Radiation after Surgery
This information is for men who have already had surgical removal of the prostate gland, and now they have been recommended to undergo radiation therapy.
Who needs radiation therapy after prostatectomy?
Sometimes prostate removal does not completely cure the cancer. Even if the surgeon has done an excellent surgery, and it looks like he got all the cancer, there may still be some cancer cells left behind. This is especially common if the cancer was breaking through the outer lining of the prostate gland and going into tissues around the prostate (see picture on right). It’s also more common when there was a lot of cancer present in the prostate gland. Radiation therapy after prostatectomy may be recommended in the following four situations:
- The pathologist finds that cancer has broken through the prostate capsule (lining) and has gone into tissues surrounding the prostate. This is stage 3 cancer and includes cancer that has spread into the tissues around the prostate, into the seminal vesicles, or in more advanced cases into the lymph nodes or bladder.
- There are “positive surgical margins”. This means that cancer cells were seen at the edge of the tissue that was removed by the surgeon, and therefore cancer cells may still be inside the body.
- The PSA does not drop down to zero after surgery, but remains detectable.
- The PSA starts to climb again at some time after surgery.
Often there is a combination of these factors present.
Adjuvant or Salvage? The timing of Radiation after Prostatectomy
It is debatable when a patient should be referred for radiation. Some urologists will see warning signs on the pathology report and will refer the patient early before giving the cancer a chance to grow back. This is also called adjuvant radiation, and is typically started within 3 – 6 months of surgery. Other urologists prefer to wait until the PSA starts to rise before referring the patient. This is called salvage radiation, and is typically started more than 6 months after surgery.
If there are risk factors found at the time of surgery the patient may be referred for adjuvant radiation. Adjuvant treatment is additional treatment, given in conjunction with the surgery. For adjuvant radiation, it is best to wait 3 to 6 months after surgery if possible before starting the radiation, in order to give a chance for full healing. It is best for urinary control to improve as much as it is going to before starting radiation.
When do we start salvage radiation?
If the PSA is rising, the patient may be referred for salvage radiation. Salvage treatment is a second attempt at cure. The higher the PSA climbs, the lower the success rate of salvage radiation will be. If a patient wishes to avoid adjuvant radiation and do early salvage treatment (if required) then typically the PSA should be monitored closely and radiation should be started when the PSA is still less than 0.5 if possible. PSA progression after surgery is defined as three consecutive PSA rises, or alternatively two consecutive rises and a PSA over 0.1.
A study by AJ Stephenson in 2009 looked at how the PSA level at the time of starting salvage therapy affects the success of salvage radiation:
|PSA at the start of salvage radiation||6-Year freedom from cancer progression|
|0.20 – 0.50||48%|
|0.51 – 1.00||40%|
|1.01 – 1.50||28%|
|1.51 or above||18%|
In the RADICALS-RT study, they started salvage radiation very early, when patients had an average PSA of just 0.20. Their 5-year freedom from cancer progression rate was excellent, at 0.88.
How do we know where do we aim the radiation and how many treatments?
When we radiate after prostatectomy, we treat the tissues where the prostate gland used to be. This region is known as the “prostate surgical bed”. Once the prostate is removed, the bladder and the rectum and the other surrounding tissues get pulled into the empty area where the prostate previously was. When we radiate, we end up treating more bladder and rectum than we typically would with normal prostate radiation. We have to go slower and use a lower radiation dose because of this. Our typical dose is 180 cGy daily for 38 days = 6840 cGy total. Other cancer centers may use higher or lower dosages than this.
The options of adding androgen deprivation therapy (ADT) and radiating the lymph glands
The SPPORT trial enrolled men who had a rising PSA after surgery, and were going to receive salvage radiation therapy. The were randomly selected to receive either:
- Radiation to the prostate surgical bed
- Radiation to the prostate surgical bed + short term ADT of 4 – 6 months
- Radiation to the prostate surgical bed + short term ADT of 4 – 6 months + radiation to the pelvic lymph nodes
The 5 year success rates (no sign of any cancer progression) were 71%, 83%, and 89%. So, the men that received 4 – 6 months of ADT and radiation to the prostate bed + pelvic nodes had the best results. This is my default to recommend this combination to men who are getting adjuvant or salvage radiation but I think this can be individualized!
What does a detectable PSA after surgery actually mean?
PSA is a protein released by both healthy prostate cells, and by prostate cancer cells. Even if prostate cancer cells have spread to other parts of the body they will still release PSA. When the PSA is detectable after surgery it can be due to 3 possibilities:
- Some healthy prostate gland tissue was left behind during surgery (a prostatic remnant) and is making PSA
- Prostate cancer cells remain in the immediate prostate surgical area
- Prostate cancer cells are present in more distant sites, including pelvic lymph nodes, abdominal lymph nodes, or the bones.
If the PSA is detectable after surgery but is low and remains stable and does not rise, then the situation could be #1, prostatic remnant.
If the PSA is rising slowly after surgery, such as doubling every 12 months or slower then it is most likely scenario #2, cancer in the prostate region.
If the PSA is doubling quickly then this raises the possibility of #3, node or bone metastases.
Generally, there is no way to know for sure which of the above situations is occurring, but cancer remaining in the prostate region is most likely. When we give post-prostatectomy radiation we are playing the odds that the PSA is coming from cancer cells that are located in the tissues around where the prostate used to be. Scans are mostly useless to determine where the cancer is unless the PSA is at 0.5 or higher, because when the PSA is very low the cancer will be too tiny to be seen on any scan.
Often the urinary side effects from radiation are actually milder compared with men who still have their prostate gland. There can be some urgency, i.e. having to rush to the bathroom to urinate. There can be some increased leakage. The rectum can become irritated causing some looseness, mucous, and hemorrhoid irritation. These short term side effects usually clear up within 6 weeks after completing radiation. There is also the risk of long term (permanent) worsening of urine control, but this is not common. If you have been able to get erections since the surgery they may become further weakened by the radiation.
The success rate for radiation after surgery
Radiation after surgery is not a sure thing because:
- After surgery the area has a reduced blood supply, and cancer cells with less available oxygen may be more radiation resistant. In addition, we have to give a lower dose of radiation (39 treatments instead of 45) to limit the side effects. The aiming of radiation is also a little trickier, as there is no prostate gland to aim at.
- Some cancer cells may already be in the lymph nodes or bones. Even if scans are all clear, there can be small amounts of cancer in those areas that do not yet show up. The radiation does not treat the lymph nodes or bones. If there are any cancer cells there, tumors may develop in those area in the future.
So, cancer cells may survive radiation therapy inside the radiated area or outside the radiated area. There is an online calculator (google “MSKCC prostate nomogram”) which estimates the chance that you’ll still be cancer free 6 years after having salvage radiation. A typical result is 50 – 60%. Ask your doctor for help with this. If your PSA stays very low for 3 – 5 years after radiation then there is an excellent chance of long term success.
Monitoring after Radiation
Typically we will check the PSA three months after radiation, then every 3 – 6 months after that. Ideally the PSA will drop down to 0.00 – 0.05 within 12 months after finishing radiation, but as long as it drops some and stabilizes that is encouraging.
What happens if radiation after prostatectomy fails?
If the PSA is rising once more after previous surgery and radiation then there is usually no other treatment that can be used to try to cure the cancer. The main treatment becomes androgen deprivation therapy (ADT), to try to slow the cancer down. There is no rush to start on the ADT. ADT can often keep the cancer under control for several years. In occasional cases the cancer may be found in only a couple areas which have not been radiated before, and sometimes we can give some stereotactic radiation (SBRT) to these few areas.