The biological basis for conformal three-dimensional radiation therapy

Clinical use of a simulation-multileaf collimator

BACKGROUND

At the University of Lübeck, radiotherapy is delivered by a 6/18-MV linear accelerator. Using the integrated multileaf collimator, irradiation of individually shaped treatment fields is possible in place of alloy blocks. Due to unsatisfactory pretherapeutic review of the radiation-field-specific multileaf collimator (MLC) configuration, we developed a simulation-multileaf collimator (SMLC) and assessed its feasibility at different tumor sites.

MATERIAL AND METHODS

The SMLC is made of a perspex carrier with 52 horizontal sliding leaves. The position of each leaf is calculated by a 3D treatment-planning computer. The technician manually adjusts the leaves according to the beams-eye-view plot of the planning computer. Consequently, the SMLC is mounted on the therapy simulator at a distance of 64.8 cm from the focus. The treatment fields and the position of the leaves are documented by X-ray films.

RESULTS

Using the SMLC, radiation oncologists are able to review exactly the leaf configuration of each MLC-shaped radiation field and to correlate the MLC-shaped radiation field with the treated volume, the organs at risk and the port films acquired by the Portal Vision system.

CONCLUSION

The SMLC is a new tool to review radiation planning that uses an MLC in daily routine. The use of the SMLC improves the documentation and the quality assurance. It accelerates the treatment field review at the linear accelerator by comparing the SMLC simulator films with the portal images.

An audit of 3D treatment planning facilities and practice in the UK

The availability and use of 3D treatment planning facilities in the UK was investigated by questionnaire. Fifty-eight of the 62 UK radiotherapy centres responded (94%). There was considerable variation in the facilities available and in the manner in which they were used. Although 36 centres (62%) have the facilities to undertake complex, non-coplanar treatment planning, only 12 did so on a regular basis. More surprising was the inconsistent implementation of coplanar CT planning. It is suggested that we need to work towards reaching a consensus on best practice in radiotherapy planning. This will require the creation of systems for guidance and further training of the various staff involved.

Dosimetric verification of the dynamic intensity-modulated radiation therapy of 92 patients

PURPOSE

To verify that optimized dose distributions provided by an intensity-modulated radiation therapy (IMRT) system are delivered accurately to human patients.

METHODS AND MATERIALS

Anthropomorphic phantoms are used to measure IMRT doses. Four types of verification are developed for: I) system commissioning with beams optimized to irradiate simulated targets in phantoms, II) plans with patient-optimized beams directed to phantoms simulating the patient, III) patient-phantom hybrid plans with patient-optimized beams calculated in phantom without further optimization, and IV) in vivo measurements. Phantoms containing dosimeters are irradiated with patient-optimized beams. Films are scanned and data were analyzed with software. Percent difference between verified and planned maximum target doses is defined as "dose discrepancy" (deltavp). The frequency distribution of type II deltavp from 204 verification films of 92 IMRT patients is fit to a Gaussian. Measurements made in vivo yield discrepancies specified as deltaivp, also fit to a Gaussian.

RESULTS AND DISCUSSION

Verification methods revealed three systematic errors in plans that were corrected prior to treatment. Values of [deltavp] for verification type I are <2%. Type II verification discrepancies are characterized by a Gaussian fit with a peak 0.2% from the centroid, and 158 [deltavp] <5%. The 46 values of [deltavp] >5% arise from differences between phantom and patient geometry, and from simulation, calculation, and other errors. Values of [deltavp] for verification III are less than half of the values of [deltavp] for verification II. A Gaussian fit of deltaivp from verification IV shows more discrepancy than the fit of deltavp, attributed to dose gradients in detectors, and exacerbated by immobilization uncertainty.

CONCLUSIONS

Dosimetric verification is a critical step in the quality assurance (QA) of IMRT. Hybrid Verification III is suggested as a preliminary quality standard for IMRT.

[Conformational radiotherapy with multi-leaf collimators: one year experience at the Leon-Berard Centre]

Taking advantage of the renewal of a linear accelerator, the Radiation Therapy Department of the Centre Léon Bérard implemented, in collaboration with Philips Systèmes Médicaux, a conformal therapy set-up procedure using CT-scan for 3D treatment planning and a multileaf collimator that allows achievement of numerous irregular-shaped beams via the multileaf preparation system. The various elements of this equipment make possible well defined and structured procedures for treatment planning with different steps and essential tools used by this technique. We describe the means used and indicate future improvements that will lead to automation in order to provide good quality assurance, better security and substantial time saving. During the first year, 115 patients were treated with this new technique. They presented with central nervous system tumors (32 patients), lung cancer (29 patients), prostate cancer (20 patients), paranasal sinus tumors (14 patients) and tumors located in other sites (13 patients with soft sarcoma, hepato-bilary tumor, etc).

Potential clinical efficacy of intensity-modulated conformal therapy

PURPOSE

The purpose of this study was to examine the potential benefit of using intensity-modulated conformal therapy for a variety of lesions currently treated with stereotactic radiosurgery or conventional radiotherapy.

METHODS AND MATERIALS

Intensity-modulated conformal treatment plans were generated for small intracranial lesions, as well as head and neck, lung, breast, and prostate cases, using the Peacock Plan treatment-planning system (Nomos Corporation). For small intracranial lesions, intensity-modulated conformal treatment plans were compared with stereotactic radiosurgery treatment plans generated for patient treatment at the University of Florida Shands Cancer Center. For other sites (head and neck, lung, breast, and prostate), plans generated using the Peacock Plan were compared with conventional treatment plans, as well as beam's-eye-view conformal treatment plans. Plan comparisons were accomplished through conventional qualitative review of two-dimensional (2D) dose distributions in conjunction with quantitative techniques, such as dose-volume histograms, dosimetric statistics, normal tissue complication probabilities, tumor control probabilities, and objective numerical scoring.

RESULTS

For small intracranial lesions, there is little difference between intensity-modulated conformal treatment planning and radiosurgery treatment planning in the conformation of high isodose lines with the target volume. However, stereotactic treatment planning provides a steeper dose gradient outside the target volume and, hence, a lower normal tissue toxicity index. For extracranial sites, objective numerical scores for beam's-eye-view and intensity-modulated conformal planning techniques are superior to scores for conventional treatment plans. The beam's-eye-view planning technique prevents geographic target misses and better excludes healthy tissues from the treatment portal. Compared with scores for the beam's-eye-view planning technique, scores for intensity-modulated conformal plans using the Peacock Plan were significantly better for the lung and head and neck cases studied, equivalent for prostate cases, and inferior for breast cases.

