bNED) rates (bNED failure is Prostate Specific Antigen (PSA) > or = 1.5 ng/ml and rising) at 2 and 3 years for 375 consecutive patients treated with conformal technique from 66 to 79 Gy. Median follow-up was 21 months. Biochemical freedom from disease was analyzed for patients treated above and below 71 Gy as well as above and below 73 Gy. Each dose group was subdivided by pretreatment PSA level (< 10, 10-19.9, and > or = 20 ng/ml). Dose was stated to be at the center of the prostate gland.

RESULTS

There was significant improvement in bNED survival for all patients divided by a dose above or below 71 Gy (p = 0.007) and a marginal improvement above or below 73 Gy (p = 0.07). Subdividing by pretreatment PSA level showed no benefit to the PSA < 10 ng/ml group at the higher dose but there was a significant improvement at 71 and 73 Gy for pretreatment PSA 10-19.9 ng/ml (p = 0.03 and 0.05, respectively) and for pretreatment PSA > or = 20 ng/ml (p = 0.003 and 0.02, respectively).

CONCLUSIONS

Increasing dose above 71 or 73 Gy did not result in improved bNED survival for patients with pretreatment PSA < 10 ng/ml at 2 or 3 years. Further dose escalation studies may not be useful in these patients. A significant improvement in bNED survival was noted for patients with pretreatment PSA > or = 10 ng/ml treated above 71 or 73 Gy; further dose escalation studies are warranted.

The "critical volume tolerance method" for estimating the limits of dose escalation during three-dimensional conformal radiotherapy for prostate cancer

PURPOSE

To describe the "Critical Volume Tolerance" (CVT) method for defining normal tissue tolerance during 3D-based dose escalation studies for prostate cancer.

METHODS AND MATERIALS

The CVT method predicts the tolerance to radiation for "in series"-type functional units based on the assumption that tolerance depends on a critical threshold "low-volume high-dose region." The data used for describing this model were generated from 3D analysis of randomly selected patients with prostate cancer. Commonly used coplanar four-and six-field conformal (SFC) techniques were chosen as the comparison techniques. For purposes of comparison, rectal tolerance was assumed to be reached following whole pelvic irradiation using a four-field box technique to 50 Gy, followed by a conedown boost to 70 Gy using bilateral 9 x 9 cm 120 degree arcs as popularized by investigators from Stanford University (SUH).

RESULTS

Based on the average dose volume histograms for the patients studied, the maximum safe increase in dose for the SFC technique compared to the SUH technique, would be 10% if 30% of the rectal volume was the critical dose limiting volume (CVT = 30%), 5% if the CVT = 10%, or greater than 20% if the CVT = 40%. Commonly used four-field conformal techniques would not be expected to allow significant escalation of the dose without increasing the risk of complications.

CONCLUSIONS

The CVT method is relatively simple, and data generated based on it can be used to support normal tissue complication probability equations. The CVT method can be verified or modified as partial tolerance data become available. Based on the CVT model, sophisticated treatment techniques should allow a modest increase in the total dose of radiation delivered to the prostate without an increase in late complications.

Prostate cancer. Who is best benefited by external beam radiation therapy?

The major indications for radical radiation therapy of prostate cancer for both early-stage and locally advanced disease are discussed. Important issues in the interpretation of long-term treatment series are reviewed. The outcomes of therapy are analyzed for both early-stage and locally advanced disease, including alternative therapeutic strategies. On the basis of this review of the literature, current treatment recommendations delineate patients most likely to benefit from radiation therapy as opposed to alternative therapeutic modalities.

Lateral rectal shielding reduces late rectal morbidity following high dose three-dimensional conformal radiation therapy for clinically localized prostate cancer: further evidence for a significant dose effect

PURPOSE

Using conventional treatment methods for the treatment of clinically localized prostate cancer central axis doses must be limited to 65-70 Gray (Gy) to prevent significant damage to nearby normal tissues. A fundamental hypothesis of three-dimensional conformal radiation therapy (3DCRT) is that, by defining the target organ(s) accurately in three dimensions, it is possible to deliver higher doses to the target without a significant increase in normal tissue complications. This study examines whether this hypothesis holds true and whether a simple modification of treatment technique can reduce the incidence of late rectal morbidity in patients with prostate cancer treated with 3DCRT to minimum planning target volume (PTV) doses of 71-75 Gy.

METHODS AND MATERIALS

The 257 patients with clinically localized prostate cancer who completed 3DCRT by December 31, 1993 and received a minimum PTV dose of 71-75 Gy are included in this report. The median follow-up time was 22 months (range: 4-67 months); 98% of patients had follow-up of longer than 12 months. The calculated dose at the center of the prostate was < 74 Gy in 19 patients, 74-76 Gy in 206 patients, and > 76 Gy in 32 patients. Late rectal morbidity was graded according to the Late Effects Normal Tissue (LENT) scoring system. Eighty-eight consecutive patients were treated with a rectal block added to the lateral fields. In these patients the posterior margin from the prostate to the block edge was reduced from the standard 15 to 5 mm for the final 10 Gy, which reduced the dose to portions of the anterior rectal wall by approximately 4-5 Gy. Estimates of rates for rectal morbidity were determined by Kaplan-Meier actuarial analysis. Differences in morbidity percentages were evaluated by the Pearson chi-square test.

RESULTS

Grade 2-3 rectal morbidity developed in 46 out of 257 patients (18%) and in the majority of cases consisted of rectal bleeding. No patient has developed Grade 4 or 5 rectal morbidity. The actuarial rate of Grade 2-3 morbidity is 23% at 24 months and the median time to the development of Grade 2-3 complications is 15 months. A statistically significant dose effect is evident. The incidence of Grade 2-3 rectal morbidity increased as the dose at the center of the prostate increased (p = 0.05). In patients receiving minimum PTV doses of < or = 76 Gy the use of a rectal block significantly reduced the incidence of Grade 2-3 toxicity; 6 out of 88 (7%) with a block vs. 30 out of 137 (22%) without a block, (p = 0.003).

