Tolerance of normal tissue to therapeutic irradiation

Preservation of visual fields after peri-sellar gamma-knife radiosurgery

Radiosurgical treatment of pituitary and peri-sellar tumors has become an increasingly utilized modality as an alternative to conventional radiotherapy and surgery. Such radiosurgery results in a relatively high dose of radiation to the optic chiasm. The clinical data establishing safe single-fraction doses to the chiasm is immature, although taken together previous literature suggests a recommended maximal dose of 8 Gy. Optic neuropathy, when it occurs, tends to take place within 2 years of treatment. We evaluated the visual fields of 20 sequential patients that received significant doses to the optic chiasm by Gamma-knife radiosurgery. There were 17 cases of pituitary adenoma and 3 cases of meningioma, and two patients refused follow-up testing. Preoperative visual field and cranial nerve examinations were done prior to radiosurgery and in follow-up, with a median follow-up of 24 months. There were no cases of quantitative visual field deficit induced by treatment. No patients developed symptomatic visual deterioration. Radiat. Oncol. Invest. 90:343-350, 2000. 2000 Wiley-Liss, Inc.

Normal tissue complication probability (NTCP) calculations as a means to compare proton and photon plans and evaluation of clinical appropriateness of calculated values

Calculation of normal tissue complication probabilities (NTCP) for proton radiation therapy (PRT) and two photon radiation therapy techniques for cranial irradiation of childhood optic nerve gliomas was made. Evaluation of usefulness of calculated NTCP values for comparison of treatment plans and clinical appropriateness of computed data was used. Three radiation plans were calculated on datasets of children treated previously for optic nerve gliomas with PRT. Dose-volume histograms (DVH) were computed and used to calculate NTCP. Evaluated complication endpoints were necrosis, blindness, and cognitive impairment. Calculated NTCP depended strongly on tumor volume and the normal tissue volume exposed to high radiation doses. Dose conformity and steeper dose-gradient correlated with reduced NTCP. Regarding the chosen complication endpoints, PRT was superior to 3D photons; conventional photons were calculated to have the highest NTCPs. Differences might reach clinical significance for cognitive impairment, a frequently observed toxicity. Calculated NTCP values were highly dependent on implemented clinical data. Calculation of NTCP can be used for ranking of treatment plans and modalities. Highly dependent on implemented clinical data, the calculated percentage of NTCP might be more of a figure of merit than a real predictive value and requires comparison to clinical experience. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 351-358 (2000).

Radiosurgery for malignant meningioma: results in 22 patients

Object. The initial treatment of malignant meningiomas in the past has included surgical removal followed by fractionated external-beam radiotherapy. Radiosurgery has been added to the options for treatment of primary or recurrent tumors over the last 10 years. The authors report their results of using gamma knife radiosurgery (GKS) to treat 22 patients over an 8-year period.

Methods. Twenty-two patients who underwent GKS for malignant meningioma between December 1991 and May 1999 were evaluated. Three patients were treated with GKS as a boost to radiotherapy and 19 for recurrence following radiotherapy. Outcome factors including patient survival, freedom from progression, and complications were analyzed. In addition, in the recurrent group, variables such as patient age, sex, tumor location, target volume, margin dose, and maximum dose were also analyzed. Univariate and multivariate analyses were performed.

Overall 5-year survival and progression-free survival estimates were 40% and 26%, respectively. Age (p ≤ 0.003) and tumor volume (p ≤ 0.05) were significant predictors of time to progression and survival in both univariate and multivariate analyses. Five patients (23%) developed radiation necrosis. Significant relationships between complications and treatment variables or patient characteristics could not be established.

Conclusions. Tumor control following GKS is greater in patients with smaller-sized tumors (< 8 cm3) and in younger patients. Gamma knife radiosurgery can be performed to treat malignant meningioma with acceptable toxicity. The efficacy of GKS relative to other therapies for recurrent malignant meningioma as well as the value of GKS as a boost to radiotherapy will require further evaluation.

Feasibility and efficacy of high dose conformal radiotherapy for patients with locally advanced pancreatic carcinoma

BACKGROUND

The feasibility and efficacy of high dose conformal radiotherapy were examined in the treatment of patients with locally advanced, unresectable pancreatic carcinoma.

METHODS

Forty-four patients with pathologically confirmed, unresectable pancreatic adenocarcinoma without distant metastases were treated in a Phase II study. The patients received three-dimensional, planned, high dose conformal radiotherapy (70-72 grays). Toxicity was scored according to the World Health Organization criteria. Follow-up time ranged from 7 months to 25 months (median, 9 months).

RESULTS

The treatment was feasible. Forty-one patients received the intended total dose. Treatment was never stopped because of toxicity. Acute toxicity was mainly Grade 1 and Grade 2 (in 70% and 57% of patients, respectively), whereas Grade 3 toxicity was seen in 9% of patients. One fatal event occurred that was not treatment related. Late Grade 3 and Grade 4 gastrointestinal toxicity was seen in 3 patients and 2 patients, respectively. Late (Grade 5) gastrointestinal bleeding was observed in 3 patients, 2 of whom had local tumor progression. At 3 months, reduction in tumor size was seen in 27% of patients, stable disease was seen in 20% of patients, and local disease progression was seen in 40% of patients. Ultimately, local disease progression was observed in 44% of patients. No true partial or complete responses were documented. The median survival from the time of diagnosis was 11 months (10 months from the start of radiotherapy). Seventeen of 25 patients (68%) experienced pain relief.

CONCLUSIONS

High dose conformal radiotherapy for the treatment of patients with locally advanced pancreatic carcinoma is feasible with acceptable toxicity. In case of pain, it can offer palliation. The efficacy of the treatment in terms of prolongation of life is not proven. Distant metastases remain the major problem.

A quantitative treatment planning study evaluating the potential of dose escalation in conformal radiotherapy of the oesophagus

BACKGROUND AND PURPOSE

This study aims to evaluate the reduction in radiation dose to normal thoracic structures through the use of conformal radiotherapy techniques in the treatment of oesophageal cancer, and to quantify the resultant potential for dose escalation.

MATERIALS AND METHODS

Three different CT-derived treatment plans were created and compared for each of ten patients. A two-phase treatment with conventional straight-edged fields and standard blocks (CV2), a two-phase conformal plan (CF2), and a three-phase conformal plan where the third phase was delivered to the gross tumour only (CF3), were considered for each patient. Escalated dose levels were determined for techniques CF2 and CF3, which by virtue of the conformal field shaping, did not increase the mean lung dose. The resulting increase in tumour control probability (TCP) was estimated.

RESULTS

A two-phase conformal technique (CF2) reduced the volume of lung irradiated to 18 Gy from 19.7+/-11.8 (1 SD) to 17.1+/-12.3% (P=0.004), and reduced the normal tissue complication probability (NTCP) from 2.4+/-4.0 to 0.7+/-1.6% (P=0.02) for a standard prescribed dose of 55 Gy. Consequently, technique CF2 permitted a target dose of 59.1+/-3.2 Gy without increasing the mean lung dose. Technique CF3 facilitated a prescribed dose of 60.7+/-4.3 Gy to the target, the additional 5 Gy increasing the TCP from 53. 1+/-5.5 to 68.9+/-4.1%. When the spinal cord tolerance was raised from 45 to 48 Gy, technique CF3 allowed 63.6+/-4.l Gy to be delivered to the target, thereby increasing the TCP to 78.1+/-3.2%.

CONCLUSIONS

Conformal radiotherapy techniques offer the potential for a 5-10 Gy escalation in dose delivered to the oesophagus, without increasing the mean lung dose. This is expected to increase local tumour control by 15-25%.

Fractionated stereotactic conformal radiation therapy of brain stem gliomas: outcome and prognostic factors

BACKGROUND AND PURPOSE

Evaluation of outcome and prognostic factors in patients with brain stem glioma (BSG) following fractionated stereotactic radiotherapy (FSRT).

MATERIALS AND METHODS

Between 1990 and 1997, we treated 41 patients with FSRT in a phase I/II trial. Median age was 24 years. Out of 36 patients with histologically proven glioma, ten had a partial tumour resection. Histology revealed low grade gliomas in 30 patients and anaplastic gliomas in six patients. A mean total dose of 54 Gy was given in daily fractions of 1.8 Gy. Median follow-up was 12 months.

RESULTS

Three patients died during FSRT. Neurological improvement was achieved in 19/38 patients. Reduction of tumour size was reported in 12/38, in 16 patients the lesion was unchanged, ten showed progression. Median time to progression was 23 months, median overall survival 40 months with an actuarial survival of 83% at 1 year, 55% at 3 years and 33% at 5 years. In 20 of 22 patients with recurrence progression was inside the target volume. Significant prognostic factors for survival were clinical and radiological response 6 weeks after FSRT. Treatment toxicity was mild. Ototoxicity occurred in one patient.

CONCLUSIONS

FSRT is a feasible treatment modality for BSG with tolerable toxicity. The risk of marginal failure is low.

Technical aspects of the deep inspiration breath-hold technique in the treatment of thoracic cancer

PURPOSE

The goal of this paper is to describe our initial experience with the deep inspiration breath-hold (DIBH) technique in conformal treatment of non-small-cell lung cancer with particular emphasis on the technical aspects required for implementation.

