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![Dosimetry
• Sapareto & Dewey proposed concept of "Cumulative Equivalent Minutes" [CEM]
• Normalize thermal data from hyperthermia treatments using this relationship
• CEM 43°C = t R(43-T)
➤ where CEM 43°C is the cumulative equivalent minutes at 43°C , breakpoint temperature
• 43c ; above this temp 1c rise decrease time factor by 2 ,, below this temp 1c rise decrease need of time by 4 to 6 times ---
arrhenius plot
▸t is the time of treatment,
➤ T is this average temperature during desired interval of heating,
➤ R is a constant. (Above breakpoint R=0.5 and below=0.25)
For complex time-temperature history, heating profile is broken into intervals of time "t" length, where the temperature remains
relatively constant
CEM 43°C = [tR(43 -Tavg)
4/6/2022 23
Dr.G K PRAGATHEESWARI MMC](https://image.slidesharecdn.com/hyperthermia-220110180533/75/Hyperthermia-23-2048.jpg)
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Hyperthermia
- 1. HYPERTHERMIA PG – Dr.PragatheeswariG K Asst – Dr.Balaji S Chief –Dr Jeeva S 4/6/2022 1 Dr.G K PRAGATHEESWARI MMC
- 2. synopsis • Introduction • History •Effects of HT • Arrhenius plot • Factors influencing the effect of HT • Methods of heating • Thermal tolerance • Dosimetry • TER and therapeutic gain • HT RT CT 4/6/2022 2 Dr.G K PRAGATHEESWARI MMC
- 3. Introduction • Elevation oftemperature to supra- physiological level • >39 degree c 4/6/2022 3 Dr.G K PRAGATHEESWARI MMC
- 4. HISTORY • 3500 yearsago Egyptian papyrus – breast tumor treated with hyperthermia • Hippocrates 470 -377BC - those who cannot be cured by medicine can be cured by surgery . Those who can not be cured by surgery can be cured by fire. Those who can not be cured by fire are indeed incurable. • 1866 – german physician W.BUSCH patient with sarcoma of face disappeared after a prolonged infection with erysipelas • Erysipelas – infectious disease streptococcus pyogens , causes high fever 4/6/2022 4 Dr.G K PRAGATHEESWARI MMC
- 5. • Coley toxin– WILLIAM B COLEY mixed bacterial toxin, which induces high fever with which he treated many patients • 1898- westermark : Swedish gynaecologist published a paper – marked regression of large uterine sarcomas when treated with local hyperthermia 4/6/2022 5 Dr.G K PRAGATHEESWARI MMC
- 6. Effects of hyperthermia •Effects of hyperthermia is equal in both differentiated and undifferentiated cells • there is no major difference between normal and tumor cells, for response to hyperthermia • Heat kills cells ina predictable and repeatable way • Main target for cytotoxicity due to hyperthermia are proteins • Membrane components – changes in permeablity • Cytoskeleton - changes in architecture and stability, signal transduction pathways • DNA repair proteins - DNA damage and cell death , mech for heat induced radio and chemo sensitization 4/6/2022 6 Dr.G K PRAGATHEESWARI MMC
- 7. • Centriole damage– heat induced chromosomal aberrations • Activation energy for protein denaturation and activation energy for cytotoxicity are similar • There is a increased expression of heat shock proteins after tumor cells got heated 4/6/2022 7 Dr.G K PRAGATHEESWARI MMC
- 8. 4/6/2022 8 Dr.G KPRAGATHEESWARI MMC
- 9. HT AND CSS •Cells exposed for various temperature for different duration • Cell survival curve for heat are similar to those for xrays • But different mechansims for cell killing by heat and xrays • Energy involved in cell killing is 1000 times greater in heat than xrays • for lower temperatures the curves flatten out after protracted exposure, due to thermotolerance 4/6/2022 9 Dr.G K PRAGATHEESWARI MMC
- 10. • HT killscells in a log linear fashion depending on the time • Initial shoulder region indicates that damage has to accumulate to a certain level before begin to die • At lower temperature plateau is due to thermo tolerance 4/6/2022 10 Dr.G K PRAGATHEESWARI MMC