CONCLUSION

The incidence of late rectal morbidity with 3DCRT to minimum PTV doses of 71-75 Gy is acceptable and to date no Grade 4-5 rectal morbidities have been observed. In our experience, higher doses to the center of the prostate are associated with an increased likelihood of developing Grade 2-3 rectal morbidity but treatment techniques that reduce the total dose to the anterior rectal wall have reduced the incidence of late rectal morbidity. If clinical studies indicate improved tumor control with minimum PTV doses above 71 Gy, then dose escalation above 76 Gy to the center of the prostate should be pursued cautiously with treatment techniques that limit the total dose to the anterior rectal wall.

Reproducibility of conformal radiation therapy in localized carcinoma of the prostate without rigid immobilization

The reproducibility of 3-dimensional (3D) conformal therapy in localized prostate cancer was studied in 14 patients, based on retrospective analysis of 196 anteroposterior-posteroanterior (AP/PA) and lateral portal images. The patients were treated supine without rigid immobilization using six isocentric coplanar conformal fields. Three different observers independently compared the portal and simulation images, determining the deviation of each portal film from the corresponding simulation film. No significant deviations were observed in the cephalo-caudal or lateral axes (0 mm median values). However, a systematic median shift of 5 mm (0 to + 10, range) was observed in the anteroposterior direction, presumably as a consequence of a sagging in the treatment couch under the patient's weight. After modification of the treatment couch, no further systematic anteroposterior shifts have been observed. These results demonstrate that the daily setup of conformal prostate irradiation fields can be performed with acceptable reproducibility without the use of special immobilization devices.

Hyperfractionated conformal radiotherapy in locally advanced prostate cancer: results of a dose escalation study

PURPOSE

This study was initiated to assess the incidence of chronic complications and histologic and biochemical control following hyperfractionated conformal radiotherapy in patients with locally advanced prostate cancer.

METHODS AND MATERIALS

Between October 1991 and October 1994, 49 patients with locally advanced prostate cancer were entered on the first two dose levels of a prospective dose-escalation study using hyperfractionated three dimensional conformal radiotherapy. The first 25 patients received a minimum tumor dose of 78 Gy to the prostate and seminal vesicles in 6 weeks at 1.3 Gy, b.i.d. No increase in chronic toxicity compared with conventional radiotherapy was noted; therefore, an additional 24 patients were treated to a minimum tumor dose of 82.8 Gy to the prostate and seminal vesicles in 7 weeks at 1.15 Gy, b.i.d. Toxicity was scored according to the Radiation Therapy Oncology Group morbidity grading scale. Efficacy was assessed through scheduled postradiation prostate specific antigen values and ultrasound-guided biopsies. The median follow-up for the entire group was 20 months.

RESULTS

The hyperfractionated external radiation was well tolerated with minimal acute morbidity. At 30 months, the actuarial probability of Grade 2 gastrointestinal toxicity was 17%. At 30 months, the actuarial probability of Grade 2 genitourinary toxicity was 16%. There was no statistically significant difference between the two dose levels. No Grade 3 or 4 gastrointestinal or genitourinary toxicity was noted. At 12 months, 84% of patients had a prostate specific antigen < or = 4; and 53% < or = 1 ng/ml. At 12 months, 71% of patients had post radiation biopsies that were either negative (55% or showed a marked therapeutic effect (16%).

CONCLUSION

The use of hyperfractionated conformal radiotherapy facilitated dose escalation with no increase in chronic toxicity compared to standard doses. The initial tumor response based on prostate specific antigen measurements and postradiation biopsies is highly encouraging. Based on these results, an increase in dose to 87.4 Gy has been planned according to the schema of this ongoing dose escalation study.

Conformal prostate brachytherapy: initial experience of a phase I/II dose-escalating trial

PURPOSE

To improve treatment results on prostatic adenocarcinoma, conformal radiation therapy (CRT) has been used. Two major drawbacks of external CRT are: (a) internal organ motion/daily set-up variations, and (b) exclusion of several patients for CRT based on poor geometrical relationships as identified by three dimensional (3D) treatment planning. To overcome the above problems, we began the first prospective Phase I/II dose-escalating clinical trial of conformal brachytherapy (CB) and concurrent external beam irradiation.

METHODS AND MATERIALS

Fifty-nine patients with T2b-T3c prostatic adenocarcinoma received 176 transperineal ultrasound-guided conformal high-dose rate (HDR) boost implants. All patients received concomitant external beam pelvic irradiation. Dose escalation of the three HDR-CB fractions proceeded as follows: 5.5 Gy (30 patients), 6 Gy (20 patients), and 6.5 Gy (9 patients). The CB dose was prescribed to the prostate contour as outlined using an online biplanar transrectal ultrasound probe. The urethra, anterior rectal wall, and prostate boundaries were identified individually and outlined at 5 mm intervals from the base to the apex of the gland. The CB using real-time ultrasound guidance with interactive online isodose distributions was performed on an outpatient basis. As needles were placed into the prostate, corrections for prostate displacement were recorded and the isodose distributions were recalculated to represent the new relationship between the needles, prostate, and normal structures. No computerized tomography (CT) planning or implant preplanning was required.

RESULTS

No patient was rejected based on poor geometrical relation of pelvic structures. In every implant performed, prostate displacement was noted. Craniocaudal motion of the gland ranged from 0.5-2.0 cm (mean = 1.0 cm), whereas lateral displacement was 0.1-0.4 cm. With the interactive online planning system, organ motion was immediately detected, accounted for, and corrected prior to each HDR treatment. The rectal dose has ranged from 45 to 87%, and the urethral dose from 97 to 112% of the prostate dose. It is significant to note that operator dependence has been completely removed because the interactive online planning system uniformly guides the physicians.

