Intra-arterial infusion of radiosensitizer (BUdR) combined with hypofractionated irradiation and chemotherapy for primary treatment of osteogenic sarcoma

Radiation Chemistry and Radiation Research: A History from the Beginning to the Platinum Edition

At the dawn of the 20th Century, the underlying chemistry that produced the observed effects of ionizing radiation, e.g., X rays and Radium salts, on aqueous solutions was either unknown or restricted to products found postirradiation. For example, the Curies noted that sealed aqueous solutions of Radium inexplicably decomposed over time, even when kept in the dark. By 1928 there were numerous papers describing the phenomenological effects of ionizing radiation on a wide variety of materials, including the irradiated hands of early radiologists. One scientist who became intensely interested in these radiation effects was Hugo Fricke (Fricke Dosimetry) who established a laboratory in 1928 dedicated to studies on chemical effects of radiation, the results of which he believed were necessary to understand observed radiobiological effects. In this Platinum Issue of Radiation Research (70 years of continuous publication), we present the early history of the development of radiation chemistry and its contributions to all levels of mechanistic radiobiology. We summarize its development as one of the four disciplinary pillars of the Radiation Research Society and its Journal, Radiation Research, founded during the period 1952-1954. In addition, the work of scientists who contributed substantially to the discipline of Radiation Chemistry and to the birth, life and culture of the Society and its journal is presented. In the years following 1954, the increasing knowledge about the underlying temporal and spatial properties of the species produced by various types of radiation is summarized and related to its radiobiology and to modern technologies (e.g., pulsed radiolysis, electron paramagnetic resonance) which became available as the discipline of radiation chemistry developed. A summary of important results from these studies on Radiation Chemistry/Biochemistry in the 20th and 21st Century up to the present time is presented. Finally, we look into the future to see what possible directions radiation chemistry studies might take, based upon promising current research. We find at least two possible directions that will need radiation chemistry expertise to ensure proper experimental design and interpretation of data. These are FLASH radiotherapy, and mechanisms underlying the effects of low doses of radiation delivered at low dose rates. Examples of how radiation chemists could provide beneficial input to these studies are provided.

Outcomes for pediatric patients with osteosarcoma treated with palliative radiotherapy

BACKGROUND

Few studies have addressed the efficacy of palliative radiotherapy (RT) for pediatric osteosarcoma (OS), a disease generally considered to be radioresistant. We describe symptom relief, local control, and toxicity associated with palliative RT among children with OS.

PROCEDURE

Patients diagnosed with OS at age 18 and under and treated with RT for palliation of symptomatic metastases or local recurrence at the primary site from 1997 to 2017 were included. We retrospectively reviewed details of RT, symptom improvement, local control, survival, and toxicity.

RESULTS

Thirty-two courses of palliative RT were given to 20 patients with symptomatic metastatic and/or locally recurrent primary disease. The median equivalent dose in 2 Gy fractions (EQD2) was 40.0 Gy (range, 20.0-60.4). The median number of fractions per course was 15 (range, 5-39). Symptom improvement occurred in 24 (75%) courses of RT at a median time of 15.5 days (range, 3-43). In nine courses (37.5%), symptoms recurred after a median duration of symptom relief of 140 days (range, 1-882). Higher EQD2 correlated with longer duration of response (r = 0.39, P = 0.0003). Imaging revealed local failure in 3 of 14 courses followed with surveillance imaging studies (21.4%). The median time to progression was 12.9 months (range, 4.4-21.8). The median follow-up time following the first course of palliative RT was 17.5 months (range, 1.74-102.24), and median time to overall survival was 19.4 months. Toxicity was mild, with grade 2 toxicity occurring in one course (3.1%).

CONCLUSIONS

RT is an effective method of symptom palliation for patients with recurrent or metastatic OS, with higher delivered dose correlating with longer symptom relief and with little associated toxicity.

Radiotherapy in the Treatment of Primary Osteosarcoma – a Single Center Experience

Purpose

To analyze our experiences concerning radiation treatment in patients with osteosarcoma.

Materials and methods

Since 1981, 40 patients with osteosarcoma have undergone radiotherapy in Heidelberg; 3 of them were immediately lost to follow-up. Twenty patients with metastases were treated palliatively and 17 patients were treated with a curative intent.

Results

Interestingly, 14 of the 17 patients treated with a curative intent were referred to our clinic during the last 8 years, whereas the number of patients referred for palliation decreased. The mean dose applied for palliation was 47 Gy (range, 26 Gy to >70 GyE), for cure was 59 Gy (range, 45 Gy to >70 GyE). Local control until death could be achieved in 15 of the 20 palliatively treated patients, with a mean survival of 7 months after radiation. Five patients experienced local failure with symptom recurrence, and 3 of them had received doses >60 Gy. At last follow-up, 3 of the 17 curatively treated patients had experienced local recurrence. Median follow-up was 32 months (range, 3-144). Estimated 5-year overall survival and local control rates were 38% and 68%, respectively. Local disease-free survival was shorter in patients treated for recurrent, inoperable or incompletely resected tumors and doses below 60 Gy.

