Expert Offers Insight on Postoperative Radiation in Prostate Cancer

Peter Johnstone, MD

Radiation therapy (RT) can be a valuable treatment option for patients who receive a prostatectomy, either immediately after surgery or to treat a late recurrence. However, identifying appropriate patients for RT in these settings and deciding when to initiate treatment involves a careful consideration of several factors.

OncLive: Can you provide an overview of early immediate salvage therapy? When do you administer this type of treatment, and who is most appropriate to receive it?

Additionally, we know pathological things, such as whether there was extra capsularly extension, involvement of the seminal vesicles, whether margins were positive, and whether there was perineural invasion. Even with good MRIs, we did not have a clue on these characteristics.

You also discussed late, low, and slow recurrences at this meeting. What is new in that area?

Therefore, we are beginning to get smarter as to which patients should get postoperative RT. It could potentially be a lot of patients, especially in the era of robotic surgeries. The question then is, “How do we integrate the postoperative RT for those patients? Do we do it immediately? Do we delay things a little bit?” That is a matter, of some nuance, that will be discussed.There still will be a cadre of patients who postoperatively have a rising PSA for 2 to 3 years, subsequently. That becomes a dicey situation. Did they have positive margins? How low did their PSA go? How rapidly is it rising? These were all data that we can’t possibly have until the patient experiences this, and it is going to be unique to each individual case.

One of the postoperative problems we face if a patient is out 4, 5, 6, or 8 years is, is this really a localized recurrence into prostatic fossa where the prostate used to be? Could it be a nodule recurrence? Could it be an early sign of a metastatic focus in a bone somewhere?

What are some of the key questions a physician should consider before deciding to use RT?

We are limited, to some extent, in our ability to find these metastatic foci, and especially for patients with negative surgical margins with a rising PSA postoperatively. That is a very difficult call as to whether to begin radiation or not and when.When these patients present with a rising PSA postoperatively, the questions emerge. Were there positive seminal vesicles? Was there positive extracapsular extension? Were there positive surgical margins? These are all fairly basic things.

Looking to the future, what are some questions that still need to be answered?

Even in the absence of those things, you can still get a lasting response from RT. Does a disease exist elsewhere in a place where we can find it? Under those circumstances, if you have a late, slow recurrence of the type you are describing, CT scans of the pelvis, bone scans, and potentially even an MRI of the prostatic fossa might give us the information we need.There are new nuclear medicine—based scans that purport to be better than bone scans at finding small foci of disease. We will have to see how they play out. There are nanoparticle-based scans that are under research at this point.

What should a community oncologist consider when thinking about this area?

There are several new ways to try and find disease earlier. It will still be a thorny issue, however, for those patients for whom we can’t find disease, and with a long, slow recurrence of the type that we are talking about.The key point I want to make sure I get across is, is there a rising PSA postoperatively? To some extent, postoperative RT should be given directly afterward. These are potentially curative interventions. These are ways we can cure the patient. They should not be thought of as being adjuvant in any way because they are potentially definitive.

Under those circumstances, even if the immediate postoperative trials did show a survival benefit, we could actually cure patients as well by doing postoperative RT for a low, slow recurrence of the type that we have discussed.

In an interview with OncLive during the 2016 OncLive State of the Science Summit on Genitourinary Cancers, Peter Johnstone, MD, Moffitt Cancer Center, provided insight on post-prostatectomy RT.Johnstone: Once the prostate is taken out surgically, we know far more about the disease than we ever knew preoperatively. We know what the actual stage of disease is—meaning how much of the prostate is involved. We know the actual grade of the disease because, prior to that, we only had biopsies. We know, ultimately, how much of the gland was involved, but also how many lymph nodes were involved.