Radiosensitizers and Biological modifiers in Radiotherapy

Radiosensitizers and Biological modifiers in Radiotherapy
Dr. Sandeep G

1. RADIOSENSITIZERS Dr. Sandeep Gedela PGIMER, Chandigarh

2. Radiosensitivity Relative susceptibility of cells,tissues,organs or organisms to the harmful effect of ionizing radiation Bergonie and Tribondaeu ’s law: Tissues will be more radiosensitive if: The cells are undifferentiated They have greater proliferative capacity They divide more rapidly

3. RADIOSENSITIZATION Radiosensitization is a physical, chemical or pharmacological intervention that increases the lethal effect of radiation when administered in conjunction with it To make tumour cells more sensitive to radiotherapy Clinical benefit can be expected only if there is differential effect demonstrated between tumours and normal tissues

4. Mechanisms of radiosensitization DNA sensitivity  direct & indirect Modulate biological response of irradiated cells Counteracting tumour hypoxia Increase in initial radiation damage Cell cycle redistribution Inhibition of cellular repair Overcoming accelerated repopulation Targeting molecular events assosciated with radiation response

5. Radiosensitive phase of cell cycle

6. M> G2> G1> early S> late S

7. Need of radiosensitizer Goal  shrink tumour and kill cancer cells by high energy radiation Despite effectiveness, harmful damage caused by such radiation to normal cells is unavoidable Radiosensitiser

8. RADIOSENSITISER : Radiosensitizer is the agent that increase the lethal effects of radiation when administered in conjunction to radiotherapy. To be clinically effective they should improve the therapeutic ratio ie TCP/NTCP, because if an intervention equally increases the effect and side effect then it is not useful. A radiosensitizer may or may not have lethal effects against tumor cells when administered alone without radiation

9. Therapeutic ratio Therapeutic ratio: TCP/NTCP As the separation between these curves increases, the likelihood increases that treatment will be effective and without causing unacceptable level of morbidity Efficacy and toxicity of radiosensitizing agent directly effects  TR

10. Characterstics of ideal radiosensitiser Lack of toxicity Potent radiosensitizing effect Non-cell cycle specificity Amenable to dose intense or prolonged infusion schedules Adaptable to convenient out-patient administration

11. Evaluation of radiosensitization effect In vitro clonogenic assay by measuring no. of colonies formed after irradiation of tumour cells using several irradiation doses Comparing cell survival curves after radiation alone or in presence of radiosensitiser

12. IN VIVO

13. Types of radiosensitisers PHYSICAL CHEMICAL HYPERTHERMIA HYPERBARIC OXYGEN CARBOGEN+/- NICOTINAMIDE ARCON MODIFIERS OF HAEMOGLOBIN NON HYPOXIC CELL SENSITISERS HYPOXIC CELL SENSITISERS HYPOXIC CYTOTOXINS BIOLOGICAL MODIFIERS CHEMOTHERAPEUTIC DRUGS

14. HYPERTHERMIA Tumours are heated using exogenous energy source Heat directly kills cancer cells , but also synergises with radiotherapy and/or chemotherapy to increase therapeutic window Temperature 39-45°c Mild temperature hypothermia < 40°c Thermal ablation > 45°c

15. HISTORY OF HYPERTHERMIA Use of heat to cancer is one of the oldest therapies First application is quoted in EDWIN SMITH SURGICAL PAPYRUS where patient with breast cancer is treated with heat 5000yrs back 1800’s use of of fever induced treatment to control tumour growth by coley’s toxin 1 st real attempt  westermark in 1898 used water circulating cisterns to treat uterine carcinomas with 42-44°c

16. Hyperthermia Elevation of temperature to supraphysiological level between 40 and 45 degree C Interaction between RT & HT described by – Thermal Enhancement Ratio (TER ) – ratio of doses of radiation with & without heat to produce same biological effects Maximum interaction when heat & radiation given simultaneously TER ↓es with ↑ ing time interval between heat & RT When RT precedes HT – sensitization no longer detectable 2-3 hrs after RT When HT precedes RT – cells can be sensitized for upto several hrs