Conclusions

With adequate doses, long-term local control is possible even in inoperable or incompletely resected tumors. Improvements of systemic therapy and modern radiation techniques have begun to bring the possibly curative role of radiation treatment back to the fore. However, in disseminated tumors, even doses beyond 60 Gy do not guarantee local control, suggesting an extremely low radiosensitivity of certain kinds of osteosarcoma.

Concurrent hypofractionated radiotherapy and 5-Fluorouracil for advanced sarcomas of the bone

Purpose. 5-Fluorouracil (5-FU) has shown radiosensitizing properties in vitro. This paper reports the effects of radiotherapy and concomitant intravenous 5-FU radiosensitization in the treatment of advanced bone sarcomas.

Subjects/methods. Four patients with large inoperable bone sarcomas (three chondrosarcomas and one fibrosarcoma) were treated with hypofractionated radiotherapy and concomitant 5-FU bolus injection (300 mg m⁻²) before each fraction of radiotherapy. A radiation fraction of 5 Gy was given twice a week to a normalized total dose (α/β=4 Gy) of 75 Gy.

Results. The regimen was well tolerated, the main toxicity being grade I/II diarrhoea in two cases with pelvic irradiation. Treatment interruption for 1 week was necessary in two cases with pelvic disease but not in two patients treated for sarcoma of the extremities. A complete symptomatic relief was obtained in all cases immediately after the third to the fifth fraction and the median duration was 10 months. Computed tomography scan documented a partial response in 2/4 cases.

Discussion. Hypofractionated radiotherapy combined with potential lethal damage inhibitors for bone sarcomas requires further investigation.

Primary treatment of pelvic osteosarcoma: Report of five cases

Five patients, ages 12 to 20 years, with nonresectable primary (Patients 2, 3, and 5) and metastatic (Patients 1 and 4) pelvic osteosarcomas were treated with intraarterial cisplatin and concurrent radiation therapy from 1983 to 1987. Long-term local tumor control was achieved in all five patients. Patients 1 and 3 are alive with no evidence of local recurrence or metastatic disease at 77 and 56 months of follow-up, respectively, since diagnosis of the pelvic tumor. Patients 2, 4, and 5 died of metastatic lung disease at 25, 39, and 12 months, respectively, after diagnosis of the pelvic tumor. Patient 4 had no clinical or radiologic evidence of local recurrence. Control of tumor growth in patients with pelvic osteosarcomas can be achieved with regional chemotherapy and concurrent radiation therapy. These patients also should receive adjuvant intensive systemic chemotherapy to increase the probability of eliminating potential subclinical metastatic disease.

The role of radiotherapy in oseosarcoma

A survey of the literature shows that the experience with radiotherapy (RT) in the local treatment of osteosarcoma (OS) is limited. This is due to various reasons: OS is a rare tumor and surgery is the treatment of choice with high local control rate, and uncertainty exists in regard to the efficacy and tolerance of radiotherapy. Publications on this topic were analyzed and will be reviewed. Furthermore, experience from the Cooperative Osteosarkomstudiengruppe (COSS)-Registry, including 100 patients (pts) treated using radiotherapy for OS, was analyzed. The COSS-registry includes a total of 175 pts (5% of all pts) with histologically proven OS irradiated over the period of 1980-2007. 100 pts were eligible for analysis. The median age was 18 (3-66) years. Indication for RT was a primary tumor in 66, a local recurrence in 11, and metastases in 23 pts. 94 pts got external photontherapy; 2 pts, proton therapy; 2 pts, neutron therapy; and 2 pts, intraoperative RT. In addition, a group of 17 pts received bone-targeted radionuclide therapy by samarium-153-EDTMP-therapy alone or in combination with external RT. The median dose for external RT was 55.8 Gy (30-120). All the pts received chemotherapy in accordance with different COSS-protocols. The median follow-up was 1.5 (0.2-23) years. Survival and local control rates at 5 years were calculated, and univariate and multivariate analyses performed. 41 pts are alive, 59 pts died. The overall survival rate after biopsy was 41% at 5 years, while the overall survival rates after RT for the whole group, for treatment of primary tumors, local recurrence, and metastases were 36%, 55%, 15%, and 0% respectively.In 41 cases, local control was achieved, whereas local progression or local recurrence occurred in 59 cases, with a median time to local recurrence of 0.5 (0.1-4) years after RT. 15 pts were nonresponders to radiotherapy. Local control for the whole group was 30%. Local control rates for combined surgery and RT were significantly better than those for RT alone (48% vs. 22%, p=0.002). Local control for treatment of primary tumors, local recurrence, and metastases were 40%, 17%, and 0% respectively. Local control for pts given an addition of samarium-153-EDTMP was poor, though not statistically significant. A dose of over 60 Gy had no significant effect on local control. Prognostic factors for survival were indication for RT, RT plus surgery vs. RT alone and tumor location. Prognostic factors for local control were indication for RT, and RT plus surgery vs. RT alone. For the majority of pts, surgery remains the local treatment of choice. Radiotherapy is an important option as local treatment of unresectable tumors, following intralesional resection, or as palliation of symptomatic metastases. Survival prognosis of such pts, however, is poor. Despite the fact that many of these pts will eventually die, they may benefit in terms of prolonged survival and prolonged local control. The combination of surgery, radiotherapy, and chemotherapy can be curative. The consistent use of full-dose chemotherapy is of importance for the response to radiotherapy. Prognostic factors for survival are indication for RT, RT plus surgery vs. RT alone and tumor location. Prognostic factors for local control are indication for RT, and RT plus surgery vs. RT alone.

