18F-Piflufloastat
(PYL)

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Ga68 PSMA11 vs. F18 PYL Biodistribution

TRACER INFORMATION AND INDICATION

Pylarify was approved by the FDA in 2021 for use in prostate-specific membrane antigen (PSMA) positive lesions in men with prostate cancer who have suspected metastasis and are candidates for initial definitive therapy or who have suspected recurrence based on elevated serum prostate-specific antigen (PSA) levels.

PSMA is a good molecular target in prostate cancers as it is overexpressed in 90% of tumor cells. Pylarify binds to the active extracellular site of a PSMA molecule with high affinity.

CONTRAINDICATIONS

None.

PATIENT PREPARATION

Patients should be well hydrated both before and after Pylarify injection to reduce radiation exposure.

RADIOPHARMACEUTICAL

The recommended adult dose of administered radioactivity is 333MBq (9mCi) with an acceptable range of 296 to 370MBq (8mCi to 10mCi).

Imaging should begin 60 minutes after Pylarify injection and no more than 90 minutes post injection

IMAGING PROTOCOL AND ACQUISITION PARAMETERS

Instruct patient to void prior to imaging and change clothing if necessary.

Patient should be supine with arms above head. Patients are typically imaged from mid-thigh to the skull vertex.

Scan duration will vary based on location and scanner, but will typically fall between 12 and 40 minutes.

BIODISTRIBUTION

Normal biodistribution includes kidneys, bladder, salivary glands, liver, spleen, and proximal small bowel. Low activity is also noted in the blood pool and muscle. Elimination is through the urine with 50% being eliminated within the first 8 hours after injection.

IMAGE INTERPRETATION

Lesions seen should be considered suspicious if the uptake is greater than the physiologic uptake in that tissue or greater than background if no physiologic uptake is expected. There is some risk of misinterpretation that should be noted. A negative image does not rule out the presence of prostate cancer and the performance of Pylarify seems to be affected by serum PSA levels. Pylarify uptake is also not specific for prostate cancer and may occur with other types of cancer as well as non-malignant processes.

REIMBURSEMENT

To bill Medicare for locally covered PET services, use the single most appropriate CPT code 78811 to 78816 based on the imaging area and PET/CT or PET equipment ordered and used for the study. Regarding the Radiopharmaceutical coding, For claims with a DOS January 1, 2022, and beyond, use HCPCS Level II code A9595 Piflufolastat f-18, diagnostic, 1 millicurie.

OTHER HELPFUL INFORMATION FOR TECHNOLOGISTS

Another radiopharmeceutical that can be used for prostate cancer imaging is Ga-68 Gozetotide and is available through two different brand-names; Illucix and Locametz. Both of these tracers have been approved for initial staging and recurrence for prostate cancer patients. The recommended dose for both of these tracers is 3-7mCi (111-259 MBq), with imaging occurring 50-100 minutes post administration. Similar to Pylarify, patients should be well hydrated before injection and instruction to hydrate and void frequently once imaging has been completed. Ga68 tracers are generator produced with a half life of 68 minutes, compared to the cyclotron produced PYL which has a half life of 109.7 minutes. For radiopharmaceutical coding, Locametz uses HCPCS Level II code A9800 (NDC#: 69488-0017-61) and Illucix uses HCPCS Level II code A9596 (NDC#: 74725-100-64). Studies have shown some differences between using Ga-68 Gozetotide vs. F-18 Piflufolastat, so determination of which tracer to use should be closely assessed by the patient care team, as well as taking into consideration product availability.

Even though Ga-68 and F-18 are both used in PET imaging, it is important to recognize that there are some differences between the two isotopes that could affect which one is chosen for imaging. First, the positron yield of Ga-68 is lower compared to F-18 (89.14% vs. 96.86%) which could lead to increased image noise, leading to a potential lower sensitivity. In addition, Ga-68 has a higher positron energy leading to more positron travel, resulting in lower spatial resolution. However, Ga-68 is made with a commercially available generator, which could make it more available than its counterpart.

References

Illucix (Ga 68 Gozetotide Injection)[package insert]. Fishers, IN. Telix Pharmaceuticals. 2021.

Locametz (Ga 68 Gozetotide Injection)[package insert]. Millburn, NJ. Advanced Accelerator Applications. 2022.

Pylarify (f18 Piflufolastat Injection)[package insert]. North Billerica, MA: Progenics Pharmaceuticals, Inc., a Lantheus company. 2021.

PYLARIFYTM (F-18 labeled piflufolastat, Injection) - SNMMI. (n.d.). https://www.snmmi.org/IssuesAdvocacy/QandADetail.aspx?ItemNumber=37212

Ferreira, G., Iravani, A., Hofman, M.S. et al. Intra-individual comparison of 68Ga-PSMA-11 and 18F-DCFPyL normal-organ biodistribution. Cancer Imaging 19, 23 (2019). https://doi.org/10.1186/s40644-019-0211-y

18F-Piflufloastat (PYL)