Episode 087: Prostate Cancer Series: Pt. 4- Radiation Oncology in Prostate Cancer
Last, but not least, in our multidisciplinary discussions regarding the management of prostate cancer, we are thrilled to present a special episode featuring soon-to-be attending Radiation Oncologist Dr. Jacob Hall. Dr. Hall is a senior Radiation Oncology resident and Chief Resident at UNC-Chapel Hill. Today, he helps us better understand patient selection for radiation and helps define key terms.
As a reminder, we previously discussed the fundamentals of Radiation Oncology with Dr. Evan Osmundson in Episode 027!
Most of the time, medical oncologists are not the ones referring patients to radiation for prostate cancer, but it does happen. What is some information that is worth including in the files sent over?
Pathologic and laboratory information:
PSA
Gleason Score
How many cores were positive/other high risk features on pathology
T-staging
Background information:
Medical comorbidities
Life expectancy (if possible)
Symptomatic burden (i.e., urinary symptoms in the case of localized prostate cancer)
Recall discussion with surgeon, Dr. Sanjay Patel, about how radiation can make bladder irritative symptoms worse!
Additional imaging:
PSMA PET scan (if possible) - helps to provide information about distant metastatic disease and also nodal involvement within the pelvis itself which may be questionable by conventional imaging
There are studies being done to see if radiation boosts to areas that are very avid improve outcomes, but that is not mainstream yet
Multiparametric MRI of the prostate - provides great information about extraprostatic extension and seminal vesicle invasion, both of which are higher risk features.
Can also provide information about where the disease is located which can help with planning the margins of radiation treatment
Using all of this information, Radiation Oncologists are able to determine if a patient is best suited for radiation for definitive treatment
How do you counsel your patients on the side effects of radiation for prostate cancer?
In general, it is best to think about symptoms that are in the field of treatment (local treatment = local symptoms; fatigue can also be seen). So in general:
GI symptoms:
diarrhea/loose stools
Abdominal pain or nausea is not common
GU symptoms:
Urinary frequency: this is additive; will peak after radiation is completed and then get better with time in the order of months
Nocturia
Sexual dysfunction: erectile dysfunction can happen with time
This was explored based on the data from the ProtecT trial
NOTE: Side effects are going to vary based on the type of radiation used, including brachytherapy, external beam radiotherapy (EBRT), stereotactic body radiotherapy (SBRT)
How do you counsel patients on the time frame of treatment?
For definitive therapy for localized prostate cancer, hypofractionated radiation dose are used
Recall: This means higher doses (>2Gy) per day, meaning fewer total radiation treatments
One of the most common treatment plans is 70Gy over 28 days
There are other strategies, but one is not better than another.
What is brachytherapy? What is the difference in side effect profiles?
Brachytherapy allows for radioactive materials to be placed directly into the target tissue bed, as opposed to external radiation which enters through the skin, through the tissue, and then out the other side.
This is going to be for your lower risk patients who are nervous about active surveillance (“doing nothing”) or are patients who do not want to undergo regular MRIs and repeat prostate biopsies
Two options for brachytherapy:
High dose rate:
Use of small catheters that are temporarily placed inside the prostate
Toxicity profile is often better since the catheters come out
Low dose rate:
Use of radioactive seeds that are implanted in the prostate bed and left there indefinitely
Can have more side effects
When deciding if brachytherapy is appropriate, need to ask about urinary symptoms (fullness). The prostate tissue can swell which can make obstructive symptoms worse!
Brachytherapy has also been shown to improve rates of biochemical recurrence when used as a “boost” in intermediate or high risk patients, as demonstrated in the ASCENDE-RT Trial
What about the use of proton therapy for prostate cancer?
The fundamental principle behind proton therapy is a theoretical better side effect profile due to the Bragg-Peak effect (which we also discussed in Episode 027). This is the idea that there is a sharp increase in energy before hitting the tumor, which then drops off, therefore minimizing effect to the surrounding tissue.
To date, there are no studies that show better outcomes for prostate cancer, but studies are in process.
For patients with metastatic prostate cancer, what is the process of discussions and planning for bone mets?
Radiation can be used for patients with metastatic disease under two main conditions:
Oligometastatic disease (often defined as 5 or less metastatic sites)
Often reserved for patient who are otherwise healthy and active
Treated with SBRT
Need to consider location; radiation can increase risk of bone fractures so if the met is in an area that is weight-bearing, this needs to be considered. Can also cause bowel toxicity.
Usually better side effect profile when used on extremities
Palliation from high tumor burden
Here you are using lower doses; options include:
30Gy in 10 fractions
20Gy in 5 fractions
8Gy in a 1 fraction
For patient relief from bone mets, 8Gy is good, but higher risk of repeat pain and need for re-irradiation.
Just because an area has gotten radiation before does not necessarily mean they can’t get it again (For example: 8Gy x1 can get more radiation)
About our guest: Jacob Hall, MD is a PGY-5 Radiation Oncology resident and Chief Resident at UNC-Chapel Hill. He completed medical school at Virginia Commonwealth University School of Medicine.
References:
https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(14)70361-4/fulltext : ProtecT Trial
https://pubmed.ncbi.nlm.nih.gov/28262473/: ASCENDE-RT Trial
The crew behind the magic:
Show outline: Vivek Patel
Production and hosts: Ronak Mistry, Vivek Patel, Dan Hausrath
Editing: Resonate Recordings
Shownotes: Ronak Mistry
Social media management: Ronak Mistry