The role of preoperative radiotherapy in nonmetastatic high-grade osteosarcoma of the extremities for limb-sparing surgery

PURPOSE

To assess the role of preoperative radiotherapy in patients with nonmetastatic high-grade osteosarcoma of the extremities for limb-sparing surgery and to compare the response of neoadjuvant therapies, local control, and survival with the literature results.

METHODS AND MATERIALS

Forty-six patients with osteosarcoma of the limbs who were treated within a limb salvage protocol including preoperative radiotherapy and chemotherapy between 1987 and 2002, were retrospectively analyzed. Median age was 17 years (range, 14-66 years). Treatment was started with neoadjuvant chemotherapy. Cisplatin, epidoxorubicin, ifosfamide, and methotrexate were used in different combinations. Preoperative radiotherapy was applied, usually between the second and third cycle of chemotherapy. Radiotherapy was given (35 Gy in 10 fractions) to 44 patients. Two patients were treated with 46 Gy at 2 Gy/day. Definitive surgery was administered after the third course of chemotherapy. Chemotherapy was complete 6 courses postsurgery.

RESULTS

Median follow-up time was 44 months (range, 2-154 months). Forty-four patients had limb-sparing surgery, whereas 2 had amputation. Tumor necrosis rate was >/=90% in 87% of the patients (Huvos Grade 3-4). Two patients had local failures, and 26 patients (56.5%) had distant metastases. The 5-year local control and overall survival rates were 97.5% and 48.4%, respectively. On univariate analysis, age </=18 years, Huvos Grade 4, lower-extremity localization, and surgery within 1 month significantly survived better than the others. On multivariate analysis, Huvos grade (p = 0.01), age (p = 0.01), interval between neoadjuvant chemotherapy and surgery (p = 0.02), and extremity localization (p = 0.02) were significant prognostic factors for actuarial survival. Severe complication developed in 20% of the patients.

CONCLUSION

Preoperative radiotherapy helps to increase the chance of extremity-sparing surgery with good local control and necrosis rate when combined with chemotherapy.

Neoadjuvant chemotherapy and local radiotherapy for high-grade osteosarcoma of the extremities

OBJECTIVE

To determine the effectiveness of radiation therapy for local control of nonmetastatic osteosarcoma of the extremities after induction chemotherapy.

PATIENTS AND METHODS

Of 187 patients with nonmetastatic osteosarcoma of the extremities treated with induction chemotherapy since 1986, 31 refused surgery and underwent standard, fractionated external beam radiotherapy for local control. The median radiation dose to the limb was 60 Gy (range 40-68 Gy). Records were reviewed through April 2002, and outcomes including radiologic and biochemical response, local control, limb function, and survival were analyzed. The end points were local progression-free survival, metastases-free survival, and overall survival.

RESULTS

Overall survival, local progression-free survival, and metastases-free survival at 5 years were a mean +/- SD of 61%+/-11%, 56%+/-12%, and 62%+/-10%, respectively. The outcome correlated significantly with patients' imaging and biochemical response. In patients who had a pronounced response, overall survival and metastases-free survival at 5 years were 90%+/-9% and 91%+/-9%, respectively, but it was only 35%+/-15% and 42%+/-13% in the nonresponders (P=.005 and P=.005, respectively). Local control was also related to response after induction chemotherapy. None of the 11 patients with both a good imaging and a good biochemical response had local relapse; median follow-up was 67 months. The estimated local progression-free survival among nonresponders was 31%+/-16% at 3 years and 0% at 5 years. Of 22 patients surviving without local disease progression, 19 (86%) had excellent limb function (Enneking score between 90% and 100%) at the time of most recent evaluation.