METHODS AND MATERIALS

In the DIBH technique, the patient is verbally coached through a modified slow vital capacity maneuver and brought to a reproducible deep inspiration breath-hold level. The goal is to immobilize the tumor and to expand normal lung out of the high-dose region. A physicist or therapist monitors and records patient breathing during simulation, verification, and treatment using a spirometer with a custom computer interface. Examination of internal anatomy during fluoroscopy over multiple breath holds establishes the reproducibility of the DIBH maneuver for each patient. A reference free-breathing CT scan and DIBH planning scan are obtained. To provide an estimate of tumor motion during normal tidal breathing, additional scan sets are obtained at end inspiration and end expiration. These are also used to set the spirometer action levels for treatment. Patient lung inflation is independently verified over the course of treatment by comparing the distance from the isocenter to the diaphragm measured from the DIBH digitally reconstructed radiographs to the distance measured on the portal films. Patient breathing traces obtained during treatment were examined retrospectively to assess the reproducibility of the technique.

RESULTS

Data from the first 7 patients, encompassing over 250 treatments, were analyzed. The inferred displacement of the centroid of gross tumor volume from its position in the planning scan, as calculated from the spirometer records in over 350 breath holds was 0.02 +/- 0.14 cm (mean and standard deviation). These data are consistent with the displacements of the diaphragm (-0.1 +/- 0.4 cm; range, from -1.2 to 1.1 cm) relative to the isocenter, as measured on the (92) portal films. The latter measurements include the patient setup error. The patient averaged displacement of the tumor during free breathing, determined from the tumor displacement between end inspiration and end expiration, was 0.8 +/- 0.5 cm in both the superior-inferior and anterior-posterior directions and 0.1 cm (+/- 0.1 cm) medial-laterally.

CONCLUSION

Treatment of patients with the DIBH technique is feasible in a clinical setting. With this technique, consistent lung inflation levels are achieved in patients, as judged by both spirometry and verification films. Breathing-induced tumor motion is significantly reduced using DIBH compared to free breathing, enabling better target coverage.

[Conformal radiotherapy: tomotherapy]

Conformal radiation therapy allows the possibility of delivering high doses at the tumor volume whilst limiting the dose to the surrounding tissues and diminishing the secondary effects. With the example of the conformal radiation therapy used at the AZ VUB (3DCRT and tomotherapy), two treatment plans of a left ethmoid carcinoma will be evaluated and discussed in detail. The treatment of ethmoid cancer is technically difficult for both radiation therapy and surgery because of the anatomic constraints and patterns of local spread. A radiation therapy is scheduled to be delivered after surgical resection of the tumor. The treatment plan for the radiation therapy was calculated on a three-dimensional (3D) treatment planning system based on virtual simulation with a beam's eye view: George Sherouse's Gratis. An effort was made to make the plan as conformal and as homogeneous as possible to deliver a dose of 66 Gy in 33 fractions at the tumor bed with a maximum dose of 56 Gy to the right optic nerve and the chiasma. To establish the clinical utility and potential advantages of tomotherapy over 3DCRT for ethmoid carcinoma, the treatment of this patient was also planned with Peacock Plan. For both treatment plans the isodose distributions and cumulative dose volume histograms (CDVH) were computed. Superimposing the CDVHs yielded similar curves for the target and an obvious improvement for organs at risk such as the chiasma, brainstem and the left eye when applying tomotherapy. These results have also been reflected in the tumor control probabilities (equal for both plans) and the normal tissue complication probabilities (NTCP), yielded significant reductions in NTCP for tomotherapy. The probability of uncomplicated tumor control was 52.7% for tomotherapy against 38.3% for 3DCRT.

Reduction of small and large bowel irradiation using an optimized intensity-modulated pelvic radiotherapy technique in patients with prostate cancer

PURPOSE

To investigate the role of intensity-modulated radiation therapy (IMRT) to irradiate the prostate gland and pelvic lymph nodes while sparing critical pelvic organs, and to optimize the number of beams required.

METHODS AND MATERIALS

Target, small bowel, colon, rectum, and bladder were outlined on CT planning scans of 10 men with prostate cancer. Optimized conventional (RT) and 3-dimensional conformal radiotherapy (3D-CRT) plans were created and compared to inverse-planned IMRT dose distributions using dose-volume histograms. Optimization of beam number was undertaken for the IMRT plans.

RESULTS

With RT the mean percentage volume of small bowel and colon receiving >45 Gy was 21.4 +/- 5.4%. For 3D-CRT it was 18.3 +/- 7.7% (p = 0.0043) and for 9-field IMRT it was 5.3 +/- 1.8% (p < 0.001 compared to 3D-CRT). For 7, 5, and 3 IMRT fields, it was 6.4 +/- 2.9%, 7.2 +/- 2.8%, and 8.4 +/- 3.8% (all p < 0.001 compared to 3D-CRT). The rectal volume irradiated >45 Gy was reduced from 50.5 +/- 16.3% (3D-CRT) to 5.8 +/- 2.1% by 9-field IMRT (p < 0. 001) and bladder from 52.2 +/- 12.8% to 7 +/- 2.8% (p < 0.001). Similar benefits were maintained for 7, 5, and 3 IMRT fields.

CONCLUSIONS

The reduction in critical pelvic organ irradiation seen with IMRT may reduce side effects in patients, and allow modest dose escalation within acceptable complication rates. These reductions were maintained with 3-5 IMRT field plans which potentially allow less complex delivery techniques and shorter delivery times.

The physical parameters and molecular events associated with radiation-induced lung toxicity

Radiation therapy (RT) is frequently used to treat patients with tumors in and around the thorax. Clinical radiation pneumonitis is a common side effect, occurring in 5% to 20% of patients. Efforts to identify patients at risk for pneumonitis have focused on physical factors, such as dose and volume. Recently, the underlying molecular biological mechanisms behind RT-induced lung injury have come under study. Improved knowledge of the molecular events associated with RT-induced lung injury may translate into a better ability to individualized therapy. This review discusses our current understanding of the physical and molecular factors contributing to RT-induced pulmonary injury.

Counterpoint: better radiation treatment of non-small cell lung cancer using new techniques without elective nodal irradiation

The treatment of non-small cell lung cancer has continued to evolve with the advent of improved staging technologies, chemotherapeutic agents, and methods of radiation delivery. Treatment of clinically uninvolved, regional lymph nodes historically has been delivered in the attempt to cover unseen disease, reduce regional failure, and improve survival. None of these suppositions has been tested nor are they supported by data. With enhanced staging using modalities like positron emission tomography and esophageal ultrasonography, treatment portals can be designed to encompass known disease with greater accuracy and confidence. Data for early-stage non-small cell lung cancer is now increasing and strongly suggest that eliminating elective nodal irradiation does not result in a high incidence of nodal relapse and does not compromise survival. Three-dimensional conformal radiotherapy incorporates better targeting and beam directions to effect smaller treatment volumes that include only clinically evident disease. It provides treatment techniques that maximize tumor dose and minimize normal tissue toxicity. Using smaller fields that do not incorporate elective nodal regions may allow higher doses, and these may help improve local control and survival in a disease where current results are unacceptable.

[Radiation-induced superficial fibrosis and TGF-alpha 1]

Radiation-induced fibrosis is a late sequela of both therapeutic and accidental irradiations, which has been described in various tissues, including the lung, liver, kidney and skin. This review presents different aspects of superficial radiation-induced fibrosis, such as clinical observations, histological changes, cellular and molecular regulations, and medical management. Recent evidence on the critical role played by TGF-beta 1 in the initiation, development and persistence of fibrosis are discussed, as well as the possibility that this cytokine may constitute a specific target for antifibrotic agents.

Impact of tissues heterogeneities on monitor units calculation and ICRU dose point: analysis of 30 cases of prostate cancer treated with 18-MV photons after three-dimensional planning

PURPOSE

Analysis of dose specification of tissue heterogeneities.

METHODS AND MATERIALS

Three-dimensional dose distribution analyses of 30 patients with localized prostate cancer were reviewed with and without tissue heterogeneity correction. The number of monitor units for each portal entrance (more than 300 different fields) was calculated and the impact of targeting and number of portal entrances was also integrated.

RESULTS

The presence of gas in the rectum induces an overdosage of 0.6%, pubic bone induces an underdosage of -1.5%, and femoral heads are responsible for 6% underdosage. For the treatment as a whole, the underdosage is correlated with targeting techniques and weighting of each portal entrance (range, -0.5% to -3.2%).

CONCLUSION

Dose calculation must take into account tissue heterogeneities and more precise guidelines for dose prescription are mandatory for further intercomparison.

Prospective evaluation of early lung toxicity following three-dimensional conformal radiation therapy in non-small-cell lung cancer: preliminary results

PURPOSE

Radiation pneumonitis is the restricting complication following lung cancer irradiation. The correlation between dose-volume histograms (DVHs) and pneumonitis, with a clinical, radiological, and respiratory function evaluation was assessed. Special endpoint was the evaluation of respiratory function after three-dimensional conformal radiotherapy (3D-CRT).