CONCLUSION

Using the entire 3D data set to construct radiotherapy plans through virtual simulation is always advantageous, whether done for stereotactic radiosurgery, beam's-eye-view conformal therapy, or intensity-modulated conformal treatment. Intensity modulation of the photon beam further enhances treatment planning under specific conditions. In general, the intensity-modulated technique is advantageous for large, irregular targets with critical structures in close proximity. Intensity-modulated treatment planning does not appear advantageous for stereotactic radiosurgery or treatment of the intact breast.

Cost benefit of emerging technology in localized carcinoma of the prostate

PURPOSE

In a health care environment strongly concerned with cost containment, cost-benefit studies of new technology must include analyses of loco-regional tumor control, morbidity, impact on quality of life, and financial considerations.

METHODS AND MATERIALS

This nonrandomized study analyzes 124 patients treated with three-dimensional conformal radiation therapy (3D CRT) and 153 with standard irradiation (SRT) between January 1992 and December 1995, for histologically proven adenocarcinoma of prostate, clinical Stage T1 or T2. Mean follow-up is 1.4 years. Three-dimensional CRT consisted of six or seven coplanar oblique and lateral and, in some patients, AP fields designed to treat the prostate with a 1 to 1.7 cm margin. SRT consisted of 120 degrees bilateral arc rotation. Total doses to prostate were 67 to 70 Gy when pelvic lymph nodes were irradiated or 68.4 to 73.8 Gy when prostatic volume only was treated; dose per fraction was 1.8 Gy. Patients were interviewed weekly for severity of 12 acute intestinal and urinary pelvic irradiation side effects (0 to 4+ grading). Time and effort for 3D RTP and daily treatment with 3D CRT and SRT were recorded. Dose-volume histograms (DVHs) were calculated for gross tumor volume, planning target volume, bladder, and rectum. Actual reimbursement to the hospital and university was determined for 41 3D CRT, 43 SRT, and 40 radical prostatectomy patients treated during the same period.

RESULTS

Average treatment planning times (in minutes) were: 101 for 3D conformal therapy simulation, 66 for contouring of target volume and sensitive structures, 55 for virtual simulation, 39 for plan preparation and documentation, 65 for physical simulation, and 20 for approval of treatment plan. Daily mean treatment times were 19 min for 3D CRT with Cerrobend blocking, 16 with multileaf collimation, and 10 with bilateral arc rotation. Dosimetric analysis (DVHs) showed a reduction of 50% in volume of bladder or rectum receiving doses higher than 65 Gy. Acute side effects included dysuria, moderate difficulty in urinating, and nocturia in 25-39% of both SRT and CRT patients; loose stools or diarrhea in 5-12% of 3D CRT and 16-22% of SRT patients; moderate proctitis in 3% of 3D CRT and 12% of SRT patients (p = 0.01). Chemical disease-free survival (prostate-specific antigen < or =2 ng/ml) at 3 years was 90% with 3D CRT and 80% with SRT (p = 0.01). Average initial treatment reimbursements were $13,823 (3D CRT), $10,864 (SRT), and $12,250 (radical prostatectomy). Average total treatment reimbursement and projected cost of management of initial therapy failures per patients were $15,173, $16,264, and $16,405, respectively.

CONCLUSIONS

Three-dimensional CRT irradiated less bladder and rectum volume than SRT; CRT initial reimbursement was 28% higher than SRT and 12% higher than radical prostatectomy. Because of projected better local tumor control, average total cost of treating a patient with 3D CRT or radical prostatectomy is equivalent to cost of SRT. Treatment morbidity was lower with 3D CRT. Our findings reflect an overall benefit with 3D CRT as a new promising technology in treatment of localized prostate cancer. Dose-escalation studies may enhance its efficacy and cost benefit.

Dosimetric comparison of an integrated multileaf-collimator versus a conventional collimator

The dosimetric characteristics of both a conventional GE collimator (CC) and a GE multileaf collimator (MLC) are compared for different photon beam energies. The integrated GE MLC consists of 32 pairs of tungsten leaves, replacing the lower pair of jaws of the conventional collimator. Measurements were performed with the conventional collimator before this collimator was replaced by the MLC. All parts of the accelerator except the collimator remained the same. Leakage and transmission measurements show good agreement with the manufacturer's specification, stating a leakage between leaves of less than 1% for all energies and a transmission through leaves of less than 0.5%. The dosimetric characteristics of both collimators are very similar for square and rectangular fields. No significant change in beam quality, beam attenuation and depth of maximum dose could be detected within the measurement accuracy. The MLC output ratio variation is smaller than the one measured with the CC. The penumbra difference in the Y direction is less than 0.5 mm at a depth of 5 cm in phantom; in the X direction the penumbra is 1 mm larger for the MLC due to the rounded leaf fronts. As the two leaf banks replace the lower pair of collimator jaws the distance from the collimator end to the isocentre is similar for the two collimators, therefore the MLC does not reduce the flexibility of the treatment unit. For symmetrical and regular collimator settings the MLC can be treated as the CC.

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.

Modulated beam conformal therapy for head and neck tumors

PURPOSE

The goal of modulated-beam conformal therapy is to reduce the dose to healthy tissue and sensitive structures around a uniformly irradiated target volume. Multiple intensity-modulated fields offer improved tissue-sparing dose distributions. New computer-based systems for planning and delivering such treatments may soon be available from different commercial sources that will make the formulation of an intensity-modulated treatment plan and its execution widely available at any treatment facility that has the resources to acquire the necessary equipment. This work reports on a study of the integration of two such systems.

