Preferential cytotoxicity of 5-thio-D-glucose against hypoxic tumor cells.

5-Thio-D-glucose effectively killed hypoxic mastocytoma cells of DBA/2J mice, whereas it merely suppressed the growth of oxic cells. This specific toxicity suggested that 5-thio-D-glucose may be a useful adjuvant to radiotherapy by eliminating hypoxic protection.

Blood flow in normal tissues and tumors during hyperthermia.

The effect of hyperthermia on the blood flow was studied in skin, muscle, and Walker 256 carcinoma implanted in the legs of SD rats. The radioactive microsphere method was used to measure the blood flow. Hyperthermia for 1 hour with water at 43 degrees C increased the blood flow in skin and muscle by about threefold to fourfold. On the contrary, hyperthermia had no appreciable effect on the blood flow in tumors. Consequently, during hyperthermia blood flow in the skin and muscle surrounding the tumors was greater than that in tumors larger than about 2 g. Despite the apparent increase in heat dissipation by the increased blood flow, the temperature of the skin was 42.6-42.8 degrees C, and the temperature at the core of tumors larger than 2 cm in diameter was 42.3-42.7 degrees C during the hyperthermia. The lower temperature in the muscle could be attributed to an increase in heat dissipation as a result of the increased blood flow. This differential rise in temperature by heating may account in part for the differential effect of hyperthermia on tumors and normal tissues in vivo.

Elimination of hypoxic protection by 5-thio-D-glucose in multicell spheroids.

The effect of 5-thio-D-glucose on oxic and hypoxic V79-171 Chinese hamster cells was studied in vitro with single cells and multicell spheroids. At concentrations that were not toxic to oxic cells, this compound killed hypoxic cells with a D0 of 1 hr with a 5 mM concentration and more rapidly at 10 mM beginning 2 hr after incubation at 37 degrees. 5-Thio-D-glucose also sensitized hypoxic cells to radiation and protected oxic cells from radiation damage. Multicell spheroids irradiated after incubation with the compound demonstrated increased radiosensitivity, although the relative contribution of cytotoxicity and hypoxic cell sensitization could not be evaluated. Spheroid reoxygenation by decreased cell respiration was determined not to be a contributing factor, suggesting that the spheroid-sensitizing effect was due to drug effects on hypoxic cells. The dramatic increase in multicell spheroid radiosensitivity that resulted from treatment with 5-thio-D-glucose suggests that this compound may be used to increase the effectiveness of radiotherapy by eliminating hypoxic protection.

Changes in thermosensitivity of mouse mammary carcinoma following hyperthermia in vivo.

The time course of change in thermosensitivity of SCK tumor cells in vivo was investigated following preheating at 43.5 degrees for 30 min. At varying times after the preheating with water bath, tumors were subjected to graded doses of second heating at 43.5 degrees in vivo, and cell survival was determined by using in vitro cloning method. Thermosensitivity of the tumor cells in vivo [duration of heating for exponential inactivation of cells to 1/e (Do): 15.5 min] gradually increased after the preheating, reaching a maximum increase at 5 hr (Do: 7.5 min), and then decreased thereafter, due probably to a development of thermotolerance. Maximum thermotolerance was observed at 12 hr after the preheating, leading to a 3-fold increase in Do (48 min). The thermotolerance gradually decayed for several days thereafter. The initial increase in thermosensitivity might be attributed to the acidic and nutritionally deprived intratumor environment as a result of vascular damage in heated tumor. It appears that thermotolerance gradually develops as time elapses and that it eventually overcomes the thermal sensitization of tumor cells in vivo.

Role of vascular function in response of tumors in vivo to hyperthermia.

The response of SCK tumor cells in vivo and in vitro to heat was compared, and the relationship between the kinetics of cell death and vascular function in tumors in vivo after hyperthermia was studied. The number of clonogenic cells in tumors excised immediately after heating was significantly less than that in the in vitro culture treated with the same heat doses. This suggested that the tumor cells in vivo are far more sensitive to direct damage by heat than are the cells in vitro. When the tumors were left in situ after hyperthermia at 43.5 degrees for 30 min, there was a progressive decrease in cell survival until 6 to 12 hr after the heating. The study of intravascular volume using the 51Cr-labeled red blood cell method indicated that severe vascular occlusion occurs in the tumor after hyperthermia. It therefore appeared that delayed cell death in tumors in vivo after hyperthermia resulted from an insufficient supply of oxygen and nutrients and an increase in acidity due to the vascular occlusion. Both the direct damage to tumor cells and the indirect damage to tumor cells as a consequence of vascular occlusion may play important roles in the eradication of tumors by hyperthermia.