METHODS AND MATERIALS

Fifty-four patients with non metastatic non-small-cell lung cancer (NSCLC) were treated with a curative intent with 3D-CRT (66 Gy). Thirty-one patients were treated postoperatively (pneumonectomy in 9 patients) for residual tumor or massive nodal involvement (N2 or N3); 23 patients were treated with exclusive radiotherapy. Clinical evaluation, CT scan, and pulmonary functional tests were performed before and 6 weeks after irradiation. The DVHs were calculated applying lung density heterogeneity.

RESULTS

Twenty patients had radiation pneumonitis. Irradiation significantly decreased total lung capacity. Volume of the PTV2 (more than 200 cm(3)) was a significant prognostic factor for lung complication.

CONCLUSION

DVHs combined with initial pulmonary functional tests can predict pulmonary toxicity and could allow us to adjust volume that received total highest dose with acceptable toxicity.

Comparison of conformal radiation therapy techniques within the dynamic radiotherapy project 'Dynarad'

The objective of the dynamic radiotherapy project 'Dynarad' within the European Community has been to compare and grade treatment techniques that are currently applied or being developed at the participating institutions. Cervical cancer was selected as the tumour site on the grounds that the involved organs at risk, mainly the rectum and the bladder, are very close to the tumour and partly located inside the internal target volume. In this work, a solid phantom simulating the pelvic anatomy was used by institutions in Belgium, France, Greece, Holland, Italy, Sweden and the United Kingdom. The results were evaluated using both biological and physical criteria. The main purpose of this parallel evaluation is to test the value of biological and physical evaluations in comparing treatment techniques. It is demonstrated that the biological objective functions allow a much higher conformality and a more clinically relevant scoring of the outcome. Often external beam treatment techniques have to be combined with intracavitary therapy to give clinically acceptable results. However, recent developments can reduce or even eliminate this need by delivering more conformal dose distributions using intensity modulated external dose delivery. In these cases the reliability of the patient set-up procedure becomes critical for the effectiveness of the treatment.

Red marrow dosimetry for radiolabeled antibodies that bind to marrow, bone, or blood components

Hematologic toxicity limits the radioactivity that may be administered for radiolabeled antibody therapy. This work examines approaches for obtaining biodistribution data and performing dosimetry when the administered antibody is known to bind to a cellular component of blood, bone, or marrow. Marrow dosimetry in this case is more difficult because the kinetics of antibody clearance from the blood cannot be related to the marrow. Several approaches for obtaining antibody kinetics in the marrow are examined and evaluated. The absorbed fractions and S factors that should be used in performing marrow dosimetry are also examined and the effect of including greater anatomical detail is considered. The radiobiology of the red marrow is briefly reviewed. Recommendations for performing marrow dosimetry when the antibody binds to the marrow are provided.

Conformal radiotherapy for paranasal sinus and nasal cavity tumors: three-dimensional treatment planning and preliminary results in 40 patients

PURPOSE

To assess the possibility to deliver a high and homogeneous irradiation with respect to maximal tolerated dose to the visual pathways for paranasal sinus and nasal cavity tumors.

METHODS AND MATERIALS

Forty patients with advanced stage malignant tumors were treated with postoperative (30) or primary (10 patients) conformal radiotherapy (CRT). Five patients were previously irradiated. Six to 15 individually shaped isocentric noncoplanar field arrangements, using a multileaf collimator were designed. Dose-volume histograms (DVH) for the planning target volumes (PTV) and the optic pathways were analyzed in 31 cases.

RESULTS

Median and maximal delivered doses to the PTV were 60 (+/-3) and 66 (+/-4) Gy. Dose distributions for critical organs are detailed. Median follow-up was 19 months (3 to 48). Local, nodal, and metastatic recurrences occurred in 8, 2, and 7 cases, respectively. Major prognostic factor for local recurrences was central nervous system (CNS) involvement. One patient died of meningitis. Two patients developed cataract, and 1 patient ipsilateral blindness due to vascular glaucoma.

CONCLUSION

CRT for locally advanced paranasal sinus and nasal cavity tumors enables the delivery of high homogeneous doses to the PTV with respect to critical organs, with a low toxicity and a high local control.

The impact of three-dimensional radiation on the treatment of non-small cell lung cancer

PURPOSE

Non-small cell lung cancer (NSCLC) patients with locally advanced unresectable disease have a grim prognosis. Radiotherapeutic strategies are necessary to improve the permanent eradication of thoracic disease. The poor results achieved with conventional external beam radiation therapy reflect in part, the inadequacy of such therapy in achieving its primary objective of achieving local control. The impact of three-dimensional conformal radiation therapy (3-DCRT) on local disease eradication and its potential role in improving survival is assessed.

DESIGN

This review addresses aspects of the software and hardware technology of 3-DCRT, the clinical and technical aspects of target volume definition, the use of 3-DCRT to predict radiation pneumonitis, strategies for dose escalation in NSCLC, and analyses the clinical results to date.

RESULTS

Initially investigators compared the best treatment techniques devised with conventional planning techniques to those devised with 3-DCRT. These analyses showed that 3-DCRT had the potential to deliver high dose radiation (>70 Gy) with minimal underdosing and with a concomitant relative sparing of normal tissues. This technical demonstration of enhanced therapeutic ratio is the basis for the evolving clinical utilization of 3-DCRT for NSCLC. Software and hardware developments continue to develop and have the potential to solve evolving clinical issues. Dose-volume-histograms have been used to accurately quantify lung dose and derived parameters have the potential to predict the risk of pneumonitis for individual patients before treatment. Initial clinical results have been promising and strategies for further dose escalation are emerging.

CONCLUSION

Preliminary experience has resulted in promising survival following three-dimensional conformal radiation therapy alone for locally advanced NSCLC. More follow-up and experience will determine late toxicity, maximum dose, and efficacy of dose escalation with three-dimensional conformal radiation therapy. Strategies should be developed to integrate this modality into the combined treatment of locally advanced non-small cell lung cancer.

Internal mammary node coverage: an investigation of presently accepted techniques

PURPOSE

Recent publications have generated a renewed interest in regional nodal treatment to include the ipsilateral supraclavicular and internal mammary nodes (IMN). The purpose of this study is to evaluate three presently accepted treatment techniques for coverage of the intact breast and ipsilateral lymph node regions and to construct recommendations regarding the utilization of these techniques.

METHODS AND MATERIALS

Anatomic data were obtained from five randomly selected patients with computerized tomography (CT) in treatment position. Three patients presented with cancer of the left breast and two with cancer of the right. Using the Pinnacle 3-D planning system, normal tissue volumes of breast, ipsilateral lung, heart, sternum, and the IMN target were delineated for each patient. Three accepted techniques used to treat ipsilateral breast, internal mammary and supraclavicular nodes (extended tangents, 5-field, partly wide tangents) were configured and compared to a supraclavicular field matched to standard tangential fields. A dosage of 50 Gy in 25 fractions was prescribed to the target volume. Dose-volume histograms (DVH) were generated and analyzed with regard to target volume coverage and lung/heart volumes treated.

RESULTS

All of the treatment techniques covering IMN include at least 10% more lung and heart volume than that covered by standard tangential fields. The relative lung and heart volumes treated with each technique were consistent from patient to patient. The 5-field technique clearly treats the largest volume of normal tissue; however, most of this volume receives less than 50% of the dose prescribed. The percent of heart and ipsilateral lung treated to 20 Gy, 30 Gy, and 40 Gy have been calculated and compared. Due to the increase in chest wall thickness and depth of IMN superiorly, complete coverage was not achieved with any technique if the IMN target extended superiorly into the medial supraclavicular field where dose fall-off resulted in a significant underdosing at depth. For the same anatomic reasons, the 5-field technique underdosed 10-15% of the IMN target volume in 4 of the 5 cases. This technique also yielded a greater dose heterogeneity, which was not seen with the other techniques evaluated and correlated with the change of anterior chest wall thickness.

CONCLUSIONS

Anatomic variation in chest wall thickness and IMN depth strongly suggests the routine use of multislice CT planning to ensure complete coverage of the target volume and optimal sparing of normal tissue. All of the techniques can be constructed to look acceptable at central axis. To cover the superior most aspect of the IMN chain either high tangential fields, a supraclavicular field photon beam of energy >6 MV, or an AP/PA supraclavicular setup should be considered. The 5-field technique has the most difficulty in compensating for the increased depth of the IMN in the superior aspect of the tangent fields with up to +/-40% variation of the dose noted in isolated areas within the target volume. Based on our evaluation, the partly wide tangent technique offers many advantages. It provides optimal coverage of the target volume, reduces coverage of normal tissue volumes to an acceptable level, and is easily reproducible with a high degree of dose homogeneity throughout the target.

The role of proton therapy in the treatment of large irradiation volumes: a comparative planning study of pancreatic and biliary tumors

PURPOSE

The purpose of this study was to examine the potential benefit of proton therapy for abdominal tumors. Extensive comparative planning was conducted investigating the most up-to-date photon and proton irradiation technologies.

