Combined effects of X rays, Ro 03-8799, and hyperthermia on growth, necrosis, and cell proliferation in a mouse tumor

Post-operative re-irradiation with hyperthermia in locoregional breast cancer recurrence: Temperature matters

PURPOSE

To investigate the impact of hyperthermia thermal dose (TD) on locoregional control (LRC), overall survival (OS) and toxicity in locoregional recurrent breast cancer patients treated with postoperative re-irradiation and hyperthermia.

METHODS

In this retrospective study, 112 women with resected locoregional recurrent breast cancer treated in 2010-2017 with postoperative re-irradiation 8frx4Gy (n = 34) or 23frx2Gy (n = 78), combined with 4-5 weekly hyperthermia sessions guided by invasive thermometry, were subdivided into 'low' (n = 56) and 'high' TD (n = 56) groups by the best session with highest median cumulative equivalent minutes at 43 °C (Best CEM43T50) < 7.2 min and ≥7.2 min, respectively. Actuarial LRC, OS and late toxicity incidence were analyzed. Backward multivariable Cox regression and inverse probability weighting (IPW) analysis were performed.

RESULTS

TD subgroups showed no significant differences in patient/treatment characteristics. Median follow-up was 43 months (range 1-107 months). High vs. low TD was associated with LRC (p = 0.0013), but not with OS (p = 0.29) or late toxicity (p = 0.58). Three-year LRC was 74.0% vs. 92.3% in the low and high TD group, respectively (p = 0.008). After three years, 25.0% and 0.9% of the patients had late toxicity grade 3 and 4, respectively. Multivariable analysis showed that distant metastasis (HR 17.6; 95%CI 5.2-60.2), lymph node involvement (HR 2.9; 95%CI 1.2-7.2), recurrence site (chest wall vs. breast; HR 4.6; 95%CI 1.8-11.6) and TD (low vs. high; HR 4.1; 95%CI 1.4-11.5) were associated with LRC. TD was associated with LRC in IPW analysis (p = 0.0018).

CONCLUSIONS

High thermal dose (best CEM43T50 ≥ 7.2 min) was associated with significantly higher LRC for patients with locoregional recurrent breast cancer treated with postoperative re-irradiation and hyperthermia, without augmenting toxicity.

Temperature and thermal dose during radiotherapy and hyperthermia for recurrent breast cancer are related to clinical outcome and thermal toxicity: a systematic review

Objective: Hyperthermia therapy (HT), heating tumors to 40-45 °C, is a known radiotherapy (RT) and chemotherapy sensitizer. The additional benefit of HT to RT for recurrent breast cancer has been proven in multiple randomized trials. However, published outcome after RT + HT varies widely. We performed a systematic review to investigate whether there is a relationship between achieved HT dose and clinical outcome and thermal toxicity for patients with recurrent breast cancer treated with RT + HT. Method: Four databases, EMBASE, PubMed, Cochrane library and clinicaltrials.gov, were searched with the terms breast, radiotherapy, hyperthermia therapy and their synonyms. Final search was performed on 3 April 2019. Twenty-two articles were included in the systematic review, reporting on 2330 patients with breast cancer treated with RT + HT. Results: Thirty-two HT parameters were tested for a relationship with clinical outcome. In studies reporting a relationship, the relationship was significant for complete response in 10/15 studies, in 10/13 studies for duration of local control, in 2/2 studies for overall survival and in 7/11 studies for thermal toxicity. Patients who received high thermal dose had on average 34% (range 27%-53%) more complete responses than patients who received low thermal dose. Patients who achieved higher HT parameters had increased odds/probability on improved clinical outcome and on thermal toxicity. Conclusion: Temperature and thermal dose during HT had significant influence on complete response, duration of local control, overall survival and thermal toxicity of patients with recurrent breast cancer treated with RT + HT. Higher temperature and thermal dose improved outcome, while higher maximum temperature increased incidence of thermal toxicity.