17. Hyperthermia… Clinical hyperthermia achieved by exposing tissues to – Conductive heat sources Non – ionizing radiation – e.g. electromagnetic or ultrasonic Deposit energy in tissues by different mechanisms Sensitive to heterogeneity of tissue properties, geometry of blood flow Can be administered using – Invasive sources –– designed for direct application into tissue or for intracavitary use -- include radiofrequency antennas, RF electrodes, hot water tubes, ferromagnetic metals & US transducers Noninvasive - using externally applied power Side effects – superficial or subcutaneous tissue burns – occurs in approx 5% of all HT t/t sessions

18. Magnetic hyperthermia therapy Heat generation using magnetic nanoparticles in response to an externally applied alternating magnetic field MNPs are specifically targeted to tumour site for homogenous heating Localised and controlled heating Repeated and intracellular heating possible with single injection Efficient targeting of resistant tumour cells

19. Prospective randomized trials Trial n CR for RT CR for RT +HT p value Advanced H & N cancer Datta et al 52 13% 46% <0.05 Valdagni et al 40 41% 83% 0.016 ESHO-2 et al 62 53% 50% NS Advanced Breast Cancer MRC et al 143 64% 71% NS

20. Prospecti v e randomized trials Trial n CR for RT CR for RT + HT p value Advanced Cervix/Rectal/Bladder Cancers DDHG 143(rectal) 114(cervix) 101(bladder) 15% 57% 51% 21% 83% 73% NS 0.003 0.01 Harima 40 50% 80% 0.048

21. HYPOXIA Tumour vasculature Slow rate of proliferation  decreased sensitivity to chemotherapy and radiotherapy concentration of anticancer drugs lesser in cells away from blood vessels leads to less killing of hypoxic cells

22. Hypoxia  tumour progression

23. Oxygen effect Oxygen acts at the level of free radicals Oxygen sensitization occurred as late as 0.01 msec after irradiation Rapidly growing cells have OER 2.5 Phase of cell cycle

24. H & N tumor oxygenation

25. Methods to Sensitize or Eliminate Hypoxic Cells Physical Overcoming hypoxia by eliminating it with treatment that increases delivery of oxygen to tumor i.e. increases the oxygen carrying capacity of blood and increasing the tumor blood flow Hyperbaric oxygen Carbogen with or without nicotinamide

26. Hyperbaric oxygen An increase in barometric pressure of the gas breathed by the patient during radiotherapy is termed as hyperbaric oxygen therapy Pioneered by Churchill and Davidson in 1968 at st. Thomas hospital in London Increases plasma and tissue oxygen 10times  maintain tissue viability Increases VEGF secretion as well as secretion of matrix by fibroblasts

27. Placing the patient in a compression chamber, increasing the environmental pressure within the chamber, and administering 100% oxygen for respiration Tumour o2 sensitisation involves pressurisation to between 2 to 4 atmospheres absolute for periods of 20 to 30 minutes, following which radiation therapy is delivered

28. Meta analysis

29. Advantages Stimulates oxygenation  increasing radiosensitivity Promotes growth of new capillaries and blood vessels boosts the efficacy of chemptherapeutic drugs Treatment of radiation induced bone and soft tissue necrosis in head and neck region Used along with anti coagulation therapy in treatment of cerebral radionecrosis Boosts circulating stem cells Supports faster wound healing

30. Problems Feeling of claustrophobia being sealed in closed narrow tube Cumbersome logistics assosciated with delivery, use of non conventional hypofractionated regimens Side effects Barotruma  ears ,sinuses and lungs Temporary worsening of myopia Oxygen toxicity seizures With the advent of better chemical radiosensitisers that would acheueve same end by the simpler means

