Impact of margin on tumour and normal tissue dosimetry in prostate cancer patients treated with IMRT using an endorectal balloon for prostate immobilization

  • S. Ahmad
  • M. T. Vlachaki
Scientific Papers


In IMRT treatment, margin for planning target volume is determined by organ motion and set-up error. The margin width that achieves the desired dose escalation, while minimizing normal tissue exposure is dependent upon patient immobilization and/or organ localization techniques. In this study, we compare the impact of margin width on the dosimetry of tumour and normal tissues using an endorectal balloon filled with 100 cc of air. Plans were generated for ten patients using margin widths of 0, 3, 5, 8 and 10 mm. The prescription dose to prostate and seminal vesicles was 70 Gy in 35 fractions with 15% of bladder allowed to receive above 65 Gy, 15% of rectum above 68 Gy and 10% of femurs above 45 Gy. Margins above 5 mm produced significantly lower mean doses for both prostate and seminal vesicles without affecting TCP. For normal tissues, mean doses, percent volumes above prescription constraints and NTCP increased as a function of margin width, especially when this was 5 mm or above. We conclude that planning with tighter margins of ≤5 mm improves IMRT dosimetry for prostate and normal tissues and is only possible when target localization and/or immobilization devices are routinely used.

Key words prostate cancer

IMRT margin 


  1. 1.
    Ghilezan, M., Yan, D., Liang, J., Jaffray, D., and Wong, M. A.,Online image-guided intensity-modulated radiotherapy for prostate cancer: How much improvement can we expect? A theoretical assessment of clinical benefits and potential dose escalation by improving precision and accuracy of radiation delivery, Int. J. Radiat. Oncol. Biol. Phys., 60(5):1602–1610, 2004, and references therein.PubMedGoogle Scholar
  2. 2.
    Teh, B. S., Woo, S. Y., Mai, W. Y., Mc Gary, J. E., Carpenter, L. S., Lu, H. H., Chiu, J. K., Vlachaki, M. T., Grant, W. H. III and Butler, E. B.,Clinical experience with intensity-modulated radiation therapy (IMRT) for prostate cancer with the use of rectal balloon for prostate immobilization, Med. Dosim., 27(2):105–113, 2002.CrossRefPubMedGoogle Scholar
  3. 3.
    Teh, B. S., Mai, W. Y., Uhl, B. M., Augspurger, M. E., Grant, W. H. III, Lu, H. H., Woo, S. Y., Carpenter, L. S., Chiu, J. K. and Butler, E. B.,Intensity-Modulated Radiation Therapy (IMRT) for Prostate Cancer with the Use of a Rectal Balloon for Prostate Immobilization: Acute Toxicity and Dose-Volume Analysis, Int. J. Radiat. Oncol. Biol. Phys., 49(3):705–712, 2001.PubMedGoogle Scholar
  4. 4.
    Ahmad, S., Vlachaki, M. T., Teslow, T. N., Amosson, C. M., McGary, J., The, B. S., Woo, S. Y., Butler, E. B., and Grant, W. H. III,Impact of setup uncertainty in the dosimetry of prostate and surrounding tissues in prostate cancer patients treated with Peacock/IMRT, Med. Dosim., 30(1):1–7, 2005.CrossRefPubMedGoogle Scholar
  5. 5.
    McGary, J. E. and Grant, W. H. III,A clinical evaluation of setup errors for a prostate immobilization system, J. Appl. Clin. Med. Phys., 1(4):138–147, 2000.CrossRefPubMedGoogle Scholar
  6. 6.
    McGary, J. E., Teh, B. S., Butler, E. B. and Grant, W. H. III,Prostate immobilization using a rectal balloon, J. Appl. Clin. Med. Phys., 3(1):6–11, 2002.CrossRefPubMedGoogle Scholar
  7. 7.
    Carol, M. P.,Beam Modulation Conformal Radiotherapy.In: Purdy, J. A., Emami, B., editors,3D Radiation Treatment Planning and Conformal Therapy, Advanced Medical Publishing, Madison, 435–445, 1993.Google Scholar
  8. 8.