METHODS AND MATERIALS

Treatment planning was done using a commercially available inverse planning algorithm based on simulated annealing. The plans arbitrarily assumed nine coplanar x-ray beams at nonopposed gantry angles. Intensity modulation was computed for each beam. The modulated field at each gantry angle was broken down into a series of uniform (nonmodulated) subfields, which could be delivered as a sequence to produce the desired dose distribution. Because a large number of subfields was delivered, a multileaf collimator (MLC) was used for field shaping. This allowed rapid and accurate field shaping for treatments made up of several hundred subfields. Computer control of the MLC and linear accelerator allowed delivery of doses less than .01 Gy per subfield. Treatment was delivered on a prototype, computer-controlled accelerator and MLC system. Resulting dose distributions were analyzed using film and an anatomically specific, homogeneous phantom.

RESULTS

The treatment plans were evaluated using dose-volume histogram analysis. The plans provided acceptably uniform irradiation of the target volume without exceeding dose tolerances for nearby critical structures. The plans were successfully delivered by a prototype dynamic MLC. The time needed to deliver a sequence of subfields at one gantry angle ranged from 0.7 to 2.0 min. Isodoses from film agreed reasonably well with planned isodose distributions.

CONCLUSIONS

It is feasible to plan and deliver fixed gantry, modulated-beam conformal therapy for head and neck tumors with systems being developed commercially. The planned dose distributions exhibit significant potential for sparing closely spaced normal tissue structures in the head and neck.

Estimates of whole-body dose equivalent produced by beam intensity modulated conformal therapy

PURPOSE

To estimate the dose delivered to patients by photons and neutrons outside the radiation fields when beam intensity modulation conformal radiotherapy is given. These estimates are then used to compute the risk of secondary cancers as a sequela of the radiation therapy.

MATERIALS AND METHODS

The x-ray and neutron leakage accompanying two beam-intensity modulation techniques delivered by currently available linear accelerators were estimated for 6-MV, 18-MV, and 25-MV x-ray energies. Estimates of whole-body dose equivalents were determined using leakage measurements reported in the literature and treatment parameters derived for two modulated beam-intensity conformal therapy techniques. Risk values recommended by the National Council on Radiation Protection and Measurements (NCRP) were used to estimate the resulting risk of fatal radiation-induced cancer for 70.00 Gy prescribed tumor doses.

RESULTS

The computed worst-case risks of secondary cancers increased in the range from 1.00% for 6-MV x-rays to 24.4% for 25-MV x-rays.

CONCLUSIONS

Careful consideration should be made of the risks associated with secondary whole-body radiation before implementation of beam intensity modulated conformal therapy at x-ray energies greater than 10 MV.

Impact of cradle immobilization on setup reproducibility during external beam radiation therapy for lung cancer

PURPOSE

To compare the setup accuracy during fractionated radiation therapy for two patient groups with lung cancer treated with and without an immobilization cradle.

METHODS

Three hundred ninety-seven port films from 30 patients immobilized in the Alpha Cradle were compared with 329 port films from 30 patients who were not immobilized with the cradle. All patients were treated with curative intent for nonmetastatic lung cancer. The frequency of physician-requested isocenter shifts were compared in the two groups using a two-tailed chi-square test. Initial port films taken on the first day of treatment, routine films taken usually weekly during radiation therapy, and requested films taken after a requested shift were considered separately. The immobilization device consisted of a custom-made foam cradle that extended from above the head to the knees. Patients were generally treated with their arms above their heads, and treatment setup marks in the immobilized patients were placed on both the patients' skin and the immobilization cradle. For the noncradle patients, setup marks were placed only on the patients' skin.

RESULTS

For the routine films, the frequency of physician-requested isocenter shifts was lower in immobilized patients than in the nonimmobilized group (p = 0.139). Most of this reduction was seen on oblique fields (p = 0.038). No benefits were seen among initial or requested films. The two groups were well balanced with regard to stage, age, field size, and total dose.

CONCLUSIONS

The use of aggressive immobilization improves the setup reproducibility in patients receiving external beam radiation therapy for lung cancer, especially during treatment with oblique fields. This improvement in treatment accuracy might improve the therapeutic ratio.

Radiotherapy of localised prostate cancer. Analysis of late treatment complications. A prospective study

PURPOSE

To describe the late side-effects of radical radiotherapy of prostatic carcinoma and to analyse how pretreatment and treatment-related factors contribute to the toxicity.

MATERIALS AND METHODS

184 patients have regularly been followed after terminated radical external beam radiotherapy treatment (70 Gy) for a mean of 46 (range 24-96) months. For registration of toxicity a modified RTOG scale was used. The Cox regression model was used for multivariate analysis.

RESULTS

37% of the patients had no late side-effects at all. Mild complications were reported by 53%, mainly gastrointestinal (42%) and urogenital (23%). A persistent improvement of the mild toxicity was seen in nearly half of the patients with gastrointestinal or nocturnal frequency side-effects. Only 16 (9%) patients had moderate or severe complications. The multivariate analysis revealed that the risk of posttreatment complications was strongly correlated to pretreatment presence of symptoms from the organs at risk. Posttreatment complications presenting first 3 years after irradiation were rare.

CONCLUSIONS

Radical external beam radiotherapy (70 Gy) can be given with a low risk of severe complications. It appears reasonable to assume that the risk can be further reduced by excluding patients with gastrointestinal and urinary tract disease or symptoms.

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.

Accuracy of pelvic radiotherapy: prospective analysis of 90 patients in a randomised trial of blocked versus standard radiotherapy