31. carbogen Pure oxygen if breathed – vasoconstriction - closing down of some blood vessels – defeats the object Carbogen – 95% O 2 +5% CO 2 Rationale – addition of CO 2 to gas breathing mixture - shift the oxyHb association curve to right – facilitate unloading of oxygen into most hypoxic tissues Simple attempt to overcome chronic hypoxia Can be given with or without concurrent administration of nicotinamide

32. Nicotinamide Vitamin B3 or niacinamide Co factor of NADPH oxidase2  angiogenesisprevent fluctuations in tumour blood flow increases prevents acute hypoxia Inhibition of PARP  inhibition of DNA repair 60-80mg/kg, 1to 1 1/2hr before radiation

33. Phase II study by Hoskin et al 335 patients with locally advanced bladder cancer randomly assigned to RT alone versus RT with carbogen and nicotinamide 55Gy in 20#/4weeks are given OS  59% vs 46% RFS  54% vs 43%

34. ARCON Use of acclererated radiotherapy with carbogen and nicotinamide tested in head and neck cancer patients

35. Phase III study in head and neck cancer patients

36. ARCON in GBM

37. Modifiers of hemoglobin

38. Blood transfusion Anemia – adverse prognostic factor in pts of Ca Cervix, H& N cancers & lung cancer Haemoglobin is the first investigation in cervical cancer patients Transfusion to pts with low Hb levels - ↑ed oxygen tension within tumor Transfusion to Hb level of 11g/dl or higher – improved survival H & N Cancer pts – 2 phase II trials from DAHANCA study group – failed to demonstrate any benefit

39. Erythropoetin Recombinant human erythropoietin : alternative means of raising haemoglobin during radiotherapy Two studies conducted in H & N cancers failed to show any benefit Dose : 200u/kg/day x 5 days/week  increase in Hb by 1-3gm/dl Induces prompt reticulocyte response from 2.4 to 4.9% Expensive than BT In one of the studies – pts who received erythropoetin showed significantly poor outcome than those who did not ? Erythropoietin may stimulate tumor growth STUDY

40. perfluorocarbons Artificial blood substances Small particles capable of carrying more oxygen or manipulating the oxygen unloading capacity of blood Potential usefulness uncertain

41. Non hypoxic cell sensitiser Halogenated pyrimidines Non hypoxic cell sensitizer ( Halogenated pyrimidines) Sensitizes cell to degree dependent on amount of analogue incorporated Differential effects --Tumor cells cycles faster and therefore incorporates more drug than normal tissue 5- bromodeoxyuridine 5-iododeoxyuridine Incorporated into DNA in place of thymidine Cell cycle specific radiosensitisers

42. Extended exposure must be required for incorporation into DNA Tumour responses are good but tissue damage is unacceptable

43. Budr & iudr

44. Hypoxic radiosensitisers Instead of forcing oxygen into hypoxic cells by use of high pressure tanks, the approach shifted to oxygen substitutes These compounds selectively activated in the hypoxic environment of tumour cells Electronisc affinic compounds oxidise radiation induced free redical damage in the cell to produce increased kill Useful in hypoxic tumour microenvironment

45. Properties of clinically useful hypoxic cell sensitizer Selectively sensitize hypoxic cells at concentration that would result in acceptable normal tissue toxicity Chemically stable & not subject to rapid metabolic break down Highly soluble in water or lipids & must be capable of diffusing a considerable distance through a nonvascularized cell mass to reach the hypoxic cell It should be effective at relatively low daily dose /# used in conventional fractionated radiotherapy

46. Development of nitroimidazoles

47. Metronidazole 1 st generation 5-nitroimidazole Sensitizer Enhancement ratio - 1.2 Formulations - 500 mg tablets or 500mg /100 ml solution Half life – 9.8 hrs Total cumulative dose not to exceed 54 gm/m 2 Multiple doses 6gm/m 2 3 times/wk for 3- 4week Optimal time for administration - 4 hour before radiation Dose limiting toxicity – Gastrointestinal Sensory peripheral neuropathy

