3D Conformal Radiotherapy Allows More Aggressive Prostate Cancer Treatment

Three-dimensional conformal radiotherapy allows men with prostate cancer to be treated safely with high doses of radiation, according to the November 15, 2002, issue of the International Journal of Radiation Oncology, Biology and Physics, the official journal of ASTRO, the American Society for Therapeutic Radiology and Oncology.

Research has shown that prostate cancer responds well to high doses of radiation. Physicians have been limited in how high a dose they can administer, however, fearing that surrounding normal tissue may be adversely affected. With the increasing availability of three-dimensional conformal radiotherapy (3D-CRT) treatment planning systems, prostate cancer has been one of the first diseases to undergo dose escalation trials. 3D-CRT allows higher doses of radiation to be delivered to the tumor by tightly conforming the radiation beam to the targeted area, thereby sparing surrounding normal tissues, such as the bladder or rectum.

A prospective Phase I dose escalation study was conducted to determine the maximum tolerated radiation dose that can be delivered to the prostate gland and the surrounding normal tissues using 3D-CRT. Between November 1996 and October 1998, 173 patients with localized, stage T1 and T2 prostate cancer received a radiation dose of 79.2 Gy in 44 daily doses. One hundred sixty-nine patients were available for analysis of toxicity. The incidence of Grade 3 or higher late effects was compared to that in similar groups of patients who had received smaller doses.

Tolerance of the 79.2 Gy treatment was excellent, with no patients experiencing Grade 3 or higher acute toxicity. The acute toxicity rate was comparable to that reported for lower dose levels. With a median follow-up of 3.3 years, a total of four patients (2.4 percent) experienced Grade 3 late toxicity, three cases of which were related to the bladder, and one related to the rectum. There were no Grade 4 or 5 late complications noted during the period of observation. These results are comparable to those reported at smaller dose levels. Based on the excellent tolerance of 3D-CRT for stages T1 and T2 prostate cancer, researchers have decided to investigate the toxicity when the dose is escalated biologically to 74 Gy and 78 Gy in larger daily fraction sizes.

"Now that we've established that high doses of radiation can be delivered safely to the prostate using 3D-CRT, the next step is to find out whether this innovation helps lead to more cures," said Janice K. Ryu, M.D., of the Department of Radiation Oncology at the University of California, Davis, and lead author of the study. "Because 3D-CRT is more costly and time-consuming than conventional radiation, it is important that we prove that it will improve outcomes for men with prostate cancer before it will be accepted by the medical community."

The American Society for Therapeutic Radiology and Oncology is the largest radiation oncology society in the world, with 7,000 members who specialize in treating patients with radiation therapies. As a leading organization in radiation oncology, biology and physics, the Society's mission is to advance the practice of radiation oncology by promoting excellence in patient care, providing opportunities for educational and professional development, promoting research and disseminating research results and representing radiation oncology in a rapidly evolving socioeconomic healthcare environment.