In what one of the authors has described as “a somewhat critical and light-hearted look at our current enthusiasm for aggressive approaches to oligometastatic prostate cancer”, an article currently in press asks some serious questions about the use of metastasis-directed therapy or MTD in the management of such patients.
It is worth noting that
- MTD is usually defined as either the surgical resection of or the use of stereotactic forms of radiotherapy in the treatment of such limited and focused metastatic sites of “oligometastatic” prostate cancer and
- “Oligometastatic” prostate cancer is commonly referred to as a description of a form of advanced prostate cancer characterized by up to three simultaneously apparent (“synchonous”) metastatic lesions within the bones or the lymph nodes.
Let us be clear immediately that (in their article entitled ‘“Gotta catch ’em all”, or do we? Pokemet approach to metastatic prostate cancer‘) Murphy et al. are not suggesting that enthusiasm to treat such patients effectively by using treatments targeted to individual sites of metastasis is mis-directed. Rather, what they are saying is that we have very little good information, as yet, with regard to such things as:
- How best to select patients who are most appropriate for this type of ablative therapy
- Whether appropriate imaging techniques are being used to optimize the identification of the right areas of metastasis to treat
- How best to define and monitor appropriate outcomes for such patients post-treatment
- How to define “success” of such treatment in terms of outcomes
As a consequence, however one may want to look at the opportunity that is available to treat patients with (say) one to three focal sites of metastasis from a clinical perspective, the patients themselves (as well as their doctors) need to understand that we have very little sound information (as yet) about things that are critical to defining clinical success:
- Does such treatment really extend patient survival?
- Does it improve quality of life over time?
- Are there definable subsets of patients who seem to do better (or worse) in response to such treatment?
- Is there a specific form of imaging technique (e.g., gallium-68 PMSA-enhanced PET/CT scanning) that should be seen as the “gold standard” for identification of appropriate metastatic lesions in patients who are the best candidates for such treatment?
Murphy et al. note that, over the past few years, there has been a massive growth in the number of publications in medical journals about the management of patients with oligometastatic prostate cancer (from about 20 in 2014 to nearly 250 in 2016) that has paralleled the growth in the number of publications about PSMA PET/CT scanning for prostate cancer (from about 10 in 2014 to > 35 in 2016). In other words, we are seeing the same massive growth in the treatment of oligometastatic prostate cancer as we saw in the uptake of the game Pokemon Go in 2016. But is this growth really justified?
At the end of the day, at best, the use of metastasis-directed treatment (MTD) in the management of oligometastatic prostate cancer is currently an “investigational” technique (and many would use the term “experimental” as opposed to “investigational”). It is going to take a while before we shall really know how well-justified the use of MTD is for the majority of men with oligometastatic prostate cancer.
Like Dr. Murphy and his colleagues, The “New” Prostate Cancer InfoLink isn’t saying that MTD is a bad idea. On the other hand, we are saying that this is an unproven form of therapy and needs some really serious and organized study before everyone simply jumps onto the bandwagon. Playing an advanced version of “Whack-a-Mole” with one’s prostate cancer metastases is probably not going to have long-term benefits for an awful lot of patients. On the other hand, if we could really define the patients who demonstrably benefit from MTD, then this would be an enormous step forward.
We expect Jim Waldenfels to be commenting promptly!
Editorial note: We thank Dr. Declan Murphy of the Peter MacCallum Cancer Centre and the Australian Prostate Cancer Research Centre in Victoria, Australia, for providing us with a full-text copy of this paper for our review.