48. Misonidazole 2 nd generation 2- nitroimidazole Higher electron affinity Sensitizer Enhancement ratio – 1.4 with multiple dose of 2 gm/m 2 1.15 with 0.5mg/m 2 Formulations 500 and 100 mg tablets and capsules once or twice/ wk for 5-6 wks Total cumulative dose not to exceed 12 gm/m 2 Optimal time for administration -- 4 hour before radiation Dose limiting toxicity- gastrointestinal Sensory peripheral neuropathy that progress to central nervous system toxicity

49. Radiation Sensitization by Misonidazole

50. Reasons for Failure of Misonidazole Clinically Dose limiting toxicity – peripheral neuropathy If drug not stopped – progression to CNS toxicity Toxicity prevented use of drug at adequate dose levels throughout multifraction regimens

51. Etanidazole (SR 2508) 3 rd generation, analog of Misonidazole SER- 2.5-3 with dose of 12 g/m 2 Shorter half life Lower lipid solubility, less neurotoxicity Arthralgia seen more often with 48 hr continuous infusion 1000mg/19.4 ml saline solution Total dose - 40.8 g/m 2 at 1.7-2g/m 2 3 times/ wk for 6 wks 30 min before radiation

52. pimonidazole 4- nitroimidazole More potent than Misonidazole Several – fold ↑ in tumor concentration Maximum tolerated dose – 750 mg/m2 Dose limiting toxicity – CNS manifesting as disorientation & malaise Randomized trial conducted in advanced Ca Cervix –showed no benefit

53. Nimorazole A 5-nitroimidazole of same structural class as metronidazole Administered in form of gelatin-coated capsules containing 500 mg active drug Given orally 90 min prior to irradiation. Daily dose 1200 mg/m 2 body surface given in connection with first 30 radiation treatment fractions. Total dose should not exceed 40g/m 2 or 75 g in total. Less effective radio sensitizer then Misonidazole or Etanidazole Less toxic, no cumulative neuropathy Large dose can be given dose-limiting toxicity is nausea and vomiting however, the drug can be administered with each radiation treatment

54. Multicentre randomized trials with nitroimidazoles

55. Etanidazole RTOG phase III study with Etanidazole in head and neck tumors n- 521 patients Conventionally fractionated RT RT with Etanidazole 2mg/m2 with out Etanidazole three times wk No grade III or IV central nervous system or peripheral neuropathy was observed. The 2-year actuarial local tumor control was 40% in each arm, and the survival was 41% and 43%, respectively, in the irradiation alone and the irradiation plus etanidazole arms No overall benefit when Etanidazole added to conventional radiotherapy

56. Nimorazole

57. Nimorazole – dahanca 5 Significant improvement in terms of LRC & OS Nimorazole significantly improves the effect of radiotherapeutic management of supraglottic and pharynx tumors and can be given without major side-effects

58. Head & neck CA TRIALS No. of pts Sensitizer RT & Sensitizer RT alone DAHANCA 2 (1989) 626 Miso 41% 34% MRC (1984) 267 Miso 40% 365 EORTC (1986) 163 Miso 52% 44% RTOG (1987) 306 Miso 19% 24% RTOG 79-04 (1987) 42 Miso 17% 10% DAHANCA 5 (1992) 414 Nim 49% 34% RTOG 85-27 (1995) 500 Eta 39% 38%

59. Ca cervix TRIALS No. of pts Sensitizer RT & Sensitizer RT alone Scandinavian (1989) 331 Miso 50% 54% MRC (1984) 153 Miso 59% 58% RTOG (1987) 119 Miso 53% 54% MRC (1993) 183 Pim 64% 80%

60. GBM & BRONCHOGENIC CA TRIALS No. of pts Sensitizer RT & Sensitizer RT alone GLIOBLASTOMA MRC (1983) 384 Miso 8 mths 9 mths EORTC (1983) 163 Miso 11 mths 12 mths BRONCHOGENIC CA RTOG (1987) 117 Miso 7 mths 7 mths RTOG (1989) 268 Miso 7 mths 8 mths

