Once upon a fairly recent time, radical prostatectomy (RP) was the treatment of choice for prostate cancer (PCa), even for high risk disease. There were two main reasons for this:

1. It was believed that PCa was a multifocal disease scattered throughout the gland, even if too small to be picked up by biopsy. Therefore, aggressively removing the gland was a take-no-chances strategy intended to eradicate all the cancer, even if it was a low risk Gleason 3+3=6.
2. Since there was no reliable way to determine if the cancer had metastasized (spread) to the lymph nodes, RP was the best way to remove nearby lymph nodes at the same time for examination. If cancer was found to be present, the surgeon had to deliver the bad post-op news that PCa remained in the body and would be able to travel through the lymph system to remote locations. Therefore, further treatment was needed in hopes of preventing more advanced disease—but the patient now had a worse prognosis in terms of survival.

Thus, if lymph node involvement could have been identified before surgery, the patient might have been offered an alternative treatment plan that bypassed RP in favor of a course of androgen deprivation therapy (ADT or hormone therapy) plus radiation that included the lymph nodes in the groin as well as the prostate gland.

Cancer stage matters

RP is an aggressive treatment because it removes the entire gland, placing urinary and sexual function at risk of side effects. Another way to bypass surgery is to know in advance if there’s lymph node metastasis (LNM). As a rule, low risk disease is still confined to the gland, but it’s important to know the tumor’s stage. Stage is determined by factoring in PSA, imaging results, tumor grade, the extent/location of the tumor, and detecting any cancer involvement in the lymph nodes, bones or other areas.

Back in that once-upon-a-time, if a patient’s biopsy was positive for PCa, he would also be sent for a bone scan and CT scan. If those were negative for PCa there would be a sign of relief. RP would be given a green light, provided the patient was a candidate for surgery in terms of age and any other co-existing conditions.

The problem was, CT scan was not 100% reliable at detecting PCa in lymph nodes. That was then, but now we have multiparametric MRI (mpMRI). mpMRI is like your one-stop photo studio for a complete and comprehensive portrait of your prostate and surrounding structures. How does mpMRI stack up against CT when it comes to determining stagy by identifying possible LNM, especially in higher risk PCa?

The best imaging for staging and planning

In December, 2021 a German research team published a head-to-head comparison between mpMRI and CT.^[i] All 228 patients in the study were treated with RP, so their gland and lymph node specimens were the reference standard for their pre-op imaging results. In addition, each patient’s clinical factors (PSA, PI-RADS, Grade Group, and tumor stage) were compared between the presence or absence of PCa in the lymph nodes. LNM was evaluated according to size and localization, and whether they had been detected by imaging prior to surgery.

Out of the 228 patients, surgery confirmed that 24 had LNM. These patients had significantly higher PSA, PI-RADS, Grade Group and stage than patients without LNM. MRI proved superior to CT in detecting even small LNM in their pelvic locations. Statistically, MRI had 81% sensitivity vs. 33% for CT, and 99% specificity vs. 97% for CT. Reassuringly, the authors report that LNM as very rare in patients with PSA less than 10, PI-RADS less than or equal to 4, and stage lower than T2.

The authors concluded that MRI can optimize pretreatment diagnostic and treatment planning, including for RP, whereas CT was “clearly limited” for evaluating lymph node involvement.

Thanks to our state-of-the-art 3T magnet and the expertise of Dr. Sperling and our team, the Sperling Prostate Center offers superior diagnostic services to match the broadest possible range of treatment options to each patient’s PCa. Whereas RP used to be more or less a cookie-cutter option for most patients, today’s therapy choices range from Active Surveillance and focal treatment to more aggressive forms of surgery and radiation.

In the case of lymph node metastasis, forewarned is indeed forearmed. Patients and their doctors can tailor treatment approaches to maximize the possibility of complete cancer control and reduced chances of cancer-specific mortality. The starting point is, of course, mpMRI for complete imaging information. Together with all other clinical factors, this becomes the best available navigational kit for the journey ahead.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

[i] Valentin B, Arsov C, Ullrich T, Demetrescu D et al. Comparison of 3 T mpMRI and pelvic CT examinations for detection of lymph node metastases in patients with prostate cancer. Eur J Radiol. 2021 Dec 17;147:110110.