Originally published 5/3/2016
Six years after we posted the blog below, the Journal of the American Medical Association (JAMA) published an article on the “small but statistically significant increase in the risk” of a different cancer following radiation for prostate cancer (PCa).[i] What makes this article noteworthy is the size of the study population: 143,886 PCa cases from 2000-2015, drawn from the Veterans Affairs Corporate Data Warehouse. All cases were patients who were diagnosed with localized disease (still confined to the prostate) and no other history of cancer. In that study cohort, 52,886 (36.8%) received radiation as their primary or first treatment, and 91,000 (63.2%) did not. The authors write, “A second primary cancer more than 1 year after prostate cancer diagnosis was present in 4257 patients (3.0%), comprising 1955 patients (3.7%) in the radiotherapy cohort and 2302 patients (2.5%) in the nonradiotherapy cohort.” This means that following radiation, more men developed a new, different cancer compared with the men who did not receive radiation. In addition, the risk of a second primary cancer increased over time, leading to what is called a late-onset side effect of exposure to radiation. As we noted in the original blog, there are many PCa patients for whom radiation is the best available treatment choice. The point of the new article is the importance of doctor-patient discussion before making a decision, so the doctor can be transparent about the risks as well as the benefits of each choice. Patients with 10+ years of life expectancy should carefully consider the possibility of a new cancer such as bladder or rectal cancer, occurring years after their radiation treatment is through.
I have written several blogs on external beam radiation for prostate cancer along with its side effects. Radiation is a good choice for the right patient. As with all prostate cancer treatments, it is essential to match a treatment with an individual’s cancer because many factors go into the choice: clinical findings (PSA, Gleason grade tumor stage and patient age); family history and genomic considerations; and a person’s lifestyle preferences.
Most patients are concerned about the risk profile of each treatment. When it comes to beam radiation, short-term side effects are few. During the series of treatments, patients may notice increased fatigue, possible urinary irritation, and bowel symptoms such as diarrhea. These conditions generally clear up quickly, and for the next few years life continues much as it always has.
There are, however, side effects that may gradually show up over the next 3-5 years, including urinary and sexual difficulties. They are highly treatable so, while troublesome, they are not dangerous.
However, beam radiation has been linked with a very serious side effect, which is the increased of risk of developing a secondary cancer. This means a new cancer not related to prostate cancer, such as rectal cancer. I have previously addressed the increased chance of rectal cancer at https://sperlingprostatecenter.com/radiation-therapy-prostate-cancer-cause-rectal-cancer/. Now I want to report on a new study linking prostate radiation with three below-the-belt cancers. According to the study, after prostate radiation the risk increased for bladder, colorectal and rectal cancer.[ii]
The study team examined 21 published studies on prostate radiation and secondary cancers. While they found no evidence for higher risk of blood or lung cancers, they found that the development of bladder, colorectal and rectal cancers took a long period of time to occur (5-10 years). Thus, we might consider these long-term side effects of radiation. Often, patients are not explicitly told about a link between prostate radiation and the risk of secondary cancers in the pelvic area.
The authors caution that the evidence suggests, but does not confirm, that beam radiation therapy actually causes secondary cancers. More research is needed, they say. They also point out that the analysis involved conventional external beam radiation therapy rather than brachytherapy (seed implants) or newer, more “focused” radiation such as IMRT (intensity modulated radiation therapy). They explain, “‘The current move with all types of radiotherapy for prostate cancer — toward ‘smaller, tighter’ treatment volumes —‘might well shift the contemporary risk back.’”[iii] This implies that traditional beam radiation has more scatter effect than seed implants or IMRT. Put another way, since the first nuclear weapons were deployed in 1945, and more recently nuclear accidents such as Chernobyl have occurred, we know that radiation is difficult to control, and uncontrolled radiation results in higher cancer incidence.
To return to my opening thought, many low-to-moderate risk multifocal prostate cancer patients who can’t have (or don’t want) surgery may turn to radiation. According to the study, the absolute risk of secondary cancers is very low. However, those who think radiation has zero risk of triggering other cancers should be well-informed that radiation therapy is not a “free ride.”
NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.
[i] Bagshaw HP, Arnow KD, Trickey AW et al. Assessment of Second Primary Cancer Risk Among Men Receiving Primary Radiotherapy vs Surgery for the Treatment of Prostate Cancer. JAMA Netw Open. 2022;5(7):e2223025.
[ii] Mulcahy, Nick. “’Risky’: Prostate Radiation, Second Cancers Linked.” Medscape News (Oncology), March 2, 2016.