CONCLUSIONS

With ultrasound guidance and the interactive online dosimetry system, organ motion (as compared to external beam) is insignificant because it can be corrected during the procedure without increasing target volume margins. Common pitfalls of brachytherapy, including operator dependence and difficulty with reproducibility, have been eliminated with the intraoperative online planning system.

Prostate motion during standard radiotherapy as assessed by fiducial markers

From November 1993 to August 1994, 55 patients with localized prostate carcinoma had three gold seeds placed in the prostate under transrectal ultrasound guidance prior to the start of radiotherapy in order to track prostate motion. Patients had a planning CT scan before initial simulation and again at about 40 Gy, just prior to simulation of a field reduction. Seed position relative to fixed bony landmarks (pubic symphysis and both ischial tuberosities) was digitized from each pair of orthogonal films from the initial and boost simulation using the Nucletron brachytherapy planning system. Vector analysis was performed to rule out the possibility of independent seed migration within the prostate between the time of initial and boost simulation. Prostate motion was seen in the posterior (mean: 0.56 cm; SD: 0.41 cm) and inferior directions (mean: 0.59 cm; SD: 0.45 cm). The base of the prostate was displaced more than 1 cm posteriorly in 30% of patients and in 11% in the inferior direction. Prostate position is related to rectal and bladder filling. Distension of these organs displaces the prostate in an anterosuperior direction, with lesser degrees of filling allowing the prostate to move posteriorly and inferiorly. Conformal therapy planning must take this motion into consideration. Changes in prostate position of this magnitude preclude the use of standard margins.

Photoneutrons from medical linear accelerators--radiobiological measurements and risk estimates

PURPOSE

To assess the oncogenic potential of the photoneutrons produced by high energy medical linear accelerators.

METHODS AND MATERIALS

An established line of cells of rodent origin (C3H 10T1/2) was used to assess the oncogenic potential of the radiation dose received in the breast of an anthropomorphic "randoman" phanton, while the cervix received a dose of 70 Gy. Experiments were performed at 6 MV, below the threshold for the production of photoneutrons, and at 20 MV where the dose includes about 0.01 Gy of photoneutrons as well as scattered x-rays.

RESULTS

A significantly higher transformation incidence was observed for the 20-MV machine, consistent with the measured neutron dose of about 0.01 Gy and a quality factor of 20.

CONCLUSION

An estimate can be made of the additional deaths from second malignancies that might result from the photoneutrons generated by higher energy linear accelerators (Linacs), which must be offset against the possible improvements in survival that might result from the higher tumor doses made possible by the increased percentage depth doses.

Comparison of treatment plans for irradiating adenocarcinoma of the prostate

In a clinic with multiple megavoltage beams (Co-60, 6 MV, 10 MV, 18 MV) available, the optimal dose distributions depends on the radiation technique, patient size, and beam energy. To determine optimal dose distributions for external beam irradiation for patients with localized adenocarcinoma of the prostate, we investigated the dependence of beam energy, treatment technique, and patient size. Various radiation isodose plans were prepared at the central plane of the treatment field using computerized tomography scans of the pelvis for small, medium, and large patients. The dose uniformity in the target volume, the dose received by sensitive tissues such as bladder, rectum, and femoral heads, and the irradiated volume of these normal tissues were used as the criteria for comparing the plans. In all cases, the target volume was within the 95% isodose line with good dose uniformity (+/- 5%, of the prescribed dose). The volume of the rectum and bladder enclosed within the 90% isodose curve depended on the choice of the beam energy and the treatment technique for different patient sizes. For the small size patient the optimal dose distribution was achieved by using 10 MV box and arc or oblique boost. For the medium size patient, using 18 MV X-rays with box technique and oblique boost gave the optimal treatment plan. For the large size patient, using 18 MV or 10 MV X-rays box technique with arc boost were both acceptable.

A rationale for fractionation for slowly proliferating tumors such as prostatic adenocarcinoma

PURPOSE

The incidence of carcinoma of the prostate has recently begun to exceed that of carcinoma of the lung in males in the United States. Although survival and local tumor control after treatment are good for early stages, improvements are being sought for more locally advanced stages. Dose escalation might be of benefit and might be accomplished using "three-dimensional" conformal radiotherapy or hyperfractionation. Because carcinoma of the prostate is known to be a generally slowly growing tumor, there may be more scope for extreme hyperfractionation, even with prolongation to allow for the extra number of very small fractions. This article explores only the hyperfractionation approach, and only theoretically, to investigate when treatments might become too hyperfractionated.

METHODS AND MATERIALS

The major problem was what to assume for proliferation rates in human adenocarcinomas. A literature search yielded labeling indices (S-phase proportions) often averaging about 1%, but spreading up to 6% or more in individual cases. These data are reviewed, and three bands of rate of loss of local control were chosen for the subsequent calculations: 0.5%, 1%, and 2% loss of local control per week of prolongation. Calculations were done using the linear-quadratic model for a series of doses per fraction of 1.2, 1.0, 0.8, and 0.6 Gy, given twice a day (b.i.d.) in 7, 9, 12, and 17 weeks, respectively. They were compared with a "standard" 36 fractions of 2 Gy = 72 Gy in 7 weeks. Total doses for equal late effects were calculated assuming a late alpha/beta of 3 Gy; the tumor Biologically Effective Doses were calculated assuming tumor alpha/beta values of 30, 10, and 5 Gy. The possible increases of local tumor control were estimated assuming a gamma-37 slope of 2% (per percent increase in total tumor dose).

RESULTS

Graphs are presented of the estimated local control as a function of dose per fraction (and overall time), for advanced tumors (starting at 30% LC) and for less advanced tumors (starting at 70%). The largest increase is always for the change from 2 Gy once a day (q.d.) to 1.2 Gy b.i.d. Further changes of local control with hyperfractionation depend upon tumor proliferation rate and on the shape of the tumor cell survival curve. The largest gains are for the more advanced tumors.

