February 1, 2012 — A new study suggests that vigorous physical activity will offer protection against prostate cancer progression because of its effects on DNA repair and cell-cycle pathways. The finding might help explain previous observations that men who exercise vigorously have a reduced risk for all-cause mortality and prostate-cancer-specific mortality.
These findings were highlighted during a presscast in advance of the 2012 Genitourinary Cancers Symposium (GUCS), being held in San Francisco, California. It was organized by the American Society of Clinical Oncology, one of the sponsors of the meeting.
"We previously reported that prostate cancer patients who exercise tend to fare better after a diagnosis of prostate cancer; now we are trying to understand why," explained senior author June Chan, ScD, associate professor of epidemiology and of biostatistics and urology at the University of California, San Francisco.
Dr. Chan and colleagues, working with researchers from the Harvard School of Public Health in Boston, Massachusetts, published 2 separate studies last year showing that vigorous exercise can reduce the progression of prostate cancer and reduce the risk for both all-cause and prostate-cancer-specific mortality.
One of these studies followed 2705 men diagnosed with nonmetastatic prostate cancer for 8 years (1990 to 2008). Men who reported that they undertook vigorous physical activity for 3 hours per week or more were found to have a 49% lower risk for all-cause mortality and a 61% lower risk for prostate-cancer-specific mortality than those who exercised for less than 1 hour per week (J Clin Oncol. 2011:20:726-732).
The vigorous physical exercise consisted of jogging, cycling, tennis, or swimming. Men who reported this type of exercise for more than 3 hours per week before and after their diagnosis of prostate cancer had the lowest risk for all-cause and prostate-cancer-specific mortality. In addition, men who reported walking at a normal to very brisk pace for more than 90 minutes per week — compared with those who walked at an easy pace — had a significantly reduced risk for all-cause mortality and a suggestion of a reduced risk for prostate-cancer-specific mortality (but this did not reach statistical significance).
The other study was conducted in 1455 men with clinically localized prostate cancer (Cancer Res. 2011;71:3889-3895). It found that men who reported a brisk walking pace (>3 mph), compared with an easy walking pace (<2 mph), had a 48% lower risk for prostate cancer progression. The walking pace was associated with a decreased risk for progression, independent of duration, the researchers note.
The current study, which will be presented at the GUCS, was conducted in 70 men with low-risk prostate cancer who were undergoing active surveillance and who had been taking part in a study on nutritional supplements.
The team looked at gene expression in biopsy specimens and found differences between the 23 men who reported exercising vigorously for at least 3 hours per week and the 47 men who reported less.
The men who exercised had a differential expression of 184 genes; the upregulated genes included well-known tumor-suppressor genes such as BRCA1 and BRCA2, Dr. Chan reported.
The gene-set analysis also revealed that cell-cycle and DNA repair pathways were positively modulated in men who reported participating in vigorous physical activity for at least 3 hours per week, compared with those who reported less, she added.
However, she noted, "there were no significant genes or pathways associated with the physical activity when we compared men reporting engaging in any vigorous physical activity [and those reporting engaging in] none, suggesting that a certain threshold of intensity or duration may be important."
Dr. Chan emphasized that the study is small so the finding could be due to chance, and that potential confounding factors were not considered. Nevertheless, she believes that further study in larger populations is warranted.
"This was a small study with provocative findings that should be interpreted cautiously and warrant confirmation in a larger study," she said in a statement.
"These preliminary data suggest that DNA repair in the prostate gland is one mechanism through which vigorous physical activity may protect against prostate cancer progression, and there are potentially more," she said.
Commenting on all of these findings, Nicholas Vogelzang, MD, from US Oncology Research, who moderated the presscast, said it is important for physicians to encourage their patients to exercise. "In fact, we should be prescribing exercise," he added.
Dr. Chen noted that her team is involved in collaborative efforts to develop patient education strategies that reinforce the value of physical activity and other healthy lifestyle practices that can improve prostate cancer outcomes.
The researchers have disclosed no relevant financial relationships.
2012 Genitourinary Cancers Symposium (GUCS): Abstract 189. To be presented February 3, 2012.
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Cite this: How Exercise Might Reduce Prostate Cancer Progression - Medscape - Feb 01, 2012.