Arrays of multielement ultrasound applicators for interstitial hyperthermia

Arrays of multielement ultrasound applicators for interstitial hyperthermia have been developed and tested both in vitro and in vivo. The system includes multielement applicators, a 64 channel RF driving unit, a power measuring unit, a 112 channel multisensor temperature measuring unit, and a water cooling unit. Ninety-five arrays of single-element and nine arrays of three-element ultrasound applicators were designed, built, and characterized by measuring transducer efficiency and ultrasound field distribution. Improved uniformity in the azimuthal direction was achieved by using multiple driving frequencies. In addition, production of ultrasound in a desired sector of the transducer was possible by selecting a suitable frequency. Both in vitro and in vivo experiments showed that 92% of monitored temperature points within the target volume of 30 mm x 30 mm x 35 mm achieved a therapeutic temperature rise (above 5 degrees C) when an array of five three-element applicators were used. These results indicated that the arrays of multielement ultrasound applicators have distinct advantages over present interstitial hyperthermia modalities in terms of the capability to control the temperature distribution with a large catheter spacing. As a conclusion, the feasibility of a practical arrays of multielement ultrasound applicators for interstitial hyperthermia was demonstrated.

Levels of selected growth factors in viable and necrotic regions of xenografted HCT-8 human colon tumours

Xenografted tumours were produced in nude mice by injection of HCT-8 human colon tumour cells. At average volumes of about 750 mm3, animals were injected with fast green vital dye, and 20 min later, tumours were excised and dissected into viable (stained) and necrotic portions (unstained). Viable and necrotic regions were then examined for cell yields, colony forming efficiencies, and levels of basic fibroblast growth factor (FGF-2), transforming growth factors-beta 1 and -alpha (TGF-beta 1, TGF-alpha), platelet derived growth factor (PDGF), and vascular endothelial growth factor (VEGF) using enzyme-linked immunoassay (ELISA) procedures. Levels in the viable and necrotic regions were compared to levels in unseparated tumours. The average extent of necrosis in HCT-8 tumours of this size was 64%. The data for cell yields, colony forming efficiencies FGF-2, VEGF, TGF-beta 1 and TGF-alpha indicated that values determined in the unseparated tumours could be understood on the basis of the weighted average between viable and necrotic tissue, with the higher values occurring in the viable tissue. Low levels of FGF-2 and VEGF were found in the necrotic portions of the tumour while no measurable levels of TGF-beta 1 and TGF-alpha could be determined. PDGF levels were, however, equivalent in both the viable and necrotic regions indicating that necrotic tissue could be an important reservoir for this growth factor.

The advantageous use of hypoxic tumour cells in cancer therapy: identical chemosensitization by metronidazole and misonidazole at moderately elevated temperatures

Chemosensitization by two nitroimidazoles (NIs), metronidazole (METRO) and misonidazole (MISO), of the anti-tumour effect of alkylating agents was studied at three different temperatures: room temperature (RT), 37 and 41.5 degrees C. Three alkylating agents, cyclophosphamide (CY), 1,3 bis(2-chloroethyl)-N-nitrosourea (BCNU) and melphalan (L-PAM) were tested when the tumours reached an average diameter of 4 mm. Tumours were 4th generation isotransplants of a spontaneous fibrosarcoma, FSa-II. Treatment at 37 or 41.5 degrees C was given by immersing the tumour-bearing foot for 60 min in a water bath set at these temperatures. The test agents were injected ip immediately before immersing the foot in the water bath, whereas METRO or MISO (2.5 mmol/kg) was given ip 30 min before the injection of a test agent. Following treatment the tumour growth (TG) time, i.e. the time required for one-half of treated tumours to reach 1000 mm3 after the treatment day, was studied. For CY, MISO was a better sensitizer than METRO at RT and 37 degrees C, but the magnitude of the chemosensitization by MISO and METRO became identical at 41.5 degrees C. Notably, the chemosensitization was substantially enhanced at 41.5 degrees C, whereas neither 41.5 degrees C-heat, NIs or combined NI and heat prolonged the TG time. Although no chemosensitization was observed for BCNU at RT, both METRO and MISO equally enhanced the effect of BCNU at 41.5 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Modification of radiation-induced chromosome damage and micronucleus induction in mouse bone marrow by misonidazole and hyperthermia

