What goes up may not come down. At least, that’s what a new trend in prostate radiation therapy might lead you to believe.
The trend is radiation dose escalation. It is occurring in patients who have a radical prostatectomy but whose clinical factors are considered to be a high risk for recurrence. By clinical factors, I mean their pre-operative PSA, Gleason score, and tumor stage, as well as any upgrading or upstaging after the post-surgical prostate specimen has been analyzed. In the physician’s judgment, if there is sufficient evidence of risk, the patient is recommended for a course of what is called adjuvant radiation even though it’s too early to know if recurrence has begun.
Adjuvant means a treatment that follows a primary treatment with the intention of suppressing possible recurrence. “Adjuvant radiotherapy is considered a standard of care in a number of cancer types, including tumors of the breast, brain, head and neck, stomach, rectum, cervix, and endometrium, among others. In these cases, adjuvant radiation has been demonstrated to reduce tumor recurrence, and in some cases, to reduce cancer-specific mortality as well,” writes Dr. Rahul Tendulkar.[i]
Thus, it doesn’t seem like a bad idea to deliver a pre-emptive strike against prostate cancer for men whose high risk disease has been surgically removed. After all, as the saying goes, an ounce of prevention is worth a pound of cure.
Too much of a good thing?
Adjuvant radiation therapy as a preventive strategy has been around for at least 30 years and there is no doubt that it has saved lives. However, there is no way to know which patients will actually benefit from early adjuvant radiation and which will never experience recurrence, and which will experience recurrence even if they do receive adjuvant radiation after their surgery.
Perhaps it’s that uncertainty that is driving a trend to increase the radiation dose for adjuvant therapy. A new study finds a growing trend to use high dose radiation and even very high dose radiation. From 2003 – 2012, the use of high dose grew from 29.9% to 63.5%. As for very high dose, it rose from 4.5% to 10.8%.[ii] Yet there have not been Level 1 research studies to support this strategy.
In fact, it may be too much of a good thing. As the study authors wrote about post-prostatectomy radiation therapy, “…dose escalation cannot be achieved without increasing dose to normal tissues since most cells within the clinical target volume are in fact part of normal/uninvolved nearby organs. As such, dose escalation in this setting invariably increases risks of toxicities.”[iii]
The word “toxicity” in this context means unwanted harmful side effects. Because of the location of the prostate, nearby structures include the bladder and urinary outlet, the bowel, and nerves/blood vessels connected with sexual function.
The scatter effect of radiation can damage neighboring healthy tissues. Unlike prostate cancer treatments that take effect immediately (surgery or ablation) radiation has a gradual, cumulative effect. Urinary, sexual or bowel side effects may not show up right away, but can occur months or even years later (these are called late-onset side effects).
Needless to say, the size of the radiation dose will have an impact not only on cancer cells in the prostate bed, but also do some degree of collateral damage in the areas adjacent to where the prostate was removed. For this reason, adjuvant radiation is usually not begun until post-prostatectomy urinary function has been regained.
High risk prostate cancer patients who are having a radical prostatectomy should discuss with their surgeon the merits of adjuvant radiation for their case. At the Sperling Prostate Center, we always recommend getting more than one opinion, and if possible, do your own research to inform yourself. We applaud the authors (Alexidis et al.) who contributed their research to make us all aware of the creep in higher radiation doses for adjuvant radiation therapy.
NOTE: This content is solely for purposes of information and
does not substitute for diagnostic or medical advice. Talk to your doctor if
you have health concerns or questions of a personal medical nature.
[i] Tendulkar, Rahul. “POINT: Early Salvage vs Adjuvant Radiotherapy for High Risk Prostate Cancer.” Cancer Network, Oct. 15, 2017. http://www.cancernetwork.com/oncology-journal/point-early-salvage-vs-adjuvant-radiotherapy-high-risk-prostate-cancer
[ii] Charnow, Jody A. “Use of Post-RP High Dose Radiotherapy Increasing.” Renal & Urology News, Aug. 9, 2018. https://www.renalandurologynews.com/prostate-cancer/use-of-high-dose-radiation-therapy-after-radical-prostatectomy-on-the-rise/article/787154/
[iii] Alexidis P, Guo W, Bekelman JE, et al. Use of high and very high dose radiotherapy after radical prostatectomy for prostate cancer in the United States. https://www.nature.com/articles/s41391-018-0066-5.pdf