- 11. ARRHENIUS PLOT • Definestemperature dependence on the rate of cell killing • Biphasic curve • Obvious change in the curve is the breakpoint • Breakpoint – due to the development of thermotolerance during temp <43c and inhibition of thermotolerance >43c 4/6/2022 11 Dr.G K PRAGATHEESWARI MMC
- 12. Hyperthermia and otherfactors • pH modification – acute reduction in extracellular pH can greatly enhance sensitivity to hyperthermia • Cell cycle stage – cells in late S phase of cell cycle & hypoxic cells are radioresistant but are most sensitive to hyperthermia • Cells deficient in nutrition are certainly heat sensitive • Cells in tumor are nutritionally deprived and at acid pH , because of their remote location from blood capillary may be particularly sensitive to heat – large necrotic tumors shrink dramatically after heat treatment 4/6/2022 12 Dr.G K PRAGATHEESWARI MMC
- 13. At non cytotoxictemperatures • Temperatures <43c , mor particularly 40.5c to 41.5c • It is now seen that mild hyperthermia can promote tumor reoxygenation • The degree of reoxygenation correlates with the degree of radiosensitivity of tumor • BRIZEL and collegues showed that one HT led to reoxygenation within 24 to 48 hours , in conditions where no reoxygenation with one week of standard RT 4/6/2022 13 Dr.G K PRAGATHEESWARI MMC
- 14. IMMUNOLOGICAL EFFECTS OFHT • Thermal stimulation of anti tumor immune response • Current evidence that supports this possibility includes 1. Enhanced immunogenicity and heat shock protein expression seen after tumor cells are heated 2. Thermally enhanced immune effector cell activation and function 3. Thermally enhanced vascular perfusion and deliver or trafficking of immune effector cells to tumors 4/6/2022 14 Dr.G K PRAGATHEESWARI MMC
- 15. Methods of heating •In labs ; heating by water baths • Simplest and most reliable way to heat a petri dish or a tumor transplanted to mice leg is by – immerse it totally in a thermostatically controlled bath of water • Tumors in patients cannot be heated this way • It is challenging to produce uniform localised hyperthermia that can be correctly measured • Methods used are – microwaves , ultrasound, radiofrequency 4/6/2022 15 Dr.G K PRAGATHEESWARI MMC
- 16. • Microwaves –good localisation can be achieved at shallow depths. • But at greater depth tumors ,even if the frequency is lowered to allow deep penetration , localisatrion is poor and surface heating limits the use , recurrent chest wall nodules are treated with microwaves • Ultrasound – adequate penetration and reasonably good temperature distributions can be achieved in soft tissues , • The presence of bone and air cavities causes distortions of the heating pattern, deep seated tumors below the diaphragm are treated with focused array of ultrasound. 4/6/2022 16 Dr.G K PRAGATHEESWARI MMC
- 17. Thermal ablation • Destructionof tissue by extreme hyperthermia • The temperature change is concentrated to focal zone in and around the tumor • At 50c it takes few minutes to kill a cell • At 60c it takes only few seconds • Ablative heating is produced by needle type radiofrequency or microwave applicators ,1.5mm in diameter, which are inserted into to tumor under CT or USG guidance • Use – inoperable tumors in liver , osteoid osteoma, primary kidney tumors, inoperable pulmonary nodules 4/6/2022 17 Dr.G K PRAGATHEESWARI MMC
