FRACTIONATION & PROTRACTION FOR RADIOTHERAPY OF PROSTATE CARCINOMA

Fractionation & Protraction For Radiotherapy Of Prostate Carcinoma

David J. Brenner and Eric J. Hall

We investigate whether current fractionation and brachytherapy protraction schemes for the treatment of prostatic cancer with radiation are optimal, or could be improved.

We analyzed two mature data sets on radiotherapeutic tumor control for prostate cancer, one using external beam radiotherapy and the other permanent seed implants, to extract the sensitivity to changes in fractionation of prostatic tumors. The standard linear-quadratic model was used for the analysis.

Prostatic cancers appear significantly more sensitive to changes in fractionation than most other cancers. The estimated a/b value is 1.5 Gy [0.8, 2.2], which is much lower than for most tumors, and is comparable to typical values for late-responding tissues. This result is not too surprising as there is a documented relationship between cellular proliferative status and sensitivity to changes in fractionation, and prostatic tumors contain exceptionally low proportions of proliferating cells.

We conclude that high dose rate brachytherapy would be a highly appropriate modality for treating prostate cancer. Appropriately designed HDR brachytherapy regimens would be expected to be at least as efficacious as low dose rate, but with added advantages of logistic convenience and more reliable dose distributions. Possible dose rate schedules will be discussed.

Similarly, we show that external beam treatments for prostate cancer can be designed utilizing larger doses per fraction; appropriately designed hypofractionation schemes would be expected to maintain current levels of tumor control and late sequelae, but with reduced acute morbidity, together with the logistic and financial advantages of fewer numbers of fractions.

Back to Annual Report 1998 Table of Contents Previous Next

Website developed by CE, page last modified by MF, October 22, 2002.