The aim of this study was to assess the accuracy of pelvic radiotherapy during a trial of blocked radiotherapy at the Royal Marsden Hospital, UK. Prospective evaluation was performed on 90 patients receiving CT planned pelvic radiotherapy using weekly anterior-posterior and lateral portal films. Field placement errors (FPEs) were calculated by comparing field centres of each film with a designated point of interest. Data was evaluated to calculate the overall treatment simulator differences, the number of error free treatments, and mean treatment-simulator position and to evaluate the role of systematic versus random errors. Age, weight, disease site, position of treatment, fractionation, blocked versus conventional techniques were assessed for their effect on treatment accuracy. The mean absolute error between treatment and simulator films was anterior right-left (ARL) 0.25 cm, anterior superior-inferior (ASI) 0.32 cm, lateral anterior-posterior (LAP) 0.42 cm, and lateral superior-inferior (LSI) 0.28 cm. On average the field centre was displaced by 0.66 cm (standard deviation, S.D. = 0.34) from that intended. On each treatment day 29% of anterior films and 45% of lateral films had at least one 0.5 cm error. Overall 59% of treatments had at least one 0.5 cm error and 9% a 1.0 cm error. The field centre was more than 0.5 cm from the position intended in 66% of treatments and over 1 cm for 14% of treatments. Analysis of variance showed that both random and systematic errors occurred in all directions. Though random errors were of similar magnitude in all direction (variance sigma 2 = 0.06-0.09 cm2); systematic errors showed a 4-fold variation being greatest in the LAP direction (sigma 2 = 0.19 cm2) and least the ARL direction (sigma 2 = 0.048 cm2). No factor consistently predicted for worse outcome in all directions. Hypofractionated treatments were less accurate in the LSI direction (P > 0.05). Systematic errors were associated in the ARL direction with hypofractionation (P < 0.01) and, in the LSI direction with weight (P < 0.03) and age (P < 0.05). We conclude that significant random and systematic errors can occur during pelvic radiotherapy especially in the LAP direction. These results suggest that in the absence of a customised immobilisation device, to cover 95% of errors, margins of 0.6 cm for RL and SI directions and 0.9 cm for AP direction should be allowed between the planning and clinical target volumes. However, ideally, each centre should determine their own margin requirements according to local clinical practice.

The field-matching problem as it applies to the peacock three dimensional conformal system for intensity modulation

PURPOSE

Intensity modulated beam systems have been developed as a means of creating a high-dose region that closely conforms to the prescribed target volume while also providing specific sparing of organs at risk within complex treatment geometries. The slice-by-slice treatment paradigm used by one such system for delivering intensity modulated fields introduces regions of dose nonuniformity where each pair of treatment slices abut. A study was designed to evaluate whether or not the magnitude of the nonuniformity that results from this segmental delivery paradigm is significant relative to the overall dose nonuniformity present in the intensity modulation technique itself. An assessment was also made as to the increase in nonuniformity that would result if errors were made in indexing during treatment delivery.

METHODS AND MATERIALS

Treatment plans were generated to simulate correctly indexed and incorrectly indexed treatments of 4, 10, and 18 cm diameter targets. Indexing errors of from 0.1 to 2.0 mm were studied. Treatment plans were also generated for targets of the same diameter but of lengths that did not require indexing of the treatment couch.

RESULTS

The nonuniformity that results from the intensity modulation delivery paradigm is 11-16% for targets where indexing is not required. Correct indexing of the couch adds an additional 1-2% in nonuniformity. However, a couch indexing error of as little as 1 mm can increase the total nonuniformity to as much as 25%. All increases in nonuniformity from indexing are essentially independent of target diameter.

CONCLUSIONS

The dose nonuniformity introduced by the segmental strip delivery paradigm is small relative to the nonuniformity present in the intensity modulation paradigm itself. A positioning accuracy of better than 0.5 mm appears to be required when implementing segmental intensity modulated treatment plans.

Head and neck cancer

This synthesis of the literature on radiotherapy for head and neck cancer is based on 424 scientific articles, including 3 meta-analyses, 38 randomized studies, 45 prospective studies, and 246 retrospective studies. These studies involve 79174 patients. The literature review shows that radiotherapy, either alone or in combination with surgery, plays an essential role in treating head and neck cancers. When tumors are localized, many tumor patients can be cured by radiotherapy alone and thereby maintain full organ function (1, 2). Current technical advancements in radiotherapy offer the potential for better local tumor control with lower morbidity (3). This, however, will require more sophisticated dose planning resources. To further improve treatment results for advanced tumors, other fractionation schedules, mainly hyperfractionation, should be introduced (5). This mainly increases the demands on staff resources for radiotherapy. The combination of radiotherapy and chemotherapy should be subjected to further controlled studies involving a sufficiently large number of patients (4, 5). Interstitial treatment (in the hands of experienced radiotherapists) yields good results for selected cancers. The method should be more generally accessible in Sweden. Intraoperative radiotherapy should be targeted for further study and development.

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.

The treatment of stage III nonsmall cell lung cancer using high dose conformal radiotherapy

PURPOSE

To review our experience using conformal treatment planning and high-dose radiotherapy for Stage IIIa and IIIb nonsmall cell lung cancer (NSCLC), and to identify a subset of patients best suited for this approach by analyzing multiple pretreatment patient and tumor characteristics.

METHODS AND MATERIALS

Between December 1987 and June 1992, 37 patients with Stage III NSCLC treated with high-dose radiotherapy using conformal radiotherapy were reviewed. The patient characteristics were as follows: Stage IIIa (18 patients), IIIb [19]; T1-2 [13], T3-4 [24]; N0-1 [8], N2-3 [29]; and median age 63. All patients were treated with 1.8-2.0 Gy fractions to a median dose of 66 Gy (range 60-70 Gy). Outcome was analyzed by multiple pretreatment variables including age, sex, Karnofsky performance score, pretreatment symptoms, stage group, T and N stage, tumor volume (calculated from computed tomography (CT) contours), presence of atelectasis, and tumor histology. Outcome was also analyzed by total radiotherapy dose.

RESULTS

The median, 1-year and 2-year survival rates for the entire group were 19.5 months, 75 and 37%, respectively. The median, 1-year, and 2-year local progression-free survival rates are 15.6 months, 62 and 23%. There was no difference in survival by stage group (IIIa vs. IIIb) or by T or N stage. Tumor volumes ranged from 47-511 cc in the patients without atelectasis and were not a significant prognostic factor. Histology was found to be a significant prognostic factor, with squamous cell carcinoma having a better overall survival and local progression-free survival than other histologies. No other patient characteristic was found to be significant by either univariate or multivariate analysis. When outcome was analyzed by radiotherapy dose, no dose response was evident in the narrow dose range studied (60-70 Gy). Toxicity included two cases of pneumonitis, which resolved with conservative therapy.

CONCLUSION

High-dose conformal radiotherapy, in our experience, results in overall survival rates that compare favorably with trials of chemoradiotherapy or conventional radiotherapy with a low treatment-associated morbidity. However, local progression remains a significant problem despite median radiotherapy doses of 66 Gy. Future trials using escalating radiotherapy doses with conformal radiotherapy are therefore, indicated.