CONCLUSIONS

There is no great encouragement to proceed to more hyperfractionated and prolonged schedules than 1.2-1.0 Gy b.i.d. in 7-9 weeks. We await developments that might more reliably enable potential doubling time and cell survival curve shapes to be routinely determined for individual tumors, before further hyperfractionation might be considered. In the absence of tumor kinetic measurements, we might consider low grade tumors to be the ones to select for prolonged fractionation, whereas high grade tumors would be more suitable for 1.2 Gy b.i.d. with no prolongation, or for dose escalation using conventional fraction sizes and conformal radiotherapy.

Advanced prostate cancer: the results of a randomized comparative trial of high dose irradiation boosting with conformal protons compared with conventional dose irradiation using photons alone

PURPOSE

Following a thorough Phase I/II study, we evaluated by a Phase III trial high versus conventional dose external beam irradiation as mono-therapy for patients with Stage T3-T4 prostate cancer. Patient outcome following standard dose radiotherapy or following a 12.5% increase in total dose to 75.6 Cobalt Gray Equivalent (CGE) using a conformal perineal proton boost was compared for local tumor control, disease-free survival, and overall survival.

METHODS AND MATERIALS

Stage T3-T4, Nx, N0-2, M0 patients received 50.4 Gy by four-field photons and were randomized to receive either an additional 25.2 CGE by conformal protons (arm 1--the high dose arm, 103 patients, total dose 75.6 CGE) or an additional 16.8 Gy by photons (arm 2--the conventional dose arm, 99 patients, total dose 67.2 Gy). Actuarial overall survival (OS), disease-specific survival (DSS), total recurrence-free survival (TRFS), (clinically free, prostate specific antigen (PSA) less than 4ng/ml and a negative prostate rebiopsy, done in 38 patients without evidence of disease) and local control (digital rectal exam and rebiopsy negative) were evaluated.

RESULTS

The protocol completion rate was 90% for arm 1 and 97% for arm 2. With a median follow-up of 61 months (range 3 to 139 months) 135 patients are alive and 67 have died, 20 from causes other than prostate cancer. We found no significant differences in OS, DSS, TRFS or local control between the two arms. Among those completing randomized treatment (93 in arm 1 and 96 in arm 2), the local control at 5 and 8 years for arm 1 is 92% and 77%, respectively and is 80% and 60%, respectively for arm 2 (p = .089) and there are no significant differences in OS, DSS, and TRFS. The local control for the 57 patients with poorly differentiated (Gleason 4 or 5 of 5) tumors at 5 and 8 years for arm 1 is 94% and 84% and is 64% and 19% on arm 2 (p = 0.0014). In patients whose digital rectal exam had normalized following treatment and underwent prostate rebiopsy there was a lower positive rebiopsy rate for arm 1 versus arm 2 patients (28 vs. 45%) and also for those with well and moderately differentiated tumors versus poorly differentiated tumors (32 and 50%). These differences were not statistically significant. Grade 1 and 2 rectal bleeding is higher (32 vs. 12%, p = 0.002) as may be urethral stricture (19 vs. 8%, p = 0.07) in the arm 1 versus arm 2.

CONCLUSIONS

An increase in prostate tumor dose by external beam of 12.5% to 75.6 CGE by a conformal proton boost compared to a conventional dose of 67.2 Gy by a photon boost significantly improved local control only in patients with poorly differentiated tumors. It has increased late radiation sequelae, and as yet, has not increased overall survival, disease-specific survival, or total recurrence-free survival in any subgroup. These results have led us to test by a subsequent Phase III trial the potential beneficial effect on local control and disease-specific survival of a 12.5% increase in total dose relative to conventional dose in patients with T1, T2a, and T2b tumors.

Factors influencing incidence of acute grade 2 morbidity in conformal and standard radiation treatment of prostate cancer

PURPOSE

The fundament hypothesis of conformal radiation therapy is that tumor control can be increased by using conformal treatment techniques that allow a higher tumor dose while maintaining an acceptable level of complications. To test this hypothesis, it is necessary first to estimate the incidence of morbidity for both standard and conformal fields. In this study, we examine factors that influence the incidence of acute grade 2 morbidity in patients treated with conformal and standard radiation treatment for prostate cancer.

METHODS AND MATERIALS

Two hundred and forty-seven consecutive patients treated with conformal technique are combined with and compared to 162 consecutive patients treated with standard techniques. The conformal technique includes special immobilization by a cast, careful identification of the target volume in three dimensions, localization of the inferior border of the prostate using the retrograde urethrogram, and individually shaped portals that conform to the Planning Target Volume (PTV). Univariate analysis compares differences in the incidence of RTOG-EORTC grade two acute morbidity by technique, T stage, age, irradiated volume, and dose. Multivariate logistic regression includes these same variables.

RESULTS

In nearly all categories, the conformal treatment group experienced significantly fewer acute grade 2 complications than the standard treatment group. Only volume (prostate +/- whole pelvis) and technique (conformal vs. standard) were significantly related to incidence of morbidity on multivariate analysis. When dose is treated as a continuous variable (rather than being dichotomized into two levels), a trend is observed on multivariate analysis, but it does not reach significant levels. The incidence of acute grade 2 morbidity in patients 65 years or older is significantly reduced by use of the conformal technique.

CONCLUSION

The conformal technique is associated with fewer grade 2 acute toxicities for all patients. This conclusion is valid irrespective of selection criteria except in a few cases. Older age is associated with increased toxicity only with the standard technique and not then at a statistically significant level. Elderly patients should not be excluded from external beam radiation because of increased morbidity especially if conformal treatment is available. Volume is not significantly related to morbidity in patients with standard treatment, but it is for conformal treatment. Furthermore, it remains significant in a multivariate analysis that also shows the advantage of conformal treatment. Grade 2 acute toxicities are more volume dependent than dose dependent.

