Low dose rate versus high dose rate brachytherapy for carcinoma cervix

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Carcinoma cervix is the second most commonly occuring cancer in India.
Brachytherapy forms the most important part radiation therapy
Low dose rate Brachytherapy – Gold Standard
Experience more than a century

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Low dose rate versus high dose rate brachytherapy for carcinoma cervix

  1. 1. Low Dose Rate Versus High Dose Rate brachytherapy in Ca.Cervix
  2. 2. Introduction • Carcinoma cervix is the second most commonly occuring cancer in India. • Brachytherapy forms the most important part radiation therapy
  3. 3. • Low dose rate Brachytherapy – Gold Standard • Experience more than a century….
  4. 4. HDR for Ca. Cerix ??
  5. 5. Radiobiological advantages…..
  6. 6. Repair The lower the dose rate of radiation a cell is exposed to, the greater the likelihood of repair. Late-reacting normal tissues seem more capable of repair than tumor The tumor is preferentially killed over normal tissue.
  7. 7. Reoxygenation • Because of the duration of administration of LDR, acute hypoxia corrects within the tumor during treatment • Oxygen enhancement ratio is lower for LDR than for HDR.
  8. 8. Reassortment During the overall treatment time of LDR, tumor cells may pass from the relatively radioresistant phases of late S and early G2 to the more radiosensitive phases of G2 and M
  9. 9. Repopulation The continuous administration of LDR prevents repopulation during treatment.
  10. 10. Biological equivalent dose • Calculated from LDR • a/b ratio… • Based on formulas !!!!
  11. 11. Toxicity High dose / Fraction Increased Late complications
  12. 12. HDR delivery Total Dose? Dose per fraction? Conversion? Schedule?
  13. 13. Orton et al, Metaanalysis
  14. 14. Optimisation???
  15. 15. URETHRA RECTUM
  16. 16. HDR for all cervix patients??
  17. 17. Small tumor & good vaginal anatomy Vaginal anatomy – increase in complications Bulky central disease with high chance of central recurrance
  18. 18. • Severely criticized • Lacks any description of statistical methods, • Were not randomized trials • Many have never been published, • None were referenced. • Some of the LDR results used in the comparison are very poor, with complication rates several times higher than those described by Fletcher or Perez
  19. 19. What happens at longer follow up??
  20. 20. DSS
  21. 21. Pelvic recurrance free survival
  22. 22. • Teshima et al ; 1993 • 430 patients reported on 10-year OS • 44% (114 out of 259) in the HDR arm versus 52.6% (90 out of 171) in the LDR arm
  23. 23. Other studies…
  24. 24. Other Factors…
  25. 25. • Patient’s expense… • Source life… • Need for intense QA… • Setup up cost…
  26. 26. Important Msgs… Radiobiology Dose, Fraction & Schedule Long term survival Optimisation
  27. 27. Conclusion • Carcinoma cervix – Life threatening disease • For the price of convenience …, survival should never be compromised • LDR brachytherapy should be the standard of care in carcinoma cervix until long term efficacy of HDR is proven….

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