Implementation of three dimensional conformal radiation therapy: prospects, opportunities, and challenges

PURPOSE

To briefly review scientific rationale of 3D conformal radiation therapy (3DCRT) and discuss the prospects, opportunities, and challenges in the implementation of 3DCRT. Some of these ideas were discussed during a workshop on "Implementation of Three-Dimensional Conformal Radiation Therapy" in April 1994 at Bethesda, MD, and others have been discussed elsewhere in the literature.

METHODS AND MATERIALS

Local-regional control of cancer is an important component in the overall treatment strategy in any patient with cancer. It has been shown that failure to achieve local-regional control can lead to (a) an increase in chances of distant metastases, and (b) a decrease in the survival. In many disease sites, the doses delivered currently are inadequate to achieve satisfactory local tumor control rates; this is because in many sites, only limited doses of radiotherapy can be delivered due to the proximity of cancer to radiosensitive normal tissues. By conforming the radiotherapy beams to the tumor, doses to the tumors can be enhanced and doses to the normal tissues can be reduced. With the advances in 3DCRT, such conformation is possible now and is the rationale for using 3DCRT. However, a number of questions do remain that are not limited to the following: (a) What are the implications in terms of target volume definitions when implementing 3DCRT? (b) Are there some sites where research efforts can be focused to document the efficacy and cost effectiveness of 3DCRT? (c) How do we implement day-to-day 3DCRT treatment efficiently? (d) How do we transfer the technology from the university centers to the community without compromising quality? (e) What are all the quality assurance/quality improvement questions that need to be addressed and how do we ascertain quality assurance of 3DCRT? (f) Have we looked at cost-benefit ratios and quality of life (QOL) issues closely?

RESULTS

There is a need for defining multiple target volumes: gross tumor volume, clinical target volume(s), and planning target volume(s). Such definitions should make implementation of 3DCRT more complex, yet will make high-dose delivery a possibility. There are many sites in which single and multiinstitutional studies are ongoing that include prostate, lung, head and neck, and brain. In other areas, cooperative group trials are required because of the inability of single institutions to accrue enough patients to answer clinically relevant questions with statistical validity. Although implementation of 3DCRT will require multiple steps, these multiple steps can be brought into clinical practice gradually and one does not have to wait until all steps required for implementation of 3DCRT are available. In this respect, "3DCRT" should be used in a very broad sense, from beam's eye view blocking, use of multibeam dose distribution, use of dose-volume histograms in choosing alternative plans, noncoplanar beam arrangements, intensity modulation, inverse planning, to totally automated implementation of 3DCRT. To transfer the 3DCRT capabilities to the community from the University Centers, there is a necessity to develop quality assurance programs. RTOG and the Three-Dimensional Oncology Group are spearheading these efforts. Three-dimensional conformal radiation therapy has potential not only to improve local control and decrease toxicity, but also to improve the cost benefit ratio in the use of radiotherapy as well as in improving quality of life in patients with cancer.

CONCLUSIONS

Achieving many potential benefits of 3DCRT (improvement in local control, decreasing toxicity, organs-function preservation, improvement in cost effectiveness) will require further physics-related and clinical research in carefully conceived and successfully completed future clinical trials.

Evaluation of changes in the size and location of the prostate, seminal vesicles, bladder, and rectum during a course of external beam radiation therapy

PURPOSE

To document the size and location of the prostate, seminal vesicles, bladder, and rectum throughout the course of external beam radiotherapy. The frequency and range of motion of these organs are quantified.

METHODS AND MATERIALS

Ten patients with localized carcinoma of the prostate had conventional simulation followed immediately by a treatment planning computed tomography scan (TPCT0). Once treatment was initiated, each patient had a weekly CT (TPCT1-N) before or after his daily treatment. Anatomical structures from CT were delineated on a computer workstation for analysis. The serial CT sets were spatially registered to the initial scan using image correlation software that brings into congruence the bony pelvis of the different scans. The location of the prostate, seminal vesicles, bladder, and rectum on subsequent scans were compared to TPCT0, as well as to each other.

RESULTS

Prostate volumes were observed to vary by an average of +/- 10% during the course of radiation therapy, while the seminal vesicle volumes varied by as much as 100%. Bladder and rectal volumes varied by +/- 30%. Compared to TPCT0, movement of the prostate was demonstrated in all patients. Quantitation of the center-of-mass (CM) showed motion of less than 1 mm in the left-right direction, while motion ranging from 0 to +/- 1 cm was observed in the anterior-posterior and superior-inferior directions. The individual standard deviations of these motions varied from approximately 1-5 mm. These variations were correlated to changes in the dimensions of the bladder and rectum.

CONCLUSIONS

Changes in the location of the prostate, seminal vesicles, and normal tissue volumes during the course of radiation therapy occur and have dosimetric consequences that may impact tumor control and normal tissue complication probabilities. Conformal therapy for prostate cancer will require the incorporation of knowledge of the anatomic relationships of these structures as a function of time. Therefore, these uncertainties must be taken into account when designing treatment plans and in considering dose escalation trials.

Preliminary results of a prospective trial using three dimensional radiotherapy for lung cancer

PURPOSE

To evaluate the preliminary results of a prospective trial using three-dimensional (3D) treatment for lung cancer.

METHODS AND MATERIALS

Seventy patients with inoperable Stage I through IIIB lung cancer were treated with three-dimensional thoracic irradiation with or without chemotherapy (35% received chemotherapy). Total prescribed dose to the tumor ranged from 60-74 Gy (uncorrected for lung density). All patients were evaluated for local control, survival, and development of pneumonitis. These parameters were evaluated in respect to and compared with three-dimensional parameters used in their treatment planning.

RESULTS

With a minimum follow-up of 6 to 30 months, the 2-year cause-specific survival rate for Stages I and II was 90% and 53% for Stage III (no difference between Stages IIIA and IIIB). Patients with local tumor control had a better 2-year overall survival rate (47%) than those with local failure (31%). Volumetrically heterogeneously calculated doses were important to the accurate delineation of dose-volume coverage as there was a wide range of discrepancies between a homogeneously prescribed point dose calculation and the heterogeneously calculated volume coverage of that prescription. High-grade pneumonitis was correlated with the location of the tumor with lower lobe tumors having a much higher risk than those with upper lobe tumors. A critical volume effect and threshold dose were apparent in the development of high-grade pneumonitis.