External beam radiotherapy of localized prostatic adenocarcinoma. Evaluation of conformal therapy, field number and target margins

The purpose of the present study was to identify factors of importance in the planning of external beam radiotherapy of prostatic adenocarcinoma. Seven patients with urogenital cancers were planned for external radiotherapy of the prostate. Four different techniques were used, viz. a 4-field box technique and four-, five- or six-field conformal therapy set-ups combined with three different margins (1-3 cm). The evaluations were based on the doses delivered to the rectum and the urinary bladder. A normal tissue complication probability (NTCP) was calculated for each plan using Lyman's dose volume reduction method. The most important factors that resulted in a decrease of the dose delivered to the rectum and the bladder were the use of conformal therapy and smaller margins. Conformal therapy seemed more important for the dose distribution in the urinary bladder. Five- and six-field set-ups were not significantly better than those with four fields. NTCP calculations were in accordance with the evaluation of the dose volume histograms. To conclude, four-field conformal therapy utilizing reduced margins improves the dose distribution to the rectum and the urinary bladder in the radiotherapy of prostatic adenocarcinoma.

Primary radiation therapy in the treatment of localized prostatic cancer

Prostatic carcinoma is one of the leading causes of male cancer deaths. However, the routine diagnostic and therapeutic strategies have not yet been established. Although the outcome of surgical and radiotherapeutical approaches has frequently been reported to be comparable, the profile of side effects is different. This could offer the basis for selecting the treatment of choice in individual cases. During the last decade the radiotherapeutical technique has markedly improved, in part due to the achievements in the field of computer assisted tomography planning and conformal technique; the outcome of side-effects has decreased with concurrent increase in the rate of local control. The prescribing, recording and reporting of irradiation have also recently developed, as well as the staging of the disease. Therefore we consider it timely to review progress in this subject and to emphasize the role of radiotherapy in the treatment of localized prostatic cancer.

Radiotherapy of prostate cancer: established results and new developments

Radical radiotherapy has been established as an effective modality for eradicating localised prostate cancer. No satisfactory comparisons have been made with patients treated by total prostatectomy, but in surgically staged patients with negative lymph nodes survival after radiotherapy exceeds that of an aged matched population, cancer deaths occurring in only 6-15% of patients and 85% remaining free of local recurrence after 10 years. Results are predictably less satisfactory in surgically unstaged cases and for more advanced localised presentations. Nevertheless, radical radiotherapy achieves local control of disease in the majority of patients. Improved local control may be obtained by increasing radiation dose but at the expense of increased radiation-induced side-effects. Conformal radiotherapy and combined modality treatment with the neoadjuvant or adjuvant androgen deprivation show considerable promise as novel methods to improve the therapeutic ratio, and prospective randomised studies are underway to test these approaches.

Field displacement during external radiotherapy in prostatic adenocarcinoma treated with radioactive 198Au implants and external irradiation

The purpose of this work was to study displacement error and internal movements of the prostate during external beam radiotherapy. Verification films in the frontal (n = 194) and lateral (n = 64) portals were investigated in 14 patients treated with radioactive 198Au implants. Displacement errors of two implants were investigated. In seven patients, filling of the rectum and the bladder with contrast medium or isotonic saline was performed during CT investigation for planning purposes to detect movements of the prostate. Most (95%) of the displacement errors were less than 10 mm in the frontal portal and less than 15 mm in the lateral portals. No correlation to the patient's weight was found. The displacement errors were randomly distributed. The spatial relations between the implants were not altered during the treatments. Small movements of the prostate were observed. To conclude, the positioning system employed at present (laser) can be sufficient for the margins used (2 cm). In lateral portals, however, the system did not have the ability to detect a possible systematic displacement error from simulator to accelerator. The intention is to decrease the margins to 1 cm, which will necessitate a better positioning system.

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

Acute morbidity, late complications and tumor response were evaluated in 324 prostate cancer patients treated with 3-dimensional conformal radiation therapy in a phase I dose-escalation study. This radiotherapy technique targeted the prostate and seminal vesicles but effectively excluded the surrounding normal tissues. The minimum tumor dose was 64.8 to 66.6 Gy. in 87 patients, 70.2 Gy. in 138, 75.6 Gy. in 69 and 81.0 Gy. in 30. The treatment was well tolerated with minimal acute morbidity, observed in 15% of the patients who required medication for relief of rectal symptoms and in 34% for urinary symptoms. Two patients (0.6%) to date have had grades 3 and 4 late complications (Radiation Therapy Oncology Group morbidity grading system). The 3-year actuarial probability of survival with a normal serum prostate specific antigen level was 97% for patients with stages T1c and T2a, 86% with stage T2b, 60% with stage T2c and 43% with stage T3 disease. A multivariate analysis demonstrated that initial prostate specific antigen (20 ng./ml. or less versus more than 20 ng./ml.), stage (T2c or less versus T3) and Gleason score (6 or less versus 7 or more) were each significant independent variables that affected subsequent chemical relapse. The acute and long-term toxicities have been less compared with traditional treatment techniques. After the maximal tolerable dose with 3-dimensional conformal radiotherapy is established, future studies will test whether high dose conformal therapy has the potential to improve local tumor control and survival of patients with localized prostatic carcinoma.

Prostate cancer

Prostate cancer is the most common noncutaneous malignancy diagnosed in American men, and in 1994 it will pass lung cancer as the most common cancer diagnosed in the United States, with an estimated 200,000 new cases. The molecular biology of prostate carcinogenesis is rapidly advancing, and it is clear that, to a degree, prostate cancer is a heritable disease. The use of serum prostate-specific antigen (PSA) as a screening tool has been widely accepted by the medical community, although the evidence to support the efficacy of screening is not yet available. The curative approaches to organ-confined, clinically localized prostate cancer include radiation therapy, radical prostatectomy, and close observation in selected patients. The absence of well-designed clinical trials contributes to the confusion surrounding which curative treatment is the best option in individual patients. The standard approach to patients with evidence of extracapsular spread without distant metastases has been external-beam radiotherapy, although the results with radiation therapy alone in these patients has left considerable room for improvement. Innovative combined-modality approaches are currently being investigated at a number of institutions for these poor-prognosis patients. Three-dimensional conformal radiation therapy is currently being investigated at multiple institutions and offers some hope for improved results. The treatment of metastatic disease remains hormonal manipulation, although the exact nature of optimal androgen deprivation is currently a matter of considerable debate. In patients with hormone-refractory disease newer regimens using novel chemotherapy regimens offer some promise.

