A Clinical Interactive Technique for MR-CT Image Registration for Target Delineation of Intracranial Tumors

Replacement of current CT-based, three-dimensional (3D) treatment planning systems by newer versions capable of automated multi-modality image registration may be economically prohibitive for most radiation oncology clinics. We present a low-cost technique for MR-CT image registration on a “first generation” CT-based, 3D treatment planning system for intracranial tumors. The technique begins with fabrication of a standard treatment mask. A second truncated mask, the “minimask,” is then made, using the standard mask as a mold. Two orthogonal leveling vials glued onto the minimask detect angular deviations in pitch and roll. Preservation of yaw is verified by referencing a line marked according to the CT laser on the craniocaudal axis. The treatment mask immobilizes the patient's head for CT. The minimask reproduces this CT-based angular treatment position, which is then maintained by taping the appropriately positioned head to the MR head coil for MR scanning. All CT and MR images, in DICOM 3.0 format, are entered into the treatment planning system via a computer network. Interactive registration of MR to CT images is controlled by real-time visual feedback on the computer monitor. Translational misalignments at the target are eliminated or minimized by iterative use of qualitative visual inspection. In this study, rotational errors were measured in a retrospective series of 20 consecutive patients who had undergone CT-MR image registration using this technique. Anatomic structures defined the three CT orthogonal axes from which angular errors on MR image were measured. Translational errors at the target isocenter were within pixel size, as judged by visual inspection. Clinical setup using the minimask resulted in overall average angular deviation of 3°±2° (mean ± SD) and translational deviation within the edges of the target volume of typically less than 2 mm. The accuracy of this registration technique for target delineation of intracranial tumors is compatible with practice guidelines. This method, then, provides a cost-effective means to register MR and CT images for target delineation of intracranial tumors.

Proton beam scattering system optimization for clinical and research applications

PURPOSE

To develop and test a method for optimizing and constructing a dual scattering system in passively scattered proton therapy.

METHODS

A beam optics optimization algorithm was developed to optimize the thickness of the first scatterer (S1) and the profile (of both the high-Z material and Lexan) of the second scatterer (S2) to deliver a proton beam matching a given set of parameters, including field diameter, fluence, flatness, and symmetry. A new manufacturing process was also tested that allows the contoured second scattering foil to be created much more economically and quickly using Cerrobend casting. Two application-specific scattering systems were developed and tested using both experimental and Monte Carlo techniques to validate the optimization process described.

RESULTS

A scattering system was optimized and constructed to deliver large uniform irradiations of radiobiology samples at low dose rates. This system was successfully built and tested using film and ionization chambers. The system delivered a uniform radiation field of 50 cm diameter (to a dose of ± 7% of the central axis) while the depth dose profile could be tuned to match the specifications of the particular investigator using modulator wheels and range shifters. A second scattering system for intermediate field size (4 cm < diameter < 10 cm) stereotactic radiosurgery and radiation therapy (SRS and SRT) treatments was also developed and tested using GEANT4. This system improved beam efficiency by over 70% compared with existing scattering systems while maintaining field flatness and depth dose profile. In both cases the proton range uniformity across the radiation field was maintained, further indicating the accuracy of the energy loss formalism in the optimization algorithm.

CONCLUSIONS

The methods described allow for rapid prototyping of scattering foils to meet the demands of both research and clinical beam delivery applications in proton therapy.

Monte Carlo simulation of single-plane magnetically focused narrow proton beams

We present Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet. Such beams are narrowly focused in one longitudinal plane but fan out in the perpendicular plane producing elongated elliptical beam spots (a 'screwdriver' shape). The focused beams were compared to passively collimated beams (the current standard of delivery for small radiosurgery beams). Beam energies considered were relevant to functional radiosurgery and standard radiosurgery clinical applications. Three monoenergetic beams (100, 125, and 150 MeV) and a modulated beam were simulated. Monoenergetic magnetically focused beams demonstrated 28 to 32% lower entrance doses, 31 to 47% larger central peak to entrance depth dose ratios, 26 to 35% smaller integral dose, 25 to 32% smaller estimated therapeutic ratios, 19 to 37% smaller penumbra volumes, and 38 to 65% smaller vertical profile lateral penumbras at Bragg depth, compared to the collimated beams. Focused modulated beams showed 31% larger central peak to entrance dose ratio, and 62 to 65% smaller vertical lateral penumbras over the plateau of the spread out Bragg peak. These advantages can be attributed to the directional acceleration of protons in the transverse plane due to the magnetic field. Such beams can be produced using commercially available assemblies of permanent rare earth magnets that do not require electric power or cryrogenic cooling. Our simulations suggest that these magnets can be inexpensively incorporated into the beam line to deliver reduced dose to normal tissue, and enhanced dose to elongated elliptical targets with major and minor axes on the order of a few centimeters and millimeters, respectively. Such beams may find application in novel proton functional and standard radiosurgery treatments in and around critical structures.

Analysis of a metalloporphyrin antioxidant mimetic (MnTE-2-PyP) as a radiomitigator: prostate tumor and immune status

Due to radiation-induced immune depression and development of pathologies such as cancer, there is increasing urgency to identify radiomitigators that are effective when administered after radiation exposure. The main goal of this study was to determine the radiomitigation capacity of MnTE-2-PyP[Mn(III) tetrakis (N-ethylpyridinium-2-yl) porphyrin], a superoxide dismutase (SOD) mimetic, and evaluate leukocyte parameters in spleen and blood. C57BL/6 mice were total-body exposed to 2 Gy γ-rays (Co-60), i.e., well below a lethal dose, followed by subcutaneous implantation of 5 × 10(5) RM-9 prostate tumor cells and initiation of MnTE-2-PyP treatment (day 0); interval between each procedure was 1-2 h. The drug was administered daily (12 times). Tumor progression was monitored and immunological analyses were performed on a subset per group on day 12. Animals treated with MnTE-2-PyP alone had significantly slower tumor growth compared to mice that did not receive the drug (P < 0.05), while radiation alone had no effect. Treatment of tumor-bearing mice with MnTE-2-PyP alone significantly increased spleen mass relative to body mass; the numbers of splenic white blood cells (WBC) and lymphocytes (B and T), as well as circulating WBC, granulocytes, and platelets, were high compared to one of more of the other groups (P < 0.05). The results show that MnTE-2-PyP slowed RM-9 tumor progression and up-regulated immune parameters, but mitigation of the effects of 2 Gy total-body irradiation were minimal.

Radioprotective effect of a metalloporphyrin compound in rat eye model

PURPOSE

The purpose of this study was to evaluate the efficacy of the antioxidant Mn (III) tetrakis (N-ethylpyridinium-2-yl) porphyrin (MnTE-2-PyP) in protecting ocular tissue and retinal microvasculature from radiation damage.

MATERIALS AND METHODS

75 rats were treated with Mn TE-2-PyP at 2.5 micro g/injection into one eye an hour before proton irradiation. The radiation was delivered in a single fraction to total doses of 8 Gray (Gy) or 28 Gy; Rats were sacrificed 3 days and 3, 6, 9, and 12 months thereafter for histology and quantification of photoreceptor cell populations and retinal capillary changes.