    Grant, W. H. III,Experience with Intensity Modulated Beam Delivery.In: Mackie, T. R.; Palta, J. R., editors,Teletherapy: Present and Future, Advanced Medical Publishing; Madison, 793–804, 1996.Google Scholar
  9. 9.
    Sternick, E. S., Carol, M. P. and Grant, W. H. III,Intensity Modulated Radiotherapy.In:Khan, F. M., Potish, R. A., editors,Treatment Planning in Radiation Oncology, Williams and Wilkins, Baltimore, 187–213, 1998.Google Scholar
  10. 10.
    Niemierko, A.,Reporting and analyzing dose distribution: A concept of equivalent uniform dose, Med. Phys., 24:103–109, 1997.CrossRefPubMedGoogle Scholar
  11. 11.
    Nahum, A. E. and Tait, D. M.,Maximizing tumour control by customized dose prescription for pelvic tumours in advanced radiation therapy: Tumour response monitoring and treatment planning, Breit, A., editor, Springer, Berlin, 425–431, 1992.Google Scholar
  12. 12.
    Lyman, J. T.,Complication probability as assessed from dose volume histograms, Radiat. Res. Suppl., 8:S13–19, 1985.CrossRefPubMedGoogle Scholar
  13. 13.
    Kutcher, G. J. and Burman, C.,Calculation of complication probability factors for non uniform normal tissue irradiation: the effective volume method, Int. J. Radiat. Oncol. Biol. Phys., 16(6):1623–1630, 1989.PubMedGoogle Scholar
  14. 14.
    Burman, C., Kutcher, G. J., Emami, B. and Goitein, M.,Fitting of normal tissue tolerance data to an analytic function, Int. J. Radiat. Oncol. Biol. Phys., 21(1):123–135, 1991.PubMedGoogle Scholar
  15. 15.
    Emami, B., Lyman, J., Brown, A., Coia, L., Goitein, M., Munzenrider, J. E., Shank, B., Solin, L. J. and Wesson, M.,Tolerance of normal tissue to therapeutic irradiation, Int. J. Radiat. Oncol. Biol. Phys., 21(1):109–122, 1991.PubMedGoogle Scholar
  16. 16.
    Wang, J. Z., Li, X. A., Yu, C. X. and Dibiase, S. J.,The low α/β ratio for prostate cancer: what does the clinical outcome of HDR brachytherapy tell us?, Int. J. Radiat. Oncol. Biol. Phys., 57(4):1101–1108, 2003.PubMedGoogle Scholar
  17. 17.
    Vlachaki, M. T., Teslow, T. N., Amosson, C. M., Grant, W. H. and Butler, E. B.,Impact of endorectal balloon reposition in the dosimetry of prostate and surrounding normal tissues in patients with prostate cancer treated with the peacock/IMRT technique, Radiology, (S)217; 142, 2000.Google Scholar
  18. 18.
    Uhl, B. M., Teh, B. S., Wheeler, T., Scardino, P. T., Woo, S. Y. and Butler, E. B.,Intensity modulated radiation therapy IMRT for localized prostate cancer: a comparison of peacock conformal treatment volumes and pathologic radical prostatectomy specimens, Int. J. Radiat. Oncol. Biol. Phys., 42(1-suppl):292, 1998.Google Scholar
  19. 19.
    Teh, B. S., Bastasch, M. D., Wheeler, T. M., Mai, W. Y., Frolov, A., Uhl, B. M., Lu, H. H., Carpenter, L. S., Chiu, J. K., Mcgary, J., Woo, S. Y., Grant, W. H. and Butler, E. B.,IMRT for prostate cancer defining target volume based on correlated pathologic volume of disease, Int. J. Radiat. Oncol. Biol. Phys., 56:184–191, 2003.PubMedGoogle Scholar
  20. 20.
    Cox, J. D., Stetz, J. and Pajak, T. F.,Toxicity Criteria of the Radiation Therapy Oncology Group (RTOG) and then European Organization for Research and Treatment of Cancer (EORTC), Int. J. Radiat. Oncol. Biol. Phys., 31:1341–1346, 1995.PubMedGoogle Scholar
  21. 21.
    Hall, E. J.,Henry S. Kaplan Distinguished Scientist Award 2003, The crooked shall be made straight; dose-response relationships for carcinogenesis, Int. J. Radiat. Oncol. Biol., Phys., 80(5):327–337, 2004.Google Scholar
  22. 22.
    Brenner, D. J., Curtis, R. E., Hall, E. J. and Ron, E.,Second malignancies in prostate carcinoma patients after radiotherapy compared with surgery, Cancer, 88(2):398–406, 2000.CrossRefPubMedGoogle Scholar