- 18. Thermotolerance • The developmentof transient and non hereditary resistance to subsequent heating by initial HT • Two ways of heating induce thermo tolerance 1. At lower temp 39 to 42c – induced during heating period after an exposure of 2 to 3 hours 2. Temp >43c – takes sometime to develop after heating has been stopped, it then decays slowly • For cells in culture which developed thermotolerance it takes more than 160 hours to revert back to normal or become heat sensitive • Field and law and collehgues at hammersmith hospital showed that for normal tissues such as gut skin and cartilage thermotolerance takes 1 or 2 days to reach maximum after heating and takes 1 to 2 weeks to deacy completely • Thermotolerance is limiting factor for clinical use of HT , because it imposes a limit of one or at most two HT per week 4/6/2022 18 Dr.G K PRAGATHEESWARI MMC
- 19. Thermal enhanmcement ratio •To estimate the thermal radiosensitization • The ratio of doses of xrays to produce given biological effect with or without hyperthermia • experimental animal studies show that TER is • 1.4 at 41c. • 2.7 at 42.5c and • 4.3 at 43c. • Gillette et al and overgrid et al studied TER for canine and human tumors and it is observed that in canine oral scc the TER is 1.15 when HT was administered twice weekly during fractionated RT • Use – of HT is the dose of RT can be limited well within the values at which it cause the normal tissue damage incase of oral scc it is taken as ORN of mandible. • TER is 1.15 for several superficially located human tumors 4/6/2022 19 Dr.G K PRAGATHEESWARI MMC
- 20. Therapeutic gain factor÷ • Defined as ratio of TER in tumor to TER in normal tissues • It is complicated in terms of heat, as tumor and normal tissues are not necessarily at the same temperature • For eg if a poorly vascularized tumor is heated with microwaves, It may reach a temperature higher than that of a normal tissues because less heat is carried away by the blood • In addition overlying skin can also be cooled by the draft of air or even a cold water pack. • So exaggerates the differential response • Hence therapeutic gain factor is not applicable for and not much of use in hperthermia 4/6/2022 20 Dr.G K PRAGATHEESWARI MMC
- 21. DOSIMETRY A. DIRECT /invasive methods : • For many years the only method of treatment monitoring, controland thermal dose calculation • Sensors should be able to measure temperatures to an accuracy and precision of about 0,1c in a waterbath 0.2c in EM or ultrasound fields 1. Electrically conducting : thermistor, thermocouple sensors. These are not suitable for EM fields 2. Minimally conducting : high resistivity thermistor with carbon impregnated plastic leads , accurate measurement in EM fields 3. Non conducting : optical sensors at tip of fibres , used in EM fields 4/6/2022 21 Dr.G K PRAGATHEESWARI MMC
- 22. Non invasive methods •Several noninvasive thermal measurement approaches are under investigation, 1. including infrared thermography and thermal monitoring sheet 2. fiber-optic arrays 3. electrical impedance tomography 4. microwave tomography 5. microwave radiometry 6. ultrasonic temperature estimation techniques, 7. magnetic resonance thermal imaging (MRTI) 8. Proton resonance frequency MRTI 4/6/2022 22 Dr.G K PRAGATHEESWARI MMC
- 23. Dosimetry • Sapareto &Dewey proposed concept of "Cumulative Equivalent Minutes" [CEM] • Normalize thermal data from hyperthermia treatments using this relationship • CEM 43°C = t R(43-T) ➤ where CEM 43°C is the cumulative equivalent minutes at 43°C , breakpoint temperature • 43c ; above this temp 1c rise decrease time factor by 2 ,, below this temp 1c rise decrease need of time by 4 to 6 times --- arrhenius plot ▸t is the time of treatment, ➤ T is this average temperature during desired interval of heating, ➤ R is a constant. (Above breakpoint R=0.5 and below=0.25) For complex time-temperature history, heating profile is broken into intervals of time "t" length, where the temperature remains relatively constant CEM 43°C = [tR(43 -Tavg) 4/6/2022 23 Dr.G K PRAGATHEESWARI MMC