METHODS AND MATERIALS

A number of rival plans were generated for four patients: two inoperable pancreatic tumors, one inoperable and one postoperative biliary duct tumor. The dose prescription goal for these large targets was 50 Gy, followed by a boost dose up to 20 Gy to a smaller planning target volume (PTV). Photon plans were developed using "forward" planning of coplanar and noncoplanar conformal fields and "inverse" planning of intensity-modulated (IM) fields. Proton planning was simulated as administered using the so called spot-scanning technique. Plans were evaluated on the basis of normal tissues' dose-volume constraints (Emami B, Lyman J, Brown A, et al. Tolerance of normal tissue to therapeutic irradiation. Int J Radiat Oncol Biol Phys 1990;21:109-122) and coverage of treatment volumes with prescribed doses.

RESULTS

For all cases, none of the forward calculated photon plans was able to deliver 50 Gy to large PTVs at the same time respecting the dose-volume constraints on all critical organs. Nine evenly spaced IM fields achieved or nearly achieved all maximum dose constraints to critical structures for two out of three inoperable patients. IM plans also obtained good results for the postoperative patient, even though the dose to the liver was very close to the maximum allowed. In all cases, photon irradiation of large PTV1s to 50 Gy followed by a 20 Gy boost entailed a risk very close to or higher than 5% for serious complications to the kidneys, liver, or bowel. Simple arrangements of 2, 3, and 4 proton fields obtained better dose conformation to the target, allowing the delivery of planned doses including the boost to all patients, without excessive risk of morbidity. Dose homogeneity inside the targets was also superior with protons.

CONCLUSION

For the irradiation of large PTVs located in the abdominal cavity, where multiple, parallel structured organs surround the target volumes, proton therapy, delivered with a sophisticated isocentric technique, has the potential to achieve superior dose distributions compared with state-of-the-art photon irradiation techniques. IM photon plans obtain better results in the postoperative case, because the reduced volume lessens the effect of the unavoidable increase of integral dose to surrounding tissues.

A new three-dimensional dose distribution reduction scheme for tubular organs

In tubular structures, spatial aspects of the dose distribution may be important in determining the normal tissue response. Conventional dose-volume-histograms (DVHs) and dose-surface-histograms (DSHs) lack spatial information and may not be adequate to represent the three-dimensional (3D) dose data. A new 3D dose distribution data reduction scheme which preserves its longitudinal and circumferential character is presented. Dose distributions were generated at each axial level for esophagus or rectum in 123 patients with lung cancer or prostate cancer. Dose distribution histograms at each axial level were independently analyzed along the esophageal or rectal circumference to generate dose-circumference-histogram (DCH) sheets. Two types of plots were then generated from the DCH sheet. The first considered the percentage of the circumference at each axial level receiving various doses. The second considered the minimum dose delivered to any percentage of the circumference at each axial level. The DCH as a treatment planning tool can be easily implemented in a 3D planing system and is potentially useful for the study of the relationship between the complication risk and the longitudinal and circumferential dose distributions.

Correlation of radiation tolerance dose of normal human organs with organ weight, blood, and water content

The concerted effort to minimize the radiation exposure to normal human tissues while delivering a high radiation dose to the tumor often results in complications. This limits the efficacy of radiation treatment. Analysis of radiation tolerance dose with organ weight in 15 human organs yields a correlation coefficient of 0.62, whereas the correlation of radiation tolerance dose with blood and water content yields correlation coefficients of 0.82 and 0.60, respectively. Results indicate that as the organ weight and/or blood and water content increases, radiation tolerance dose decreases.

Beam intensity modulation using tissue compensators or dynamic multileaf collimation in three-dimensional conformal radiotherapy of primary cancers of the oropharynx and larynx, including the elective neck

INTRODUCTION

The treatment of midline tumors in the head and neck by conventional radiotherapy almost invariably results in xerostomia. This study analyzes whether a simple three-dimensional conformal radiotherapy (3D-CRT) technique with beam intensity modulation (BIM) (using a 10-MV beam of the MM50 Racetrack Microtron) can spare parotid and submandibular glands without compromising the dose distribution in the planning target volume (PTV).

METHODS

For 15 T2 tumors of the tonsillar fossa with extension into the soft palate (To) and 15 T3 tumors of the supraglottic larynx (SgL), conventional treatment plans, consisting of lateral parallel opposed beams, were used for irradiation of both the primary tumor (70 Gy) and the elective neck regions (46 Gy). Separately, for each tumor a 3-D conformal treatment plan was developed using the 3-D computer planning system, CadPlan, and Optimize, a noncommercial program to compute optimal beam profiles. Beam angles were selected with the intention of optimal sparing of the salivary glands. The intensity of the beams was then modulated to achieve a homogeneous dose distribution in the target for the given 3D-CRT techniques. The dose distributions, dose-volume histograms (DVHs) of target and salivary glands, tumor control probabilities (TCPs), salivary gland volumes absorbing a biologically equivalent dose of greater than 40 or 50 Gy, and normal tissue complication probabilities (NTCPs) of each treatment plan were computed. The parameters of the 3D-CRT plans were compared with those of the conventional plans.

RESULTS

In comparison with the conventional technique, the dose homogeneity in the target volume was improved by the conformal technique for both tumor sites. In addition, for the SgL conformal technique, the average volumes of the parotid glands absorbing a BED of greater than 40 Gy (V40) decreased by 23%, and of the submandibular glands by 7% (V40) and 6% (V50). Consequently, the average NTCPs for the parotid and submandibular glands were reduced by 7% and 6%, respectively. For the To conformal techniques, the V40 of the parotid glands was decreased on average by 31%, resulting in an average reduction of the NTCP by 49%. Both the average V50 and the NTCP of the submandibular glands were decreased by 7%.

CONCLUSION

For primary tumors of the oropharynx, the parotid glands could be spared to a considerable degree with the 3D-CRT technique. However, particularly the ipsilateral submandibular gland could not be spared. For primary tumors of the larynx, the 3D-CRT technique allows sparing of all salivary glands to a considerable and probably clinically relevant degree. Moreover, the conformal techniques resulted in an increased dose homogeneity in the PTV of both tumor sites.

Comparative analysis of dose volume histogram reduction algorithms for normal tissue complication probability calculations

A model for estimating radiotherapy treatment outcome through the probability of damage to normal tissue and the probability of tumour control is a useful tool for treatment plan optimization, dose escalation strategies and other currently used procedures in radiation oncology. Normal tissue complication estimation (NTCP) is here analysed from the point of view of the reliability and internal consistency of the most popular model. Five different dose volume histogram (DVH) reduction algorithms, applied to the Lyman model for NTCP calculation. were analysed and compared. The study was carried out for sets of parameters corresponding to quite different expected dose-response relationships. In particular, we discussed the dependence of the models on the parameters and on the dose bin size in the DVH. The sensitivity of the different reduction schemes to dose inhomogeneities was analysed, using a set of simple DVHs representing typical situations of radiation therapy routine. Significant differences were substantiated between the various reduction methods regarding the sensitivity to the degree of irradiation homogeneity, to the model parameters and to the dose bin size. Structural aspects of the reduction formalism allowed an explanation for these differences. This work shows that DVH reduction for NTCP calculation has still to be considered as a very delicate field and used with extreme care, especially for clinical applications, at least until the actual formulations are tuned against strong clinical data.

Optimizing radiotherapy of orbital and paraorbital tumors: intensity-modulated X-ray beams vs. intensity-modulated proton beams

PURPOSE

This study presents a dosimetric optimization effort aiming to compare intensity-modulated (IM) X-rays and IM protons in 4 different orbital and paraorbital tumors. These are most challenging targets for standard radiotherapy due to their close relationship with the eyes and related structures.

METHODS AND MATERIALS

A primary orbital lymphoma, an optic nerve meningioma, a sphenoidal ridge meningioma protruding into the orbit, and a pediatric parameningeal paraorbital rhabdomyosarcoma were selected for the purpose of this study. Planning target volumes (PTVs) and organs at risk (OAR) were defined in each patient CT data set for each tumor site. IM X-ray and IM proton three-dimensional treatment plans were implemented. The following total tumor doses were prescribed: 30 Gy for the orbital lymphoma, 54 Gy for both meningiomas, and 50.4 Gy for the rhabdomyosarcoma case. Dose-volume histograms (DVHs) were obtained for all targets and OAR with both treatment techniques. DVHs were used to predict normal tissue complication probabilities (NTCPs) for the OAR in the vicinity of the tumor.

RESULTS

The PTV coverage was optimal and equally homogeneous with both IM X-rays and IM proton plans in the 4 tumor sites. DVHs for most OAR were better with IM proton beams especially in the low- to mid-dose range region. The integral nontarget dose was lower with IM protons in every case (factor ranging from 1.5 to 1.9). However, predicted NTCPs (for severe late effects) were equally low for both treatment techniques in every tumor site.

CONCLUSION

Although IM proton plans optimally decreased the dose to the OAR in all tumor sites, both optimized X-ray and proton beams equally succeeded to reduce severe-toxicity prediction risks to less than 5% while optimally treating the PTV.