CONCLUSION

When used after effective induction chemotherapy for osteosarcoma of the extremities, radiation therapy can be a reliable modality to control local disease and preserve limb function.

Radiation chemistry and the Radiation Research Society: a history from the beginning

Radiation chemistry studies began in the early 20th century with observations involving the decomposition of various materials by X rays and radium. Hugo Fricke recognized that the chemical effects of radiation should be studied to help understand the response of living systems to radiation, and in 1928 he established a laboratory to conduct such studies. Early radiation chemists were intimately involved in the founding of the Radiation Research Society and contributed substantially to its interdisciplinary culture. In this historical review, the highlights of research in radiation chemistry leading up to the founding of the Radiation Research Society in 1952 are discussed. The status of the field is established at that point, and a sampling of the major accomplishments from then until the present is presented, with emphasis on those scientists who have contributed substantially to the life and culture of the Radiation Research Society.

High intratumoral accumulation of stealth liposomal doxorubicin in sarcomas--rationale for combination with radiotherapy

Sarcomas are radioresistant tumors, the only curative therapy being radical surgical resection. Stealth liposomal doxorubicin (Caelyx) is a novel drug formulation that allows prolonged circulation and high intratumoral concentration. This study investigates the concurrent use of radiotherapy with Caelyx in a cohort of 7 patients with locally advanced or recurrent sarcoma. Radiotherapy was given as a standard fractionation regimen to a total dose of 70 Gy. Caelyx was given as a 30-min infusion at a dose of 25 mg/m2 every 2 weeks. Scintigraphic imaging with Caelyx-99mTc-DTPA showed an increased (2.8 +/- 0.9 times higher) intratumoral drug accumulation compared to the surrounding healthy tissue. The regimen was well tolerated without any severe hematological or systemic toxicity. 'In field' radiation toxicity was not increased. Complete response was observed in 4/7 cases. It is concluded that combined chemo-radiotherapy with stealth liposomal doxorubicin for locally advanced sarcomas is feasible and promising, the benefit expected from the unique ability of the stealth liposomes to accumulate selectively in the tumoral tissue.

Preliminary results in heavy charged particle irradiation of bone sarcoma

Between 1979 and 1989, 17 patients with unfavorable bone sarcoma were treated wholly or in part with heavy charged particle irradiation (helium and/or neon ions) at the University of California Lawrence Berkeley Laboratory. The majority of tumors were located near critical structures such as the spinal cord or brain. Gross tumor was present in all but two patients at the time of irradiation. Six patients were treated for recurrent disease. Histologies included osteosarcoma, Ewing's sarcoma, and recurrent osteoblastoma. Four of the osteosarcomata were believed to have been induced by previous therapeutic irradiation for various tumors. Follow-up time since initiation of radiation ranged from 7 to 118 months (median 40 months). The 5-year Kaplan-Maier local control rate was 48%; the corresponding survival rate was 41%. Over half the patients succumbed to distant metastases despite the majority of patients receiving chemotherapy. In this preliminary study, we have shown that heavy charged particle irradiation can be effectively used for control of bone sarcoma. A Phase II trial is warranted to determine optimal treatment for unresectable or gross residual disease.

Hypofractionated accelerated radiotherapy in osteogenic sarcoma

A method of hypofractionated accelerated radiotherapy (3 weekly fractions of 6 Gy over 2 weeks to a total tumor dose of 36 Gy) was used as single modality in 14 patients with osteogenic sarcoma for palliative treatment of the primary tumor site (six cases) or skeletal metastases (15 sites). A durable response, radiologically assessed, was obtained in 17 of the 21 (81%) irradiated sites. When this irradiation modality was combined with chemotherapy, to treat patients presenting with synchronous metastases (eight cases) or refusing amputation (five cases), a radiologically assessed response was observed in 12 of 13 (92%). In no case did a local recurrence occur before surgery or death because of progressive disease elsewhere. Of the seven patients who later had to undergo ablative surgery, a 100% and 95% tumor necrosis was observed in 6 and 1, respectively. Because of intralesional resection of primary osteogenic sarcoma after preoperative chemotherapy, seven additional patients were irradiated. None recurred at the level of the primary site. Although effective in inducing remission of osteogenic sarcoma, this irradiation method produced severe damages to normal tissues in a high proportion of patients.