CONCLUSIONS

Three-dimensional therapy for lung cancer has been practically implemented at the Mallinckrodt Institute of Radiology and shows promising results in our preliminary analysis. The incidence of high-grade pneumonitis, however, warrants careful selection of patients for future dose escalation. Future dose escalation trials in lung cancer should be directed to volumes that limit the amount of elective nodal irradiation. However, the volume of necessary elective nodal irradiation remains unknown and should be studied prospectively. Dose escalation trials are indicated and may be facilitated by smaller target volumes.

Conversion of unresectable to resectable liver cancer: an approach and follow-up study

In the last decade, significant improvement has been achieved in the treatment of hepatocellular cancer by combining therapies from different disciplines, and using effective biologic response modifiers to improve response to existing therapy. While operative resection remains the only curative modality, a select group of patients with unresectable fibrolamellar or nodular variant, can be converted from unresectable status to resectable by combining chemotherapy and radiotherapy. We reviewed the recent experience with intra-arterial chemotherapies and use of external beam radiotherapy and isotopic immunoglobulin-directed radiotherapy in the treatment of unresectable hepatocellular cancer. While significant tumor response can be achieved with these therapies they are short-lived, and long-term survival is poor. When combined with operative resection, however, a significant survival advantage is achieved. The expected survival of the unresectable patient is then altered from 18 to 24 months for chemotherapy or radiation alone, or when used in combination, to 44 months for patients converted to resectable status. We conclude that the need for more effective chemotherapy is imperative, and the major role for chemotherapy or radiotherapy in hepatocellular cancer is to convert an unresectable patient to resectable status.

Strategy for dose escalation using 3-dimensional conformal radiation therapy for lung cancer

PURPOSE

Local failure is a major obstacle to the cure of locally advanced non-small-cell lung cancer. 3-Dimensional conformal radiation therapy (3-DCRT) selects optimal treatment parameters to increase dose to tumor and reduce normal tissue dose, potentially permitting dose escalation. There are several ongoing trials of dose escalation using 3-Dimensional conformal radiation therapy for non-small-cell lung cancer. We performed this analysis to determine if data derived from dose volume histograms could be used as the basis for designing the method of dose escalation in these trials.

METHODS AND MATERIALS

Between 1990 and 1993, 31 patients were treated with 3-DCRT and had complete normal tissue dose volume histograms created as part of the planning process. The stage distribution was stage I/II 13%, stage IIIa in 45%, and stage IIIb in 42%. The median radiation dose to gross disease was 70.2 Gy (52.2-72 Gy). Elective mediastinal irradiation (50.4 Gy) was administered to 52% (16/31) of patients.

RESULTS

The major toxicity encountered in this experience was pulmonary. Dose-volume-histogram data were used to analyze the predictors of toxicity and showed a correlation between risk of pulmonary toxicity and indices of dose to lung parenchyma. Grade 3 or higher pulmonary toxicity occurred in 38% (3/8) of pts with >30%of lung volume receiving > or =25 Gy, versus 4% (1/23) of pts. with < or = 30% lung receiving > or = 25 Gy (p=0.04). Grade 3 or higher pulmonary toxicity occurred in 29% (4/14) of patients with a predicted pulmonary normal tissue complication probability of 12% or higher versus 0% (0/17) in patients with a predicted probability of less than 12% (p=0.03). The single fatality occurred in a patient with a calculated pneumonitis probability of 85% and a high percent (49%) lung volume receiving >= 25 GY.

CONCLUSION

This preliminary experience demonstrates a correlation between lung dose-volume-histogram data and the risk of severe pulmonary toxicity. This provides an opportunity to modify the method of radiation dose escalation. Dose-volume-histogram data can allow escalation according to the risk to the lung parenchyma (which is the major organ of concern) rather than escalation according to tumor dose levels. Because of teh major inter-patient variability of intrathoracic tumor bulk and anatomic distribution, this strategy is intuitively appropriate. This approach may facilitate completion of dose escalation studies and identification of maximum tolerable pulmonary dose levels.

Three-dimensional treatment planning and conformal radiation therapy: preliminary evaluation

Preliminary clinical results are presented for 209 patients with cancer who had treatment planned on our three-dimensional radiation treatment planning (3-D RTP) system and were treated with external beam conformal radiation therapy. Average times (min) for CT volumetric simulation were: 74 without or 84 with contrast material; 36 for contouring of tumor/target volume and 44 for normal anatomy; 78 for treatment planning; 53 for plan evaluation/optimization; and 58 for verification simulation. Average time of daily treatment sessions with 3-D conformal therapy or standard techniques was comparable for brain, head and neck, thoracic, and hepatobiliary tumors (11.8-14 min and 11.5-12.1, respectively). For prostate cancer patients treated with 3-D conformal technique and Cerrobend blocks, mean treatment time was 19 min; with multileaf collimation it was 14 min and with bilateral arc rotation, 9.8 min. Acute toxicity was comparable to or lower than with standard techniques. Sophisticated 3-D RTP and conformal irradiation can be performed in a significant number of patients at a reasonable cost. Further efforts, including dose-escalation studies, are necessary to develop more versatile and efficient 3-D RTP systems and to enhance the cost benefit of this technology in treatment of patients with cancer.

Recent advances in radiation oncology

Radiotherapy remains an important component of the management of malignant disease. Especially when combined with cytotoxic chemotherapy, limited surgical excision, or both, irradiation has been shown to control disease in the primary site and regional nodes without the need for surgical extirpation as frequently as in past years. New developments in three-dimensional treatment planning and the precise delivery of high-dose radiation promise to increase the benefit of radiation treatment. Finally, molecular studies of the cell's response to radiation and the phenomena of DNA damage and repair are providing explanations for heretofore unexplained radiobiologic observations. Such research is laying the groundwork for targeted manipulation of the cell's response to radiation, which will be tested in the near future.

