Prostate cancer is the second most common cancer (next to skin cancer) and the second leading cause of death from cancer among men in the U.S. Due to the high risk of side effects associated with prostate cancer treatments, such as erectile dysfunction, urinary incontinence and fecal incontinence, physicians and consumers want to know they are choosing the best evidence-based treatment. Unfortunately, there is currently no scientific consensus to guide them.
A recent study compared three treatment options for prostate cancer to determine which was most effective. The study received a lot of media attention, with one outlet claiming “ men with early prostate cancer can safely opt out of treatment.” However, consumers must interpret media reports, and the study itself, with caution.
This study enrolled 1,643 men diagnosed with localized prostate cancer based on the prostate-specific antigen ( PSA) test. Researchers randomly assigned participants to one of the following treatment groups:
- Radical prostatectomy (n=553): Surgery to remove the entire prostate gland and the surrounding lymph nodes.
- External-beam radiotherapy (n=545): Radiation to kill the cancerous cells inside the prostate gland.
- Active monitoring (n=545): No immediate radical intervention and regular monitoring of disease progression with PSA tests. If their PSA level increased, participants had the option of undergoing radical treatment.
Researchers followed the participants over time to determine their outcomes, including metastases and prostate cancer-related deaths. The median follow-up time was 10 years.
Over half of the men assigned to the active monitoring group opted to undergo radical treatment by the end of the follow-up period. Meanwhile, the authors classified participants according to which group they were randomized to, not which treatment they received. So, for example, a participant randomized to the active monitoring group who chose to undergo radiotherapy was classified as an active monitoring group member.
Men in the active monitoring group were at higher risk of developing metastases than those in the surgery or radiotherapy groups. These findings were statistically significant.
The prostate cancer mortality rate in the active monitoring group was slightly higher than in the other groups but the findings were not statistically significant and the researchers concluded there was “no significant difference among treatments” with respect to mortality. The overall number of prostate cancer deaths was low: 8 in the active monitoring group, 5 in the surgery group, and 4 in the radiotherapy group.
On the surface, these findings suggest radical treatment for prostate cancer may not be necessary. Yet the study has a number of limitations that are important to keep in mind.
First, only 17 men died from prostate cancer (“deaths that were definitely or probably due to prostate cancer or its treatment”) during the study period. With such a small number of deaths, it is not surprising that no statistically significant finding regarding mortality from prostate cancer could be reached. We also do not know how the results would have differed if participants had been classified according to treatment received rather than group assignment. Furthermore, the assessment of the outcomes was problematic as prostate cancer deaths were not distinguished between those that were likely caused by the disease and those that were likely caused by the treatment.
The study also had a low response rate (61.6 percent; of 2,664 eligible men, 1,643 enrolled). The results may have differed substantially if more men had agreed to participate in the study. Of the men who did participate, 99 percent were white and approximately 75 percent had a Gleason score of 6, indicating less aggressive cancer and a low likelihood that the cancer would metastasize. Thus, the study findings cannot be generalized to minorities or men with more aggressive prostate cancers. Finally, new treatments for prostate cancer have emerged in the decades since the trial protocol was developed. Men seeking treatment today will have more options than those examined in this study.
Only 1 percent of study participants died as a result of their prostate cancer. Of those deaths, it’s unclear which were due to prostate cancer itself and which were due to treatment. Men who were actively monitored were at greater risk of developing metasteses.
Given the limitations mentioned above, it’s not clear if active monitoring is equivalent to more aggressive prostate cancer treatments. A larger study with a more diverse study population is needed to more conclusively determine the effectiveness of different treatment options. Treatments tailored to an individual’s genes, environment and lifestyle could also improve patient care.
Men with a prostate cancer diagnosis may want to discuss the risks and benefits of different treatment options with their health care providers, including treatments that were not included in this study.
Hamdy FC, Donovan JL, Lane JA, et al. 10-Year Outcomes after Monitoring, Surgery, or Radiotherapy for Localized Prostate Cancer. N Engl J Med. September 14, 2016. DOI: 10.1056/NEJMoa1606220
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