Beam's eye view based prostate treatment planning: is it useful?

Prostate Cancer Radiation Therapy: What Do Clinicians Have to Know?

Radiotherapy (RT) for prostate cancer (PC) has steadily evolved over the last decades, with improving biochemical disease-free survival. Recently population based research also revealed an association between overall survival and doses ≥ 75.6 Gray (Gy) in men with intermediate- and high-risk PC. Examples of improved RT techniques are image-guided RT, intensity-modulated RT, volumetric modulated arc therapy, and stereotactic ablative body RT, which could facilitate further dose escalation. Brachytherapy is an internal form of RT that also developed substantially. New devices such as rectum spacers and balloons have been developed to spare rectal structures. Newer techniques like protons and carbon ions have the intrinsic characteristics maximising the dose on the tumour while minimising the effect on the surrounding healthy tissue, but clinical data are needed for confirmation in randomised phase III trials. Furthermore, it provides an overview of an important discussion issue in PC treatment between urologists and radiation oncologists: the comparison between radical prostatectomy and RT. Current literature reveals that all possible treatment modalities have the same cure rate, but a different toxicity pattern. We recommend proposing the possible different treatment modalities with their own advantages and side-effects to the individual patient. Clinicians and patients should make treatment decisions together (shared decision-making) while using patient decision aids.

High conformality radiotherapy in Europe: thirty-one centres participating in the quality assurance programme of the EORTC prostate trial 22991

Today, conformality in radiotherapy is at the centre of many investments in equipment and staffing. To estimate the current situation within the European Organisation for Research and Treatment of Cancer (EORTC) conformal radiotherapy trial for prostate cancer, a technology questionnaire was designed to assess whether participating centres can comply with the required radiotherapy procedures of EORTC trial 22991, where a high dose is prescribed to the prostate. Questions covered various items of computed tomography, data acquisition, treatment planning, delivery and verification. All centres (n=31) replied to the questionnaire. All generate beam's eye views and dose volume histograms. All, but two, centres use digitally reconstructed radiographs to display images. The vast majority of the centres perform at least weekly treatment verification and half have access to individual in vivo dosimetry. The results of the questionnaire indicate that participating centres have access to the equipment and apply the procedures that are essential for conformal prostate radiotherapy. The technology questionnaire is the first step in the extensive quality assurance programme dedicated to this high-tech radiotherapy trial.

Evolution of toxicity after conformal radiotherapy for prostate cancer

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

In the radiotherapy of prostate cancer, technique determines the doses to the penile structures

For 11 consecutive prostate cancer patients undergoing three-dimensional conformal radiotherapy (3DCRT) in our institution, penile structures (PNS) were outlined in CT images obtained for treatment planning purposes. Dose-volume histograms (DVHs) were compared in order to study dose-volume relations for three techniques: 4FLD, an axial coplanar, four-field box technique; 6FLD, a six-field coplanar technique; and 4NAX, a coplanar but non-axial, four-field technique. All three techniques delivered equal doses to the planning target volumes (PTV). Our statistical analyses strongly indicate that the three techniques can be ranked as 6FLD better than 4FLD (and 4FLD better than 4NAX) as far as irradiating PNS volume during treatment of prostate cancer (PC) is concerned. For each technique, there is a "spread" owing to differences in patient anatomy and/or target size, position, and extent, but each technique has a similar "profile" or "shape" distinct from other techniques. Whether irradiating smaller volumes of PNS will influence the sexual potency outcome remains to be demonstrated. However, PNS should be considered as another critical structure in addition to rectum, bladder and femoral heads in the radiotherapy (RT) of PC, especially in 3DCRT dose escalation studies. Sexual potency outcomes can be correlated to dose-volume relations in the future and this will help refine radiotherapy techniques further.

