Smoking not only compromises general health — it can also undermine the effects of cancer treatment. That’s the key finding of a Memorial Sloan Kettering study published last week in the medical journal BJU International.
The researchers analyzed patients who had been treated with external beam radiation therapy for localized prostate cancer (cancer that has not spread from the prostate gland to other body parts). Patients who were smokers had a significantly higher risk of experiencing rising levels of prostate specific antigen, or PSA, in their blood — which suggests the cancer may be returning — and of dying from the disease. Smokers also had a greater likelihood of experiencing side effects related to radiation therapy, such as urinary toxicity, compared with nonsmokers.
Radiation oncologist Michael Zelefsky, the study’s lead author, and his team studied a group of 2,156 MSK patients who received external beam radiation therapy (EBRT) for prostate cancer from 1988 to 2005 and whose smoking history was recorded. The patients were grouped based on whether they were current or former smokers or nonsmokers.
The researchers determined how frequently patients in the different groups developed biochemical relapse — rising PSA — ten years after starting EBRT. On average, they found that current smokers were 1.4 times more likely to develop biochemical relapse than nonsmokers, while former smokers were not at increased risk.
For the same ten-year period following EBRT, current smokers were also at 2.3 times higher risk than nonsmokers of developing distant metastases — cancer that has spread from the original tumor — and of dying from prostate cancer. These risks were much lower for former smokers.
In addition, the study showed that both current and former smokers were at greater risk for developing a number of side effects of the radiation treatment, including complications that impair urinary function, over ten years.
Dr. Zelefsky thinks the increased risk for smokers could possibly be explained by the fact that smoking reduces oxygen concentration within the treated tumors. “This is known to lead to less sensitivity of the cells being killed off by the radiation treatments,” he says.
Regardless of the cause, quitting smoking is the best way to avoid these negative effects.
“Healthcare providers are in a position to address tobacco habits effectively as part of clinical care,” Dr. Zelefsky says, adding that they must renew efforts to help prostate cancer patients to stop using tobacco in light of the study’s findings.
These efforts apply to other cancers as well. MSK and Massachusetts General Hospital have jointly launched a program to bolster smoking cessation in cancer care. The intervention includes both FDA-approved smoking-cessation medications and additional counseling.
The National Cancer Institute has also called for reforms to enhance the quality of care of tobacco-dependent cancer patients. The recommended changes include a uniform approach for assessing smoking status, refining electronic medical records and clinical trials to identify and target smokers, and evaluating ways to overcome barriers to quitting.