Improved Conformality and Reduced Toxicity with High-Dose Intensity Modulated Radiation Therapy (IMRT) for Patients with Prostate Cancer
Presenter: Michael J. Zelefsky, M.D.
Affiliation: Memorial Sloan Kettering Cancer Center
There has been recent evidence to suggest that with increased radiation dose comes increased efficacy in the treatment of prostate cancer. However, the ability to deliver dose is most often limited by the tolerance of normal tissues proximal to the tumor. This investigation compares acute and late toxicities of conformal radiation therapy (CRT) with those of IMRT.
Patients with T1c through T3 prostate cancer were treated to a dose of 81 Gy. Sixty-one patients received CRT and 171 received IMRT, and a random sample of 20 patients were planed using both techniques.
- The IMRT plans covered the clinical target volume (CTV) better than the CRT plans, with smaller volumes of rectum and bladder carried to high doses (p < 0.001).
- Clinically, acute rectal toxicity and 2 year grade 2 rectal bleeding (bleeding not requiring transfusion or surgical correction) were lower in the IMRT arm.
- Two per cent of IMRT patients suffered from chronic grade 2 bleeding compared to 10% in the CRT arm (p < 0.001).
- Acute and late urinary toxicities were not significantly different.
These encouraging preliminary data show a toxicity profile that is comparable or superior in patients treated with high dose IMRT compared to those treated with high dose CRT.
- It is worth noting, however, that the IMRT rectal bleeding data are exceptionally good. There are data to suggest that Grade 2 bleeding is around 10% in patients receiving no therapy.
- Long term survival and local control data are necessary in establishing the population that may benefit from such intensive treatment. Also, the role of adjuvant hormone treatment has yet to be clearly defined in patients receiving high dose radiation therapy.
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