[Comparison of different 3-dimensional irradiation techniques in local radiotherapy of prostatic carcinoma]

PURPOSE

Four different three-dimensional planning techniques for localized radiotherapy of prostate cancer were compared with regard to dose homogeneity within the target volume and dose to organs at risk, dependent upon tumor stage.

PATIENTS AND METHODS

Six patients with stage T1, 7 patients with stage T2 and 4 patients with stage T3 were included in this study. Four different 3D treatment plans (rotation, 4-field, 5-field and 6-field technique) were calculated for each patient. Dose was calculated with the reference point at the isocenter (100%). The planning target volume was encompassed within the 95% isodose surface. All the techniques used different shaped portal for each beam. Dose volume histograms were created and compared for the planning target volume and the organs at risk (33%, 50%, 66% volume level) in all techniques.

RESULTS

The 4 different three-dimensional planning techniques revealed no differences concerning dose homogeneity within the planning target volume. The dose volume distribution at organs at risk show differences between the calculated techniques. In our study the best protection for bladder and rectum in stage T1 and T2 was achieved by the 6-field technique. A significant difference was achieved between 6-field and 4-field technique only in the 50% volume of the bladder (p = 0.034), between the 6-field and rotation technique (all volume levels) and between 5-field and rotation technique (all volume levels). In stage T1, T2 6-field and 4-field technique in 50% (p = 0.033) and 66% (p = 0.011) of the rectum volume. In stage T3 a significant difference was not observed between the 4 techniques. The best protection of head of the femur was achieved by the rotation technique.

CONCLUSION

In the localized radiotherapy of prostate cancer in stage T1 or T2 the best protection for bladder and rectum was achieved by a 3D-planned conformal 6-field technique. If the seminal vesicles have been included in the target volume and in the case of large planning target volume other techniques should be taken for a better protection for organs at risk e. g. a 3D-planned 4-field technique box technique.

Comparing 3-, 4- and 6-fields techniques for conformal irradiation of prostate and seminal vesicles using dose-volume histograms

BACKGROUND AND PURPOSE

Comparing some isocentric coplanar techniques for conformal irradiation of prostate and seminal vesicles.

MATERIALS AND METHODS

Five conformal techniques have been considered: (A) a 3-fields technique with an antero-posterior (AP) field and two lateral (LAT-LAT) 30 degrees wedged fields; (B) a 3-fields technique with an AP field and two oblique posterior (OBL) 15 degrees wedged fields with relative weights of 0.8, 1 and 1, respectively; (C) a 4-fields technique (AP-PA and LAT-LAT); (D) a 6-fields technique (LAT-LAT and four OBL at gantry angles 45 degrees, 135 degrees, 235 degrees and 315 degrees) with all the fields having the same weight; (E) the same 6-fields technique with lateral fields double-weighted with respect to the oblique fields. The conformal plans have been simulated on 12 consecutive patients (stages B and C) by using our 3D treatment planning system (Cadplan 2.7). The contours of the rectum, the bladder and the left femoral head were outlined together with the clinical target volume (CTV) which included the prostate and the seminal vesicles. A margin of 10 mm was added to define the planning target volume (PTV) through automatic volume expansion. Then a 7 mm margin between the PTV and block edges was added to take the beam penumbra into account. Dose distributions were normalised to the isocentre and the reference dose was considered to be 95% of the isocentre dose. Dose-volume histograms and dose statistics of the rectum, the bladder and the left femoral head were collected for all plans. For the rectum and the bladder the mean dose (Dm) and the fraction of volume receiving a dose higher than the reference dose (V95) were compared. For the femoral head, the mean dose together with the fraction of volume receiving a dose higher than 50% (V50) were compared.