RESULTS

By 6 months following radiation, there was significant loss of retinal outer and inner nuclear layers in eyes receiving radiation only (8 and 28 Gy) (p < 0.05) compared to their controls and to the eyes of rats treated with radiation plus metalloporphyrin. Retinal microvessel length density decreased significantly 6 months following 28 Gy (p < 0.05) compared to their controls and to MnTE-2-PyP treated rats. By 12 months following irradiation, irradiated eyes showed extensive damage to the photoreceptor layer, whereas the eyes of animals receiving radiation plus MnTE-2-PyP showed almost no morphological damage. MnTE-2-PyP treatment also suppressed radiation-induced apoptosis in our study.

CONCLUSIONS

These results demonstrated that MnTE-2-PyP protected both photoreceptors and retinal capillaries from radiation damage, suggesting that this metalloporphyrin antioxidant is effective in regulating the damage induced by proton radiation.

Research activities at the Loma Linda University and Proton Treatment Facility--an overview

The Loma Linda University (LLU) Radiobiology Program coordinates basic research and proton beam service activities for the university and extramural communities. The current focus of the program is on the biological and physical properties of protons and the operation of radiobiology facilities for NASA-sponsored projects. The current accelerator, supporting facilities and operations are described along with a brief review of extramural research projects supported by the program. These include space craft electronic parts and shielding testing as well as tumorigenesis and animal behavior experiments. An overview of research projects currently underway at LLU is also described. These include: 1) acute responses of the C57Bl/6 mouse immune system, 2) modulation of gene expression in the nematode C. elegans and rat thyroid cells, 3) quantitation of dose tolerance in rat CNS microvasculature, 4) behavioral screening of whole body proton and iron ion-irradiated C57Bl/6 mice, and 5) investigation of the role of cell integration into epithelial structures on responses to radiation.

Effects of proton and combined proton/photon beam radiation on pulmonary function in patients with resectable but medically inoperable non-small cell lung cancer

STUDY OBJECTIVES

We evaluated the effects on pulmonary function of irradiating lung cancer with protons alone or protons combined with photons.

DESIGN

Prospective phase I/II study.

SETTING

University medical center.

PATIENTS AND INTERVENTIONS

Ten patients with stage I-II non-small cell lung cancer (NSCLC) and FEV(1) < or = 1.0 L were irradiated with protons to areas of gross disease only, using 51 cobalt gray equivalents (CGE) in 10 fractions (protocol 1). Fifteen patients with stage I-IIIA NSCLC and FEV(1) > 1.0 L received 45-Gy photon irradiation to the primary lung tumor and the mediastinum, plus a 28.8-CGE proton boost to the gross tumor volume (protocol 2).

MEASUREMENTS

Pulmonary function was evaluated prior to treatment and 1 month, 3 months, and 6 to 12 months following irradiation.

RESULTS

In patients receiving protocol 1, no significant changes in pulmonary function occurred. In patients receiving protocol 2, at 6 to 12 months, the diffusion capacity of the lung for carbon monoxide had declined from 61% of predicted to 45% of predicted (p < 0.05), total lung capacity had declined from 114% of predicted to 95% of predicted (p < 0.05), and residual volume had declined from 160% of predicted to 132% of predicted (p < 0.05). Airway resistance increased from 3.8 to 5.2 cm H(2)O/L/s (p < 0.05). No statistically significant changes occurred in vital capacity, FEV(1), or PaO(2).

CONCLUSIONS

Our observations indicate that it is feasible to apply higher-than-conventional doses of radiation at a higher-than-conventional dose per fraction without excess pulmonary toxicity when conformal radiation techniques with protons are used.

Carbon dioxide management and the cerebral response to hemodilution during hypothermic cardiopulmonary bypass in dogs

BACKGROUND

Increases in blood flow support oxygen (O2) delivery with hemodilution. However, with alpha-stat management, the cerebral response to hemodilution is blunted. We tested the hypothesis that carbon dioxide (CO2) management is a primary determinant of the cerebral blood flow (CBF) response to hemodilution during hypothermic bypass.

METHODS

Following Animal Care Committee approval, 15 dogs underwent bypass at 18 degrees C (pH-stat, n = 7 or alpha-stat, n = 8). Measurements were obtained after progressive hemodilution, and cerebral blood flow was determined by sagittal sinus outflow. Arterial pressure was maintained at 60 to 70 mm Hg. The CBF response to hemodilution and cerebral metabolic rate were compared in the two groups of animals.

RESULTS

In both groups, hemodilution increased CBF. At every hematocrit, CBF and O2 delivery in the pH-stat group exceeded that of alpha-stat group, although O2 demand did not differ between groups. While absolute CBF in the pH-stat group was greater at every hematocrit, the relative change in CBF from control and the slope of the CBF-Hct relationship did not differ between groups.

CONCLUSIONS

pH-stat management is associated with a greater absolute CBF and a greater ratio of cerebral O2 supply to demand for any degree of hemodilution. However, over the range of hematocrits common in practice, CO2 management per se does not determine the cerebral response to hemodilution.

Distribution and hierarchy of regional blood flow during hypothermic cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass (CPB) may decrease oxygen delivery relative to the nonbypass state. We predicted that a hierarchy of regional blood flow could be characterized under hypothermic (27 degrees C) CPB.

METHODS

Ten pigs underwent bypass at 27 degrees C. Fluorescent microspheres were administered before and during CPB at four randomized flows: 1.9, 1.6, 1.3, and 1.0 L x min(-1) x m(-2). At completion, tissue samples were obtained from brain, renal cortex and medulla, pancreas, small bowel, and limb muscle for regional blood flow determination.

RESULTS

Cerebral blood flow remained unchanged between CPB flows of 1.9 and 1.3 L x min(-1) x m(-2). Renal perfusion was stable between flows of 1.9 and 1.6 L x min(-1) x m(-2), whereas perfusion of small bowel decreased linearly with pump flow. Pancreatic perfusion was unchanged over the range of flows studied; muscle blood flow was profoundly reduced at the highest CPB flow and further decreased if pump flow was reduced below 1.6 L x min(-1) x m(-2).

CONCLUSIONS

This study characterizes the organ-specific hierarchy of blood flow and oxygen distribution during hypothermic CPB. These dynamics are relevant to clinical decisions for perfusion management.

Kinetically selective binding of single stranded RNA over DNA by a pyrrolidine-amide oligonucleotide mimic (POM)

Replacing the sugar-phosphodiester backbone of nucleic acids with a pyrrolidine-amide backbone results in an oligonucleotide mimic POM 1 which binds with high affinity and specificity to complementary DNA and RNA. Unlike other modified oligonucleotides, POM binds much more rapidly to single stranded RNA than DNA.

Hierarchy of regional oxygen delivery during cardiopulmonary bypass

BACKGROUND

Relative to the nonbypass state, cardiopulmonary bypass may decrease whole-body oxygen (O2) delivery. We predicted that during cardiopulmonary bypass, a hierarchy of regional blood flow and O2 delivery could be characterized.