Through a glass darkly: predicting the future of radiation oncology

To position ourselves professionally for the inevitable transition to managed care demands serious self-appraisal. Like most procedural medical specialties, radiation oncology is currently ill prepared for a capitated system of payment. To prosper under capitation, we need to increase the utility of radiation therapy per unit cost. This can be achieved by making the following adaptive responses: (a) we must ensure that the needs of medical practice drive the use of costly technology and not vice versa; (b) we must subordinate firmly held beliefs and prejudices to solid scientific data and be prepared to modify our practice when more cost-effective alternative exist; and (c) we must be increasingly conscious of outcome, not process, in deciding among treatment options; and (d) we must acknowledge the need to prioritize the use of finite resources so that the maximum effort is expended on those who have the most to gain from treatment. These changes will permit us to develop guidelines for appropriate use of radiation therapy, and to demonstrate the excellent value of the service we can provide, which is the ultimate key to success. Though the future may at times seem bleak, we can shape it with our actions: the best way to predict the future is to create it.

Development of clinical radiotherapy since 1896

From the discovery of x-rays in November 1895 and the first publication in December 1985 it did not take long for the first x-ray therapy of cancer in January 1896. The first 25 years in the history of radiotherapy was not a very flattering period for the discipline. During the following 25 years, however, important developments in clinical radiotherapy occurred and in some countries the speciality of radiotherapy was established in the 1930s. In the last 50 years gradual changes have taken place and now modern radiotherapy is an established curative method in the treatment of cancer. The scientific background of radiotherapy is solid, and the understanding of cancer biology and radiobiology has improved drastically. The radiotherapists of today are cancer specialists, oncologists. The technical development has been enormous. The future of radiation oncology looks very promising, with local cancer treatment being shown to be most effective.

Realization and verification of three-dimensional conformal radiotherapy with modulated fields

PURPOSE

We describe the experimental demonstration of the delivery of a three-dimensional conformal radiotherapy dose distribution using in-field modulation of nine fixed-gantry fields.

METHODS AND MATERIALS

Two-dimensional in-field modulation profiles, varying from field to field, were realized by quasi-dynamic multileaf collimation using the prototype of a commercially available multileaf collimator installed on a medical linear accelerator. The profiles were calculated to deliver an optimal dose distribution for a patient with a prostate carcinoma. The target volume surface was invaginated and bifurcated. The calculated dose distribution was delivered to a homogeneous polystyrene phantom consisting of 1 cm thick slices that were cut to match the patient's outer contour. Seven therapy verification films were placed between the phantom slices.

RESULTS

Analysis of the films revealed a degree of conformation of the high-dose region to the target shape that would not be possible with unmodulated conformal therapy. However, small observed spatial displacements of the dose distribution confirm the need for very accurate positioning.

CONCLUSIONS

It is feasible to deliver clinically relevant, three-dimensional dose distributions that conform to invaginated and bifurcated target volumes using fields modulated by multileaf collimators.

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.

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.

Boron neutron capture therapy: a mechanism for achieving a concomitant tumor boost in fast neutron radiotherapy

PURPOSE

For many years neutron radiation has been used to treat malignant disease both as fast neutron radiotherapy and as thermal neutron induced boron neutron capture therapy (BNCT). To date, these two approaches have been used independently of one another due to the large difference in neutron energies each employs. In this paper we discuss the potential application of BNCT to enhance the therapeutic effectiveness of a fast neutron radiotherapy beam.

METHODS AND MATERIALS

Measurements are presented for the thermal neutron component that is spontaneously developed as the University of Washington fast neutron radiotherapy beam penetrates a water phantom. The biological effect of this thermalized component on cells "tagged" with boron-10 (10B) is modeled mathematically and the expected change in cell survival calculated. The model is then extended to estimate the effect this enhanced cell killing would have for increased tumor control.

RESULTS

The basic predictions of the model on changes in cell survival are verified with in vitro measurements using the V-79 cell line. An additional factor of 10-100 in tumor cell killing appears achievable with currently available 10B carriers using our present neutron beam. A Poisson model is then used to estimate the change in tumor control this enhanced cell killing would produce in various clinical situations and the effect is sufficiently large so as to be clinically relevant. It is also demonstrated that the magnitude of the thermalized component can be increased by a factor of 2-3 with relatively simple changes in the beam generating conditions.

CONCLUSION

BNCT may provide a means of enhancing the therapeutic effectiveness of fast neutron radiotherapy in a wide variety of clinical situations and is an area of research that should be aggressively pursued.

The effects of local and regional treatment on the metastatic outcome in prostatic carcinoma with pelvic lymph node involvement

PURPOSE

The effect of local and regional treatment on the development of distant metastases in patients with localized node negative and node positive carcinoma of the prostate is examined.

METHODS AND MATERIALS

Distant metastases-free survival was evaluated in 1078 patients with Stage B-C node negative (733 patients) or node positive (345 patients) carcinoma of the prostate, staged with pelvic lymph node dissection and treated with retropublic 125I implantation at the Memorial Sloan-Kettering Cancer Center between 1970 and 1985.

RESULTS

The 15-year actuarial distant metastases-free survival rate for the entire group of patients was 27%. Lymph node involvement was the most significant covariate affecting distant metastases-free survival, although local failure, stage, and grade were also independent variables. Distant metastases-free survival varied with the extent of lymph node involvement (N0 vs. N1, p < 0.0001; N1 vs. N2, p < 0.0001). However, the difference between N1 and N2 patients was due to a faster rate of development of distant metastases in N2 patients. The ultimate 10-year distant metastases-free survival rate was similar for the two patient groups (11% for N1 and 9% for N2). Local failure correlated with the metastatic outcome in patients with B-C/N0 disease (p < 0.00001), but not in N1 or N2 patients. Although distant metastases-free survival in locally controlled N1 patients was improved compared to N2 patients (p = 0.004), when stratified by primary tumor stage and grade, the differences were no longer significant.

CONCLUSION

Essentially all node positive patients with carcinoma of the prostate will develop distant metastatic disease if followed for sufficiently long periods of time. This is consistent with the hypothesis that in such patients distant micrometastatic dissemination already exists at the time of initial diagnosis. The data suggest that clinical trials designed to test whether improvements in local therapy impact on survival should be restricted to node negative patients. The data also raise concerns regarding the therapeutic value of elective whole pelvic irradiation.

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.

