UroToday - Robotic and medical imaging technology has made leaps and bounds over the past few decades, and the practice of brachytherapy should take advantage of these advances. Of course, any new technology cannot be implemented in the clinic without a scientifically validated foundation, which must be established in order to justify the move away from tried-and-true methods. With this in mind, we present this paper as a peek into the future -- alternative, potentially useful implant catheter patterns.

Brachytherapy places concentrated sources of radiation inside the body inside cancerous tissues and organs using an external template of fixed positions to help the physician guide the insertion needles or catheters. Studies have shown that placing radiation sources close to cancer cells results in less damage to healthy tissues than surgery or external beam radiation and does not require multiple hospital visits for treatment [1]. In terms of survival rate, brachytherapy is a highly successful method for treating prostate cancer [1,2,3], but it is a surgical procedure that can produce negative side effects due to the insertion of brachytherapy needles. [4,5,6].

The needle insertion process can be made less invasive by employing robotic brachytherapy, which can take full advantage of the plethora of information that is available when using imaging technologies like MRI to allow the physician to achieve a near-perfect implant. By near-perfect, we mean an implant that minimizes the number of needles inserted (to pierce as few as possible of the sensitive healthy structures around the targeted tissue) and still deliver radiation that conforms to the geometry of the diseased target tissue. For example, an MR image of the prostate region allows us to see the neurovascular bundles, the seminal vesicles, and the penile bulb-information entirely unutilized during a standard transrectal ultrasound-template guided implant procedure. In fact, we can also delineate the main substructures of the prostate: the peripheral zone, the transition zone, and the central zone. A robot would expand the number of possible needle/catheter paths and allow for the placement without the need for the fixed template of needle positions. The ability to see the prostate substructure and perhaps the tumor allows for more optimal placement of needles/catheters for therapeutic treatment.

The optimal placement of radiation relies on two factors: seeing where to go and going there. Imaging technology helps us see where we want to go and robot technology will help us in going there. Just as on any given day, there may be a different optimal commute to work due to traffic and weather conditions, the method of driving radiation where it needs to go depends on the conditions of the anatomy of any given patient. And while trains are an excellent mode of transportation, they lock us into pre-defined routes just as template-based brachytherapy (with its restriction to grid-based and parallel needle patterns) doesn't have the flexibility to access all parts of the prostate while avoiding sensitive tissues. The work presented in this paper shows that by using alternative methods of going there we can still deliver a standard dose distribution that has been shown to be clinically successful. This is key because it shows that alternative catheter patterns made available by robotic devices, combined with dose optimization, can allow us to deliver dose while, at the same time, avoiding the puncture of sensitive non-diseased structures. To some, the benefit of eliminating trauma to critical structures may seem obvious, but nevertheless, it is not clinically proven and it will not be possible until such technology becomes available in the clinic.

A full report of this work is available in PDF format for free at the online science archive, arXiv: arxiv/abs/0904.2358. The original journal article appears in the Medical Physics Journal: Cunha et al., "Dosimetric equivalence of nonstandard HDR brachytherapy catheter patterns ," Med. Phys. 36 (1), pp 233-239, January 2009.

References:

1. I. Thompson, J. B. Thrasher, G. Aus, A. L. Burnett, E. D. Canby-Haginoa, M. S. Cookson, A. V. D'Amicoa, R. R. Dmochowski, D. T. Etona, J. D. Formana, S. L. Goldenberga, J. Hernandeza, C. S. Higanoa, S. R. Kraus, J. W. Moul, C. M. Tangena, and Prostate Cancer Clinical Guideline Update Panel, "Guideline for the management of clinically localized prostate cancer: 2007 update," J. Urology, vol. 177, no. 6, pp. 2106-2131, 2007.
2. L. Potters, C. Morgenstern, E. Calugaru, P. Fearn, A. Jassal, J. Presser, and E. Mullen, "12-year outcomes following permanent prostate brachytherapy in patients with clinically localized prostate cancer," J. Urology, vol. 173, pp. 1562-1566, May 2005.
3. J. C. Blasko, T. Mate, J. E. Sylvester, P. D. Grimm, and W. Cavanagh, "Brachytherapy for carcinoma of the prostate: techniques, patient selection, and clinical outcomes," Seminars in Radiation Oncology, vol. 12, no. 1, pp. 81-94, 2002.
4. C. Vargas, M. Ghilezan, M. Hollander, G. Gustafson, H. Korman, J. Gonzalez, and A. Martinez, "A new model using number of needles and androgen deprivation to predict chronic urinary toxicity for high or low dose rate prostate brachytherapy," J. Urology, vol. 174, pp. 882-887, Sept. 2005.
5. L. Eapen, C. Kayser, Y. Deshaies, G. Perry, C. E, C. Morash, J. E. Cygler, D. Wilkins, and S. Dahrouge, "Correlating the degree of needle trauma during prostate brachytherapy and the development of acute urinary toxicity," Int. J. Radiat. Oncol., Biol., Phys., vol. 59, no. 5, pp. 1392-1394, 2004.
6. S. K. Kang, R. H. Chou, R. K. Dodge, R. W. Clough, H.-S. L. Kang, M. G. Bowen, B. A. Steffey, S. K. Das, S.-M. Zhou, A. W. Whitehurst, N. J. Buckley, J. H. Kim, R. E. Joyner, I. Sarmina, G. S. Montana, S. S. Ingram, and M. S. Anscher, "Acute urinary toxicity following transperineal prostate brachytherapy using a modified Quimby loading method," Int. J. Radiat. Oncol., Biol., Phys., vol. 50, no. 4, pp. 937-945, 2001.
J. Adam M. Cunha, PhD as part of Beyond the Abstract on UroToday

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