  23. 23.
    Hall, E. J. and Wuu, C. S.,Radiation-induced second cancers: the impact of 3D-CRT and IMRT, Int. J. Radiat. Oncol. Biol. Phys., 56(1):327–337, 2004.Google Scholar
  24. 24.
    Nutting, C. M., Corbishley, C. M., Sanchez-nieto, B., Cosgrove, V. P., Webb, S. and Dearnaley, D. P.,Potential improvements in the therapeutic ratio of prostate cancer irradiation: dose escalation of pathologically identified tumour nodules using intensity modulated radiotherapy, Brit. J. Radiol., 75:151–161, 2002.PubMedGoogle Scholar
  25. 25.
    Guerrero Urbano, M. T. and Nutting, C. M.,Clinical use of intensity-modulated radiotherapy: part II (Review Article), Brit. J. Radiol., 77:177–182, 2004.CrossRefPubMedGoogle Scholar
  26. 26.
    Burman, C., Chui, C. S., Kutcher, G., Leibel, S., Zelefsky, M., LoSasso, T., Spirou, S., Wu, Q., Yang, J., Mohan, R., Fuks, Z. and Ling, C. C.,Planning, delivery, and quality assurance of intensity modulated radiotherapy using dynamic multileaf collimator: a strategy for large scale implementation for the treatment of carcinoma of the prostate, Int. J. Radiat. Oncol. Biol. Phys., 39:863–873, 1997.PubMedGoogle Scholar
  27. 27.
    Muren, L. P., Ekerold, R., Kvinnsland, Y., Karlsdottir, A. and Dahl, O.,On the use of margins for geometrical uncertainties around the rectum in radiotherapy planning, Radiother. Oncol., 70:11–19, 2004.CrossRefPubMedGoogle Scholar
  28. 28.
    McKenzie, A., Van, H. M. and Mijnheer, B.,margins for geometric uncertainty around organs at risk in radiotherapy, Radiother. Oncol., 62:299–307, 2002.CrossRefPubMedGoogle Scholar
  29. 29.
    ICRU Report 62,Prescribing, Recording, and Reporting Photon Beam Therapy, (Supplement to ICRU Report 50), Bethesda, MD, 1999.Google Scholar
  30. 30.
    Stroom, J. C. and Heijmen, B. J. M.,Geometrical uncertainties, radiotherapy planning margins, and the ICRU-62 report, Radiother. Oncol., 64:75–83, 2002.CrossRefPubMedGoogle Scholar
  31. 31.
    Van, H. M., Remeijer, P., Rasch, C. and Lebesque, J. V.,The probability of correct target dosage: dose population histograms for deriving treatment margins in radiotherapy, Int. J. Radiat. Oncol. Biol. Phys., 47(4):1121–1135, 2000.Google Scholar
  32. 32.
    Manning, M. A., Wu, Q., Cardinale, R. M., Mohan, R., Lauve, A. D., Kavanagh, B. D., Morris, M. M. and Schmid-Ulrich, R. K.,The effect of setup uncertainty on normal tissue sparing with IMRT for head and neck cancer, Int. J. Radiat. Oncol. Biol. Phys., 51(5):1400–1409, 2001.PubMedGoogle Scholar
  33. 33.
    Wong, J. R., Grimm, L., Uematsu, M., Oren, R., Cheng, C. W. Merrick, S. and Schiff, P.,Image-guided radiotherapy for prostate cancer by CT-linear accelerator combination: prostate movements and dosimetric considerations, Int. J. Radiat. Oncol. Biol. Phys., 61(2):561–569, 2005.PubMedGoogle Scholar
  34. 34.
    Jaffray, D. A., Siewerdsen, J. H., Wong, J. W. and Matinez, A. A.,Flat-Panel cone beam computed tomography for image guided radiation therapy, Int. J. Radiat. Oncol. Biol. Phys., 53(5):1337–1349, 2002.CrossRefPubMedGoogle Scholar
  35. 35.
    Beavis, A. W.,Is tomotherapy the future of IMRT?, Brit. J. Radiol., 77(916):285–295, 2004.CrossRefPubMedGoogle Scholar

Copyright information

© Australasian College of Physical Scientists and Engineers in Medicine 2005

Authors and Affiliations

  1. 1.Department of Radiation OncologyThe University of Oklahoma Health Sciences CenterOklahoma CityU.S.A.
  2. 2.New York University Medical Center-School of MedicineNew YorkU.S.A.

Personalised recommendations