RESULTS

Differences among the techniques have been found for all three considered organs at risk. When considering the rectum, technique A is better than the others both when considering Dm and V95 (P = 0.002), while technique D is the worst when considering Dm (P < 0.002) and is also worse than techniques A, E (P = 0.002) and C (P = 0.003) when considering V95. Technique E is the best when considering the bladder mean dose (P = 0.002 against A and D, P < 0.01 against B and C) and technique C is the worst (P < 0.012). No relevant differences were found for the bladder V95. In the femoral heads, techniques A and E are worse than B, C and D (P < 0.003) when considering Dm and V50. Moreover, techniques B and D are better than C (P < 0.004) when considering V50.

CONCLUSIONS

There is no technique that is absolutely better than the others. Technique A gives the best sparing of the rectum; the bladder is better spared with technique E. These results are reached with a worse sparing of the femoral heads which should be carefully taken into account.

[Planned 3-dimensional low-volume conformal irradiation of a local prostatic carcinoma]

AIM

Recent data have shown a significant reduction of acute side effects by means of a three-dimensional planned conformal radiotherapy of carcinoma of the prostate compared to treatment techniques used before. Theoretically, an optimized field coverage of the planning target volume should result in a reduction of treated bladder and rectum volumes. We studied the effects of individualized blocks on treatment volumes, planning target volumes, irradiated bladder and rectum volumes on basis of three-dimensional treatment planning by means of beam's-eye-view technique.

PATIENTS AND METHOD

We compared dose-volume-histograms of 2 different planning models, a (fictitious) open 4-field-box-technique and a technique with conformal blocked fields designed from the beam's-eye-view display (prescribed dose 66 Gy, daily single fraction 2 Gy). Plans of 115 patients with localized prostate cancer treated from January 1994 to February 1996 were analyzed.

RESULTS

Using individualized fields treatment volume (covered by the 90%-isodose) was reduced by 23% on the average in comparison to the planning model without blocks. The averaged difference of treated volume and planning target volume, as a grade of efficiency of conformation, was reduced by 38% (496 cm3 303 cm3) using individualized blocks. 23% of the treated bladder volume and 13% of the treated rectum volume had been saved on the average. Nevertheless, at least 11.5% of the bladder volume and 27.6% of the contoured rectum volume were treated with the prescribed dose (55 Gy = 100%).

CONCLUSIONS

The comparison of dose-volume-histogram-data showed that especially high dose volumes of organs at risk had been saved by means of individualized blocks created from the beam's-eye-view. The blocks did not affect the dose distribution of the planning target volume adversely. Consequently the impact of these data on the extent of side effects and local tumor control has to be proven.

Potency probability following conformal megavoltage radiotherapy using conventional doses for localized prostate cancer

PURPOSE

Impotence is a familiar sequela of definitive external beam radiation therapy (EBRT) for localized prostate cancer; however, nerve-sparing radical prostatectomy (NSRP) has offered potency rates as high as 70% for selected for patients in several large series. To the authors' knowledge, age and stage-matched comparisons between the effects of EBRT and NSRP upon the normal age trend of impotence have not been performed. Herein, we report the change in potency over time in an EBRT-treated population, determine the significantly predisposing health factors affecting potency in this population, and compare age and stage-matched potency rates with those of normal males and prostatectomy patients.

METHODS AND MATERIALS

Our results are obtained from a retrospective study of 114 patients ranging in age from 52 to 85 (mean, 68) who were diagnosed with clinical stages A-C C (T1-T4N0M0) prostate cancer and then treated conformally with megavoltage x-rays to 6500-7000 cGy (180-200 cGy per fraction) using the four-field box technique. Information concerning pre-RT potency, medical and surgical history, and medications was documented for each patient as was time of post-RT change in potency during regular follow-up. The median follow-up time was 18.5 months.

