One of the treatment options for locally advanced non-metastatic prostate cancer is external beam radiation therapy in conjunction with androgen deprivation (testosterone blocking) therapy. If there are no lymph nodes (glands) that are obviously involved, then radiation would be confined to the prostatic bed. However, within the radiation oncology fraternity there has been debate whether patients should also receive prophylactic radiation (treatment given as preventative measure in case there is disease that is too small to be seen or disease that may still develop) to the nodes within the pelvis.
Results of the POP-RT trial have recently been reported in the Journal of Clinical Oncology and presented at the American Society of Clinical Oncology (ASCO) Annual meeting. Murthy et al compared radiation just given to the prostate to radiation give to the whole pelvis in patient with high risk and very high-risk prostate cancer with non-metastatic disease1.
High-risk prostate cancer was defined as:
- Clinical stage T1-T3a with pathological stage Gleason 8-10 and any PSA level or
- Gleason 7 with PSA > 15 ng/mL or
- Gleason 6 with PSA > 30 ng/mL or
- Clinical stage T3b-T4a with any GS and any PSA level
Clinical stage: defined by digital rectal examination of prostate
Pathological stage: as reported by histopathologists when looking under the microscope
Metastatic disease and lymph node involvement was assessed with one of the following imaging modalities:
- MRI (Magnetic resonance imaging) of the prostate
- Contrast-enhanced computed tomography (CT) scan of abdomen and pelvis,
- Technetium-99 bone scan
- Positron emission tomography (PET) CT with fluoride-18 or gallium-68 prostate-specific membrane antigen (PSMA) scans.
The risk of pelvic node involvement was estimated using the Roach formula. From this formula patients having a risk of pelvic node involvement more than 20% were included.
Patients also needed to be eligible to receive radiation and long-term androgen deprivation therapy.
All patients received image-guided, intensity-modulated radiotherapy and minimum 2 years of androgen deprivation therapy.
The intervention group received radiation to the following nodes in addition to the prostate:
- Bilateral common iliac nodes at vertebral level L4-5
- External iliac lymph nodes
- Internal iliac lymph nodes
- Presacral
- Obturator nodes
Biochemical progression-free survival, disease-free survival, and distant metastasis-free survival were significantly improved with whole pelvis radiotherapy compared with prostate-only radiotherapy.
- 5-year biochemical progression- free survival: 95% vs 81.2% (Period of time within a 5-year period where the PSA level did not rise)
- 5-year disease free-survival: 89.5% vs 77.2%
- 5-year distant metastasis-free survival 95.9% vs 89.2%
There was no improvement in overall survival, which could be because the median follow-up was too short (68 months). But, because distant metastasis-free survival is a strong surrogate for overall survival, the distant metastasis-free survival benefit might translate into an overall survival benefit with longer follow-up.
The findings of POP-RT Trial were consistent with a review article published this month (August 2021) in Lancet Oncology by De Meerleer et al2. A correct definition of the upper radiation field border, which should include the bifurcation of the abdominal aorta, is key in the use of pelvic radiation therapy. Due to modern technology, severe late intestinal and urinary toxic effects are rare and do not seem to increase compared with prostate-only radiation. The SPORTT trial also suggested a benefit of whole pelvis radiation therapy in biochemical recurrence-free survival in the salvage setting.
With increased use of PSMA PET–CT for staging in high-risk patients, those presenting with enlarged nodes on imaging would also benefit from the addition of whole pelvis radiation therapy to androgen deprivation therapy. Until the results of those long-term study outcomes are published this treatment should be considered in appropriately selected high risk prostate cancer patients.
References
Murthy V, Maitre P, Kannan S et al. Prostate-only versus whole-pelvic radiation therapy in high-risk and very high-risk prostate cancer (POP-RT): outcomes from phase III randomized controlled trial. J Clin Oncol. 2021; 39: 1234-1242.
De Meerleer G, Berghen C, Briganti A et al. Elective nodal radiotherapy in prostate cancer. Lancet Oncol. 2021; 22(8); E348-357.
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About the Author Kalli Spencer MBBCh, FC Urol (SA), MMed (Urol), Dip.Couns (AIPC) Kalli is an internationally renowned Urological Surgeon, specialising in oncology and robotic surgery. He trained and worked in South Africa, before relocating to Australia where he has worked at Macquarie University Hospital and Westmead Hospital. His passion for what he does extends beyond the operating room, through public health advocacy, education and community awareness of men’s health, cancer and sexuality. Kalli has been involved with the Prostate Cancer Foundation of Australia for many years, advocating for improved cancer care and facilitating community prostate cancer support groups. |
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