61. Summary of efficacy of clinical trials with nitroimidazoles Compounds Trials (n) Significant benefit No benefit Metronidazole 1 1 _ Misonidazole / Nimorazole 38 5 33 Etanidazole 7 _ 7 Pimonidazole 1 _ 1

62. Hypoxic cytotoxins…

63. Quinone antibiotic - Mitomycin C Prototype bioreductive drug Used as chemotherapy agent for many years Cytotoxic to relative radio resistant hypoxic cells But the differential cytotoxicity between hypoxic and oxygenated cells , however is small Acts as an alkylating agent after intracellular activation & inhibits DNA – DNA cross linking, DNA depolymerization Dose limiting toxicity – cumulative myelosuppression Mitomycin C plays an important role in conjunction with radiotherapy and 5FU, the definitive, chemoradiation squamous cell carcinoma of the anal canal

64. Porfiromycin A mitomycin C derivative Provides greater differential cytotoxicity between hypoxic and oxygenated cells in vitro Phase III study Compared patients treated with conventionally fractionated radiation plus mitomycin C versus radiation plus porfiromycin The median follow-up - >6 years. Hematologic and non-hematologic toxicity was equivalent in the two treatment arms Mitomycin C was superior to porfiromycin with respect to 5-year local relapse-free survival (91.6% vs. 72.7%; p = 0.01)

65. Local-regional relapse-free survival (82% vs. 65.3%; p = 0.05) Disease-free survival (72.8% vs. 52.9%; p = 0.03) There were no significant differences between the two arms with respect to overall survival (49% vs. 54%) or distant metastasis-free rate (80% vs. 76%) Their data supported the continuing use of mitomycin C as an adjunct to radiation therapy in advanced head and neck cancer and will become the control arm for future studies Porfiromycin…

66. Tirapazemine ( sr 4233 ) Highly selective toxicity against hypoxic cells both in vivo and vitro This bioreductive agent is itself cytotoxic to hypoxic tissues MOA- Drug is reduced by intracellular reductases to form highly reactive radical - produces both double & single strand breaks in DNA Analysis of DNA and chromosomal breaks after hypoxic exposure to Tirapazemine suggests that DNA double-strand breaks are the primary lesion causing cell death Efficacy depends on no. of effective doses that can be administered during course of RT & presence of hypoxic tumor cells S/E – nausea & muscle cramping

67. Tirapazemine Hypoxic/cytotoxicity ratio – ratio of drug concentration under aerated and hypoxic condition required to produce same cell survival Unlike the oxygen-mimetic sensitizers, tirapazamine -mediated therapeutic enhancement occurs both when the drug is given before or after irradiation. Tirapazamine can also enhance the cytotoxicity of cisplatin

68. N= 121 stage III/IV SCC of the head and neck randomized to receive definitive radiotherapy (70 Gy in 7 weeks) Tirapazamine On day 2 of weeks 1, 4, and 7, 290 mg/m2 was administered for 2 hours, followed 1 hour later by cisplatin 75 mg/m2 for 1 hr followed immediately by radiotherapy In addition, tirapazamine 160 mg/m2 was given before radiation three times/week in weeks 2 and 3 Cisplatin 50 mg/m2 was given before radiotherapy on day 1 of weeks 6 and 7 of radiotherapy and Fluorouracil 360 mg/m2/d was given by continuous infusion from day 1 - 5 (120-hour infusion) of weeks 6 and 7 of radiotherapy Arm 2. n-58 Arm 1,n-62

69. Three-year failure-free survival rates were 55% with TPZ/CIS and 44% with chemo RT( p .16) Three-year locoregional failure-free rates were 84% in the TPZ/CIS arm and 66% in the chemo RT arm ( p .069) Toxicity More febrile neutropenia and grade 3 or 4 late mucous membrane toxicity were observed with TPZ/CIS Compliance with protocol treatment was satisfactory on both arms