METHODS

In 8 46.5 +/- 1.2-kg pigs, fluorescent microspheres were used to determine blood flow and O2 delivery to five organ beds before and during 37 degrees C cardiopulmonary bypass at four randomized bypass flows (1.4, 1.7, 2.0, and 2.3 L/min/m2). At completion, 18 tissue samples were obtained from the cerebral cortex (n = 4), renal cortex (n = 2), renal medulla (n = 2), pancreas (n = 3), small bowel (n = 3), and limb muscle (n = 4) for regional blood flow determination.

RESULTS

At conventional cardiopulmonary bypass flow (2.3 L/min/m2), whole-body O2 delivery was reduced by 44 +/- 6% relative to the pre-cardiopulmonary bypass state (p < 0.05). Over a range of cardiopulmonary bypass flows (2.3 to 1.7 L/min/m2), brain and kidney maintained their perfusion. Blood flow and O2 delivery to both regions were reduced when the cardiopulmonary bypass flow was reduced to 1.4 L/min/m2. However, perfusion and O2 delivery to other visceral organs (pancreas, small bowel) and skeletal muscle showed pump flow dependency over the range of flows tested.

CONCLUSIONS

This study characterizes the organ-specific hierarchy of blood flow and O2 distribution during cardiopulmonary bypass. These dynamics are relevant to clinical decisions for perfusion management.

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).

Combination of pGL1-TNF-alpha gene and radiation (proton and gamma-ray) therapy against brain tumor

The major goal of this study was to determine if treatment with the newly constructed plasmid vector for tumor necrosis factor-alpha (pGL1-TNF-alpha) could enhance the radiation-induced growth reduction of C6 rat glioma. In addition, two different forms of ionizing radiation (gamma-rays and protons) were utilized. Body and spleen mass, leukocyte blastogenesis, and flow cytometry analysis of cell populations in blood and spleen were performed to detect toxicity, if any, and to identify mechanisms that may correlate with the anti-tumor action of combination therapy. C6 tumor cells were implanted subcutaneously into athymic mice and allowed to become established before treatment initiation. pGL1-TNF-alpha was injected into the implanted tumors, which were then irradiated 16-18 hr later; each modality was administered three times over 8-9 days. The addition of pGL1-TNF-alpha significantly enhanced the anti-tumor effect of radiation (p < 0.05). The effect was more than additive, since pGL1-TNF-alpha alone did not slow tumor progression and radiation alone had only a modest effect. Administration of pGL1-TNF-alpha together with proton radiation resulted in tumor volumes that were 23% smaller than those following pGL1-TNF-alpha + gamma-ray treatment; a similar differential in tumor size was observed in the groups receiving only radiation. Body weights and blood and spleen cell analyses did not reveal treatment-related toxicity. High basal proliferation of blood leukocytes and increased B cell levels in the spleen were associated with pGL1-TNF-alpha + 60Co (gamma-radiation) or proton treatment. Overall, the results suggest that the pGL1-TNF-alpha/radiation combination is effective and safe under the conditions employed. This is the first study to combine gene and proton radiation therapy and to show, under controlled experimental conditions, that proton radiation may have a greater effect against malignant tumors compared to the same physical dose of gamma-radiation.

Dose response of rat retinal microvessels to proton dose schedules used clinically: a pilot study

PURPOSE

This preclinical rat pilot study quantifies retinal microvessel, endothelial, and pericyte population changes produced by proton irradiation

METHODS AND MATERIALS

The left eyes of rats were irradiated with single doses of 8, 14, 20, and 28 Gy protons; right eyes, with two fractions. Animals were euthanized, and eyes were removed; elastase digests were prepared, and cell populations were counted in sample fields. Results were compared with unirradiated controls.

RESULTS

Progressive time- and dose-dependent endothelial cell loss occurred following all schedules. Cell loss was significantly different from control values (p < 0.001) following 28 Gy and following 20 Gy (p < 0.05) in a single dose. Endothelial cell loss was the same for single- and split-dose schedules. Progressive endothelial cell loss produced vessel collapse and acellular vessel strands. Endothelial cells were in the G(0) phase of the mitotic cycle. 28 Gy produced photoreceptor cell loss.

CONCLUSION

The retinal digest is an elegant bioassay to quantify the microvessel population response. Single- and split-dose schedules appear to yield similar outcomes, in terms of endothelial cell density.

Conformal proton radiation therapy of the posterior fossa: a study comparing protons with three-dimensional planned photons in limiting dose to auditory structures

PURPOSE

Conventional radiation therapy for pediatric posterior fossa tumors can cause sequelae such as hearing loss and impairments in language and learning. Modern three-dimensional (3D) treatment techniques have improved dose conformity to the posterior fossa. This report compares the normal tissue dose-sparing capabilities of proton radiation therapy (PRT) with 3D conformal photon plans.

METHODS AND MATERIALS

Nine children underwent previous PRT for primary CNS malignancies. Using original planning CT scans, the posterior fossa, inner and middle ear, and temporal lobes were delineated. Three-dimensional treatment plans were generated for protons and photons. Normal tissue exposures were calculated by averaging mean doses received and by analysis of dose-volume histogram.

RESULTS

The 95% isodose encompassed the posterior fossa in all plans. Normal structures received markedly less radiation from PRT plans than from 3D photon plans. The cochlea received an average mean of 25 +/- 4% of the prescribed dose from PRT, and 75 +/- 6% from photons. Forty percent of temporal lobe volume was completely excluded using protons; with photons 90% of the temporal lobe received 31% of the dose.

CONCLUSION

PRT resulted in increased dose sparing of normal structures analyzed. Posterior fossa conformity of 3D photons came at the expense of increasing amounts of normal tissue receiving low to moderate doses.

Determination of the air w-value in proton beams using ionization chambers with gas flow capability

The purpose of this work was to determine the w-value of air for protons using the paired gas method. Several plastic- and magnesium-walled chambers were used with air, synthetic air, nitrogen, and argon flowing gases. Using argon as a reference gas, the w-value of air was measured and ranged from 32.7 to 34.5 J/C for protons with energies encountered in radiotherapy. Using nitrogen as a reference gas, the w-value of air ranged from 35.2 to 35.4 J/C over the same range of proton energies. The w-value was found, at a given energy, to be independent of the ion chamber used. The uncertainty in these measurements was estimated at 5.2% at the 2sigma level. This uncertainty was dominated by the 4.4% uncertainty in the w-value of the reference gas.

Analysis of head motion prior to and during proton beam therapy

PURPOSE

We report on the use of a noninvasive patient motion monitoring system to evaluate the amount of head motion prior to and during proton radiation therapy sessions.

METHODS AND MATERIALS

Two optical displacement sensors, placed close to the patient's head, were used for online monitoring of the head position, with submillimeter accuracy. Motion data, including the difference between start and end position (Dx) and the maximum displacement during the recorded session (Dx-max), were acquired for pretreatment sessions to analyze alignment radiographs, and for treatment sessions. We have recorded 102 pretreatment and 99 treatment sessions in 16 patients immobilized with a thermoplastic mask, and 44 pretreatment and 56 treatment sessions in 13 patients immobilized with vacuum-assisted dental fixation. To avoid incorrect data analysis due to replicate observations, only 1 pretreatment and 1 treatment session per patient were selected at random for statistical comparison of mean or median motion parameters in different subgroups.