Percent tumor necrosis as a predictor of treatment response in canine osteosarcoma

The percent tumor necrosis was determined in 200 dogs with spontaneously occurring osteosarcoma. One hundred dogs had no treatment before amputation or death. One hundred other dogs were treated with either radiation therapy alone (n = 23), intraarterial (IA) cisplatin alone (n = 16), intravenous (IV) cisplatin alone (n = 6), radiation therapy plus IA cisplatin (n = 47), or radiation therapy plus IV cisplatin (n = 8). Eighty-nine of these 100 dogs had their tumors resected 3 weeks after the end of therapy (6 weeks after the initiation of therapy) and replaced with a cortical bone allograft. Dogs with preoperative treatment were evaluated for local tumor control and time to metastasis. The mean percent tumor necrosis in untreated osteosarcoma was 26.8%. The mean percent tumor necrosis for dogs receiving radiation only, IA cisplatin only, and IV cisplatin only was 81.6%, 49.1% and 23.8%, respectively. The mean percent tumor necrosis for dogs receiving radiation therapy plus IA cisplatin or radiation therapy plus IV cisplatin was 83.7% and 78.2%, respectively. There was no significant difference between percent tumor necrosis in untreated osteosarcoma compared with those receiving IV cisplatin, but there was a significant increase in percent tumor necrosis with all other treatments. A mathematic model for the effect of cisplatin and radiation dose was developed using multiple regression analysis. The radiation dose calculated to cause at least 80% tumor necrosis was 42.2 Gy (95% confidence interval [CI], 38.0 to 47.6 Gy) when radiation was given alone and 28.1 Gy (95% CI, 21.3 to 36.6 Gy) when radiation was combined with IA cisplatin. Areas of viable tumor tended to be most frequent adjacent to the articular cartilage and in the joint capsule. Percent tumor necrosis was strongly predictive for local tumor control; 28 of 32 dogs with greater than 80% tumor necrosis had local control, and only eight of 29 dogs with less than 79% tumor necrosis had local control (P = 0.0047). There was no correlation between percent tumor necrosis and time to metastasis.

A method for determination of iododeoxyuridine substitution of thymidine using reversed-phase high-performance liquid chromatography

An assay for thymidine substitution by iododeoxyuridine (IdUrd) using reversed-phase high-performance liquid chromatography (HPLC) has been developed. Three principal steps in this procedure are: extraction of DNA from cell or tissues, hydrolysis of DNA into deoxynucleosides and separation using HPLC. Approximately 1 microgram of DNA was recovered from 10(5) cells by phenol extraction, and subjected to hydrolysis into deoxynucleosides which required a three-stage DNA digestion using enzymes DNAse I. phosphodiesterase I and alkaline phosphatase. The deoxynucleosides were separated on the Microsorb C18 column with isocratic elution; 90-100% of the DNA was recovered as deoxynucleosides on the column. The method was used to determine quantitatively the percent IdUrd substitution of thymidine in Chinese hamster lung cells in vitro and BA1112 rhabdomyosarcoma in WAG/Rij rats perfused with IdUrd. It was possible to determine the thymidine substitution by IdUrd as small as 1% using a few micrograms of DNA. The close correspondence between the percent substitutions determined by HPLC and those determined by radioactive assay using [125I]-labelled IdUrd, confirmed the accuracy of our HPLC method. The HPLC analysis is especially suitable for the determination of percent IdUrd substitution of thymidine in tissue biopsies from animals used in in vivo experiments or humans undergoing radiation treatment.

Effects of preoperative radiotherapy on rectal cancer. Preliminary report on combining radiation with intratumor injections of peplomycin and bromodeoxyuridine

Between 1976 and 1983, 61 patients with advanced rectal cancer underwent Miles' operation at the authors' institution. All lesions were located 10 cm or less from the anal verge. Of these patients, 25 were treated by surgery alone and 36 were given preoperative radiotherapy. The total dose was 42.6 Gy, (30.6 Gy [1.8 Gy/fr x 5/week]) delivered to the entire pelvis plus an additional 12 Gy (3.0 Gy/fr x 4/week) delivered to the primary tumor. Of 36 patients, 21 were administered intratumor injections of peplomycin and bromodeoxyuridine at the time of boost radiation and 15 were treated without intratumor injections. During the follow-up period (3 to 9 years), in the groups of patients who underwent radiation, there was only one local failure (2.8 percent). In contrast, in the group of patients treated by surgery alone, eight local failures occurred (32 percent). The intratumor injection significantly enhanced the effect of radiation on tumor regression. The incidence of positive lymph nodes was higher in patients in the surgery alone group than it was in the groups treated with radiation. There was no difference in the rate of distant metastasis among the three treatment groups. The five-year survival rate for the radiation with intratumor injection group, radiation alone group, and surgery alone group, was 77.8, 69.2, and 56.0 percent, respectively. No severe complication was experienced.