Difference in the thermotolerance of mouse mammary carcinoma cells in vivo and in vitro.

The kinetics of thermotolerance development were compared for cells in the SCK mammary carcinoma of A/J mice, and the same cells cultured in vitro. Tumors in the legs of mice or cells in culture flasks were conditioned with heat in a water bath at 43 degrees C for 30 min and the cells were left in the tumors or the culture flasks for various lengths of time after heat conditioning. The magnitude of thermotolerance was determined by preparing single cells and subjecting them to a test heating in a controlled environment in vitro at 43 degrees C, and the survival of the cells was determined by measuring the colony-forming ability in vitro. Thermotolerance in tumors reached its maximum 12 h after heat conditioning, at which time the survival response was characterized by Do (the duration of heating required for exponential cell inactivation to 1/e) of 116 min. This changed to a Do of 170 min when the cells in tumors were incubated in culture medium of neutral pH during the development of thermotolerance. In contrast, the thermotolerance of cells cultured in vitro was fully developed within 8 h, at which time the Do was 306 min. The kinetics of thermotolerance development, therefore, varied significantly between the cells of the same origin but grown in vivo or in vitro. Killing of tumor cells in vivo caused by the heat-conditioning dose was about three times greater than that for tumor cells in vitro, but the greater damage did not result in a greater development of thermotolerance. The above results indicate that the development of thermotolerance in tumors is suppressed by the influence of intratumor environment.

Increase in pO2 and radiosensitivity of tumors by Fluosol-DA (20%) and carbogen.

The potential usefulness of i.v. injection of perfluorochemicals and breathing carbogen (95% O2 and 5% CO2) to improve the radiation-induced control of tumors was investigated. When C3H mice, bearing RIF-1 tumors in the legs, were given i.v. injections of Fluosol-DA (20%) at 12 ml/kg, and allowed to breathe carbogen for 1 h before and during a single dose of X-irradiation, the curability of tumors increased by a dose modification factor of 1.47 +/- 0.03 (SE). Such a treatment also increased the radiation-induced skin damage by a factor of 1.15 +/- 0.12, resulting in a therapeutic gain of 1.28 +/- 0.04. Measurement of intratumor pO2 by oxygen microelectrodes demonstrated small increases in pO2 when the animals breathed carbogen, and marked increases in pO2 when Fluosol-DA (20%) was injected into the animals and the animals breathed carbogen. It was concluded that i.v. injection of Fluosol-DA (20%) followed by carbogen breathing significantly improved the oxygen supply to hypoxic cells in the RIF-1 tumors and thus increased the control of tumors by radiation.

Benefits versus risks in conservation surgery with irradiation for breast cancer.

This report analyzes the survival and complications inherent in the conventional treatment of breast cancer, radical mastectomy, and the more conservative procedure, conservation surgery with irradiation. Both procedures have benefits and risks. The benefits as measured by survivorship appear to be approximately the same. The major benefit of conservation surgery with irradiation is that the breast is left intact. The possible complication of irradiation carcinogenesis is addressed, and the literature analyzed. This review indicates that the absolute risk of breast cancer developing in the second breast is not nearly as great as originally thought. It is concluded that if a woman with breast cancer is a candidate for either mastectomy or the conservative procedure, it is the clinician's obligation to objectively present the evidence regarding the benefits and risks of these procedures.

The rush to judgment: Does the evidence support the enthusiasm over three-dimensional conformal radiation therapy and dose escalation in the treatment of prostate cancer?.

PURPOSE: To discuss the assumptions behind and current clinical evidence on three-dimensional conformal radiation therapy (3D-CRT) and dose escalation in the treatment of prostate cancer. METHODS: We first define 3D-CRT in comparison to standard radiation therapy and discuss the assumptions on which the technology of 3D-CRT and dose escalation are based. We then examine the evidence on the benefits and limitations from the current most commonly cited studies on dose-escalation trials to treat prostate cancer. RESULTS: The assumption that 3D-CRT can provide a tighter margin around the tumor area to allow for dose escalation is not yet proven by studies that show continual difficulty in defining the planning treatment volume because of extrinsic and intrinsic difficulties, such as imaging variabilities and patient and organ movement. Current short-term dose-escalation studies on the use of 3D-CRT to treat prostate cancer are limited in their ability to prove that increasing dose improves survival and does not incur potential long-term complications to normal tissue. CONCLUSION: Although 3D-CRT is a promising technology that many radiation oncologists and clinics are quickly adopting to treat such tumors as prostate cancer, the long-term evidence on the benefits and limitations of this technology is still lacking. Until we have solid long-term evidence on the true clinical potential of this new technology, let us not rush to judgment, but exercise caution, diligence, and thoughtfulness in using this new technology to treat our patients.

