Acute and late radiation toxicities of proton beam radiation therapy

Over the years there have been almost no publications addressing the complications of proton beam radiation therapy (PBRT) among well-defined series of prostate cancer patients. With the number of PBRT centers now growing fast, good data on the side effects of PBRT are an urgent priority.

Nihei et al. have conducted a prospective Phase II study in Japan, designed to assess the incidence of late rectal toxicities after PBRT among patients with organ-confined prostate cancer. Their study also provides us with information about acute rectal toxicities as well as acute and late bladder toxicities.

The study was carried out by a consortium of three Japanese PBRT facilities. Patients were all intended to be clinical stage T1 or T2, with PSA levels of ≤ 20 ng/ml and Gleason scores ≤ 7. Patients received no hormone therapy either while on study or for 12 months prior to enrollment in the study. The patients were all treated between 2004 and 2007 and received a total dose of 74 GyE in 37 fractions.

The results of the study showed the following:

  • 151 patients were enrolled in the study.
  • The clinical stages of the patients were T1c (n = 75), T2a (n = 49), T2b (n = 9), T2c (n = 17), and T3a (n = 1).
  • The Gleason scores of the patients were 4 (n = 5), 5 (n = 15), 6 (n = 80), and 7 (n = 51).
  • The initial PSA level was < 10  ng/ml in 102 patients and 10-20 ng/ml in 49 patients, respectively.
  • 42 patients (28 percent) had previously received hormonal therapy.
  • Median follow-up was 43.4 months.
  • Acute (temporary) Grade 2 rectal toxicity developed in 0.7 percent of patients (2/151).
  • Acute (temporary) Grade 2 bladder toxicity developed in 12 percent of patients (18/151).
  • Late rectal toxicity of Grade 2 or higher was observed in 2 percent of patients (3/147) followed for  > 2 years.
  • Late bladder toxicity of Grade 2 or higher was observed in 4.1 percent of patients (6/147) at 2 years post-treatment.

In this cohort of Japanese patients, the incidence of acute and late rectal toxicities following PBRT for localized prostate cancer was extremely low. The incidence of acute and late bladder toxicities is clearly higher. The abstract does not provide us with detail about the incidence of late bladder toxicities of Grade 3 or Grade 4. Grade 2 toxicities are generally considered to be mild to moderate.

The “New” Prostate Cancer InfoLink looks forward to seeing data on other complications of PBRT in comparable patient cohorts — most particularly the incidence of erectile dysfunction in men who had high erectile function immediately prior to treatment.

5 Responses

  1. Pardon my ignorance, but please define what “toxicity” means in this study?

    [Are you telling us] that erectile dysfunction was simply ignored as an effect of treatment?

  2. A “toxicity” in the context of any study of radiation therapy is an adverse effect of the radiation. In the context of the current study, the rectal toxicities could include a whole variety of things, from chronic diarrhea or radiation burns to the rectum. The bladder toxicities could include urinary tract urgency or frequency, evidence of radiation burns, and similar factors. The details are probably given in the actual paper, but I don’t have access to the full text.

  3. Hi Mike,

    Thanks for the clarification re “toxicity.” In other words, they’re using it as a euphemism in order to not have to address negative consequences of treatment.

    I’ve talked some on this site about my husband, but have I ever mentioned my granddad? He was treated with RPP and radiation for PCa in the late 90s. He continues to suffer from rectal “toxicity.” This “side” effect has turned a gregarious, involved-in-his-community, happy man and turned him into a chronically-depressed, near recluse. He refuses to travel and won’t leave the house for even short trips until he’s had his daily “constitutional” in order to avoid uncontrollable, explosive diarrhea.

    His rectal “toxicity” played an important role in the treatment decisions my grandparents made when my grandmother was diagnosed with multiple myeloma. They had the opportunity for her to participate in clinical trials (that are now on the market, and quite effective), but chose not to because of his (perceived) inability to travel. She died two years ago this January and I miss her every single day.

    Now, I understand that it was their decision to not participate in the clinical trials, but his condition — caused wholly by treatment — is physically uncomfortable and sometimes painful, psychologically devastating, and, combined with the impotence, infantilizing, and socially distancing.

    There are no “side effects.” There are only effects.

    By the way, I wasn’t asking a question about the study’s omission of erectile dysfunction. I was making an editorial comment. It is telling of the values of the researchers that they are so dismissive of erectile function that they don’t even bother to study it.

  4. Dear Tracy:

    (1) We have no idea whether the researchers in this study collected data on erectile function or not. For all you or I know there is another publication waiting to come out in another journal tomorrow. Maybe they didn’t; maybe they did, but I don’t think you have the right to categorize the researchers as “dismissive” of erectile function on the basis of the current information.

    (2) I would not agree that “toxicity” is a euphemism at all. It is a very clearly defined term that includes all adverse consequences of any specific treatment, whether common or rare, potentially including death. It comes from exactly the same stem as the word “toxicology” (the study of the nature, effects and detection of poisons and the treatment of poisoning).

    (3) I am sorry to hear about your grandfather’s situation, which perhaps explains your viewpoints on the topic of prostate cancer far more clearly than what you have said about your husband’s situation.

    (4) I am also sorry to hear about your grandmother. I should be clear that I have been a member of the board of directors of the International Myeloma Foundation for most of the past 20 years.

  5. The VA Medical Center in Richmond, VA, treated me for prostate cancer [with radiation therapy and] burned my bladder up and rectal area bad. The place is run by interns.

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