RESULTS

Both techniques showed similar immobilization efficiencies. The median Dx and Dx-max values were 0. 18 mm and 0.46 mm, respectively, for 16 treatment sessions with mask immobilization, and 0.22 mm and 0.50 mm, respectively, for 13 treatment sessions with dental immobilization. Motion parameters for pretreatment and treatment sessions were not statistically different.

CONCLUSION

Online verification of patient's head motion is feasible and provides valuable data for confirmation of proper treatment delivery in individual patients, as well as for the evaluation of different immobilization methods.

Acute effects of whole-body proton irradiation on the immune system of the mouse

The acute effects of proton whole-body irradiation on the distribution and function of leukocyte populations in the spleen and blood were examined and compared to the effects of photons derived from a (60)Co gamma-ray source. Adult female C57BL/6 mice were exposed to a single dose (3 Gy at 0.4 Gy/min) of protons at spread-out Bragg peak (SOBP), protons at the distal entry (E) region, or gamma rays and killed humanely at six different times thereafter. Specific differences were noted in the results, thereby suggesting that the kinetics of the response may be variable. However, the lack of significant differences in most assays at most times suggests that the RBE for both entry and peak regions of the Bragg curve was essentially 1.0 under the conditions of this study. The greatest immunodepression was observed at 4 days postexposure. Flow cytometry and mitogenic stimulation analyses of the spleen and peripheral blood demonstrated that lymphocyte populations differ in radiosensitivity, with B (CD19(+)) cells being most sensitive, T (CD3(+)) cells being moderately sensitive, and natural killer (NK1.1(+)) cells being most resistant. B lymphocytes showed the most rapid recovery. Comparison of the T-lymphocyte subsets showed that CD4(+) T helper/inducer cells were more radiosensitive than the CD8(+) T cytotoxic/suppressor cells. These findings should have an impact on future studies designed to maximize protection of normal tissue during and after proton-radiation exposure.

Value and perspectives of proton radiation therapy for limited stage prostate cancer

BACKGROUND

This review article will focus on clinical results and limitations of proton beam irradiation. Possible technological, biological and medical perspectives will be addressed.

PATIENTS AND METHODS

A total of 911 patients with limited stage prostate cancer were treated with proton beam irradiation at Loma Linda University between 1991 and 1996. Endpoints of this evaluation were biochemically no evidence of disease survival (bNED) as well as acute and late treatment-related toxicity.

RESULTS

The bNED survival rate was 82% at 5 years. Among 870 patients evaluable for late toxicity the following late effects were observed: Grade 3/4: 0%, Grade 2 rectal: 3.5% and bladder: 5.4%.

CONCLUSIONS

Despite relatively short follow-up times it seems justified to conclude that proton beam irradiation of prostate cancer can improve bNED rates by 10% and decrease Grade 2 late effects by more than 10%. There were no Grade 3 and 4 late effects.

Proton radiation therapy (PRT) for pediatric optic pathway gliomas: comparison with 3D planned conventional photons and a standard photon technique

PURPOSE

Following adequate therapy, excellent long-term survival rates can be achieved for patients with optic pathway gliomas. Therefore, avoidance of treatment-related functional long-term sequelae is of utmost importance. Optimized sparing of normal tissue is of primary concern in the development of new treatment modalities. The present study compares proton radiation therapy (PRT) with a three-dimensional (3D)-planned multiport photon and a lateral beam photon technique for localized and extensive optic pathway tumors.

METHODS AND MATERIALS

Between February 1992 and November 1997, seven children with optic pathway gliomas underwent PRT. For this study, we computed proton, 3D photon, and lateral photon plans based on the same CT data sets, and using the same treatment planning software for all plans. Radiation exposure for normal tissue and discrete organs at risk was quantified based on dose-volume histograms.

RESULTS

Gross tumor volume (GTV) ranged from 3.9 cm3 to 127.2 cm3. Conformity index (relation of encompassing isodose to GTV volume) was 2.3 for protons, 2.9 for 3D photons, and 7.3 for lateral photons. The relative increase of normal tissue (NT) encompassed at several isodose levels in relation to NT encompassed by the 95% proton isodose volume was computed. Relative NT volume of proton plan isodoses at the 95%, 90%, 80%, 50%, and 25% isodose level increased from 1 to 1.6, 2.8, 6.4, to a maximum of 13.3. Relative volumes for 3D photons were 1.6, 2.4, 3.8, 11.5, and 34.8. Lateral plan relative values were 6, 8.3, 11.5, 19.2, and 26.8. Analysis for small (<20 cm3) and larger (> 80 cm3) tumors showed that protons encompassed the smallest volumes of NT at all isodose levels. Comparable conformity and high-dose gradient were achieved for proton and 3D photon plans in small tumors. However, with increasing tumor volume and complexity, differences became larger. At the 50% isodose level, 3D photons were superior to lateral photons for small tumors; this advantage was equalized for larger tumors. At the lowest isodose level, 3D photons encompassed the highest amount of NT. Analysis of organs at risk showed that PRT reduced doses to the contralateral optic nerve by 47% and 77% compared to 3D photons and lateral photons, respectively. Reductions were also seen for the chiasm (11% and 16%) and pituitary gland (13% and 16%), with differences at clinically relevant tolerance levels. Furthermore, reduced dose exposure of both temporal lobes (sparing 39% and 54%) and frontal lobes was achieved with PRT.

CONCLUSION

PRT offered a high degree of conformity to target volumes and steep dose gradients, thus leading to substantial normal tissue sparing in high- and low-dose areas. It is expected that this will result in decreased long-term toxicity in the maturing child. Advantages of proton versus 3D photon plans became increasingly apparent with increasing target size and tumor complexity. Even in small tumors, conformity of 3D photon irradiation came at the expense of a larger amount of NT receiving moderate to low radiation doses. Lateral photons resulted in inferior dose distribution with high radiation exposure of clinically relevant normal tissues.

Dosimetry techniques for narrow proton beam radiosurgery

Characterization of narrow beams used in proton stereotactic radiosurgery (PSRS) requires special efforts, since the use of finite size detectors can lead to distortion of the measured dose distributions. Central axis depth doses, lateral profiles and field size dependence factors are the most important beam characteristics to be determined prior to dosimetry calculations and beam modelling for PSRS. In this paper we report recommendations for practical dosimetry techniques which were developed from a comparison of beam characteristics determined with a variety of radiation detectors for 126 and 155 MeV narrow proton beams shaped with 2-30 mm circular brass collimators. These detectors included small-volume ionization chambers, a diamond detector, an Hi-p Si diode, TLD cubes, radiographic and radiochromic films. We found that both types of film are suitable for profile measurements in narrow beams. Good agreement between depth dose distributions measured with ionization chambers, diamond and diode detectors was demonstrated in beams with diameters of 20-30 mm. The diode detector can be used in smaller beams, down to 5 mm diameter. For beams with diameters less than 5 mm, reliable depth dose data may be obtained only with radiochromic film. The tested ionization chambers are appropriate for calibration of beams with diameters of 20-30 mm. TLD cubes and diamond detectors are useful to determine relative dose in beams with diameters of 10-20 mm. Field size factors for smaller beams should be obtained with diode and radiochromic film. We conclude that dosimetry characterization of proton beams down to several millimetres in diameter can be performed using the described procedures.

