Prostate Cancer
Prostate Cancer
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Newsfeed display by CaRP Higher Radiation Dose Reduces Recurrence of Local Prostate Cancer

Summary

Men with early-stage prostate cancer who got higher doses of radiation were half as likely to see their cancer return in five years as men who received the conventional dose. This is the first large trial to show a high-dose radiation benefit in the treatment of low-risk patients.

Source

Journal of the American Medical Association, September 14, 2005.

Background

Patients diagnosed with early-stage prostate cancer that hasn’t spread generally face the choice of surgery to remove the gland (radical prostatectomy) or radiation to kill the tumor cells (radiotherapy). In some cases, especially when the patient is older, watchful waiting may be a safe third alternative because prostate cancer generally grows very slowly.

Even after treatment, however, prostate cancer can come back (recur). Several studies have shown that higher doses of radiation make recurrence less likely, but at the risk of more side effects, including more severe stomach and intestinal problems and difficulty with erections and urination. Because of this, doctors typically have used high-dose radiation only with patients at high risk of recurrence.

Recent studies of advanced prostate cancer patients have suggested that new “conformal” radiation therapy techniques might allow radiologists to safely deliver higher doses of radiation, and thus cut down on recurrences. Conformal techniques use computers to produce a three-dimensional picture of the target area, which makes it easier to leave more of the normal tissue untouched. The tighter targeting also permits the safe delivery of greater amounts of radiation.

The phase III trial described here was designed to test whether higher-than-conventional doses of radiation given with conformal radiation techniques would improve prostate cancer control in patients with early-stage disease.

The Study

Between January 1996 and December 1999, researchers at the Loma Linda University Medical Center (California) and the Massachusetts General Hospital (Boston) enrolled 393 patients with stage II prostate cancer that had not spread (metastasized) beyond the prostate gland. All of the patients were treated using proton beam conformal radiation techniques: 197 received a total dose of 70.2 Gy, which is the conventional amount; 195 received a total dose of 79.2 Gy.

While they were receiving radiation, patients underwent no other treatment for their cancer. Researchers then followed them for a median of 5.5 years, periodically testing the patients’ prostate-specific antigen (PSA) levels. (Because prostate cancer grows so slowly, researchers use a pattern of rising PSA levels to detect “biochemical recurrence,” which in turn may predict actual recurrence 15 years or more in the future.) Biopsies were given in some cases to test for local recurrence. Researchers asked the patients’ doctors about the severity and number of side effects.

The lead author was Anthony L. Zietman, M.D., from the Harvard Medical School and the Massachusetts General Hospital.
Results

After five years, 80.4 percent of men in the high-dose group were free from biochemical recurrence. Compared to 61.4 percent for men in the conventional group, this represents a 49 percent reduction in the risk of failure. It is too soon to see any difference that may yet develop in the overall survival rates.

According to criteria developed since this trial was designed, 227 men in the study were at low risk of recurrence. In this low-risk subgroup, 60.1 percent of those receiving the conventional dose were biochemically cancer free compared to 80.5 percent of the high-dose group.

There were 162 men at high risk of recurrence. In this subgroup, 63.4 percent of those receiving the lower dose were cancer free compared to 79.5 percent of those receiving the higher dose. Others who were determined to be an intermediate risk of recurrence also did better with the higher dose.

Overall, side effects were moderate for everyone in the trial. Only eight patients in the conventional dose group and five in the high-dose group suffered side effects that were rated Grade 3 or higher. One patient had a total prostatectomy, and doctors put another 20 (13 who had received the conventional dose and seven who had received the higher dose) on androgen deprivation therapy, primarily because of rising PSA levels.

Comments

This trial demonstrates that most men whose cancer is confined to the prostate will benefit from higher-dose radiotherapy, regardless of their risk of recurrence. “As clinicians, we have been moving toward higher doses than 70 Gy,” said radiation oncologist Anurag K. Singh, M.D., of the National Cancer Institute’s Center for Cancer Research. “But until this trial, we did not have good evidence to justify the risk of possible side effects for the low-risk patient. Now we can unequivocally say that more radiation is better.”

In an accompanying editorial, Theodore L. DeWeese, M.D., and Danny Y. Song, M.D., from Johns Hopkins University School of Medicine, call the results “significant,” “novel,” and “pivotal” because the decrease in biochemical recurrence in men with lower-risk disease provides “an important foundation for future work.”
Limitations

The side effects were reported by the patients’ physicians and may not have accurately reflected the patients’ actual experience. More follow-up is underway with a cross-section of patients.
The trial was not designed to compare proton-beam therapy with photon radiation or other conformal techniques, wrote DeWeese and Song. However, “in general the biological effectiveness is similar. As such, the impact and potential applicability of the findings . . . reach beyond the two centers in the United States that currently offer proton-beam therapy.”

U.S. National Institutes of Health
Clinical Trial Results


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Submitted: 06/11/06

Description: Men with early-stage prostate cancer who got higher doses of radiation were half as likely to see their cancer return in five years as men who received the conventional dose. This is the first large trial to show a high-dose radiation benefit in the treatment of low-risk patients.

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