Effects of 5-bromo-2-deoxyuridine and 2-deoxy-D-glucose on radiation-induced micronuclei in mouse bone marrow

Effects of 2-deoxy-D-glucose (2-DG) and 5-bromo-2-deoxyuridine (BrdU) on 60Co gamma-radiation-induced damage in normal mouse bone marrow have been investigated. Cytogenetic damage as measured by the frequency of cells with micronuclei was studied at various time intervals after irradiation. Intravenous administration of 2-DG (0.1 ml, 1 g/kg body weight) just before or after whole-body irradiation (absorbed dose 2.5 Gy) significantly reduced the micronuclei fraction as compared with irradiated controls. Incorporation of BrdU given intraperitoneally in 13 injections (0.3 ml) (total dose 2 g/kg body weight) at intervals of 1 h increased the micronuclei frequency, but administration of 2-DG significantly decreased cytogenetic damage. The results have interesting implications for improving tumour radiotherapy.

Enhanced IUdR radiosensitization by 241Am photons relative to 226Ra and 125I photons at 0.72 Gy/hr

The dependence of IUdR radiosensitization on photon energy was investigated by irradiating Chinese hamster cells in vitro under aerobic conditions at a dose rate of 0.72 Gy/hr which is typical of temporary brachytherapy implants. It had been observed previously that the IUdR radiosensitization with the 60 keV photons from 241Am is about 1.5 times greater than that with 830 keV (average) photons from 226Ra. It was hypothesized that the enhanced IUdR radiosensitization for 60 keV photons was a result of a larger production of Auger electron cascades from the filling of K-shell vacancies in the iodine atoms, which have a K-shell binding energy of 33.2 keV. Since most of the photons from a 125I source have energies below 33.2 keV, it would be expected that IUdR radiosensitization with 28 keV (average) photons from 125I and 830 keV (average) photons from 226Ra would both be smaller than the radiosensitization with the 60 keV photons from 241Am. To test this hypothesis we compared IUdR radiosensitization for 226Ra, 241Am, and 125I at 0.72 Gy/hr, using Chinese hamster lung cells in vitro. The measured survival curves led to RBEs of 1.20 +/- 0.10 and 1.30 +/- 0.11 for 241Am and 125I photons relative to 226Ra; to IUdR radiosensitization factors at a 10(-5) M concentration of 1.35 +/- 0.11, 1.67 +/- 0.09, and 1.47 +/- 0.08 for 226Ra, 241Am, and 125I, respectively; and to radiosensitization factors at a 10(-4) M concentration of 1.89 +/- 0.16, 3.04 +/- 0.13, and 2.48 +/- 0.17 for 226Ra, 241Am, and 125I, respectively. These results indicate that IUdR produces significant radiosensitization with all three isotopes (226Ra, 241Am, and 125I) for continuous low dose rate irradiations at 0.72 Gy/hr. Also, we observed greater radiosensitization with 241Am photons compared to 226Ra on the higher energy side and to 125I on the lower energy side. These findings support the concept that photon-induced Auger electrons produce a significant increase in IUdR radiosensitization when photons with energies just above the K-edge of the iodine atom are employed for continuous low dose rate irradiations. These findings suggest that regimens combining IUdR infusion with temporary brachytherapy implants using low energy photons in relatively quiescent sites such as brain tumors may have clinical potential, and indicate the need for rigorous preclinical evaluation of this approach.

Correlation of exposure time, concentration and incorporation of IdUrd in V-79 cells with radiation response

These experiments were designed to find the minimum concentration at which incorporation of and sensitization by IdUrd (Iododeoxyuridine) would occur and the effect of concentrations from .1 to 100 microM for exposures of 8 to 96 hr in cultured V-79 cells exposed to 137Cs gamma rays at 2 Gy per minute. At 0.1 microM thymidine replacement averaged 1% and the SER ranged from 1.1 to 1.28, significant at the 95% level. The maximum thymidine replacement was 49% after 48 hr exposure to 30 microM yielding an SER of 2.7. SER generally peaked after 72 hr of exposure. This cell line has an 8 hr cycle time in our hands and thus optimal sensitization would occur after 9 cell cycles. These ranges need testing in human cells in culture and in Phase I clinical trials.

Improved high-performance liquid chromatographic assay for the quantification of 5-bromo-2'-deoxyuridine and 5-bromouracil in plasma

A sensitive and specific procedure using high-performance liquid chromatography (HPLC) was developed for the quantification of 5-bromo-2'-deoxyuridine (BUdR) and 5-bromouracil (BU) in plasma. BUdR and BU were first extracted with a mixture of ethyl acetate and 2-propanol from plasma presaturated with solid ammonium sulfate. Following evaporation of the organic extract, the remaining residue was reconstituted in saturated ammonium sulfate solution, washed with a mixture of n-pentane-methylene chloride and re-extracted with the original solvent mixture. The organic extract was evaporated, reconstituted in mobile phase and chromatographed on a regular-bore ODS HPLC column using ultraviolet absorbance detection. The BUdR and BU quantification limits were both 0.1 microM, the mean intra-assay coefficients of variation were 5.0 and 5.6%, respectively, and the mean inter-assay coefficients of variation were 5.4 and 10.7%, respectively. This method was used to determine steady-state femoral arterial and hepatic venous plasma concentrations of BUdR and BU in a patient receiving a continuous intravenous infusion of BUdR (20 mg/kg per day).