RESULTS

The actuarial probability of potency for all patients gradually decreased throughout post-RT follow-up. At months 1, 12, 24, and 36, potency rates were 98, 92, 75, and 66%, respectively. For those patients who became impotent, the median time to impotence was 14 months. Factors identified from logistic regression analysis as significant predictors of post-EBRT impotence include pre-EBRT partial potency (p < 0.001), vascular disease (p < 0.001), and diabetes (p = 0.003). Next, an actuarial plot of potency probability to patient age for the EBRT-treated population was compared to that obtained from the Massachusetts Male Aging Study of normal males. The two curves were not significantly different (logrank test, p = 0.741) between ages 50 and 65. Finally, potency probability after follow-up of 1 year or more in EBRT-treated patients was stratified by age and substratified by clinical stage and then compared to similarly stratified potencies for patients treated with NSRP. The prostatectomy data were derived from the pooled data of six large (total n, 952), independent series conducted at academic centers. For patients older than 70 years, 79.1% of EBRT patients and 32.9% of NSRP patients remained potent after treatment. For patients with stage B2 disease, 75.0% of EBRT patients and 49.3% of NSRP patients remained potent after treatment. Overall EBRT patient potency was 76.1% vs. 66.2% for NSRP patients.

CONCLUSIONS

1) By 36 months after completion of EBRT for localized prostate cancer, fully one-third of all patients becomes impotent; however, for patients younger than 70 years, the probability of impotence does not depart significantly from that for normal males. 2) In the EBRT-treated population, pre-EBRT partial potency, vascular disease, and diabetes are the most significant predispositions to the development of impotence. Patients with these predispositions, though, do not become impotent significantly earlier than other patients. 3) When comparing age and stage-stratified potency rates for EBRT and NSRP patients, potency is roughly equal for both modalities for most age and stage groups; however, for patients older than 70 years or with stage B2 disease, EBRT offers notably higher posttreatment potency rates than NSRP. Thus, for the treatment of localized prostate cancer, EBRT may not affect the normal age trend of impotence in younger patients and may induce impotence less frequently than NSRP in older patients or in patients with later stage disease.

Localization of the prostatic apex for radiotherapy planning: a comparison of two techniques

Autopsy and pathology studies have shown that the caudal portion of the prostate gland harbors tumour in 64-75% of specimens examined. Accurate localization of the prostatic apex may be important in improving local control with external beam radiation therapy. We compared the location of the apex obtained with CT based treatment planning versus localization using retrograde urethrography in 32 consecutive patients. The prostatic apex, localized by CT and retrograde urethrography, was compared relative to the ischial tuberosities and the symphysis pubis. Discordance between the location of the prostatic apex as defined on CT scan and retrograde urethrography was found in 50% of patients evaluated. There was 31% discordance between the location of the prostatic apex as defined on CT and retrograde urethrography when data were analysed with the location of the prostatic apex 1 cm above the narrowing on urethrography, a definition others have suggested. The urethrogram defined prostatic apex, as compared with the CT definition, necessitated the treatment of more of the surrounding normal tissues in 31% of our cases, with four-field techniques. Comparison of dose-volume histograms of the bladder, rectum and penis irradiated for target volumes defined by CT versus retrograde urethrography showed that more penis was irradiated in some patients with the urethrogram defined prostatic apex; irradiation of the base of the penis could be relatively avoided by using a six-field treatment plan instead of the standard four-field box. There is discordance between the CT and urethrogram defined prostatic apex. Dose-volume histogram information suggests that differences in apex localization can significantly affect doses to normal adjacent prostatic tissues. Combining CT localization with the urethrogram localization of the prostatic apex optimizes radiotherapy planning and dose delivery.

Advanced interactive planning techniques for conformal therapy: high level beam descriptions and volumetric mapping techniques

PURPOSE

To aid in design of conformal radiation therapy treatment plans involving many conformally shaped fields, this work investigates the use of two methodologies to enhance the ease of interactive treatment planning: high-level beam constructs and beam's-eye view volumetric mapping.