The effect of misonidazole (MISO), local hyperthermia (HT) and their combination on radiation-induced chromosome damage and micronucleus (MN) induction was studied in mouse bone marrow cells. It was found that MISO treatment did not enhance the clastogenic effect of radiation, which indicates a lack of radiosensitization of bone marrow chromosomes. But post-irradiation HT increased the frequency of aberrant cells and MN. A combination of MISO and HT produced a significant increase in the frequency of radiation-induced aberrant cells and MN at all the radiation doses as compared to radiation alone. The percentage of aberrant cells as well as the percentage of MN showed a linear quadratic increase with radiation dose in all the treatment groups. At higher radiation doses, cells with > 1 MN increased quadratically with a pronounced increase in cells bearing > 2 MN and severely damaged cells (SDCs) at radiation doses above 3.0 Gy in the HT and MISO+HT treated groups. Our results indicate that though MISO itself may not have a radiosensitizing effect on mouse chromosomes, a combination of MISO with HT can enhance the radiation damage in normal bone marrow.

Effects of local hyperthermia on the tissue levels and toxicity of three radiosensitizers in mice

The toxicity of the radiosensitizers misonidazole (MISO), demethylmisonidazole (DEMISO) and pimonidazole (PIM) in mice can be affected differently when combined with local hyperthermia at 43 degrees C for 30 min. At a dose of 1 mg/g, only MISO plus heat resulted in 50% lethality in animals over a period of 7 days post-treatment, whereas 100% survival was observed in the case of DEMISO and PIM. The enhanced lethality may be associated with the production of toxic intermediates of MISO. Heat did not affect the levels of DEMISO in the tissues studied (plasma, brain and tumour), whereas those of PIM were markedly lowered in tumour but not affected in brain for up to 4 h after combined treatment. MISO was found to be decreased in the tumour at all times but affected differently in brain after 1 and 2 h, initially decreasing and then increasing significantly. In all cases the treatment sequence, i.e. sensitizer plus heat or vice-versa, did not affect the rate of survival. At a dose of 2 mg/g, DEMISO plus heat was found to be more toxic when DEMISO was given first (25% survival) compared to 58% on reversal. However, the levels of DEMISO in the tissues were not affected by heat. Thus, it would appear that there is no correlation between parent drug levels measured in plasma, tumour or brain and hyperthermia-induced drug lethality.

Quantitative histological changes in a human melanoma xenograft following exposure to single dose irradiation and hyperthermia

The purpose of the present paper is, in terms of quantitative histology, to explain the growth response of a human melanoma xenograft after exposure to single dose irradiation (7.5 Gy, 15.0 Gy, and 25.0 Gy) and hyperthermia (42.5 degrees C for 60 min). Data from several experiments on the mitotic activity, the occurrence of different modes of cell death and reproductively dead cells in the tumors are discussed. The tumor cell proliferation is only transiently reduced after 7.5 Gy and 15.0 Gy, and tumor regression mainly results from an increased cell loss. Cell loss through apoptosis and cell disintegration during mitosis show a dose-dependent increase after irradiation. Although the fraction of necrosis, relative to the number of tumor cells, increases after 7.5 Gy and 15.0 Gy, the cell loss through necrosis, that is, the production of necrosis, is probably reduced. Compared to the cell loss through apoptosis and mitotic death, the removal of necrosis is probably less important in determining the regression rate of the tumors after 7.5 Gy and 15.0 Gy. After 25.0 Gy the cell production is markedly reduced, and cell loss increases, partly due to radiation injury to the vascular system, resulting in necrotization of the tumor core. Thereafter, the tumor regression rate depends mainly on the rate of necrosis removal. The mitotic activity of remaining cells is not reduced after hyperthermic treatment, and the tumor growth response is a result of an increased cell loss. Although the occurrence of apoptosis and cell disintegration in mitosis increases after hyperthermia, these modes of cell loss are of minor importance for the tumor regression after treatment. The increased cell loss is mainly due to massive necrosis formation in the central tumor areas, a result of heat injury to tumor blood vessels. After necrotization of the tumor core, the regression rate depends mainly on the rate of necrosis removal.