Surgery with intraoperative radiotherapy for sarcomas of the pelvic girdle: a pilot experience

Sarcomas of the pelvic girdle represent difficult treatment problems. Many are not treatable for cure, and among the patients who are technically resectable, there is high risk for local tumor recurrence and distant spread. Intraoperative radiotherapy (IORT) has been used in conjunction with surgical resection in five patients with extensive sarcomas of the pelvic girdle. Patients underwent a hemipelvectomy and IORT (dose 20-30 Gy) to the sacral resection margin and surrounding soft tissues. Three patients developed pulmonary metastases within 3 months and eventually died from metastatic disease (8-38 months). Two patients have remained disease-free (43 and 53 months). Four patients (80%) have remained locally free of tumor with follow-ups of 8-53 months. The only treatment complication was late osteonecrosis of the coccyx which appeared 7 months after treatment. By contrast, six historical control patients with sarcomas of the pelvic girdle treated with resection alone showed a local control rate of only 27% over a 40-month follow-up. On the basis of this preliminary experience, it appears that IORT may substantially help to control local disease in patients with grossly resectable sarcomas of the bony pelvis.

Radiosensitization produced by iododeoxyuridine with high linear energy transfer heavy ion beams

Little is known about radiosensitization produced by iododeoxyuridine (IUDR) with high linear energy transfer radiation. Likewise, the effect of IUDR on repair of sublethal or potentially lethal damage is unclear. A series of in vitro experiments was performed examining these aspects of IUDR radiosensitization. Human T1 cells were grown in the presence of 3.0 micromolar IUDR for 72 hours (approximately three doubling times), an exposure which resulted in minimal cytotoxicity to unirradiated cells. As the cells entered plateau phase they were exposed to X rays and a variety of heavy ion beams. Sensitization was found to decrease as linear energy transfer (LET) increased. No sensitization took place in an extremely high LET Lanthanum ion beam (1000 keV/micrometer). However, IUDR produced significant sensitization in the Neon ion beam currently used to treat cancer patients at Lawrence Berkeley Laboratory. Sensitization enhancement ratios at the 40% cell survival level were found to be 1.8 for X rays, 1.5 for the proximal Bragg peak of the clinical Neon beam, and 1.3 for the distal peak of the clinical Neon beam. Cell survival curves fitted to the linear-quadratic model showed IUDR significantly increased the value of the linear component (alpha) in beams with LETs below 40 keV/micron. The value of the quadratic component (beta) was unaffected by IUDR, regardless of LET. Split-dose experiments with both X rays and proximal peak Neon ions revealed IUDR did not affect sublethal damage repair. Similarly, delayed-plating experiments showed IUDR did not affect repair of potentially lethal damage. In contrast to cells unexposed to IUDR, IUDR-treated cells showed near-equal levels of cell killing throughout the extended Bragg peak of the clinical Neon beam. These findings suggest that the addition of IUDR to Neon ion radiotherapy could enhance the therapeutic ratio of the clinical Neon beam.

Bromodeoxyuridine amplifies the inhibitory effect of oxygen on cell proliferation

The BrdUrd-Hoechst method was used to analyze the interaction of various oxygen concentrations with BrdUrd substituted DNA with respect to cellular proliferation. At oxygen concentrations above 5%, human diploid fibroblast-like cells and amniotic fluid fibroblast-like cells showed reduced proliferation rates, which resulted from an increase in noncycling cells and from a permanent arrest of cells in the G2 phase of the cell cycle. At 35% oxygen the increase in noncyling cell fraction and the permanent arrest in G2 was strongly dependent upon the concentration of BrdUrd. Incorporation of BrdUrd into DNA, therefore, amplifies the adverse effects of increasing oxygen concentrations upon cell proliferation. The mechanism of this amplification might involve a free radical attack on DNA similar to the radiation sensitizing effect of BrdUrd.