METHODS AND MATERIALS

High-performance computer graphics running on various workstations using a graphical visualization system (AVS) have been used in this work. Software specific to this application has been written in standard FORTRAN and C languages. A new methodology is introduced by defining radiation therapy "fields" to be composed of multiple beam "segments." Fields can then be defined as higher-level entities such as arcs, cones, and other shapes. A "segmental cone" field, for example, is defined by a symmetry axis and a cone angle, and can be used to rapidly place a series of beam segments that converge at the target volume, while reducing the degree of overlap elsewhere. A new beam's-eye view (BEV) volumetric mapping technique is presented to aid in selecting the placement of conformal radiation fields. With this technique, the relative average dose within an organ of interest is calculated for a sampling of isocentric, conformally shaped beams and displayed either as a "globe," which can be combined with the display of anatomical surfaces, or as a two-dimensionally mapped projection. The dose maps from multiple organs can be generated, stacked, or composited with relative weightings to aid in the placement of fields that minimize overlap with critical structures.

RESULTS

The use of these new methodologies is demonstrated for prostate and lung treatment sites and compared to conventional planning techniques.

DISCUSSION

The use of many beams for conformal treatment delivery is difficult with current interactive planning. The use of high-level beam constructs provides a means to quickly specify, place, and configure multiple beam arrangements. The BEV volumetrics aids in the placing of fields, which minimize involvement with critical normal tissues.

CONCLUSIONS

Early experience with the new methodologies suggest that the new methods help to enhance (or at least speed up) the ability of a treatment planner to create optimal radiation treatment field arrangements.

Potential underdosing with the use of electron beam therapy in patients with cervical adenopathy and advanced head and neck cancer

To define the adequacy of electron beam therapy in the treatment of N1-N3 head and neck cancer, 24 patients with primary head and neck cancers and N1-N3 cervical adenopathy received primary radiation therapy with or without chemotherapy for definitive control of their disease. All patients underwent computerized tomography (CT) to assist in the design of treatment to the posterior neck with electron beams after photon therapy to the level of spinal cord tolerance. Treatment with electrons to the posterior neck in patients with N1 disease was adequate in 92% (11/12) of patients. However, in patients with N2 and N3 disease, electron beam treatment failed, because of spinal cord tolerance problems, to cover the disease adequately in 92% (11/12). It is concluded that CT should be employed routinely in patients with N1-N3 neck disease to determine the proper electron energy prescription. For some patients, electron beam may not be appropriate, making it necessary to use individual planning to treat adequately the neck disease and avoid the spinal cord.

Potential underdosing with the use of electron-beam therapy in patients with cervical adenopathy and advanced head and neck cancer

To define the adequacy of electron-beam therapy in the treatment of N1-N3 head and neck cancer, 24 patients with primary head and neck cancers and N1-N3 cervical adenopathy received primary radiation therapy with or without chemotherapy for definitive control of their disease. All patients underwent computerized tomography (CT) to assist in the design of treatment to the posterior neck with electron beams after photon therapy to the level of spinal cord tolerance. Treatment with electrons to the posterior neck in patients with N1 disease was adequate in 92% (11/12) of patients. However, in patients with N2/N3 disease, electron beam failed, because of spinal-cord tolerance problems, to adequately cover disease in 92% (11/12). It is concluded that CT should be routinely employed in patients with N1-N3 neck disease to determine the proper electron-energy prescription. For some patients, electron beam may not be appropriate, making it necessary to use individual planning to treat adequately the neck disease and avoid the spinal cord.

Acute toxicity during external-beam radiotherapy for localized prostate cancer: comparison of different techniques

PURPOSE

The chronic and acute toxicities associated with conventional radiotherapy of localized prostate cancer are well documented. However, the degree and incidence of toxicities with conformal techniques are not known. Studying side effects associated with modern radiotherapeutic techniques is more important now since there has been a general trend to use computerized tomography-based techniques in recent years; beam's eye view-based conformal techniques are also becoming more commonplace. It is possible that the local disease control can be improved with the delivery of higher doses than currently used. Conformation of the treatment volume to the target volume may facilitate such dose-escalation. However, prior to such dose-escalation, it is important to know the toxicities associated with such techniques with conventional doses.