- 24. Combining RT ANDHT • Cell in late S phase of cell cycle & Hypoxic cells are radio resistant but are most sensitive to hyperthermia. Cells in all stages of cell cycle are killed • Hyperthermia can lead to Reoxygenation which improves radiation response-Radiosensitization • Inhibits the repair of sub lethal & potentially lethal damage 4/6/2022 24 Dr.G K PRAGATHEESWARI MMC
- 25. Hyperthermia and chemotherapy •There may be several different mechanisms that underlie the interaction of heat with chemotherapeutic drugs These include 1. increased drug uptake and/or retention in cells, 2. increased DNA damage and inhibition of repair processes, 3. increased oxygen radical formation, and 4. increased vascular delivery and tumor penetration. 5. It is also clear that the extent of hypoxia and the pH of the tumor may affect the interaction between heat and chemotherapy 4/6/2022 25 Dr.G K PRAGATHEESWARI MMC
- 26. • Potentiated byheat Melphalan Cyclophosphamide BCNU Cis-DDP Mitomycin C Bleomycin Vincristine Unaffected by heat Hydroxyurea Methotrexate Vinblastine Complex interaction Doxorubicin 4/6/2022 26 Dr.G K PRAGATHEESWARI MMC
- 27. THERMOSENSITIVE LIPOSOMES • Liposomesconsist of a lipid membrane that can be filled with a cytotoxic chemotherapeutic agent such as doxorubicin. • Enhanced permeability and retention (EPR) effect:Long circulating liposomes that are covered with polyethylene glycol reduce recognition by the reticuloendothelial system and can extravasate from tumor blood vessels and accumulate in the extravascular space. • hyperthermia can increase the size of these pores and enhance drug delivery by four- to five fold over what can be achieved from just the EPR effect. • Further enhancement of drug delivery can be achieved by using thermally sensitive liposomes that are engineered to melt at mild temperatures (e.g., 41° to 42° C). These formulations yield further improvement in drug delivery by an additional factor of 4 to 5 versus nonthermally sensitive liposomes. 4/6/2022 27 Dr.G K PRAGATHEESWARI MMC
- 28. • Indeed, theselatter formulations have been shown to enhance doxorubicin delivery by 25- to 30-fold, compared with free drug, resulting in impressive antitumor effects in tumor that were completely refractory to free drug 4/6/2022 28 Dr.G K PRAGATHEESWARI MMC
- 29. TRIALS • CARCINOMA CERVIX- phase 3 in netherlands RT vs RT + HT , 361 patients - Complete response 57% vs 83% , 3yr sr - 27% vs 51% • RECURRENT CHEST WALL TUMORS - collaborative study of 5 trials • RT vs RT + HT , complete response in later , significant improvement in previously irradiated site • HEAD AND NECK CANCER - Valdagni Amichetti , stage III H & N cancers , 58% CR in RT+HT vs 20% RT • GBM - sneed et al ,also for • ESOPHAGEAL CANCER , HIGH GRADE SARCOMA , it is seen that HT + CT is more beneficial than CT alone 4/6/2022 29 Dr.G K PRAGATHEESWARI MMC
- 30. • SUPERFICIAL MALIGNANCIES- single institution randomized trial by JONES ET AL , superficial lesions <3cm . RT vs RT +HT - CR 42% vs 66% , • this was the study to capitalise on the idea that for hyperthermia act as a radio sensitizer 4/6/2022 30 Dr.G K PRAGATHEESWARI MMC
- 31. MAGNETIC HYPERTHERMIA • experimentalcancer treatment • magnetic nano particles ,when subjected to alternating magnetic field , generate a great deal of heat • in studies , transplanted tumors in mice , iron nanoparticles were injected iv, alloweed to circulate in blood,. • when nano particles accumlate in tumors, alternating magnetic field is applied ad it is seen that 60 c rise within few minutes • human studies for - prostate ca and GBM , iron particles were injected directly into the tumor than into blood • temperature of 40 to 48c rise is observed, this HT combined with RT 4/6/2022 31 Dr.G K PRAGATHEESWARI MMC
- 32. REFERENCE - ERIC.J.HALLtextbook of radibiology 4/6/2022 32 Dr.G K PRAGATHEESWARI MMC
- 33. THANK YOU 4/6/2022 33 Dr.GK PRAGATHEESWARI MMC