Cardiovascular malformations induced by bromodeoxyuridine in the chick embryo

For the study of morphogenesis and early embryonic development, 5-bromodeoxyuridine (BUdR), a halogenated analogue of thymidine, is incorporated into replicating DNA and serves as a valuable tool. To study the teratogenicity of BUdR on the developing chick cardiovascular system, we topically administered graded doses of BUdR (32.6-325.6 nmol) in ovo during Hamburger-Hamilton stages 15 to 16. We also administered to a parallel group of embryos corresponding nanomole doses of thymidine during identical stages of development. In the thymidine-treated group, survival rates and cardiovascular anomaly rates did not differ statistically from those in the chick Ringer's control group. Both survival rates and cardiovascular anomaly rates in the BudR-treated group were dose-responsive. Among 78 embryos with cardiovascular anomalies induced by BUdR, vascular malformations were found in 96%. These anomalies included interruption of the right fourth aortic arch, absence or hypoplasia of the right and/or left sixth aortic arch, and persistence of the left fourth aortic arch. Interruption of the right fourth aortic arch was always associated with intracardiac anomalies. Intracardiac anomalies were found in 54% of the embryos; these included ventricular septal defect, double outlet right ventricle, and persistent truncus arteriosus. Subclavian artery malformations were noted in 95% of the embryos. Possible mechanisms for BUdR-induced malformations in the cardiovascular system of the chick are discussed.

Enhancement of IUdR radiosensitization by low energy photons

The effect of the photon energy on the radiosensitization produced by iododeoxyuridine (IUdR) was examined using Chinese hamster cells in vitro. Radiosensitization by IUdR was considerably higher for 60 keV photons from 241Am sources than for the 860 keV photons (average energy) from 226Ra sources, under continuous low dose rate conditions applicable to intracavitary brachytherapy (a dose rate of 0.57 Gy/hr). Also, IUdR radiosensitization was higher for 250 kV X rays than for 4 MV X rays under the acute exposure conditions used in external beam radiation therapy (dose rates of 1 to 2 Gy/min). These data support the hypothesis that photons with energies just greater than 32.2 keV, the K-absorption edge of iodine, are more effective in causing cell damage than are photons of other energies, because their absorption results in the production of Auger electron cascades and therefore in the production of high linear energy transfer (LET) radiations.

Clinical experience with intravenous radiosensitizers in unresectable sarcomas

Traditionally, adult bone and soft tissue sarcomas have been considered to be "radioresistant." Because of this philosophy, patients who present with locally advanced, unresectable sarcomas often are treated in a palliative fashion, usually with low-dose radiotherapy. Over the last 6 years, 29 patients with unresectable primary or metastatic sarcomas were treated using a combination of intravenous chemical radiosensitizers and high-dose irradiation. Twenty-two of 29 patients achieved clinical local control, with six patients having a complete clinical response. The time to tumor response is often several months or longer, which is in contrast to other tumor histologies (carcinomas, lymphomas), where tumor response usually occurs over several weeks. Several large tumors have shown only a minimal tumor response, yet were found to be sterilized in posttreatment biopsy or autopsy examination. Of 15 patients with primary sarcomas without metastases, 11 patients (73%) remain free of local tumor progression from 12 to 83 months. Adult high-grade sarcomas can be controlled with high-dose radiotherapy and intravenous radiosensitizers, although the precise role of these agents is unclear.

Advances in pediatric radiotherapy in the last ten years and future proposals

Advances made can be divided into five main categories. Firstly, the problem of geographic miss which has been reduced by delivering effective radiation doses with greater precision. This has been accomplished with more sophisticated diagnostic and therapeutic equipment, immobilization techniques and computerized treatment planning. Second is the recognition of the interplay of radiation and chemotherapy on normal tissue tolerance and local tumor control. This interaction has necessitated reduction in both dose and volume of irradiation. Third is the use of wide field irradiation as a systemic treatment. Fourthly, the utilization of cooperative group trials to define the role of irradiation. Finally, with the improvement in survival has come the recognition of late effects of irradiation in the growing child and the means of reducing such effects. The current role of radiation therapy in childhood malignancies is summarized, controversies are identified, and future prospects explored.

Hypofractionated radiotherapy for sarcomas

In an effort to improve local control in the radiation treatment of sarcomas, up to 7 weekly fractions of 6.6 Gy each were administered to 64 patients. They were divided into two groups: Group A consisted of 37 patients with measurable disease who achieved a partial response rate of 22%, with no complete responses. Group B consisted of 27 postoperative patients with varying degrees of completeness of surgical excision, two have relapsed locally to date. Early radiation damage was documented in 26%, but was not a dose-limiting or incapacitating event in any case. Late normal tissue damage occurred in 23 out of 32 evaluable patients (72% of those at risk), and was a cause of serious morbidity in 6 patients. Response rates were low in Group A compared with other series, but in Group B the local recurrence rate is comparable with other centers using "conventional" fractionation. No apparent improvement in therapeutic gain was demonstrated for large weekly fractions.