Modeling normal tissue complication probability from repetitive computed tomography scans during fractionated high-dose-rate brachytherapy and external beam radiotherapy of the uterine cervix

PURPOSE

To calculate the normal tissue complication probability (NTCP) of late radiation effects on the rectum and bladder from repetitive CT scans during fractionated high-dose-rate brachytherapy (HDRB) and external beam radiotherapy (EBRT) of the uterine cervix and compare the NTCP with the clinical frequency of late effects.

METHODS AND MATERIALS

Fourteen patients with cancer of the uterine cervix (Stage IIb-IVa) underwent 3-6 (mean, 4.9) CT scans in treatment position during their course of HDRB using a ring applicator with an Iridium stepping source. The rectal and bladder walls were delineated on the treatment-planning system, such that a constant wall volume independent of organ filling was achieved. Dose-volume histograms (DVH) of the rectal and bladder walls were acquired. A method of summing multiple DVHs accounting for variable dose per fraction were applied to the DVHs of HDRB and EBRT together with the Lyman-Kutcher NTCP model fitted to clinical dose-volume tolerance data from recent studies.

RESULTS

The D(mean) of the DVH from EBRT was close to the D(max) for both the rectum and bladder, confirming that the DVH from EBRT corresponded with homogeneous whole-organ irradiation. The NTCP of the rectum was 19.7% (13.5%, 25. 9%) (mean and 95% confidence interval), whereas the clinical frequency of late rectal sequelae (Grade 3-4, RTOG/EORTC) was 13% based on material from 200 patients. For the bladder the NTCP was 61. 9% (46.8%, 76.9%) as compared to the clinical frequency of Grade 3-4 late effects of 14%. If only 1 CT scan from HDRB was assumed available, the relative uncertainty (standard deviation or SD) of the NTCP value for an arbitrary patient was 20-30%, whereas 4 CT scans provided an uncertainty of 12-13%.

CONCLUSION

The NTCP for the rectum was almost consistent with the clinical frequency of late effects, whereas the NTCP for bladder was too high. To obtain reliable (SD of 12-13%) NTCP values, 3-4 CT scans are needed during 5-7 fractions of HDRB treatments.

Calculation of cranial nerve complication probability for acoustic neuroma radiosurgery

PURPOSE

Estimations of complications from stereotactic radiosurgery usually rely simply on dose-volume or dose-diameter isoeffect curves. Due to the sparse clinical data available, these curves have typically not considered the target location in the brain, target histology, or treatment plan conformality as parameters in the calculation. In this study, a predictive model was generated to estimate the probability of cranial neuropathies as a result of acoustic schwannoma radiosurgery.

METHODS AND MATERIALS

The dose-volume histogram reduction scheme was used to calculate the normal tissue complication probability (NTCP) from brainstem dose-volume histograms. The model's fitting parameters were optimized to provide the best fit to the observed complication data for acoustic neuroma patients treated with stereotactic radiosurgery at the University of Florida. The calculation was then applied to the remainder of the patients in the database.

RESULTS

The best fit to our clinical data was obtained using n = 0.04, m = 0.15, and alpha/beta = 2.1 Gy(-1). Although the fitting parameter m is relatively consistent with ranges found in the literature, both the volume parameter, n, and alpha/beta are much smaller than the values quoted in the literature. The fit to our clinical data indicates that brainstem, or possibly a specific portion of the brainstem, is more radiosensitive than the parameters in the literature indicate, and that there is very little volume effect; in other words, irradiation of a small fraction of the brainstem yields NTCPs that are nearly as high as those calculated for entire volume irradiation. These new fitting parameters are specific to acoustic neuroma radiosurgery, and the small volume effect that we observe may be an artifact of the fixed relationship of acoustic tumors to specific regions of the brainstem. Applying the model to our patient database, we calculate an average NTCP of 7.2% for patients who had no cranial nerve complications, and the average NTCP for was 66% for patients who sustained a cranial neuropathy. For the entire patient population, the actual percentage of patients suffering either facial or trigeminal neuropathy was 14.7%, whereas the calculated average NTCP was 14.8%.

DISCUSSION

NTCP calculations using brainstem dose-volume histograms can be used to estimate the rate of cranial neuropathies from acoustic neuroma radiosurgery. More clinical data and further study will lead to refinement of the model with time.

Low grade gliomas treated with adjuvant radiation therapy in the modern imaging era

The purpose of this study is to evaluate tumor control and failure patterns in patients with low grade gliomas treated with surgery and conventional adjuvant radiation therapy. Twenty-eight patients with low grade gliomas (7 grade I, 21 grade II) were retrospectively evaluated. Extent of resection was gross total (3), subtotal (17), and biopsy alone (8). All grade I tumors underwent subtotal resection. Median radiation therapy dose was 54 Gy delivered to localized fields. Tumor control and patterns of failure were determined from follow-up computed tomography and/or magnetic resonance scans. Median follow-up was 86 months (range, 2.4-177 months). Thirteen patients (46%) (four grade I, nine grade II) developed tumor progression. The 5-year actuarial progression-free survival rates for grade I and grade II patients were 86% and 51%, respectively. Corresponding 5-year actuarial survival rates were 100% and 70%. All recurrences were within the treated volume. Our results reveal that conventional adjuvant radiation therapy is associated with high rates of local tumor progression in both grade II and incompletely resected grade I low grade gliomas. Alternative strategies need to be explored in these patients in an effort to improve tumor control and outcome.

Radioimmunotherapy of colorectal cancer liver metastases: combination with radiotherapy

The expected therapeutic gain of a combined radioimmunotherapy (RIT) with conventional radiotherapy (RT) would be a synergy of tumor irradiation, provided that toxic, dose-limiting side effects concern different organs. We have shown in a model of subcutaneous human colon cancer transplants in nude mice that RIT with 131I-labeled anti-CEA antibody fragments combined with fractionated RT give an additive therapeutic effect without increase of side effects. A second study of different timing schedules of RIT and RT has shown that close association of both therapies without delay is more efficient than a therapy with a treatment-free interval of two weeks. In a new model of human colon cancer liver metastases in nude mice, early treatment with RIT and with RT has been curative, whereas therapies initiated later were less efficient, suggesting that the combined therapy is likely to be more efficient in an adjuvant situation after surgery. At the clinical level, six patients with limited liver metastatic disease from colorectal cancer were treated with RIT using 200 mCi 131I-labeled anti-CEA MAb F(ab')2 fragments combined with fractionated external beam RT of 20 Gy to the entire liver. As expected, spontaneously reversible bone marrow toxicity grade 3 to 4 and reversible liver toxicity grade 1 to 3 have been observed. By computerized tomography, three patients showed stable disease and one patient partial remission, whereas two patients had progressive disease. In conclusion, animal experiments have shown a clear advantage of combined RT and RIT, and the clinical study shows the feasibility of such a therapy in patients with colorectal cancer liver metastases.

Laryngeal radionecrosis and hyperbaric oxygen therapy: report of 18 cases and review of the literature

Laryngeal radionecrosis is a difficult late complication of radiotherapy. It is associated with hoarseness, edema, pain, weight loss, and upper airway obstruction. The medical treatment options are limited, and in severe cases, the patient may require tracheostomy or laryngectomy. We report clinical results in 18 patients treated with adjunctive hyperbaric oxygen (HBO) therapy for severe radionecrosis of the larynx. Of these 18 patients, 2 had grade 3 and 16 had grade 4 radionecrosis. The patients received a mean number of 41 HBO treatments (range, 6 to 80) at 2 atmospheres absolute for 2 hours, twice a day, 6 days a week. Thirteen patients (72.2%) had a major improvement after HBO therapy, and none of them required total laryngectomy. All patients preserved their voice and deglutition in good or normal condition. Five patients (27.8%) failed to have a good response to HBO and underwent total laryngectomy. One of these patients had local recurrence of his cancer 4 months later, and the other 3 had significant concurrent medical problems. The remaining patient received only 6 HBO treatments because of emergency heart surgery. These encouraging results are comparable to those of smaller previous studies suggesting that HBO has a beneficial effect in the management of advanced laryngeal radionecrosis.

The use of intensity modulated radiotherapy for the treatment of extensive and recurrent juvenile angiofibroma

These case series are presented to describe the application and advantages of intensity modulated radiotherapy (IMRT) for the treatment of extensive and/or recurrent juvenile angiofibroma. Two patients were diagnosed with recurrence at 11 and 13 months postoperatively, and one was surgically unresectable. The affected areas included the base of skull, cavernous sinus, pterygopalatine fossa, infratemporal fossa, posterior orbit and nasopharynx. Highly conformal IMRT was delivered with limited radiation doses to the optic nerves, optic chiasm, brainstem, brain, spinal cord, lens, retina, mandible, and parotid. The total dose delivered to the tumor varied from 3400 to 4500 cGy. The tumor shrunk radiographically in all three cases and there was no endoscopic evidence of disease in two cases at 15 months and 40 months. There was no acute toxicity. Late toxicity was limited to one episode of epistaxis and persistent rhinitis in one patient. In conclusion, IMRT provides several advantages over conventional radiotherapy in the treatment of recurrent juvenile angiofibroma.