The effect of definitive irradiation on local control and disease free survival in breast cancer.

The prognostic factors important in determining local regional control or failures can be divided into two groups. The first, the intrinsic factors, relate to the initial inherent condition of the tumor, that is, the tumor labeling index, progesterone receptors, the degree of involvement of the lymph nodes in he area, the size of the tumor, etc. The second, extrinsic factors, relate to type and adequacy of treatment. The presentation demonstrates that the most critical factors in determining failure and patterns of failure are the intrinsic factors, that is, histologic grade tumor labeling index, number of nodes involved, progesterone receptors and size, and that the adequacy of treatment affects failure and patterns of failure in patients treated. This paper shows that adequate radiation reduces local recurrence and, consequently, increases the survival rate; it also demonstrates that inadequate radiation will lead to increased local recurrence and decreased survival. The factors involved in determining the adequacy of irradiation are discussed.

The Lampe lecture. Radical radiation therapy in the treatment of laparotomy staged Hodgkin's disease patients.

In 1970, a policy for the treatment of Stage IIIA Hodgkin's disease patients at the University of Minnesota, which included complete staging procedures and extended field or total nodal irradiation (TNI), was introduced. Evaluation of the results 4 years later indicated that certain patients, especially those with large mediastinal masses and/or hilar disease, or who were spleen positive, were having higher recurrence rates than patients without these characteristics. In 1974, a new approach to treatment for patients with large mediastinal masses or spleen positive disease was instituted which involved treating the whole lung or hemi lung in patients with large mediastinal masses and/or hilar disease, and the liver in patients who had positive spleens. The results of this treatment modification are reported in this study. Long term follow-up reveals that this approach has led to a recurrence free survival and overall survival similar to that noted in patients treated with combined modality treatment without the obvious risk of subsequent leukemia related to combination chemotherapy and radiotherapy. In addition, the complications of the treatment are tolerable and do not demonstrate an increase over patients not treated in this manner. Radical radiation therapy is recommended as a treatment of choice for Stage IA, IIA, and IIIA patients with or without splenic involvement, and with or without hilar disease and/or large mediastinal masses with appropriate radiation field modification to adjust for disease extent.

Thyroxine administration during radiation therapy to the neck does not prevent subsequent thyroid dysfunction.

In an attempt to reduce the incidence of hypothyroidism following irradiation of the neck, we administered oral L-thyroxine in doses sufficient to suppress serum TSH to 20 patients receiving radiation therapy for Hodgkin's disease or other lymphomas. L-thyroxine was discontinued when radiation therapy was completed. Twenty similar patients who did not receive L-thyroxine during radiation therapy served as a control group. After a mean follow-up period of 33 months, seven patients (35%) in the L-thyroxine group developed elevation of serum TSH and were started on chronic L-thyroxine therapy. In the control group, after mean follow-up of 19 months, five patients (25%) developed elevation of TSH and were started on chronic L-thyroxine. We conclude that suppression of serum TSH during neck irradiation does not prevent subsequent thyroid dysfunction.

Increases in tumor response by pentoxifylline alone or in combination with nicotinamide.

Pentoxifylline (PENTO), a derivative of methylxanthine, has been reported to improve fluidity of red blood cells (RBC), and thus improve the flux of RBC through narrow capillaries. Additionally, PENTO increases 2,3-DPG levels in RBC, thereby increasing the O2 release from RBC. Nicotinamide (NA) has been known to increase tumor blood flow, reducing the hypoxic cell fractions in the tumors. The purpose of this study was to examine the effects of PENTO alone or in combination with NA (PENTO + NA) on the oxygenation and radio-response of FSaII murine fibrosarcomas of mice. We observed a significantly enhanced, radiation-induced growth delay of the FSaII tumors by the treatment of either single or multiple injections of PENTO. The combination of PENTO and NA further delayed the growth of tumors. The TCD50 of control tumors was about 56.6 Gy, whereas that of PENTO + NA treated tumors was about 31.9 Gy. Thus, TCD50 was modified by a factor of 1.8. PENTO + NA exerted no effect on the acute skin damage of C3H mice after local irradiation and the gastrointestinal death after whole body irradiation. However, PENTO + NA slightly increased the bone marrow death as demonstrated by the decrease in LD50(30) from 5.5 Gy to 5.2 Gy. The average pO2 in the saline-treated control group of FSaII tumors was 8 mmHg and it significantly increased to 19 mmHg in the PENTO + NA treated group (p less than 0.001). We concluded that the PENTO + NA treatment increased the radio-response of tumors by improving tumor oxygenation.