Report of long-term follow-up in a randomized trial comparing radiation therapy and radiation therapy plus hyperthermia to metastatic lymph nodes in stage IV head and neck patients

PURPOSE

The treatment of inoperable metastatic lymph nodes in patients with head and neck cancer represents a therapeutic challenge. Clinical results using conventional radiation therapy are disappointing; on the other hand, the evaluation of recent innovative radiotherapeutic methods is still pending. The end points of this analysis were focused on long-term local control, on its potential influence on survival, and on late toxicity of a previously reported randomized Phase III study comparing conventionally fractionated radical irradiation alone or combined with local hyperthermia in fixed and inoperable metastatic neck lymph nodes.

METHODS AND MATERIALS

The medical records of 41 patients (44 nodes) with advanced locoregional Stage IV squamous cell cancer of the head and neck and randomized to treatment in the period 1985-1986 with irradiation alone (22/23 evaluable nodes) or combined with external hyperthermia (18/21 evaluable nodes), were re-evaluated.

RESULTS

The statistically significant difference observed in "early" response (p = 0.0164) in favor of the combined treatment results in improved 5-year actuarial nodal control (p = 0.015). Clinical improvement noted in tumor control positively affects survival, leading to a statistically significant difference in survival at 5 years (p = 0.02). With respect to side effects, no clearly enhanced acute or late toxicity has been found; as severe late effects, two patients with bone necroses possibly related to the combined treatment have been observed. Thermal analysis failed to show a significant correlation between heating parameters and the end points of the study.

CONCLUSION

This report with 5-year follow-up confirms the efficacy and the absence of severe toxicity of the combination of radical radiation and hyperthermia in the treatment of metastatic lymph nodes in Stage IV squamous cell carcinoma of the head and neck.

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.

Perspectives of multidimensional conformal radiation treatment

We consider the present technological advancement that underlies the implementation of computer-controlled conformal radiotherapy. We also consider the developments in modern biology that may provide input to therapy planning. The concept of multidimensional conformal radiotherapy is advanced, which integrates geometrical precision and biological conformality, to optimize the treatment planning for individual patients, with a view to improve the overall success of radiotherapy.

Technical and tumor-related factors affecting outcome of definitive irradiation for localized carcinoma of the prostate

PURPOSE

The influence of some tumor-related and technical factors on therapeutic outcome is analyzed in 738 patients with histologically confirmed carcinoma of the prostate treated with definitive irradiation.

METHODS AND MATERIALS

This is a retrospective study of the records of the Radiation Oncology Center. The information was coded on computer-compatible forms and analyzed with multiple cross-reference checks to ensure data reliability. Detailed analysis of portal films and dose distribution isodose curves was carried out in 310 patients on whom this information was readily available. All patients were followed-up for a minimum of 3 years (median observation, 6.5 years).

RESULTS

Disease-free survival rates in Stages A2 (T1b) and B (T2) were 76% at 5 years and 62% at 10 years; in Stage C (T3) it was 57% at 5 years and 38% at 10 years. Overall, prostate recurrence rates were: 8% for Stage A2, 17% for Stage B, 28% for Stage C, and 46% for Stage D1 (T4). The 10-year actuarial local failure rate by stage was 20% in Stage A2 (T1b), 24% in Stage B (T2), 40% in Stage C (T3), and 70% in Stage D1 (T4) tumors. When the inferior margin of the portals was at or caudal to the ischial tuberosity, the actuarial 5-year pelvic failure rate was 0% for Stage A2 (T1b), 18% for Stage B (T2), and 20% for Stage C (T3), in contrast to 60% for Stage A2 (T1b), 27% for Stage B (T2), and 38% for Stage C (T3) when the inferior margin was cephalad to the ischial tuberosity (p = 0.05 in Stage C). Local tumor control was comparable in Stages A2 (T1b) and B (T2) when either small fields limited to the prostate and periprostatic tissues were used or, in addition, the pelvic lymph nodes were irradiated (85% and 80%, respectively). In Stage C (T3) there was significantly better pelvic tumor control (80% of 274 patients) when all of the pelvic (including common iliac) lymph nodes were treated compared with 65% in a group of 137 patients on whom the lymph nodes were irradiated with smaller fields (14 x 14 cm) (p = 0.01). In Stage C (T3), 30 patients treated with doses less than 6000 cGy had a 50% overall pelvic failure rate compared with 35% in 20 patients receiving 6500 cGy and 24% in 362 patients treated with 7000 cGy (p = 0.01). Pelvic tumor control or failure was closely associated with development of distant metastasis. In patients with pelvic tumor control, the distant metastasis rate was 18% for stages A2 (T1b) and B (T2) and 30% for stage C (T3), in contrast to 30% (p = 0.02) and 65% (p < 0.01), respectively, when prostate/pelvic failure was detected.

CONCLUSION

Volume treated and dose of irradiation are important factors influencing local/pelvic recurrence rate in carcinoma of the prostate, particularly in stage C tumors. With recent advances in three-dimensional treatment planning and conformal radiation therapy techniques, it is imperative to determine optimal volumes and doses of irradiation to be delivered to these patients while minimizing morbidity to enhance the role of irradiation in the management of localized carcinoma of the prostate.

Initiation of multi-leaf collimator conformal radiation therapy

Clinical studies have been initiated in conformal radiotherapy using a computer controlled multi-leaf collimator. Quantitative dosimetry and treatment planning studies comparing field shaping by lead alloy blocks and the multi-leaf collimator demonstrate the clinical acceptability of the multi-leaf collimator. Sixteen patients with tumors in multiple sites have received some part of their treatments with both blocking systems. Studies of dosimetry and field shaping show that the multi-leaf collimator produces clinically acceptable blocking for most field shapes and disease sites. The 80-20% penumbra was characterized for a wide range of shaped beams. For straight edges perpendicular to the leaf travel, the penumbra of measured dose distributions from the multi-leaf collimator is equal to conventional divergent blocking. When the multi-leaf collimator leaves approach a contour at an angle, the penumbra increases. At forty-five degrees, the maximum angle of approach, the penumbra is approximately 4 mm wider than that for divergent blocks. Three-dimensional treatment planning demonstrates that equivalent dose distributions can be obtained from the two field shaping systems. The multi-leaf collimator can be used effectively and efficiently to treat a variety of disease sites. Its optimal utility may be in treating complex fields--five or more shaped coplanar or non-coplanar beams. It is well suited for conformal therapy applications.

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.