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After IMRT, almost 90% of men with prostate cancer were disease-free at eight years
All patients maintained urinary continence and only 1.6% experienced rectal bleeding.
Results from a long-term follow-up study of men with prostate cancer who were treated with intensity-modulated radiation therapy showed that the treatment modality had impressive local control.
The majority of patients who were treated with intensity-modulated radiation therapy (IMRT) remained alive with no evidence of disease after an average follow-up period of eight years. Researchers followed 561 men who were treated for prostate cancer with IMRT at Memorial Sloan-Kettering Cancer Center.
The men were classified into three different prognostic risk groups. After an average of eight years, 89% of the men in the favorable-risk group were disease-free and none of the men in any group developed secondary cancers as a result of the radiation therapy.
“Our results suggest that IMRT should be the treatment of choice for delivering high-dose, external beam radiotherapy for patients with localized prostate cancer,” said Michael J. Zelefsky, MD, chief of the brachytherapy service at MSKCC. “We were able to show long-term safety and long-term efficacy in a very diverse group of prostate cancer patients that we followed, many for as long as ten years. Despite the fact that some patients had an aggressive form of the disease with high Gleason scores and [prostate specific antigen,] the overwhelming majority of patients had good tumor control with neither recurrence of their original cancer nor development of second cancers, which one might have expected from the high doses of radiation.”
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Pre-treatment diagnostic evaluations were performed for all of the patients to better define their clinically localized prostate cancer. They were classified into prognostic risk groups as defined by National Comprehensive Cancer Network guidelines. The guidelines are based on clinical characteristics including age, T stage, Gleason score, PSA level and pre-treatment with neoadjuvant androgen deprivation.
The researchers saw 561 patients between April 1996 and January 2000. The men ranged in age from 46 to 86 years, with a median age of 68. All men received IMRT, which uses enhanced treatment planning software to target radiation to the prostate, while attempting to spare surrounding healthy tissue. The researchers were able to deliver an 81 Gy dose of radiation to the tumor.
They were able to effectively spare the bladder and rectum from experiencing any radiation-associated toxicity from such a high dose. At eight years, researchers observed that all patients maintained urinary continence and only 1.6% of all patients experienced rectal bleeding.
High-dose radiotherapy was curative for the majority of the patients in all three prognostic risk groups, with 89% of men in the favorable-risk group, 78% of men in the intermediate-risk group, and 67% of men in the unfavorable-risk group alive after an average period of eight years (P=.0004).
Three patients experienced grade-3 rectal toxicity requiring either one or more transfusions or a laser cauterization procedure, according to the study. No grade-4 rectal complications were observed. The 8-year likelihood of late grade-2 and -3 (urethral strictures) urinary toxicities was 9% and 3%, respectively. Erectile dysfunction developed in 49% the men who were potent prior to receiving IMRT.
“This study confirms that we can improve patients’ quality of life by reducing the side effects of radiotherapy while maintaining disease-free survival,” Zelefsky said. “However, there is still room for improvement. We are incorporating image-guided approaches that may continue the excellent tumor control but further limit the area we are irradiating and reduce side-effects.”
For more information:
- Zelefsky MJ, Chan H, Hunt M, et al. Long-term outcome of high dose intensity modulated radiation therapy for patients with clinically localized prostate cancer.J Urol. 2006;176:1415-1419.