METHODS AND MATERIALS

We have compared week-by-week acute toxicities associated with conventional (Group A, 16 patients), computerized tomography-based, manual (Group B, 57 patients) and beam's eye view-based (Group C, 43 patients) techniques during 7 weeks of radiotherapy. Group B and C patients were treated contemporaneously (1988-1990).

RESULTS

Acute side effects gradually increased from week 1 through weeks 4-5 and generally declined or plateaued after that. The incidence of acute toxicities was significantly less with the beam's eye view/based technique than with the other two methods. For instance, the percentages of Grade 2 acute genitourinary toxicities for Groups A, B, and C were as follows: Week 1-0, 0, 0; Week 2-6, 0, 0; Week 3-6, 9, 2; Week 4-12, 14, 9; Week 5-35, 14, 9; Week 6-31, 16, 7; Week 7-33, 8, 8, respectively. The p values associated with differences in acute genitourinary toxicities for Weeks 1-7 using chi-square test were 0.072, 0.627, 0.389, 0.538, 0.123, 0.06, and 0.012; the p values for acute gastrointestinal toxicities were 0.512, 0.09, 0.031, 0.031, 0.003, < 0.0001, and 0.004, respectively. Pairwise comparison (Wilcoxon rank-sum test) showed statistically significant lower acute toxicity in Group C than Group B (e.g., p values, Weeks 1-7 for gastrointestinal toxicity: 0.633, 0.056, 0.010, 0.014, < 0.0001, < 0.0001, and < 0.0001, respectively) in the latter part of the treatment course. No correlation was found between the extent of toxicity and the patient age or the overall treatment time. Also, no correlation was found between the degree of toxicity and the radiation dose and fraction size, within the narrow ranges used (65-70 Gy and 180-200 cGy, respectively). A trend suggesting increased severity of toxicity with increase in the volume of treatment was seen.

CONCLUSION

The findings in this retrospective study need to be confirmed by other prospective studies.

An analysis of image segmentation time in beam's-eye-view treatment planning

In this work we tabulate and histogram the image segmentation time for beam's eye view (BEV) treatment planning in our center. The average time needed to generate contours on CT images delineating normal structures and treatment target volumes is calculated using a data base containing over 500 patients' BEV plans. The average number of contours and total image segmentation time needed for BEV plans in three common treatment sites, namely, head/neck, lung/chest, and prostate, were estimated.

Comparison of CT-based treatment planning and retrograde urethrography in determining the prostatic apex at simulation

In 20 consecutive patients who underwent treatment planning, localization of the prostatic apex with CT-based techniques at simulation was compared to location of the apex as defined by retrograde urethrography. In addition, the location of the urethrogram-defined prostatic apex was compared with the bottom of the ischial tuberosities, which is often recommended as the inferior margin of the field. In 15% of the patients there was agreement between the CT-defined apex and the urethrogram-defined apex; in 85% there was discordance. In a majority of patients with discordance, the urethrogram apex was located caudad to the CT-defined apex (71%) with a median difference of .65 cm. In 29% of the patients the urethrogram apex was located superior to the CT-defined apex. Overall, 75% of the patients had discordance between the urethrogram apex and the CT apex of 0.5 cm or greater; 30% had an absolute difference of 1.0 cm or greater. Comparing the location of the prostatic apex with the bottom of the ischial tuberosities revealed that in 15% of the patients the apex was 1.0 cm or less from the bottom of the tuberosities and in 45% it was less than 1.5 cm. This would place the apex of the prostate in the penumbra region of the field and risk undertreatment of the prostate if the bottom of the ischial tuberosities was the inferior margin of the field. Measuring the location of the prostatic apex from the top of the symphysis pubis revealed that a distance of 4.9 cm encompassed the apex in all 20 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Maximizing setup accuracy using portal images as applied to a conformal boost technique for prostatic cancer

