When facing a new cancer diagnosis, some people ask their doctors, “What would you do if you were me?” Here, our Curious Dr. George asks Marc B. Garnick, MD, how he would handle his own advanced prostate cancer. Dr. Garnick is the Gorman Brothers Professor of Medicine at Harvard Medical School (HMS) and Beth Israel Deaconess Medical Center in Boston, MA. He is also Editor in Chief of the HMS Annual Report on Prostate Diseases.
Curious Dr. George: Last year, you shared with our readers how you, as an expert, would proceed with handling your own severe back pain and spine lesions.
Let’s revisit that hypothetical scenario with some new developments: Further rapid lab studies demonstrated normal peripheral blood counts and no abnormal serum proteins. The back pain stabilized. Digital rectal exam discovered an enlarged, diffusely firm prostate gland with scattered hard foci. Ten transrectal prostate biopsy cores all contained adenocarcinoma with varying degrees of dedifferentiation, Gleason score of 8, repeat PSA was 25.
How should the pathologist handle the remaining tissues? What procedures should a reference laboratory perform? How would genomic, metabolomic, or proteomics inform next steps? And would imaging be helpful?
Marc B. Garnick, MD: With these new developments, the differential diagnosis has now been narrowed. The likelihood of the bone lesions being related to a plasmacytoma or multiple myeloma, though not completely excluded, are less likely. The lead diagnosis now has been established to be a Gleason score 8 prostate adenocarcinoma, which I presume is a Gleason 4+4. Please recognize that based upon the International Expert Consensus on Prostate Cancer nomenclature, this is now best described as Grade Group 4 (GG 4). Grade Group 1 (GG 1) contains Gleason patterns 3+3; GG 2 contains Gleason patterns 3+4; GG 3 contains Gleason patterns 4+3; GG 4 contains Gleason patterns 4+4; and GG 5 contains Gleason patterns 4+5 or 5+5. If this patient did not have suspected metastases to the bones (and even in the setting of metastatic prostate cancer), the pathology biopsy note should mention the presence of any intraductal component, perineural invasion, or lymphovascular invasion, all of which commonly accompany high-grade Gleason cancers.
Recent recommendations now suggest that genomic profiling of the patient both for germline and somatic mutations be assessed. The importance of BRCA (either germline or somatic) mutation has increased in significance, especially since there are emerging associations of prostate cancer being found in families of women with BRCA mutations. The finding of a BRCA2 mutation is associated with a more aggressive biology and could help inform treatments at some later day with the PARP class of therapeutics of platinum-containing agents, given the increased sensitivity of BRCA + cancers to respond to these therapies.
Additionally, if MSI high is noted during molecular testing of tumor tissue, the patient may at some later time be eligible for treatment with an immune checkpoint inhibitor, such as pembrolizumab.
The above consideration of more precise pathologic assessment is more important in a patient who has a GG 4 or 5, in whom there is no obvious evidence of metastatic disease. In such cases, one is trying to assess a probability of the patient having subclinical metastatic disease or being likely to develop metastatic disease. For the patient with already-established evidence of abnormal foci (in this case, the bone lesions), we in the past would have assessed with an Axumin scan; now, the availability of either Ga or F linked prostate-specific membrane antigen (PSMA) scanning would be indicated, both for diagnostic purposes as well as assessing down-the-line utility of PSMA-specific therapeutic ligands, such as Lutetium 177.
Curious Dr. George: What additional testing and what therapy would you deem to be most appropriate at this point?
Marc B. Garnick, MD: Please recall that this patient (hypothetically me) presented with back pain and multiple bony lytic lesions. Regardless of the etiology of these lesions, identification of any impending spinal cord compression must be assessed. While spinal cord compression is an unusual manifestation of de novo metastatic prostate cancer, it is clinically more common in the setting of treated prostate cancer that has progressed to become castration resistant. I would reassess the anatomic locations of the bone lesions, and then obtain a spinal MRI directed diagnostic evaluation, along with a good neurological examination to inform preemptive radiation or surgical considerations if either impending or actual compression is found.
For treatment of newly diagnosed presumably castration-sensitive metastatic prostate cancer, we now have multiple advances that have been established in this disease setting. First-line ADT (generally with an LHRH agonist or GnRH antagonist) is now supplanted with second-generation agents, such as abiraterone (+ prednisone) or enzalutamide, or other androgen-receptor inhibitor agents, such as apalutamide. ADT + chemotherapy with docetaxel is also appropriate. Given the bone pain and potential neurological issues here, I would select a GnRH antagonist (either degarelix or relugolix) as the preferred therapy.
Dr. Garnick can be reached at firstname.lastname@example.org.
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