Radiation for Prostate Cancer

The role of radiation in prostate cancer can be broadly thought of as having 2 purposes or intents:

  1. Curative: attempt to cure prostate cancer such that the cancer is eradicated from the body
  2. Palliative: attempt to reduce sufferring and prolong life even if the cancer is not completely removed from the body

It is only possible in hindsight to determine if the cancer has been eradicated - and for prostate cancer this can take years. Even if the goal cure has not been achieved, there are palliative benefits to radiation (or other treatments) - in some cases the disease process can be slowed such that the appearance of some of the cancer-related sufferring is delayed (and as a result the need for additional treatment may be postposponed).

 

Radiation may play a role in 'multimodality' treatment. That is, as one piece of a group of cancer treatments (radiation, surgery, medications) to cure or palliate disease. Medical terminology reflects these roles:

 

  • Primary treatment modality: the treatment without which the stated goal could not be achieved (this can be surgery, radiation or medication)
  • Adjuvant: when used AFTER the primary treatment modality has been used
  • Neo-adjuvant: when used BEFORE the primary treatment modality has been used
  • Salvage: when used AFTER another primary treatment modality has been used but recognized to have failed or not met its goal

 

A treatment plan to treat a high risk prostate cancer with radiation might look like this:

  1. Consultation with a Radiation Oncologist and then a treatment planning session (this sometimes occurs after neoadjuvant hormones have been started by your Urologist)
  2. Neoadjuvant hormone treatment for 6 months (starting with 30 days of an antiandrogen such as Bicalutamide (Casodex) with an injection of an LHRH agonist every 3 months starting 1-2 weeks after the bicalutamide) 
  3. External beam radiation (IMRT/VMAT or similar approach) for 5-7 weeks starting 6 months after neoadjuvant hormones were started. Radiation administered for 30 minutes each day of the workweek (Monday-Friday)
  4. Adjuvant hormone treatment for 2-3 years after completion of radiation (shorter if lower risk, longer if higher risk cancer)

You can appreciate that the total treatment time with a multimodality radiation treatment may last a few years with the hormone components. In some cases, a radiation 'boost' is applied - more than one type of radiation may be used for your treatment; for example, brachytherapy seeds may be follwed by a course of external beam radiation.

 

Sequencing

The order in which treatments is used is important. a good example is the toxcity (side-effects) that can be expected when radiation and surgical treatments are ordered. When surgery is used as 'salvage' treatment after radiation the risk of urinary incontience (leakage, wetting underpants) is very high (30-50%) whereas if 'salvage' or 'adjuvant' radiation is used after surgery the risk of incontinence is very low (less than 5%). Balancing the risks and benefits of differenet strategies is what the team of specialists is there to help you navigate and make recommendations on.

 

Radiation for Cure

 

Radiation is capable of curing prostate cancer. The chance of cure will be dependent on a number of circumstances and in some cases requires the use of neo-adjuvant/adjuvant treatments to achieve the best results. Your radiation oncologist will discuss the pros and cons of the different strategies. Here is an overview.

 

Use of Hormone Treatment with Radiation

Hormone treatment can take several forms but the primary goal is to reduce the availability of testosterone to prostate cancer cells. Anti-androgens (androgen receptor blockers/antagonists), LHRH agonists (which turn of testosterone production by the testicles), and other newer hormone active medications (e.g. abiraterone, enzalutamide) are all being used or tested to increase the success of radiation.

 

As a general rule, the higher the risk of your prostate cancer (as defined by PSA, Gleason grade and stage), the more likely you are to benefit from the use of hormone treatments. If you have a low risk prostate cancer, the risks of the hormone treatments may outweight the potential for benefit.

 

The duration of treatment and whether the hormones are used before and/or after the radiation is administered involve a discussion with the radiation oncologist. Your treatment may be modified over time - it's important to know that you can see how you respond to hormones over time and shorten the duration of treatment if the side-effects cannot be addressed without completely discontinuing treatment.

 

Types of Radiation Modalities

There are several different types of radiation therapy available - each has the goal of maximizing cure and minimizing toxicity (side-effects or sufferring caused by the treatment itself). Because the prosate sits beside the rectum, the bladder and the nerves responsible for erections, these structures are always exposed the the highest 'spillage' of radiation. No matter how well the treatment plan is executed, the bladder and rectum always receive undesireable radiation which can cause bowel, bladder and sexual toxicity.

 

There is no one type of radiation that is better than the others (and in some cases the different approaches of radiation are used the same patient). There is little to no scientific data which allows for a good direct comparison of the different modalites of radiation - this is where having a discussion with the radiation oncologist is critical. A radiation oncologist has the expertise to individualize your treatment and cut through the marketing and advertising that you may encounter on the web (especially as medical centers in the United States 'compete' for patient's business).

 

Exterma Beam Modalities (Outside-In) Brachytherapy Modalities (Inside-Out)
Photon Radiation (X-rays and Gamma Rays)
  • 3-D Conformal Radiation
  • IMRT: Intensity modulated radiation therapy
  • VMAT: Volumetric intensity modulated arc therapy

Particle radiation (Protons and Neutrons)

  • Proton beam therapy

  • Commonly referred to as 'seed therapy'
  • HDR: high dose rate
  • LDR: low dose rate
  • These use Iodine 125, Palladium 103 or Cesium 121

 

You may see the terms "sterotactic radiosurgery (SRS)" and "knife" (e.g. cyberknife, gammaknife, SABR - Stereotactic Ablative Radiation) used for different types of external beam radiation. These are simply marketing terms to try and draw customers for radiation treatment by implying that the radiation is similar has the precision of surgery when in fact the treatment is radiation and not surgical. The common marketing is that it is "entirely non-invasive", "very short treatment course", "equivalent cancer control to brachytherapy, conventional XRT, surgery", "less exposure of rectum and bladder". The "long term" follow-up is described as 'excellent at 3 years'. It is important to note that SHORT term follow-up is anything less than 5 years (long term data in prostate cancer is over 10 years). In addition, many of the trials are of very short duration and 'uncontrolled'. The risks of SABR, cyberknife and the like have been grossly understated - the actual measured risks of serious rectal bleeding requiring transfusion is in the range of 1 in 5 - and this is just early bleeding. Patients can expect this to become worse and more difficult to address as they get older (Musunuru et al IJROB 2016).

 

Be very suspicious if anything is marketed as having a low or no side-effects (this applies to surgery, radiation, medication or any treatment). It may be that the appearance of side-effects is delayed (in the case of radiation, it may be years), that the side effects are rare (but may infact be very serious or incurable).

 

Radiation for Palliation

Even when prostate cancer cannot be cured, there is the potential to reduce suffering and extend life. Radiation can be used to treat specific areas of cancer pain in the bones. In addition to traditional external beam radiation, use of 'radiopharmaceuticals' (drugs that are radioactive) can be used in select circumstances. An example is Radium-223 Dichloride (Xofigo) for advanced incurable prostate cancer.