70. Tirapazemine …… A phase III trial has been conducted to validate the concept of targeting of hypoxic cells in head and neck cancer Concurrent chemoradiation with standard fractionation RT (70 Gy ) and tirapazamine /cisplatin was tested against conventional chemoradiation with standard single agent cisplatin This trial enrolled 880 patients and is in a follow-up phase

71. Biologic modifiers

72. Biologic Modifiers of Radiation Response The EGFR system represents a promising therapeutic target because it is commonly over expressed in H & N tumor Tumor levels of EGFR and its ligand -significant predictors of tumor staging and clinical outcome. In addition, several studies have reported that repopulation of epithelial tumor cells after exposure to radiation is related to the activation and expression of EGFR These findings suggest that EGFR blockade may be important in reducing tumor cell repopulation by modulation of cellular proliferation and enhancement of tumor radioresponse

73. Cetuximab Specifically targets EGFR with high affinity & blocks ligand binding Enhances antitumor activity of cisplatin Enhances antitumor activity of radiotherapy Showed activity in pts with SCCHN & documented platinum resistance EGFR inhibition is a promising new approach for radiosensitization Need to drive predictive biomarkers to assess response to molecular therapies Optimize radiotherapy fractionation schemes to complement targeted agents

74. Dose, schedule & toxicity Intravenous cetuximab given one week before radiotherapy Loading dose of 400 mg per square meter of BSA over a period of 120 minutes, followed by weekly 60-minute infusions of 250 mg per square meter for the duration of radiotherapy Premedication to be given Before the initial dose , a test dose of 20 mg should be infused over a 10-minute period, followed by a 30-minute observation period Side effects Infusion reaction - angioedema , urticaria , hypotension , bronchospasm Hypersenstivity reactions, acniform rash

75. Results Bonner , Harari , Giralt etal N Engl J Med 354;567-78. 2006

76. Results contd… Bonner , Harari , Giralt etal N Engl J Med 354;567-78. 2006

77. Drug Radiation Interactions : Mechanisms Enhancement of tumour Radioresponse Denotes interaction between drugs & radiation at molecular, cellular or metabolic level Increasing initial Radiation damage Acts through DNA damage------Cell Death Drugs make DNA more susceptible to radiation eg Halogenated pyrimidines Inhibition of repair of Sublethal radiation damage or recovery from Potentially lethal damage Chemotherapeutic agents interact with cellular repair mechanisms & inhibit repair----enhance response to radiation

78. Drug Radiation Interactions : Mechanisms Cell cycle redistribution & synchronization Cells in G 2 -M phase - thrice as sensitive as S phase cells Agents may block transition of cells thru mitosis – accumulates in G 2 -M phase – enhanced radiosensitivity . E.g.. Taxanes Elimination of radioresistant S phase cells. E.g.. Gemcitabine – gets incorporated in S phase – induce apoptosis

79. 5- fluorouracil (Anti-metabolite) Incorporation into RNA----disruption of RNA function Inhibition of Thymidylate Synthetase function – inhibits DNA synthesis and results in accumulation of cells in early S phase Combination of these effects underlie its radio sensitizing effect The combination of FU and radiation is a mainstay of treatment for GI tumors, where it has a proven role in improving locoregional control and survival

80. Cisplatinum (cis diamminedichloroplatinumII ) Cell cycle non specific More toxic to hypoxic then aerated cell i.e hypoxic cell sensitizer though not powerful as nitroimidazole Also, radiation induces increased cellular Cisplatin uptake When used concurrently with radiation, substantial enhancement of cell kill observed Coughlin and Richmond and Douple suggested two mechanisms of radiation enhancement by platinum: (a) in hypoxic or oxygenated cells, free radicals with altered binding of platinum to DNA are formed at the time of irradiation (b) interaction inhibits repair of radiotherapy induced potentially lethal or sub lethal damage

81. taxanes Taxanes (Mitotic spindle Inhibitors) Cellular arrest in G2/M phase – highly radiosensitive Induction of apoptosis Reoxygenation

82. Mechanisms of Radiosensitization for Antimetabolites