Indications for and the significance of seminal vesicle irradiation during 3D conformal radiotherapy for localized prostate cancer

PURPOSE

To evaluate the use of pretreatment prostate specific antigen, Gleason score, and clinical stage as predictors of the risk of seminal vesicle involvement in patients with clinically localized prostatic cancer, and to determine the impact of excluding the seminal vesicles on the dose received by surrounding normal tissues.

METHODS AND MATERIALS

An empirically derived equation combining the preoperative prostate specific antigen and Gleason score was applied to 188 patients treated with radical prostatectomy, for whom pathologic evaluation of the seminal vesicles was available. High and low risk groups for seminal vesicle involvement were defined using this equation. The observed risks of seminal vesicle involvement was compared to the predicted risk using the preoperative prostate specific antigen, Gleason score or clinical stage alone or using the empirical equation. Dose-volume histograms for five patients treated using six-field conformal radiotherapy were compared including and excluding the seminal vesicles.

RESULTS

Using the empirically derived equation, a low risk group of 109 patients was identified with a calculated risk of seminal vesicle involvement of < or = 13% and an observed incidence of 7.3%. Among the high risk group of 79 patients, which included all patients with a calculated risk > 13%, 37% had seminal vesicle involvement (p < 0.001 low vs. high risk). Twenty percent of the rectal volume received on average above 86% of the total dose for the five plans which included the seminal vesicles compared to 68% for the five plans excluding the seminal vesicles. The doses to 40% of the rectal volume were 64% and 37% if the seminal vesicles were included and excluded, respectively. The dose to the bladder and femoral heads was also decreased but to a lesser extent.

CONCLUSION

The empirical formula predicts risk of seminal vesicle involvement with a higher degree of significance for a larger number of patients than either Gleason score, clinical stage, or prostate specific antigen alone. Based on an analysis of our first 100 patients treated with definitive conformal therapy alone, approximately 47% of those patients could have been treated excluding the seminal vesicles. Excluding the seminal vesicles may allow us to go to a higher total dose with less rectal toxicity.

Definitive therapy for prostate carcinoma: Mayo Clinic results at 15 years after treatment

Data on long-term follow-up for definitive therapy of prostate cancer are limited, especially for radiation therapy. Either surgery or radiation was used in 322 patients for treatment with curative intent, and follow-up was for a minimum of 15 years. Overall survival was nearly identical to that in age-matched cohort. 5-, 10-, and 15-year recurrence-free survival rates were 77%, 63% and 53%, respectively. Grade and stage were significant prognostic factors for both recurrence and survival. More than 60% of the initial failures were local, and more than 25% of the failures occurred after 10 years. Radiation therapy was used in 137 patients with clinically staged disease. Radical retropubic prostatectomy and perineal prostatectomy were performed in 133 and 44 patients, respectively. In this group, pathological staging was used. Survival rates for surgically treated patients were better than those in the cohort population. In conclusion, overall long-term follow-up demonstrates that definitive treatment does not have an adverse effect on survival from prostate cancer. Local recurrence is a frequent cause of failure. Caution must be used in interpreting any prostate study with less than 10 years of follow-up, because 25% to 50% of the failures occur after that time.

The potential and limitations of the inverse radiotherapy technique

The objective of the work presented in this paper is to explore the scope of the applicability of the inverse radiotherapy technique for designing optimized intensity distributions to achieve a desired dose distribution. A specified desired uniform dose to the target volume is inverted, subject to constraints on the surrounding normal tissue dose, to produce optimum intensity distributions in a set of beams arranged around the target volume. We employed the inverse technique and software developed by Bortfeld and evaluated results both qualitatively and quantitatively using dose distribution displays, dose-volume histograms and biological indices including tumor control probability and normal tissue complication probabilities. So far we have applied this methodology to prostate and lung treatment plans. For prostate the inverse technique produces satisfactory approximations of the desired dose distributions. However, for lung its performance is considerably inferior. Our investigations point to a number of factors for this difference, the primary ones being differences in the tolerance doses of neighboring normal tissues, magnitudes of volume effect, tissue architectures, and the achievability of the specified desired dose distributions. We conclude that, for certain clinical situations, it is not sufficient to specify the objectives of optimization purely in terms of the desired pattern of the dose. The objectives must also include dose-volume effects and biological indices. Furthermore, the mathematics of optimization must be able to incorporate these factors into the process. We find that the inverse technique is not suitable for situations where dose-volume considerations and biological indices are important and that other methods of optimization of intensity distributions should be explored.

Neoadjuvant hormonal therapy improves the therapeutic ratio in patients with bulky prostatic cancer treated with three-dimensional conformal radiation therapy

PURPOSE

To determine the extent of reduction of volume of normal tissue structures exposed to high doses of radiation therapy (RT) after administration of neoadjuvant hormonal therapy (NHT) in patients with bulky, geometrically unfavorable prostatic cancers.

METHODS AND MATERIALS

Twenty-two patients with bulky prostatic cancers were treated with a 3 month course of neoadjuvant leuprolide acetate and eulexin prior to three-dimensional (3-D) conformal radiotherapy. Patients were included if 3-D treatment planning revealed that either > 30% of the rectal wall would receive 95% of the prescription dose (D95) (n = 13); > or = 50% of the bladder wall would receive D95 (n = 10); or that any volume of small bowel would receive > or = 65% of the prescription dose (n = 16). All patients underwent simulation and conformal treatment planning before and after NHT. Pre and posthormone cumulative dose volume histogram (DVH) calculations for all normal tissue structures were analyzed and compared for each patient.