A design procedure of a patient setup verification protocol based upon frequent digital acquisition of portal images is demonstrated with an application for conformal prostatic boost fields. The protocol aims at the elimination of large systematic deviations in the patient setup and includes decision rules which indicate when correction of the patient setup is needed. The decision rules were derived from the results of a theoretical and quantitative analysis of patient setup variations measured in three pelvic fields (one anterior-posterior and two lateral fields) of 105 fractions for nine patients. Deviations in the patient positioning, derived from one field, were quantified as two-dimensional (2-D) displacement vectors in the plane perpendicular to the beam axis by alignment of anatomical features in the portal and the simulator image. The magnitude of the overall setup variations along the anterior-posterior, superior-inferior and lateral directions varied between 2.6 and 3 mm (1 S.D.). Inter- and intra-treatment variations could be separated, both having equal magnitudes of 1.7 to 2.2 mm (1 S.D.). In addition, intra-treatment variations appeared to be predictable which was a prerequisite for the development of the decision rules. The 2-D setup deviations, measured in the three fields of one fraction were strongly correlated and a 3-D displacement vector was calculated. Utilization of this 3-D vector in a setup verification protocol may lead to an early detection of systematic setup deviations.

Radiotherapy for prostate cancer: should the seminal vesicles be considered target?

During radiotherapy for prostate cancer, the ability to predict occult seminal vesicle invasion is important since irradiation of the entire seminal vesicles necessitates enlarging the radiation fields beyond what is usually used to irradiate the prostate gland alone. We analyzed the records of 302 patients with clinical Stage T1 or T2 adenocarcinoma of the prostate treated with radical surgery at Duke University Medical Center between 1970 and 1983. Univariate and multivariate analyses were used to examine the relationship between the risk of occult seminal vesicle involvement (defined herein as histologic involvement of the seminal vesicles not detected by physical or radiologic examination) and the following factors: histologic grade, age, clinical stage, and preoperative acid phosphatase. Among 249 patients with complete information, increasing histologic grade (p < 0.001) and clinical stage (p < 0.04) were found to be the strongest predictors of occult seminal vesicle invasion. Conversely, seminal vesicle invasion was very unusual in well-differentiated T1-T2 tumors (6%). This low risk group represented 28% (70/249) of this patient population. There appears to be a substantial subset of patients with well differentiated T1 or T2 tumors who are at very low risk for occult seminal vesicle involvement and in whom the seminal vesicles can be excluded from the target volume. The reduction in target volume may reduce normal tissue reactions, facilitate dose escalation, and possibly increase local control rates.

Beams eye view-based photon radiotherapy I

Geographic miss, dosimetric miss (underdosing), and proximity of the tumor to sensitive normal tissues are some of the causes of inadequate radiation dose delivery; this is one of many causes of failure after radiotherapy. In the past decade, computerized tomography (CT)-based treatment planning has helped to overcome some of these problems. Beam's eye view (BEV)-based radiotherapy planning is an improvement over CT-based treatment planning that may further increase the therapeutic ratio. Since January 1988, we have treated 198 patients with BEV-based photon radiotherapy. About 40% of our patients treated with radical radiotherapy undergo BEV-based treatment, and about 70% of patients who undergo planning CT in the treatment position receive BEV-based radiotherapy. Our findings are as follows: (a) routine use of BEV-based RT (BEVRT) is possible in a busy radiation oncology department; (b) BEVRT improves geometric coverage of tumors; (c) BEVRT is extremely useful in the design of oblique portals; (d) time commitments for various members of the RT treatment-planning team are reasonable; (e) BEVRT helps individualize RT technique; (f) preliminary data suggest decreased acute toxicity with the use of BEVRT for prostate cancer patients. Whether these advantages will help to improve the outcome (i.e., improve local control and survival) and/or decrease the long-term toxicity is not yet known.