Proton-beam radiotherapy for early-stage lung cancer

STUDY OBJECTIVE

A prospective study was undertaken to assess the efficacy and toxicity of conformal proton-beam radiotherapy for early-stage, medically inoperable non-small cell lung cancer.

DESIGN

Eligible patients had clinical stage I to IIIa non-small cell lung cancer and were not candidates for surgical resection for medical reasons or because of patient refusal. Patients with adequate cardiopulmonary function received 45 Gy to the mediastinum and gross tumor volume with photons with a concurrent proton boost to the gross tumor volume of an additional 28.8 cobalt gray equivalents (CGE). Total tumor dose was 73.8 CGE given over 5 weeks. Patients with poor cardiopulmonary function received proton-beam radiotherapy to the gross tumor volume only, with 51 CGE given in 10 fractions over a 2-week period.

RESULTS

Thirty-seven patients were treated in the study from July 1994 to March 1998. Clinical staging of patients was as follows: stage I, 27 patients; stage II, 2 patients; and stage IIIa, 8 patients. Eighteen patients received a combination of protons and x rays, while 19 patients received proton-beam radiation only. Follow-up of evaluable patients ranged from 3 to 45 months, with a median of 14 months. Two patients in the proton and photon arm developed pneumonitis that resolved with oral steroids; otherwise, no significant toxicities were encountered. The actuarial disease-free survival at 2 years for the entire group was 63%; for stage I patients, disease-free survival at 2 years was 86%. Local disease control was 87%.

CONCLUSION

Preliminary results from this study indicate that proton-beam radiotherapy can be used safely in this group of patients. Disease-free survival and local control appear to be good and compare favorably with published reports utilizing conventional photon irradiation.

Effects of proton and gamma radiation on lymphocyte populations and acute response to antigen

BACKGROUND

The clinical use of proton radiation in the management of cancer, as well as benign disorders, is rapidly increasing. The major goal of this study was to compare the effects of proton and gamma (60Co) radiation on cell-mediated and humoral immunological parameters.

MATERIALS AND METHODS

C57BL/6 mice were exposed to a single dose of 3 Gray (Gy) protons or gamma-rays and intraperitoneally injected 1 day later with sheep red blood cells (sRBC). On 4, 10, 15, and 29 days after exposure, subsets from each group were euthanised; nonirradiated controls (with and without sRBC injection) were included. Body and relative spleen weights, leukocyte counts, spontaneous blastogenesis, lymphocyte populations, and anti-sRBC titers were evaluated.

RESULTS

The data showed significant depression (p < 0.05) in nearly all assays on days 4 and 10 after irradiation. B lymphocytes (CD19+) were the most radiosensitive, although reconstitution back to normal levels was observed by day 15. T cell (CD3+) and T helper cell (CD4+) recovery was evident by day 29, whereas the T cytotoxic cell (CD8+) count remained significantly below normal. Natural killer cells (NK1.1+) were relatively radioresistant. Anti-sRBC antibody production was slow and low titers were obtained after irradiation. No significant differences were noted between the two types of radiation.

CONCLUSIONS

Taken together, the data show that whole-body irradiation with protons or gamma-rays, at the dose employed, results in marked, but transient, immunosuppression. However, at the time points of testing and with the assays used, little or no differences were found between the two forms of radiation.

Nasopharyngeal carcinoma: repeat treatment with conformal proton therapy--dose-volume histogram analysis

PURPOSE

To analyze control, survival, and complication rates of conformal proton radiation for recurrent nasopharyngeal carcinoma.

MATERIALS AND METHODS

Sixteen patients with nasopharyngeal carcinoma initially treated with 50.0-88.2 Gy photons were re-treated with protons to additional doses of 59.4-70.2 CGE. Local-regional control and survival were correlated with extent of relapse, recurrence versus persistence, and prescribed dose and were subjected to dose-volume histogram analysis. Mean follow-up was 23.7 months (range, 4-47 months).

RESULTS

Twenty-four-month actuarial overall and local-regional progression-free survival rates were both 50%. The 24-month actuarial overall survival rates for patients with "optimal" dose-volume histogram coverage versus "suboptimal" coverage were 83% and 17%, respectively (P = .006). Doses to critical structures were low (0-22.0 Gy); no central nervous system side effects supervened.

CONCLUSION

Adequate tumor coverage, as evaluated by using dose-volume histogram analysis, was found to be the most important variable influencing local-regional control and survival. No central nervous system complications were observed; increases in the dose to adjacent critical structures are being evaluated.

Proton radiation therapy for chordomas and chondrosarcomas of the skull base

OBJECT

Local tumor control, patient survival, and treatment failure outcomes were analyzed to assess treatment efficacy in 58 patients in whom fractionated proton radiation therapy (RT) was administered for skull base chordomas and chondrosarcomas.

METHODS

Between March 1992 and January 1998, a total of 58 patients who could be evaluated were treated for skull base tumors, 33 for chordoma and 25 for chondrosarcoma. Following various surgical procedures, residual tumor was detected in 91% of patients; 59% demonstrated brainstem involvement. Target dosages ranged from 64.8 and 79.2 (mean 70.7) Co Gy equivalent. The range of follow up was 7 to 75 months (mean 33 months). In 10 patients (17%) the treatment failed locally, resulting in local control rates of 92% (23 of 25 patients) for chondrosarcomas and 76% (25 of 33 patients) for chordomas. Tumor volume and brainstem involvement influenced control rates. All tumors with volumes of 25 ml or less remained locally controlled, compared with 56% of tumors larger than 25 ml (p = 0.02); 94% of patients without brainstem involvement did not experience recurrence; in patients with brainstem involvement (and dose reduction because of brainstem tolerance constraints) the authors achieved a tumor control rate of 53% (p = 0.04). Three patients died of their disease, and one died of intercurrent disease. Actuarial 5-year survival rates were 100% for patients with chondrosarcoma and 79% for patients with chordoma. Grade 3 and 4 late toxicities were observed in four patients (7%) and were symptomatic in three (5%).

CONCLUSIONS

High-dose proton RT offers excellent chances of lasting tumor control and survival, with acceptable risks. In this series all small- and medium-sized tumors with no demonstrable brainstem involvement have been controlled; all such patients are alive. Surgical debulking enhanced delivery of full tumoricidal doses, but even patients with large tumors and disease abutting crucial normal structures benefited.

An automated technique for the simultaneous determination of cations in nanoliter volumes

BACKGROUND

The study of ion transport along the renal tubule in vivo or in vitro requires a technique capable of analyzing ion concentrations in sample volumes of only a few nanoliters. This article describes a method for the analysis of cations at physiological concentrations in samples of tubular fluid taken from single renal tubules in vivo. Method. A background electrolyte composed of 2-[N-Morpholino] ethane-sulfonic acid (MES) (50 mmol/liter) and L-histidine (50 mmol/liter; pH congruent with 6.2), with the additives 18-crown-6 (1 mmol/liter) and methanol (30%) was used for the cation separation combined with conductivity detection.

