BERKELEY, CA (UroToday.com) - Dose-escalated IMRT beyond the 78 Gy prescription dose has raised the rates of acute and chronic grade ≥ 2 rectal toxicity from 3% to 20% and 5% to 21%, respectively.[1, 2, 3] The risk of rectal toxicity depends on the volume of the rectum that receives a high radiation dose. In a large prospective series, the percentage volume of rectum receiving > 70 Gy (V70rectum) correlated with the occurrence of chronic rectal toxicity. Grade ≥ 2 chronic rectal toxicity occurred in 54% and 13% of patients in whom the V70rectum was > 26.2% and ≤ 26.2%, respectively.
Therefore, it is important to implement techniques that prevent these high rectal volume doses. As the prostate is directly adjacent to the rectal wall, the anterior rectal wall cannot be spared completely from the high dose region, irrespective of the radiation technique. A spacer is an application of an absorbable hydrogel, and it is inserted into the Denonvilliers’ space, between the prostate and the rectum under transrectal ultrasound guidance. It allows targeted prostate radiation, with a decreased radiation dose to the rectum.
The results presented in this paper are valuable for decision-making in terms of policy making and future research. If all the assumptions are correct, IMRT+S is less toxic and more effective than IMRT-O for all prostate cancer patients. Sensitivity analysis revealed that the model was robust to changes in individual parameters and IMRT+S remained cost-effective in most scenarios given a ceiling ratio of €80,000 is adopted.
The main research implication is that the applied study method is a feasible and informative method to explore the potential cost-effectiveness of the spacer in individual patients and different RT techniques, such as stereotactic body RT (SBRT). The current paper demonstrates that, according to the Dutch health costs, the spacer can be cost-effective for prostate cancer patients due to less severe toxicity and a reduction in treatment costs associated with these side effects. If we acknowledge patient heterogeneity and we can select a population of patients with a high risk of late rectal complications (e.g., re-irradiation, inflammatory bowel disease, diabetes or anticoagulantia[6, 7]), the cost-effectiveness of the spacer will most likely improve because those patients will benefit even more from the use of a spacer.
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- Al-Mamgani A, Heemsbergen WD, Peeters ST, Lebesque JV. Role of intensity-modulated radiotherapy in reducing toxicity in dose escalation for localized prostate cancer. Int J Radiat Oncol Biol Phys 2009;73(3):685–91.
- Zelefsky MJ, Levin EJ, Hunt M, et al. Incidence of late rectal and urinary toxicities after three-dimensional conformal radiotherapy and intensity-modulated radiotherapy for localized prostate cancer. Int J Radiat Oncol Biol Phys 2008;70(4):1124–9.
- Kuban DA, Tucker SL, Dong L, et al. Long-term results of the M.D. Anderson randomized dose-escalation trial for prostate cancer. Int J Radiat Oncol Biol Phys. 2008;70(1):67-74.
- Huang EH, Pollack A, Levy L, et al. Late rectal toxicity: Dose–volume effects of conformal radiotherapy for prostate cancer. Int J Radiat Oncol Biol Phys 2002;54(5):1314–21.
- Herold DM, Hanlon AL, Hanks GE. Diabetes mellitus: a predictor of late radiation morbidity. Int J Radiat Oncol Biol Phys 1999;43(3):475–9.
- Willett CG, Ooi CJ, Zietman AL, et al. Acute and late toxicity of patients with inflammatory bowel disease undergoing irradiation for abdominal and pelvic neoplasms. Int J Radiat Oncol Biol Phys. 2000;46(4):995-8.
Ben Vanneste, MD as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Department of Radiation Oncology (MAASTRO), GROW – School for Oncology and Developmental Biology, Maastricht University Medical Center+, The Netherlands