Recurrent Prostate Cancer

By: Nat Lenzo, MMed MSc(Oncol) EMBA FRACP FAANMS; Jaideep S. Sohi, MD; Tee-Sin Lim, MBBS, FRANZCR

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CASE SUMMARY

A 58-year-old man with a Gleason score of 4+5=9 prostate cancer underwent radical prostatectomy in January 2016. At the time of surgery, the cancer had progressed through the capsule and into the seminal vesicles. However, no nodes were involved. His post-operative prostate specific antigen (PSA) was 0.27 ng/ml. Patient was deemed at high risk for recurrence and was referred for salvage pelvic and prostatic bed radiotherapy in October 2016. A⁶⁸Ga PSMA-11 PET/CT was performed with no abnormal activity detected.

After radiotherapy, the patient’s PSA decreased from 0.58 ng/ml to nadir of 0.46 ng/ml and then spiked to 0.63 ng/ml in July 2017. Repeat⁶⁸Ga PSMA-11 PET/CT demonstrated no abnormal activity, and the patient entered an active surveillance program with repeat PSA tests every 3-6 months. At this time, the patient was not placed on hormone therapy or androgen deprivation therapy (ADT).

In March 2018, the patient’s PSA levels rose significantly to 2.9 ng/ml, necessitating a third⁶⁸Ga PSMA-11 PET/CT, which demonstrated PSMA-positive pathology. Patient received stereotactic radiotherapy to lymph nodes in the left internal iliac and right internal iliac stations. Active surveillance was again employed with no concomitant ADT.

IMAGING FINDINGS

Pursuant to the patient’s rising PSA, a third⁶⁸Ga PSMA-11 PET/CT exam in March 2018 (Figures 1-2) revealed a moderately PSMA avid lymph node in the left internal iliac station at the presacral region and a small, mildly PSMA avid lymph node in right internal iliac station. Activity was also detected in the bladder.

Due to continued rising PSA levels, the patient received a fourth⁶⁸Ga PSMA-11 PET/CT exam in July 2020 (Figures 3-4), which detected a new PSMA avid right internal iliac node and a new PSMA avid right para-aortic node. Ureteric activity was also apparent. Sequential Ga-68 PSMA-11 PET/CT exams demonstrated an increase in physiologic activity. However, the previously treated nodal disease was improved.

DIAGNOSIS

Recurrent prostate cancer with possible metastasis to right paraaortic and pelvic lymph nodes

FOLLOW-UP

Patient reinitiated stereotactic radiotherapy without ADT.

DISCUSSION

Contrary to declining death rates for many common cancers, prostate cancer deaths are rising, with an increase of 5 percent from 2019 to 2020.¹ Although most primary prostate cancer cases can be managed with radiotherapy or radical prostatectomy, 40 percent of men treated for this cancer will have disease relapse,² with castration-resistant prostate cancer accounting for most deaths.³⁶⁸Ga PSMA-11 PET/CT suggests better sensitivity to low levels of PSA,⁴ and the ability to identify the location of disease recurrence after radical prostatectomy in half of the patients with a PSA level between 0.5 and 1 ng/ml,^5,6 as demonstrated in this case study.

Additionally,⁶⁸Ga PSMA-11 PET/CT is substantially more likely to detect metastases from prostate cancer than conventional imaging using CT and bone scan and using⁶⁸Ga PSMA-11 PET/CT is more likely to change the course of treatment than conventional imaging.^7,8

CONCLUSION

This case report confirms the value of⁶⁸Ga PSMA-11 PET/CT in following patients with castration-resistant prostate cancer post-surgery and determining the most appropriate course of treatment when metastatic disease is detected.

Ureteric activity may be prominent. Physiologic increased activity may be seen in the kidneys, salivary glands and small bowel. The sensitivity of⁶⁸Ga PSMA-11 PET increases with rising PSA levels, with a lower yield at PSA < 0.5 ng/ml and a higher yield at PSA > 2.0 ng/ml. Stereotactic radiotherapy may delay introduction of ADT, however, there is a survival advantage in treating oligometastatic disease.⁹

REFERENCES

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8. Pomykala KL, Czernin J, Grogan TR, Armstrong WR, Williams J, Calais J. Total-Body 68Ga-PSMA-11 PET/CT for Bone Metastasis Detection in Prostate Cancer Patients: Potential Impact on Bone Scan Guidelines. J Nucl Med. 2020 Mar;61(3):405-411. doi: 10.2967/jnumed.119.230318. Epub 2019 Sep 20. PMID: 31541035; PMCID: PMC7067527.
9. Broughman JR, Fleming CW, Mian OY, Stephans KL, Tendulkar RD. Management of Oligometastatic Prostate Cancer. Appl Radiat Oncol. 2020 Sep;9(3):6-10. Epub 2020 Sep 9. PMID: 33134438; PMCID: PMC7595346.