RESULTS

Capillary zone electrophoresis was used to separate NH4, K, Na, Ca, Li, Mg, and Ba in six minutes. Simultaneous quantitative analysis was performed for sodium and potassium, providing detection limits of 0.2 pmol for sodium and 30 fmol for potassium. The calibration plots were linear over three orders of magnitude, including the range of interest to clinical analysis. Data on the reproducibility and repeatability of peak areas and of the repeatability of migration times are reported.

CONCLUSION

The results for sodium and potassium are in close agreement with those obtained by atomic absorption spectrometry, indicating that this is a suitable technique for the routine measurement of these cations in tubule fluid samples.

Proton dosimetry intercomparison based on the ICRU report 59 protocol

BACKGROUND AND PURPOSE

A new protocol for calibration of proton beams was established by the ICRU in report 59 on proton dosimetry. In this paper we report the results of an international proton dosimetry intercomparison, which was held at Loma Linda University Medical Center. The goals of the intercomparison were, first, to estimate the level of consistency in absorbed dose delivered to patients if proton beams at various clinics were calibrated with the new ICRU protocol, and second, to evaluate the differences in absorbed dose determination due to differences in 60Co-based ionization chamber calibration factors.

MATERIALS AND METHODS

Eleven institutions participated in the intercomparison. Measurements were performed in a polystyrene phantom at a depth of 10.27 cm water equivalent thickness in a 6-cm modulated proton beam with an accelerator energy of 155 MeV and an incident energy of approximately 135 MeV. Most participants used ionization chambers calibrated in terms of exposure or air kerma. Four ionization chambers had 60Co-based calibration in terms of absorbed dose-to-water. Two chambers were calibrated in a 60Co beam at the NIST both in terms of air kerma and absorbed dose-to-water to provide a comparison of ionization chambers with different calibrations.

RESULTS

The intercomparison showed that use of the ICRU report 59 protocol would result in absorbed doses being delivered to patients at their participating institutions to within +/-0.9% (one standard deviation). The maximum difference between doses determined by the participants was found to be 2.9%. Differences between proton doses derived from the measurements with ionization chambers with N(K)-, or N(W) - calibration type depended on chamber type.

CONCLUSIONS

Using ionization chambers with 60Co calibration factors traceable to standard laboratories and the ICRU report 59 protocol, a distribution of stated proton absorbed dose is achieved with a difference less than 3%. The ICRU protocol should be adopted for clinical proton beam calibration. A comparison of proton doses derived from measurements with different chambers indicates that the difference in results cannot be explained only by differences in 60Co calibration factors.

Stereotactic radiosurgery--the role of charged particles

Stereotactic radiosurgery using charged-particle beams has been the subject of biomedical research and clinical development for more than 50 years. Charged particles of proton mass or greater manifest unique physical properties that can be used to place a high dose of radiation preferentially within the boundaries of a deeply located intracranial target volume. Since 1954, nearly 10000 patients have been treated using this technique. Treated disorders include pituitary tumors, vascular malformations, primary and metastatic brain tumors, and subfoveal neovascularization. Charged-particle radiosurgery is particularly advantageous for the conformal treatment of large and/or irregularly shaped lesions, or for the treatment of lesions located in front of or adjacent to sensitive brain structures.

Treatment of macular degeneration with proton beams

Subfoveal neovascular membranes (SNVMs) are a leading cause of severe visual loss in the elderly in the United States. Previously, the only treatment that could halt progression of this disease was laser photocoagulation, which was, however, accompanied by immediate reduction in visual acuity. A single narrow proton beam was used to irradiate 45 patients to either 8 or 14 Cobalt Gray Equivalent. The alignment technique and dosimetry of these treatments are described. The proton beam direction, range, and modulation were planned with the assistance of an eye-specific planning program. A single anterior beam was used, with patients looking nasally toward a blinking fixation light at an angle of 30 degrees. Patients were aligned using a light field projected through a slit collimator. Patients' positions were monitored during treatment with a short-focal-length camera. Depth dose in a flat phantom was measured with a small-diameter parallel plate ionization chamber. Lateral profiles were measured at several depths with silver halide film. Each treatment session lasted 15 min, of which 1 min consisted of beam delivery. The proton beam stopped in the orbital cavity, delivering no primary proton dose to the brain. Dose to the center of the lens of the involved eye was less than 0.5% of the dose delivered to the macula. Treatments of SNVMs with proton beams require only a short visit to the hospital, little immobilization effort, and a minimal amount of treatment room and beam time. Compared to previous treatment trials using x-ray beams, the dose to nonocular tissues is reduced significantly.

Conformal proton therapy for early-stage prostate cancer

OBJECTIVES

To assess the effect of proton radiation on clinical and biochemical outcomes for early prostate cancer.

METHODS

Three hundred nineteen patients with T1-T2b prostate cancer and initial prostate-specific antigen (PSA) levels 15.0 ng/mL or less received conformal radiation doses of 74 to 75 cobalt gray equivalent with protons alone or combined with photons. No patient had pre- or post-treatment hormonal therapy until disease progression was documented. Patients were evaluated for biochemical disease-free survival, PSA nadir, and toxicity; the mean and median follow-up period was 43 months.

RESULTS

Overall 5-year clinical and biochemical disease-free survival rates were 97% and 88%, respectively. Initial PSA level, stage, and post-treatment PSA nadir were independent prognostic variables for biochemical disease-free survival: a PSA nadir 0.5 ng/mL or less was associated with a 5-year biochemical disease-free survival rate of 98%, versus 88% and 42% for nadirs 0.51 to 1.0 and greater than 1.0 ng/mL, respectively. No severe treatment-related morbidity was seen.

CONCLUSIONS

It appears that patients treated with conformal protons have 5-year biochemical disease-free survival rates comparable to those who undergo radical prostatectomy, and display no significant toxicity. A Phase III randomized dose-escalation trial is underway to define the optimum radiation dose for early-stage prostate cancer.

Pulmonary injury from proton and conventional radiotherapy as revealed by CT

OBJECTIVE

Although radiation therapy is used in early-stage inoperable lung cancer, it often results in injury to functional lung tissue. A study was undertaken to determine the frequency and severity of pulmonary injury revealed by CT in patients who had undergone conformal proton (to a limited volume) radiation therapy. We compared these findings with those from a group of patients who had undergone a combination of photon and conformal proton (to a larger volume) radiation therapy.

CONCLUSION

Proton radiation therapy was associated with a lower frequency of pulmonary injury than the combined regimen. Injury correlated well with the volume of normal lung that was irradiated. Conformal proton radiation therapy appears to be able to reduce the incidence and severity of pulmonary injury revealed by CT.

Applications of capillary electrophoresis in nephrology

Capillary electrophoresis has recently emerged as a powerful technique for separating components in biological samples. A family of separation methods capable of handling a diverse range of samples has been developed, the sample volumes required are very small and a wide range of specialised detectors can be employed. This review examines some methods with particular application to the analysis of urine and tubular fluid samples and references relevant applications.