RESULTS

The median percentage of target volume reduction after NHT was 25% (range: 3-52%). Ten of 13 patients (78%) whose prehormone rectal DVH demonstrated > 30% of the rectal wall receiving D95 responded to NHT with a median 25% (range: 16-48%) reduction of rectal volume receiving the D95. A median reduction of 50% (range: 6-64%) of the bladder volume receiving D95 was observed in nine of ten patients (90%), while 13 of 16 (81%) showed a reduction of small bowel volume to a median percentage of 88% (range: 67-100%) of the prehormonal values.

CONCLUSION

Neoadjuvant hormonal therapy is an effective method for decreasing the size of bulky prostatic tumors as well as for optimizing the geometry of the target volume in relation to the adjacent normal tissue structures prior to radiation therapy. Such an approach allows for reduction of the volume of normal tissues exposed to high doses in the majority of treated patients. Currently, studies are underway to determine whether NHT will lead to a decreased likelihood of long-term complications associated with radiotherapy of bulky, geometrically unfavorable prostatic tumors, and permit the safe delivery of escalated dose levels using conformal treatment techniques.

Platinum drug delivery and radiation for locally advanced prostate cancer

Combined therapies of cisplatin and radiation have resulted in clinical reports of apparent efficacious control of locoregional cancer and enhanced survival. Mechanisms of interaction between platinum and radiation that may explain these clinical observations all have in common the prediction that higher concentrations of platinum in all tumor cells close in time to irradiation should lead to greater potentiation of radiation-induced killing of those cells. Cisplatin is thus viewed as providing some radiation-equivalent, or a radiation dose-effect factor, for sterilization of tumors. One disease site that has not been well investigated for response to cisplatin plus radiation therapy, but that could benefit from it, is locally advanced prostate cancer. A body of literature now supports the view that local control of stage C (T3, N0, M0) prostate cancer is correlated with disease-free survival. This correlation makes prostate cancer a candidate for potentially achieving improved cure rates following local tumor sterilization by combining cisplatin with radiation therapy. The need and approaches to optimize delivery of cisplatin within tumor tissue is explored. Increasing cisplatin concentration to all the cells of a tumor, i.e., homogeneously delivering systemic high-dose cisplatin, should benefit the efficacious response otherwise expected for cisplatin combined with radiation. Strategies to increase the homogeneity of cisplatin delivery to a tumor are considered to be those that increase perfusion to that tumor. Vasoactive agents used in anticancer protocols are especially considered for their potential value in serving to increase tumor perfusion. These protocol-inclusive agents include certain cytokines and L-arginine antagonists, and should be better managed and accepted in practice compared to other vasoactive agents that need to be developed as specific additives to protocol designs.

Three-dimensional conformal radiation therapy in locally advanced carcinoma of the prostate: preliminary results of a phase I dose-escalation study

PURPOSE

The acute morbidity of doses of 64.8-75.6 Gy and preliminary observations of late complications and tumor response using 3-dimensional conformal radiation therapy in carcinoma of the prostate are assessed.

METHODS AND MATERIALS

123 patients (Stage A2-12, B1-17, B2-43, C-51) were irradiated to the prostate and seminal vesicles using a 3-dimensional conformal radiation therapy technique. The median follow-up time was 15.2 months. The minimum tumor dose was 64.8-66.6 Gy in 49 patients, 70.2 Gy in 46, and 75.6 Gy in 28. Toxicity was scored according to the Radiation Therapy Oncology Group morbidity grading system.

RESULTS

This technique of 3-dimensional conformal radiation therapy was well-tolerated with minimal acute morbidity. Only 32% of patients had grade 2 or 3 acute morbidity requiring short-term medication for relief of urinary symptoms or diarrhea. Only one patient (0.8%) has so far developed a severe (grade 4) late complication. Serum prostate specific antigen concentrations normalized in 67% of patients (64/96) within 1-14 months (median 4.5 months) after treatment and were progressively decreasing at last measurement in an additional 22% (21/96). Abnormal rising prostate specific antigen levels were observed in 15 patients, 11 of whom have already developed other evidence of relapsing disease.

CONCLUSION

Acute toxicity for the doses tested with this 3-dimensional conformal radiation therapy technique is reduced compared to traditional treatment techniques, and the initial tumor response as assessed by prostate specific antigen measurement is highly encouraging with prostate specific antigen levels returning to normal in the majority of patients. Based on these results, a further increase of the dose to 81 Gy has been implemented in accordance with the schema of an ongoing Phase I dose-escalation study.

Rate of relapse following treatment for localized prostate cancer: a critical analysis of retrospective reports

PURPOSE

Controversy exists over the optimal treatment for patients with clinically localized prostate cancer. Almost all of the treatment results are from non-randomized trials and interseries comparison is difficult since the apparent success of a treatment, as judged by the actuarial freedom from relapse and survival data, depends on patient selection criteria and post-treatment evaluation, in addition to the efficacy of the therapeutic intervention. In this report the calculation of a hazard function is used to estimate and compare the rate of relapse for the different treatments.

METHODS AND MATERIALS

Clinical reports from major surgery and radiation oncology treatment institutions were analyzed. The actuarial recurrence data were used to calculate the annual rate of recurrence within each series.

RESULTS

For all but the lowest volume tumors, patients continue to be at risk of relapse for as long as these series have been followed. Despite the heterogeneity of patient populations, the recurrence rates by stage are similar for patients treated with surgery or irradiation. This result is consistent with pathologic data from prostatectomy specimens which indicate that for lesions > 12 cm3 (approx. 3 cm in diameter) there is high likelihood of extraprostatic disease.