Tolerance of the normal canine brain to epithermal neutron irradiation in the presence of p-boronophenylalanine

Twelve normal dogs underwent brain irradiation in a mixed-radiation, mainly epithermal neutron field at the Brookhaven Medical Research Reactor following intravenous infusion of 950 mg of 10B-enriched BPA/kg as its fructose complex. The 5 x 10 cm irradiation aperture was centered over the left hemisphere. For a subgroup of dogs reported previously, we now present more detailed analyses including dose-volume relationships, longer follow-ups, MRIs, and histopathological observations. Peak doses (delivered to 1 cm3 of brain at the depth of maximum thermal neutron flux) ranged from 7.6 Gy (photon-equivalent dose: 11.8 Gy-Eq) to 11.6 Gy (17.5 Gy-Eq). The average dose to the brain ranged from 3.0 Gy (4.5 Gy-Eq) to 8.1 Gy (11.9 Gy-Eq) and to the left hemisphere, 6.6 Gy (10.1 Gy-Eq) to 10.0 Gy (15.0 Gy-Eq). Maximum tolerated 'threshold' doses were 6.7 Gy (9.8 Gy-Eq) to the whole brain and 8.2 Gy (12.3 Gy-Eq) to one hemisphere. The threshold peak brain dose was 9.5 Gy (14.3 Gy-Eq). At doses below threshold, some dogs developed subclinical MRI changes. Above threshold, all dogs developed dose-dependent MRI changes, neurological deficits, and focal brain necrosis.

Evaluation of a standard breast tangent technique: a dose-volume analysis of tangential irradiation using three-dimensional tools

PURPOSE

A thorough dose-volume analysis of a standard tangential radiation technique has not been published. We evaluated the adequacy of a tangential radiation technique in delivering dose to the breast and regional lymphatics, as well as dose delivered to underlying critical structures.

METHODS AND MATERIALS

Treatment plans of 25 consecutive women with breast cancer undergoing lumpectomy and adjuvant breast radiotherapy were studied. Patients underwent two-dimensional (2D) treatment planning followed by treatment with standard breast tangents. These 2D plans were reconstructed without modification on our three-dimensional treatment planning system and analyzed with regard to dose-volume parameters.

RESULTS

Adequate coverage of the breast (defined as 95% of the target receiving at least 95% of the prescribed dose) was achieved in 16 of 25 patients, with all patients having at least 85% of the breast volume treated to 95% of the prescribed dose. Only 1 patient (4%) had adequate coverage of the Level I axilla, and no patient had adequate coverage of the Level II axilla, Level III axilla, or the internal mammary lymph nodes.

CONCLUSION

Three-dimensional treatment planning is superior in quantification of the dose received by the breast, regional lymphatics, and critical structures. The standard breast tangent technique delivers an adequate dose to the breast but does not therapeutically treat the regional lymph nodes in the majority of patients. If coverage of the axilla or internal mammary lymph nodes is desired, alternate beam arrangements or treatment fields will be necessary.

Intensity modulated radiation therapy: a clinical review

Intensity modulated radiotherapy represents a significant advance in conformal radiotherapy. In particular, it allows the delivery of dose distributions with concave isodose profiles such that radiosensitive normal tissue close to, or even within a concavity of, a tumour may be spared from radiation injury. This article reviews the clinical application of this technique to date, and discusses the practical issues of treatment planning and delivery from the clinician's perspective.

Surgical treatment of recalcitrant radiation-induced gastric erosions

BACKGROUND

Uncontrolled bleeding as a result of radiation gastritis in patients who have pharyngo-laryngo-esophagectomy and gastric pull-up is seldom reported. Surgical resection in the management of this condition has rarely been described.

METHOD

A 66-year-old man with hypopharyngeal cancer was treated by pharyngo-laryngo-esophagectomy and gastric transposition. He received postoperative radiotherapy and had recurrent hemorrhagic gastritis, necessitating surgical resection. The manubrium was resected to access the mediastinal part of the gastric conduit. The diseased part of the gastric conduit was removed and a free jejunal graft was interposed to replace the resected stomach.

RESULTS

Manubrial resection offered adequate access to the stomach transposed in the mediastinum, and the life-threatening bleeding gastritis was successfully controlled by surgical resection.

CONCLUSION

Surgical resection of the radiation-damaged transposed stomach through a manubrial resection approach can safely be performed. Free jejunal graft is the choice of reconstruction of the circumferential defect.

Long-term cardiac mortality following radiation therapy for Hodgkin's disease: analysis with the relative seriality model

PURPOSE

(a) To assess the increased risk of death due to ischemic heart disease (IHD) in a group of patients treated for Hodgkin's disease (HD) with radiation therapy (RT) as the primary treatment. (b) To quantify the dose response of IHD using a biophysical model.

MATERIALS AND METHODS

Patient material consisted of 157 patients diagnosed for HD between 1972 and 1985 who received RT as the primary treatment at Radiumhemmet, Karolinska Hospital. The general population formed the control group. The RT treatments were reconstructed based on the individual treatment data and simulator films. Individual clinical and dosimetrical data were analyzed with the relative seriality model. The material was also analyzed grouping the material according to dose-volume constraints.

RESULTS

Of the 157 patients, 13 (8.3%) died due to IHD. The standardized mortality ratio (SMR) was 5.0 (95% CI, 2.7-8.6). Analysis of dose-volume histograms (DVH) showed an increasing risk with increasing dose to a larger volume fraction. The observed individual clinical complication data could not be modeled unambiguously. The group analysis resulted in the dose-response parameters: D(50)=71 Gy, gamma=0.96 and s=1.0.

CONCLUSIONS

A significantly increased risk of death due to IHD following RT for HD was found. The risk was found to increase with higher dose and larger volume fraction irradiated.

[Dosimetric evaluation of conformal radiotherapy: conformity factor]

The aim of three-dimensional conformal therapy (3DCRT) is to treat the Planning Target Volume (PTV) to the prescribed dose while reducing doses to normal tissues and critical structures, in order to increase local control and reduce toxicity. The evaluation tools used for optimizing treatment techniques are three-dimensional visualization of dose distributions, dose-volume histograms, tumor control probabilities (TCP) and normal tissue complication probabilities (NTCP). These tools, however, do not fully quantify the conformity of dose distributions to the PTV. Specific tools were introduced to measure this conformity for a given dose level. We have extended those definitions to different dose levels, using a conformity index (CI). CI is based on the relative volumes of PTV and outside the PTV receiving more than a given dose. This parameter has been evaluated by a clinical study including 82 patients treated for lung cancer and 82 patients treated for prostate cancer. The CI was low for lung dosimetric studies (0.35 at the prescribed dose 66 Gy) due to build-up around the GTV and to spinal cord sparing. For prostate dosimetric studies, the CI was higher (0.57 at the prescribed dose 70 Gy). The CI has been used to compare treatment plans for lung 3DCRT (2 vs 3 beams) and prostate 3DCRT (4 vs 7 beams). The variation of CI with dose can be used to optimize dose prescription.

Intensity-modulated radiation therapy in head and neck cancers: The Mallinckrodt experience

The purpose of the study was to investigate the feasibility and the optimization of tomotherapy-based intensity-modulated radiation therapy (IMRT) in patients with head and neck cancer. From February 1997 to November 1997, 17 patients with squamous cell carcinoma of the head and neck were treated with IMRT. Patients were immobilized with a noninvasive mask and treated using a serial tomotherapy device on a 6 MV linear accelerator. Treatment planning was performed on a Peacock inverse planning system and prescription optimization was used to achieve the best plan for target coverage and parotid sparing. The treatment planning system process has a dosimetric characteristic of delivering different doses to different target structures simultaneously in each daily treatment; therefore, the biological equivalent dose was implemented using the linear-quadratic model to adjust the total dose to the target volume receiving a daily dose of less than 1.9 Gy. All eight patients with gross disease (six in the nasopharynx, two in the tonsil) and one patient with recurrent nasopharyngeal carcinoma received concurrent cisplatin chemotherapy. Six postoperative patients were treated with irradiation alone. Median follow-up was 2.2 years (range 2.6-1.8 years). All patients completed the prescribed treatment without unexpected interruption. Acute side effects were comparable to those of patients treated with conventional beam arrangements during the same period. No patient required gastrostomy during irradiation. The preliminary experience showed that the noninvasive immobilization mask yielded high positioning reproducibility for our patients. To spare the parotid gland, which is in the proximity of the target, a fraction of the target volume may not receive the prescribed dose. In the best-achievable plan of our studied cohort, only 27% +/- 8% of parotid gland volumes were treated to more than 30 Gy, while an average of 3.3% +/- 0.6% of the target volume received less than 95% of the prescribed dose. This is mainly related to the steep dose gradient in the region where the target abuts the parotid gland. The inverse planning system allowed us the freedom of weighting normal tissue-sparing and target coverage to select the best-achievable plan. Local control was achieved in eight patients with gross tumor; six were treated postoperatively. Of three reirradiated patients, two had symptomatic improvement but persistent disease, and one is without evidence of disease. In summary, a system for patient immobilization, setup verification, and dose optimization for head and neck cancer with parotid sparing without significantly compromising target coverage is being implemented for a tomotherapy-based IMRT plan at the Mallinckrodt Institute of Radiology. The initial clinical experience in tumor control is promising, and no severe adverse acute side effects have been observed. Further refining of delivery technology and the inverse planning system, gaining clinical experience to address target definition and dose inhomogeneity within the targets, and understanding the partial volume effect on normal tissue tolerance are needed for IMRT to excel in the treatment of head and neck cancer. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 92-103, (2000).