Conformal proton therapy for prostate carcinoma

BACKGROUND

The role and optimum dose of radiation to eradicate prostate cancer continues to be evaluated. Protons offer an opportunity to increase the radiation dose to the prostate while minimizing treatment toxicity.

METHODS

Six hundred forty-three patients with localized prostate cancer were treated with protons, with or without photons. Treatments were planned with a 3D planning system; patients received 74-75 CGE (Cobalt Gray Equivalent) at 1.8-2.0 CGE per fraction. Patients were evaluated for response to therapy and treatment-related toxicity.

RESULTS

The overall clinical disease-free survival rate was 89% at 5 years. When post-treatment prostate-specific antigen (PSA) was used as an endpoint for disease control, the 4.5-year disease-free survival rate was 100% for patients with an initial PSA of < 4.0 ng/ml, and 89%, 72%, and 53% for patients with initial PSA levels of 4.1-10.0, 10.1-20.0, and > 20.0, respectively. Patients in whom the post-treatment PSA nadir was below 0.5 ng/ml did significantly better than those whose nadir values were between 0.51-1.0 or > 1.0 ng/ml: the corresponding 5-year disease-free survival rates were 91%, 79%, and 40%, respectively. Minimal radiation proctitis was seen in 21% of patients; toxicity of greater severity was seen in less than 1%.

CONCLUSION

Proton therapy to 74-75 CGE produced minimal treatment-related toxicity and excellent PSA normalization and disease-free survival in patients with low initial PSA levels. A prospective randomized dose-escalation trial is now underway to help define the optimum dose of radiation for patients with early stage prostate cancer.

Particle beam radiation therapy in prostate cancer: is there an advantage?

Hadron therapy uses heavy particles to deliver therapeutic ionizing energy. Each particle's inherent attributes determine the pattern of energy deposited by its beam, expressed in macro (conformability to a three-dimensional target volume) and micro (radiobiologic properties) distributions. Mass and charge regulate the inherent properties; beam energy provides a controllable, variable characteristic. Generally, heavy charged particles provide superior macrodosimetric properties; heavy particles (charged or not) have microdosimetric characteristics that produce high linear energy transfer (LET). Neutron macrodosimetry is similar to that of photons. Protons and helium ions possess superior macrodosimetric properties, plus microdosimetric characteristics resulting in low LET, yielding beam characteristics that approach the ideal for clinical radiotherapy. Hadron therapy for prostate cancer has been limited by the availability of appropriate treatment facilities. Nonetheless, encouraging results have been obtained. Neutron therapy demonstrated improved overall survival in a multi-institutional randomized trial, and improved local disease control in a subsequent trial. Proton radiation forms the boost component of several conformal dose-escalation studies. A Loma Linda University study demonstrated low treatment-related morbidity despite a prostate dose of 75 CGE; late-morbidity data were superior to published reports from multi-field, conformal photon therapy. A Phase III dose-escalation study of protons for early prostate cancer is proceeding.

What is the role of radiation in the treatment of subfoveal membranes: review of radiobiologic, pathologic, and other considerations to initiate a multimodality discussion

BACKGROUND

Single-dose-fraction conformal proton beam and multiple-fraction X ray dose schedules have been used to treat subfoveal neovascular membranes. All schedules successfully controlled membrane progression, stabilized vision in most patients, and increased visual acuity in some. Conformal protons also decreased the radiation dose to healthy tissues outside the designated volume (16 mm in diameter). It appears that radiation therapy could be useful and cost-effective, but neither the optimal time-dose schedule single or multiple dose fractions nor the type of radiation proton conformal beam or x-ray therapy are defined.

METHODS

By means of an extensive literature survey, we reviewed the rationale for using radiation to treat subfoveal neovascularization, examined a paradigm of radiation interaction with tissue, reviewed the histopathology of neovascular membranes, and documented the role of growth factors in the pathophysiology of the disease. Accepting that the eye is an extracranial brain extension, and that its microvasculature has properties similar to brain microvessels, we reviewed the radiobiologic response of brain microvessels. We also revisited the controversy concerning the efficacy of single-dose-fraction vs. multifraction schedules.

RESULTS

This paper outlines parameters within which radiation therapy's role might be defined, and proposes a clinical radiation-biology scoring program to evaluate radiation effects, based on the SOMA concept.

CONCLUSION

A prospective, controlled clinical trial is feasible and is indicated to determine radiation therapy's role in managing the proliferative component of age-related macular degeneration.

Pilot evaluation of cytokine levels in patients undergoing radiotherapy for brain tumor

This study was undertaken to evaluate plasma levels of interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha) transforming growth factor-beta (TGF-beta), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), and vascular endothelial growth factor (VEGF) in 3 pediatric and 14 adult patients receiving radiotherapy for brain tumor. Patients with glioblastoma, astrocytoma, chondrosarcoma, meningioma, schwannoma, and lung adenocarcinoma that had metastasized to the brain were included. Peripheral blood samples were collected before and after treatment with conventional photon and/or proton radiation; samples from healthy volunteers served as controls. Enzyme-linked immunosorbent assays were performed to quantitate the cytokines. Before irradiation, most patients had greater amounts of one or more of the cytokines compared with the mean obtained for control plasma. This was especially striking in patients with chondrosarcoma; the mean values for TGF-beta 1, TNF-alpha, bFGF, and EGF were 1458, 1289, 332, and 92% higher than in healthy subjects, respectively. After irradiation, bFGF and total TGF-beta 1 decreased in the majority of tested subjects. In contrast, IL-1 beta was detected only in pediatric patients (all with astrocytoma) and its levels after radiation were 33 to 67% higher than at pretreatment. EGF was found in four patients; post-treatment values were 125 to 608% higher in three of the individuals. These data show that cytokines are present at elevated concentrations in the blood circulation of patients with certain types of brain tumors and that changes in their levels can be detected after radiotherapy. Further investigations are warranted to determine whether these findings contribute to morbidity or therapeutic outcome.

Tumor necrosis factor-alpha enhances antitumor effects of radiation against glioma xenografts

Long-term control of high-grade brain tumors is rarely achieved with current therapeutic regimens. The aim of this study was to determine if low doses of tumor necrosis factor-alpha (TNF-alpha) could augment the effects of radiation in a glioma xenograft model and to evaluate hematological and other parameters that might indicate treatment-related toxicity. Nude mice were injected subcutaneously with C6 rat glioma cells and randomized into groups. Two different time-dose protocols were employed using intravenous human recombinant TNF-alpha and radiation beginning within 24 h after tumor cell implantation. The administration of radiation as a single agent slowed tumor progression, whereas TNF-alpha alone had no effect. However, TNF-alpha, especially when given twice per week before radiation for a total of four doses each, significantly increased the efficacy of the radiation. Low leukocyte counts were associated with combination treatment, whereas transforming growth factor-beta 1 levels were depressed in all treated groups. TNF-alpha did not modulate radiation-induced inhibition of C6 cell proliferation in vitro. The data show that TNF-alpha at relatively nontoxic doses can significantly enhance the antitumor effects of radiation against a rapidly growing glioma. This effect was more than additive, because TNF-alpha alone did not slow tumor progression.

