Recent London Improvements In Curative Radiation Therapy For Relevant Early Prostate Cancer

Main Category: Prostate / Prostate Cancer
Also Included In: Urology / Nephrology;  Cancer / Oncology;  Radiology / Nuclear Medicine
Article Date: 14 Dec 2008 - 1:00 PDT

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UroToday.com - The most effective form of treatment for localized prostate cancer remains a matter of great debate. There are no randomized controlled trials comparing radiotherapy with prostatectomy. Long-term outcome data from historical series, even those from the 1990s, have limited relevance as rapid advances in radiotherapy techniques have since permitted further dose escalation to the prostate. The published article describes recent advances in radiotherapy techniques and discusses the improved outcomes with regard to cure and toxicity.

External Beam Radiotherapy

It has been demonstrated in the last decade that delivering a conventionally fractionated dose above 72Gy to early prostate cancer improves cure rates. Whilst delivery of this dose is possible with the previous gold-standard modality (3D-conformal radiotherapy), intensity modulated radiation therapy (IMRT) allows the prostate and seminal vesicles to be irradiated to higher doses, delivered in distributions bespoke for the size and shape of the individual's gland, with further reductions in dosage to surrounding tissues. Our team has compared two different methods of IMRT (Linac and Tomotherapy) and found they provide very similar dosimetry, hence equivalent efficacy. The anterior wall of the rectum is the main dose-limiting structure and IMRT techniques allow better conformal shaping of the dose distribution around this structure. We have demonstrated that by studying that portion of rectum between the axial limits of the target volume one may more accurately predict the long-term rectal side-effects of the different techniques. We have shown that IMRT techniques better spare this area than 3D-conformal radiotherapy.

Low Dose Rate Brachytherapy

The use of low dose rate (LDR) iodine-125 seed prostate brachytherapy as a radical treatment for prostate cancer was initially confined to low risk patients. Technical developments including one-step planning and seed insertion, use of stable seed-trains and more peripheral loading techniques have produced ten year biochemical progression-free survival rates equivalent to surgery with less morbidity. Recent data suggest LDR brachytherapy may have a role in the treatment of some intermediate risk patients but only optimization of the dose distribution plan will ensure improvements in outcomes for such patients. Although the large number of radioisotope seeds used in LDR brachytherapy means the technique can be forgiving with respect to occasional seed misplacement, a method of immediate feedback and plan modification is desirable. To address this, the London team has introduced intra-operative dynamic interaction between clinicians and physicists. Sophisticated software immediately flags any seeds misplaced by more than 5mm and iterative computer planning re-configures the optimal distribution of subsequent seeds. Sustained reduction in PSA attests to the success of the technique.

Written by J.D. Maclean MRCP; D. Smith, FRCR; and P.N. Plowman, MD as part of Beyond the Abstract on UroToday.com.

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