An evaluation of three-field coplanar plans for conformal radiotherapy of prostate cancer

BACKGROUND AND PURPOSE

A series of coplanar three-field configurations for two different clinical treatment volumes, prostate only (PO) and prostate plus seminal vesicles (PSV) were studied to determine the optimal three-field plan arrangement for prostate radiotherapy.

MATERIALS AND METHODS

A variety of conformal three-field 6 MV plans prescribed to both 64 and 74 Gy were created for PO and PSV volumes in each of ten patients. For description, the orientation of each sequential beam was named in a clockwise fashion. Plans included series with arrangements of 0 degrees, 60-150 degrees, 210-300 degrees; 0 degrees, 90 degrees, 225-255 degrees; 90 degrees, 210-240 degrees, 300-330 degrees and a four-field (4F) box plan for comparison. Six-hundred and eighty plans were compared using the rectal volume irradiated to greater than 50% (V(50)), 80% (V(80)), and 90% (V(90)) of the prescribed dose, normal tissue complications (NTCP) for rectum, bladder, and femoral heads (FH), and tumour control probabilities (TCP). FH tolerance was set at 52 Gy to 10% volume.

RESULTS

In comparing the 34 different three-field configurations for each of the PO and PSV groups, the greatest rectal sparing was achieved by a three-field plan with gantry angles of 0 degrees, 90 degrees, 270 degrees (PO: rectal V(80)=22.8+/-5.5% (1S.D.), V(90)=18.4+/-5.7%, and PSV: rectal V(80)=41.9+/-5.8%, V(90)=35.5+/-5.9%). This also improved on the 4F-box plan (PO: rectal V(80)=26.0+/-5.8%, V(90)=21.4+/-5.2%, P<0.001; and PSV: rectal V(80)=47.3+/-5.5%, V(90)=41.6+/-5.1%, P<0.001). The worst rectal sparing was seen with the 0 degrees, 120 degrees, 240 degrees plan (PO: rectal V(80)=35.2+/-8.0%, V(90)=30.3+/-7.1%, P<0.001; and PSV: rectal V(80)=65.7+/-9.0%, V(90)=58.8+/-8.8%, P<0.001). In the PO group, the increase in predicted rectal NTCP with dose escalation from 64 to 74 Gy was 3.3% using the 0 degrees, 90 degrees, 270 degrees plan, 4.7% with the 4F-box plan, and 6.9% with the 0 degrees, 120 degrees, 240 degrees plan. In the PSV group, dose escalation increased the predicted rectal NTCP by 7.9, 10.1 and 15.7% for the 0 degrees, 90 degrees, 270 degrees plan, 4F-box plan, and 0 degrees, 120 degrees, 240 degrees plan, respectively.

CONCLUSIONS

For both PO and PSV volumes, the three-field plan which afforded the greatest rectal sparing with acceptable bladder and femoral head doses was the 0 degrees, 90 degrees, 270 degrees plan. This plan also improved on the 4F-box. The increase in predicted rectal NTCP when escalating dose from 64 to 74 Gy was smaller using this plan compared to either the three-field 0 degrees, 120 degrees, 240 degrees plan or the 4F-box plan.

Absorbed dose estimates for 131I-labelled monoclonal antibody therapy in patients with intraperitoneal pseudomyxoma

Seven patients with intraperitoneal pseudomyxoma originating from the appendix (4 cases) and from the ovary (3 cases) were treated with radioimmunotherapy. During the therapy, nine infusions of 3.0-4.2 GBq of 131I-labelled B72.3 monoclonal antibody were administered. We developed three-dimensional dose calculation software that can utilize activity maps based on SPET images to calculate the absorbed dose distribution using point source kernels. The dose calculation program was employed to calculate absorbed doses to various organs. The calculated dose distributions enable us to evaluate the variation in dose within the organs, which is normally not available using approaches based on geometric models. The patient-specific absorbed dose calculations were compared with doses based on a model that uses photon S-factors derived from a standard phantom. The compared doses agreed well on average, but in some organs showed large discrepancies.

Thoracic reirradiation for symptomatic relief after prior radiotherapeutic management for lung cancer

Limited information is available in the medical literature on thoracic reirradiation for patients with recurrent/persistent lung carcinoma or new primary lung tumors. Controversy exists regarding the retreatment because of concerns regarding the risk of radiation toxicity. The medical and radiotherapeutic records of more than 1,500 patients with lung cancer seen in the Department of Radiation Oncology at Thomas Jefferson University Hospital from 1982 through 1997 were searched. Twenty-three patients with history of previous thoracic radiation therapy underwent thoracic reirradiation for either biopsy-proven and/or radiographically evident tumor recurrence, metastasis, or second lung primary. Most patients were reirradiated because of progressive dyspnea, cough, thoracic pain, or hemoptysis. Each of these symptoms was evaluated separately with regard to the subjective response to reirradiation. The median follow-up time from completion of reirradiation to last correspondence with the patient and/or family was 3.2 months, with a range of 0 to 17.5 months. In six patients with hemoptysis, a decrease or resolution of this symptom was noted. Of five patients with thoracic pain attributed to carcinoma, four noted an improvement in pain after reirradiation. Of 15 patients with cough, 9 had an improvement in cough, and of 15 patients with dyspnea, 11 had an improvement. Thoracic reirradiation is an effective modality in patients with hemoptysis, thoracic pain, cough, and dyspnea attributed to a radiographically defined recurrence and/or progression of lung cancer.

Can angiotensin-converting enzyme inhibitors protect against symptomatic radiation pneumonitis?

This study was designed to determine whether patients taking angiotensin-converting enzyme (ACE) inhibitors while receiving radiation therapy for lung cancer are protected from developing symptomatic radiation pneumonitis. The records of 213 eligible patients receiving thoracic irradiation for lung cancer with curative intent at Duke University Medical Center from 1994-1997 were reviewed. Of the 213 patients, 26 (12.2%) were on ACE inhibitors (usually for the management of hypertension) during radiotherapy (group 1); the remaining 187 patients (group 2) were not. Patients were irradiated, with fields shaped to protect normal tissues, with total doses of 50-80 Gy. After treatment, patients were generally followed every 3 months for 2 years, then every 6 months thereafter. Symptomatic radiation pneumonitis was scored according to modified National Cancer Institute Common Toxicity Criteria (i.e., radiographic changes alone were not sufficient for the diagnosis of pneumonitis). There was no difference in the incidence of pneumonitis between the two groups (P = 0.75). Fifteen percent of the patients on ACE inhibitors (group 1) developed symptomatic radiation-induced lung injury compared to 12% of the patients not receiving these drugs (group 2). Although patients in group 1 tended to develop pneumonitis slightly sooner than did patients in group 2, this difference also was not significant (P = 0. 8). Within the dose range prescribed for treating hypertension, ACE inhibitors do not appear to either decrease the incidence or delay the onset of symptomatic radiation pneumonitis among lung cancer patients receiving thoracic irradiation.

Conformal irradiation of concave-shaped PTVs in the treatment of prostate cancer by simple 1D intensity-modulated beams

BACKGROUND

In the case of concave-shaped PTVs including prostate (P) and seminal vesicles (SV), intensity-modulated radiation therapy (IMRT) should improve the therapeutic ratio of the treatment of prostate cancer.

PURPOSE

Comparing IMRT by simple 1D modulations with conventional 3D conformal therapy (i.e. non-IMRT) in the treatment of concave-shaped PTVs including P+SV.

MATERIALS AND METHODS

For five patients having a concave-shaped PTV (P+SV) previously treated at our Institute with conformal radiotherapy, conventional 3- and 4-fields conformal plans were compared with IMRT plans in terms of biological indices. IMRT plans were generated by using five equi-spaced beams with a partial shielding of the rectum obtainable with our single-absorber modulation technique (Fiorino C, Lev A, Fusca M, Cattaneo GM, Rudello F, Calandrino R. Dynamic beam modulation by using a single dynamic absorber. Phys. Med. Biol. 1995;40:221-240). The modulation was one-dimensional and the shape of the beams was at single minimum in correspondence with the 'core' of the rectum; the beam intensity in the minimum was set equal to 20 or 40% of the open beam intensity. All plans were simulated on the CADPLAN TPS using a pencil-beam based algorithm (with 18 MV X-rays). Tumour control probability (TCP) and normal tissue complication probabilities (NTCPs) (for rectum, bladder and femoral head) were calculated for all situations when varying the isocentre dose from 60 to 90 Gy. Dose distributions were corrected taking dose fractionation into account through the linear-quadratic model; for the TCP/NTCP estimations the Webb-Nahum and the Lyman-Kutcher models were respectively applied. Three different scores were considered: (a) increase of TCP while keeping rectum NTCP equal to 5% (TCP(5%)); (b) increase of the uncomplicated tumour control probability (P+); (c) increase of the biological-based scoring function (S+), developed by Mohan et al. (Mohan R, Mageras GS, Baldwin B, Clinically relevant optimization of 3D conformal treatments. Med. Phys. 1992;19:933-944). The impact of the uncertainty in the knowledge of the parameters of the biological models was investigated for TCP(5%).