Radiation therapy in early carcinoma of the glottic larynx T1N0M0.

PURPOSE: The Purpose of this report is to present the local control rate and survival of patients treated by radiation therapy for T1N0M0 squamous cell carcinoma of the glottic larynx. METHODS AND MATERIALS: A total of 41 patients with squamous cell carcinoma of the glottis were treated at the Veterans Administration Medical Center Minneapolis, MN, between 1976 and 1990. Of the 41 patients, 40 are available for retrospective analysis with a minimum of a 2-year follow-up and a median follow-up of 5.8 years. Treatment was given to all the patients by a 4 MeV linear accelerator. The vast majority of the patients were treated with bilateral laryngeal opposed wedged 6 x 6 cm fields with a dose of 1.75 Gy per fraction to a total of 70 Gy in 40 fractions over 56 elapsed treatment days. RESULTS: The data indicated local control and survival of 92.3 % at 2 years and 91.8 % at 3 years, post irradiation, with ultimate disease-free survival after surgical salvage of 97.4 % and 97.2 % at 2 years and 3 years, respectively. These local control and survival rates are comparable to those published in the literature when a higher fractional dose was given. No patients developed notable complications with our technique. CONCLUSIONS: A dose of 1.75 Gy to 1.8 Gy per fraction to a total of 70 Gy in 56 elapsed treatment days is well tolerated and yields ultimate disease free-survival of 97.2% at 3 years. This time-dose fractionation could be used safely for treating patients who demonstrate low tolerance to irradiation with a risk of laryngitis, laryngeal edema, or difficulty of swallowing, with a higher fractional dose.

External beam radiation therapy for squamous cell carcinoma of the soft palate.

PURPOSE: External beam radiation therapy for carcinoma of the soft palate aims to achieve loco-regional control with normal speech, nasal function, swallowing mechanism, and minimal side effects such as nasal speech and regurgitation of food into the nasopharynx. In this report we present our results of radiotherapy in the treatment of 24 patients with squamous cell carcinoma of the soft palate. METHODS AND MATERIALS: A total of 24 patients with squamous cell carcinoma of the soft palate were treated at the Veterans Administration Medical Center Minneapolis, MN, between February 1977 and May 1992. Of the 24 patients 2 had T1, 19 T2, 1 T3, and 2 had T4 lesions. Nineteen patients did not have clinical nodal disease, stage (N0), 1 had N1, 2 N2, and 2 N3 disease (Table 1). All the patients were treated by 4 MeV linear accelerator. A 1.75 Gy median dose was administered per fraction to a total of 70 Gy median dose. Bilateral opposed compensated shrinking fields technique was used. RESULTS: The 3-year disease free survival rate after external beam radiation therapy was 100% (1 out of 1), 64.7% (11 out of 17), 100% (1 out of 1), and 0%, for patients with T1, T2, T3, and T4 disease, respectively. Salvage surgery for recurrent disease was successful in 57.1% (4 out of 7 patients (Table 2). The ultimate 3-year disease free survival rate for the entire group, including surgical salvage, was 81% (17 out of 21) (Fig 1). CONCLUSION: Radiation therapy alone in our institution resulted in tumor control and survival rates compare favorably to previously published reports in the literature. Surgery can be reserved as salvage procedure.

Aneurysm, arachnoiditis and intrathecal Au (gold).

This report is a 20-year follow-up of 14 patients treated with external beam craniospinal irradiation and intrathecal gold (10-45 mCi) for medulloblastoma. Six of the patients died within 2 years of treatment from persistent disease. No patients are alive without complications. Six of eight surviving patients developed arachnoiditis and cauda equina syndrome within 5 to 10 years of treatment. Seven of eight survivors developed aneurysms and/or cerebrovascular accidents 9 to 20 years after treatment. Four of the cerebrovascular events were fatal. Intrathecal gold pools in the basal cisterns and cauda equina delivering an extremely inhomogeneous dose throughout the neuroaxis. Its use is discouraged.