Proton therapy for pediatric cranial tumors: preliminary report on treatment and disease-related morbidities

PURPOSE

Accelerated protons were used in an attempt to limit treatment-related morbidity in children with tumors in or near the developing brain, by reducing the integral dose to adjacent normal tissues.

METHODS AND MATERIALS

Children treated with protons at Loma Linda University Medical Center between August 1991 and December 1994 were analyzed retrospectively. Twenty-eight children, aged 1 to 18 years, were identified as at risk for brain injury from treatment. Medical records, physical examinations, and correspondence with patients, their parents, and referring physicians were analyzed. The investigators tabulated post-treatment changes in pre-treatment signs and symptoms and made judgments as to whether improvement, no change, or worsening related to disease or treatment had supervened. Magnetic resonance images were correlated with clinical findings and radiographic impressions were tabulated.

RESULTS

Follow-up ranged from 7 to 49 months (median 25 months). Four instances of treatment-related morbidity were identified. Forty-one instances of site-specific, disease-related morbidity were identified: 15 improved or resolved and 26 remained unchanged after treatment. Four patients had radiographic evidence of local failure. Three of these patients, including two with high-grade glioma, have died.

CONCLUSION

Early treatment-related morbidity associated with proton therapy is low. Tumor progression remains a problem when treating certain histologies such as high-grade glioma. Escalating the dose delivered to target volumes may benefit children with tumors associated with poor rates of local control. Long-term follow-up, including neurocognitive testing, is in progress to assess integral-dose effects on cognitive, behavioral and developmental outcomes in children with cranial tumors.

Enhancement of prostate cancer xenograft growth with whole-body radiation and vascular endothelial growth factor

Prostate cancer research has been limited by the slow growth of human prostate tumors In athymic rodent models. This study sought to determine if low-dose radiation and vascular endothelial growth factor (VEGF) could enhance the development of PC-3 human prostate adenocarcinoma xenotransplanted into nude mice. Whole body radiation (2 Gy) was delivered only once, whereas VEGF (39 ng total/mouse) was injected subcutaneously over a 17-day period. The combination of the two agents, compared to nontreated controls, resulted in significantly higher tumor incidence (100% versus 50%) and more-rapid tumor progression (1288 mm3 versus 190 mm3 by day 60). Treatment-associated changes were observed in body weights and assays of blood and spleen cells. In addition, 3H-thymidine uptake by PC-3 cells cultured in the presence of VEGF and transforming growth factor-beta 1 was compared. These results show that low-dose, whole-body radiation and VEGF can be used in concert safely and effectively to facilitate growth of PC-3 prostate tumor and that the mechanisms of interaction may involve leukocyte modulation.

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.

Phase I/II study of proton beam irradiation for the treatment of subfoveal choroidal neovascularization in age-related macular degeneration: treatment techniques and preliminary results

PURPOSE

Age-related macular degeneration is the prevalent etiology of subfoveal choroidal neovascularization (CNV). The only effective treatment is laser photocoagulation, which is associated with decreased visual acuity following treatment in most patients. This study assessed both the response of subfoveal CNV to proton beam irradiation and treatment-related morbidity. We evaluated preliminary results in patients treated with an initial dose of 8 Cobalt Gray Equivalents (CGE) using a relative biological effectiveness (RBE) of 1.1.

METHODS AND MATERIALS

Twenty-one patients with subfoveal CNV received proton irradiation to the central macula with a single fraction of 8 CGE; 19 were eligible for evaluation. Treatment-related morbidity was based on Radiation Therapy Oncology Group (RTOG) criteria; response was evaluated by Macular Photocoagulation Study (MPS) guidelines. Fluorescein angiography was performed; visual acuity, contrast sensitivity, and reading speed were measured at study entry and at 3-month intervals after treatment. Follow-up ranged from 6 to 15 months.

RESULTS

No measurable treatment-related morbidity was seen during or after treatment. Of 19 patients evaluated at 6 months, fluorescein angiography demonstrated treatment response in 10 (53%); 14 (74%) patients had improved or stable visual acuity. With a mean follow-up of 11.6 months, 11 (58%) patients have demonstrated improved or stable visual acuity.

CONCLUSION

A macular dose of 8 CGE yielded no measurable treatment morbidity in patients studied. Fluorescein angiography demonstrated that regressed or stabilized lesions were associated with improved visual acuity as compared with MPS results. In the next phase, a dose of 14 CGE in a single fraction will be used to further define the optimal dose fractionation schedule.

Effect of pre-irradiation on radiopharmaceutical localization in human colon tumor xenografts using mono- and bispecific monoclonal antibodies

In previous investigations we found that pre-irradiation of a tumor can significantly increase site-specific accumulation of radiolabeled monoclonal antibodies (MAb). The aims of the present study were to compare the effects of radiation on the localization of conventional MAb and a bifunctional delivery system and to evaluate a new time-dose schedule. T380 human colon tumors in athymic nude mice were irradiated (60Co, 10 Gy single dose) and the antibodies were injected 2 hours later. For mice given 111In-ZCE025, an anti-carcinoembryonic antigen (CEA) MAb, the biodistribution of activity was determined 7 days later. The animals receiving ECA001, a bispecific antibody binding to CEA and to a hapten on 111In-DBX, were injected with the radiolabeled hapten 5 days after cold annbody and sacrificed 2 days later. The mean percentage of injected dose (%ID/g) within tumors was significantly increased (p < 0.05) for both anti-CEA antibodies after pre-irradiation compared to their respective nonirradiated controls (%ID/g = 22.8 versus 47.8 for conventional MAb; %ID/g = 12.5 versus 25.9 for bifunctional system). Tumor-to-normal tissue ranos were also higher in the pre-irradiated groups. The data show that pre-irradiation can increase the delivery of conventional MAb within solid tumors by over 200%. In addition, the efficacy of the approach can be enhanced by manipulation of the time-dose schedule. The results with the bispecific antibody system were unexpectedly confounded by significant differences in tumor growth rate after treatment a phenomenon not seen in the groups receiving the conventional MAb.

Relationship between ZCE 025 blood clearance and liver accumulation in patients with colorectal cancer

Clinical interest in radiolabelled monoclonal antibodies (mAbs) derives from their ability to target tissues and deliver radioisotopes thereto. Diagnostic and therapeutic trials suggest that the potential of mAbs would be optimized with better understanding of factors which influence blood clearance. This study sought to advance that understanding. Nine colon cancer patients were injected with 20 mg 111In radiolabelled ZCE 025 mAb, then laser-positioned and imaged daily for one week via nuclear medicine views. Laser-positioned CT images were also obtained, enabling image registration. Blood samples were taken at 30, 60, and 90 min and at every imaging time point. Sample activity was plotted to estimate the elimination half-life (t1/2 beta). Liver radiation dose was calculated from the images and evaluated for total organ (mCi-h) and region of interest (microCi-h/g). Laboratory values and patients' physical parameters were also studied to determine their impact on liver uptake and mAb blood clearance. Liver radiation dose, as measured in this study, correlated with terminal half-life of the mAb in blood; patients' liver enzymes and physical parameters did not. Radioactivity in a 48-h or 72-h blood sample correlates with t1/2 beta and liver radiation dose, suggesting that a single 72-h sample can predict both.