RESULTS

(a) The average gain in TCP(5%) when considering IMRT against non-IMRT conformal plans was 7.3% (range 5.0-13.5%); (b) the average increase of P+ was 3.4% (range: 1. 0-8.5%); and (c) the average increase of S+ was 5.4% (range 2.9-12. 4%). The largest gain was found for one patient (patient 5) showing a significantly larger overlapping between PTV and rectum.

CONCLUSIONS

Simple 1D-IMRT may clearly improve the therapeutic ratio in the treatment of concave-shaped PTVs including P and SV. In the range of clinically suitable values, the impact of the uncertainty of the parameters n and sigma(alpha) does not significantly alter the main results concerning the gain in TCP(5%). The reported gain in terms of P+ and S+ should be considered with great caution because of the intrinsic uncertainties of the model's parameters and, for bladder, because the 'true' DVH (considering variations of the shape and dimension due to variable filling) may be very different from the DVH calculated on a single CT scan. Further investigations should consider inversely-optimised 1D and 2D-IMRT plan in order to compare them in terms of cost-benefit.

Patterns of local-regional recurrence following parotid-sparing conformal and segmental intensity-modulated radiotherapy for head and neck cancer

PURPOSE

To analyze the patterns of local-regional recurrence in patients with head and neck cancer treated with parotid-sparing conformal and segmental intensity-modulated radiotherapy (IMRT).

METHODS AND MATERIALS

Fifty-eight patients with head and neck cancer were treated with bilateral neck radiation (RT) using conformal or segmental IMRT techniques, while sparing a substantial portion of one parotid gland. The targets for CT-based RT planning included the gross tumor volume (GTV) (primary tumor and lymph node metastases) and the clinical target volume (CTV) (postoperative tumor bed, expansions of the GTVs and lymph node groups at risk of subclinical disease). Lymph node targets at risk of subclinical disease included the bilateral jugulodigastric and lower jugular lymph nodes, bilateral retropharyngeal lymph nodes at risk, and high jugular nodes at the base of skull in the side of the neck at highest risk (containing clinical neck metastases and/or ipsilateral to the primary tumor). The CTVs were expanded by 5 mm to yield planning target volumes (PTVs). Planning goals included coverage of all PTVs (with a minimum of 95% of the prescribed dose) and sparing of a substantial portion of the parotid gland in the side of the neck at less risk. The median RT doses to the gross tumor, the operative bed, and the subclinical disease PTVs were 70.4 Gy, 61.2 Gy, and 50.4 Gy respectively. All recurrences were defined on CT scans obtained at the time of recurrence, transferred to the pretreatment CT dataset used for RT planning, and analyzed using dose-volume histograms. The recurrences were classified as 1) "in-field," in which 95% or more of the recurrence volume (V(recur)) was within the 95% isodose; 2) "marginal," in which 20% to 95% of V(recur) was within the 95% isodose; or 3) "outside," in which less than 20% of V(recur) was within the 95% isodose.

RESULTS

With a median follow-up of 27 months (range 6 to 60 months), 10 regional recurrences, 5 local recurrences (including one noninvasive recurrence) and 1 stomal recurrence were seen in 12 patients, for a 2-year actuarial local-regional control rate of 79% (95% confidence interval 68-90%). Ten patients (80%) relapsed in-field (in areas of previous gross tumor in nine patients), and two patients developed marginal recurrences in the side of the neck at highest risk (one in the high retropharyngeal nodes/base of skull and one in the submandibular nodes). Four regional recurrences extended superior to the jugulodigastric node, in the high jugular and retropharyngeal nodes near the base of skull of the side of the neck at highest risk. Three of these were in-field, in areas that had received the dose intended for subclinical disease. No recurrences were seen in the nodes superior to the jugulodigastric nodes in the side of the neck at less risk, where RT was partially spared.

CONCLUSIONS

The majority of local-regional recurrences after conformal and segmental IMRT were "in-field," in areas judged to be at high risk at the time of RT planning, including the GTV, the operative bed, and the first echelon nodes. These findings motivate studies of dose escalation to the highest risk regions.

Toxicity of high-dose radiotherapy combined with daily cisplatin in non-small cell lung cancer: results of the EORTC 08912 phase I/II study. European Organization for Research and Treatment of Cancer

The purpose of this work was to study the feasibility of concurrent chemoradiation in patients with inoperable non-small cell lung cancer (NSCLC). 40 patients with inoperable NSCLC were treated with escalating doses of radiotherapy and cisplatin (cDDP). The radiation dose was increased step by step from 60.5 to 66 Gy in daily fractions of 2.75 Gy. Chemotherapy was also increased step by step from 20 to 24 daily doses of cDDP 6 mg/m(2) and given concurrently with radiotherapy. A dose of 40 Gy/2 Gy/20 fractions (fx) was given to the EPTV (elective planning target volume) which included the gross tumour volume with a margin of 2 cm and part of or the entire mediastinum. During each session a boost dose of 0.75 Gy was given simultaneously to the BPTV (boost planning target volume), which encompassed the GTV (gross tumour volume) with a margin of 1 cm, for the first 20 fx, so the total dose to the tumour was 55 Gy. Cisplatin 6 mg/m(2) was given 1 h prior to radiotherapy at each fraction. From then on the dose of radiation to the BPTV and the dose of cDDP were increased step by step. In group I the BPTV was irradiated with two extra fractions of 2.75 Gy to a total dose of 60. 5 Gy without cDDP. In group II the same total dose of 60.5 Gy was given but the last two fractions were combined with cDDP. In group III four extra fractions of 2.75 Gy were given to the BPTV to a total dose of 66 Gy, only two of these fractions combined with cDDP. Finally, in group IV a total dose of 66 Gy was given in 24 fractions, all fractions combined with cDDP. All patients were planned by means of a CT-based conformal treatment planning. The maximal length of the oesophagus receiving >/=60.5 Gy was 11 cm. 40 patients were evaluable for acute and late toxicity and for survival. Acute toxicity grade >/=3 (common toxicity criteria, CTC) was rarely observed; nausea/vomiting in 3 patients (8%), leucopenia in 2 patients (5%), thrombocytopenia in 2 patients (5%), whilst 2 patients (5%) suffered from severe weight loss. Late side-effects (European Organization for Research and Treatment of Cancer/Radiation Therapy Oncology Group, EORTC/RTOG) were: oesophageal toxicity >/=grade 3 in 2 patients (5%) and radiation pneumonitis grades 1 (3%) and 2 (3%) in 1 patient each. Overall actuarial 1- and 2-year survival was 53% and 40%, respectively. The 1- and 2-year local disease-free interval was 65% and 58% respectively. Radiotherapy at a dose of 66 Gy/2.75 Gy/24 fx combined with daily cDDP 6 mg/m(2) given over 5 weeks is feasible and results in a good local disease-free interval and a good survival rate. This treatment schedule is at present being tested as one of the two treatment arms of EORTC phase III study protocol 08972/22973.

Multicenter phase II study of iodine-131 tositumomab for chemotherapy-relapsed/refractory low-grade and transformed low-grade B-cell non-Hodgkin's lymphomas

PURPOSE

This multicenter phase II study evaluated the efficacy, dosimetry methodology, and safety of iodine-131 tositumomab in patients with chemotherapy-relapsed/refractory low-grade or transformed low-grade non-Hodgkin's lymphoma (NHL).

PATIENTS AND METHODS

Patients received a dosimetric dose that consisted of 450 mg of anti-B1 antibody followed by 35 mg (5 mCi) of iodine-131 tositumomab. Serial total-body gamma counts were then obtained to calculate the patient-specific millicurie activity required to deliver the therapeutic dose. A therapeutic dose of 75 cGy total-body dose (attenuated to 65 cGy in patients with platelet counts of 101,000 to 149,000 cells/mm(3)) was given 7 to 14 days after the dosimetric dose.

RESULTS

Forty-five of 47 patients were treated with a single dosimetric and therapeutic dose. Twenty-seven patients (57%) had a response. The response rate was similar in patients with low-grade (57%) or transformed low-grade (60%) NHL. The median duration of response was 9.9 months. Fifteen patients (32%) achieved a complete response (CR; 10 CRs and five clinical CRs), including five patients (50%) with transformed low-grade NHL. The median duration of CR was 19.9 months, and six patients have an ongoing CR. Treatment was well tolerated, with the principal toxicity being hematologic. The most common nonhematologic toxicities that were considered to be possibly related to the treatment included mild to moderate fatigue (32%), nausea (30%), fever (26%), vomiting (15%), infection (13%), pruritus (13%), and rash (13%). Additionally, one patient developed human-antimouse antibodies.

CONCLUSION

Iodine-131 tositumomab produced a high overall response rate, and approximately one third of patients had a CR despite having chemotherapy-relapsed or refractory low-grade or transformed low-grade NHL.