CONCLUSION

Treatment outcome for patients with localized prostate cancer may be more dependent on the inherent tumor biology than the particular type of treatment. Accordingly, the expectation and recommendation of a treatment must take into consideration the continued risk of relapse with either radiation therapy or surgery. There are, as yet, insufficient data regarding the impact of screening and earlier diagnosis on the curability of patients with localized prostate cancer.

Bilateral arcs using "averaged beam's eye views": a simplified technique for delivering 3-D based conformal radiotherapy

The purpose of this study is to describe a conformal radiotherapy technique for treating only the prostate with bilateral 120 degrees arcs using "averaged beams-eye-views" (A-BEV). For this study a CT scan from a patient with a large prostate but with a low risk for seminal vesicle involvement was chosen for comparing several different treatment techniques. Dose volume histograms (DVHs) of the prostate, femoral heads, bladder, and rectum were compared for plans using "standard" bilateral 120 degree unblocked arcs (8 x 8 and 9 x 9 cm), similar sized arcs with "generic" (small corner) blocks applied, arcs using hand drawn "semi-conformal" blocks added, and arcs using the A-BEV. The A-BEV was generated by averaging the shapes of fixed lateral and oblique BEVs from a six-field plan. These arc techniques were compared to four-field conformal (4-FC) and six-field conformal (6-FC) techniques. The addition of generic corner blocks to a 9 x 9 field resulted in a more favorable dose distribution than using open unblocked 9 x 9 arcs. The technique employing the A-BEV resulted in an improvement in the DVHs compared to other arc techniques and to 4-FC techniques. The dose volume histograms associated with using this technique approached those associated with using a 6-FC technique. Treating only the prostate with blocked arcs generated using an A-BEV results in an improved dose distribution compared to unblocked arcs and 4-FC techniques. This blocked arc technique also results in a DVH that is comparable to using a more complex 6-FC technique. Blocks that are drawn on manually reduce the dose to the surrounding normal tissues but are associated with a greater risk of underdosing the target volume. This problem is diminished when computer generated conformal blocks are used.

Estramustine potentiates the radiation effect in human prostate tumor transplant in nude mice

In this study, we have investigated the combined effect of estramustine treatment and external beam radiation on human prostatic cancer tumor cells (DU 145) transplanted in nude mice. The treatment was given according to two different schedules. In the first treatment regimen, estramustine was administered intraperitoneally (i.p.) intermittently for 20 days. The radiation therapy, which was started on day 9, was given with 6 Gy fractions during an 11-day-long period to a total dose of 36 Gy. The combination treatment (estramustine + radiation) resulted in a significant tumor growth retardation as compared to the control group. This pronounced effect was seen neither with radiation alone nor with estramustine alone. In order to further extend the radiation treatment time, a second therapy regimen was employed. In this part of the study, estramustine was administered i.p. intermittently for 26 days. The radiation therapy, which was started on day 6, was given with 4 Gy fractions during a 21-day-long period to a total dose of 40 Gy. Under these conditions, a significant tumor growth retardation was disclosed, when comparing the combination treatment (estramustine + radiation) with radiation alone. The tumors were analyzed for content of necrosis and proliferative activity. The largest proportion of necrosis was seen in the combination (estramustine + radiation) treatment group. Also, the tumors from this group expressed a decreased proliferative activity. The data indicate that estramustine acts as a radiosensitizing agent in human prostatic cancer cells in vivo. The radiosensitizing properties of the drug encourage further studies with respect to clinical application.

Localized carcinoma of the prostate (stages T1B, T1C, T2, and T3). Review of management with external beam radiation therapy

BACKGROUND

Optimal treatment for patients with localized carcinoma of the prostate is controversial. Radiation therapy is an established modality in the management of these patients, and several reports indicate the results are comparable to those achieved with radical prostatectomy. Recently effectiveness of therapy for carcinoma of the prostate is being evaluated in light of post-treatment prostate-specific antigen (PSA) determinations.

METHODS

A review was performed of multiple publications and data from selected institutions with large experience in the management of carcinoma of the prostate. Survival and clinical incidence of local recurrence and distant metastases were analyzed as well as preliminary data on postirradiation PSA levels. Factors that affect the outcome of therapy and relevant clinical trials are discussed.

RESULTS

Reported differences in the age of patients treated with radical prostatectomy (59-63 years), irradiation (63-69 years), or observation (69-75.5 years) were identified. The effect of surgical staging on outcome of irradiation was significant. In multiple series of patients clinically and radiographically staged, the 5-year disease-free survival (DFS) with external irradiation was 95-100% for clinical stage T1a, 80-90% for Stage T1b,c, and 50-70% for clinical Stage T3. A correlation has been identified between the initial PSA levels and the probability from freedom of chemical failure (PSA elevation) after definitive irradiation. In five series comprising 814 patients with Stage T1c and T2 tumors, the DFS (end point chemical failure) was 95%, with initial PSA of less than 4 ng/ml, 83-92% with 4.1-10 ng/ml, 35-85% with 10.1-20 ng/ml, and 10-63% with PSA higher than 20 ng/ml. In the various series, follow-up ranged from a median of 1.5 years to a minimum of 4 years. In two series of 225 and 201 patients receiving doses of 7500-8000 cGy, less morbidity has been observed with three-dimensional treatment planning conformal radiation therapy than with conventional irradiation. New directions for future clinical trials are discussed, including dose escalation studies; use of high linear energy transfer to improve locoregional tumor control; and combination of irradiation and androgen suppression to enhance local tumor control, decrease distant metastasis, and improve survival. Preliminary results of a randomized study recently reported by RTOG strongly suggest that the use of goserelin acetate and flutamide decreases the incidence of clinical local recurrence (12.4% in 225 patients) compared with a control group treated with irradiation alone (25.2% in 230 patients) and enhances disease-free survival.

CONCLUSIONS

Although modern approaches to the management of patients with localized carcinoma of the prostate with irradiation are effective, investigators must continue to critically assess policies of treatment, develop appropriately designed prospective clinical trials, and define the optimal management of patients with localized carcinoma of the prostate.