Relationship between vascular thermotolerance and intratumor pH.

The changes in blood flow, intratumor pH, and clonogenicity of tumor cells after one and two heatings were studied in SCK tumors of A/J mice. When SCK tumors were heated at 42.5 degrees C for 1 hr, vascular thermotolerance promptly developed and peaked at 18 hr post-heating. The intratumor pH was 7.05 +/- 0.14 (mean +/- S.D.) in control SCK tumors of A/J mice, with a significant decrease (p less than or equal to 0.001) to 6.86 +/- 0.08 and 6.70 +/- 0.08 when heated for 1 hr at 43.5 degrees C and 44.5 degrees C, respectively. However, when the vascular thermotolerance was at its peak, heating at the same doses caused little change in the intratumor pH. When SCK tumors were heated for the first time at 44.5 degrees C for 1 hr and left in situ, the number of clonogenic cells significantly declined. Such a secondary cell death could be attributed to the deterioration of the intratumor environment ensuing from the vascular damage. When the tumor vessels were thermotolerant, however, virtually no secondary cell death occurred after heating.

The radioprotective effect of 5-thio-D-glucose on normal tissues in vivo.

The radioprotective effect of 5-thio-D-glucose (5-TG, NSC 204984) on normal tissues of mice was investigated. The LD50 of 5-TG in A/J mice injected intraperitoneally (i.p.) is 5.5 g/kg. The animals were injected i.p. with saline or 5-TG followed by whole-body irradiation or localized irradiation of the foot. Mice injected with 1.5 g/kg of 5-TG were protected from gastrointestinal or bone marrow death following whole-body irradiation by a dose modification factor (DMF) of 1.1--1.3. The same dose of 5-TG protected mice from foot skin damage between days 0 and 40 post-irradiation by a DMF of 1.3, and from late foot deformity during days 60 to 90 post-irradiation by a DMF of 1.2. Foot skin reactions indicated that 5-TG provided maximal radioprotection up to 4 hours after an intraperitoneal injection. We have previously reported that 5-TG selectively kills and radiosensitizes hypoxic cells. Consequently, it may be possible to use this compound as an adjuvant to radiotherapy in order to kill or radiosensitize hypoxic cells and to radioprotect normal tissue.

Effect of hyperthermia on hypoxic cell fraction in tumor.

The effect of hyperthermia on the proportion of hypoxic cells in SCK mammary tumor of A/J mice was investigated. About 45% of clonogenic cells in the unheated control tumor were radiobiologically hypoxic. Upon heating with a 43.5 degree C water bath for 30 min, the proportion of hypoxic cells increased and then decreased: it was 95% at 5 hr and 60% at 12 and 24 hr after heating. Despite the increase in the proportion of hypoxic cells 5 hr after heating, the absolute number of hypoxic cells in the tumors at this time was significantly smaller than that in the unheated control tumors because of a decrease in the total number of surviving tumor cells. The initial increase in the proportion of hypoxic cells after heating may be attributed mainly to vascular occlusion. Proliferation of cells in the oxic area, and thus an increase in oxic cell number, appears to account for the decline in the proportion of hypoxic cells from 5 hr after heating.

Increase in tumor pO2 by perfluorochemicals and carbogen.

The effects of perfluorochemicals (Fluosol-DA) in combination with carbogen (95% O2 and 5% CO2) breathing on the tumor pO2 was investigated. The pO2 in RIF-1 tumors grown in the leg of C3H mice was determined by polarographic method using oxygen microelectrodes with diameters of 50-60 micron. The average and median pO2 in the control RIF-1 tumors was about 13 mm Hg and 6 mm Hg, respectively. Carbogen breathing alone could cause a significant increase in pO2 in some tumors and Fluosol-DA injection (i.v.) alone caused a slight change in tumor pO2. When the animals were treated with both Fluosol-DA injection and carbogen breathing, the pO2 markedly increased in most of the tumors resulting in an average and median tumor pO2 of 80 mm Hg and 60 mm Hg, respectively. Such an increase in tumor pO2 may account for the previous observations by us and others that the response of experimental tumors to radiation could be markedly increased by treating the tumor-bearing animals with carbogen and Fluosol-DA.