Serum PSMA Imaging Driven Evaluation of Response Criteria are a criteria in development driven from a desire to incorporate 3 key features from pre-existing criteria.
- Criteria for new lesions on PSMA PET or SPECT that better align with PCWG4, to allow matchup with intake criteria for other clinical trials
- An element incorporating tumour volume changes which has been extensively evaluated in numerous observational studies, best formalized in RECIP 1.0.
- An element to factor in the significance of discordant PSA and PSMA imaging results, and how they may impact progression. This was adopted similarly to the ReSPECT algorithm from Lousie Emmett et al. and Yadav Surkha et al.
New Lesion Based Criteria (PCWG4)
| PCWG 4 lesion analysis | ||
| Modality | Follow up #1 | Follow-up #2 |
| CT/MRI | PCWG3/RECIST Any cycle | |
| PSMA IMAGING (PET or SPECT) | ||
| Bones Lymph Nodes Lung metastases | ≥6 new lesions | |
| ≤5 new lesions | 2 new lesions confirmed on subsequent scan | |
| Liver parenchyma Nonpulmonary viscera | Any single new lesion | |
Total tumour volume criteria from RECIP 1.0
| Volume Change | |
| RECIP CR | No measurable disease |
| RECIP PR | ≥ 30% TTV reduction |
| RECIP SD | <20% increase TTV |
| RECIP PD | > 20% TTV increase |
RECIP 1.0 is a set of response criteria evaluation initially validated with PSMA PET that has been subsequently validated for PSMA SPECT-CT in two additional studies.
RECIP 1.0 included two components, volume criteria and the presence or absence of new lesions. As new lesion criteria are more stringent in PCWG4, these were used as new lesion criteria in the SPIDER criteria to allow better integration into selection algorithms for new investigational agents.
ReSPECT Combination Method
| PSA | Combination | TTV Change | |
| RG1 (PARTIAL RESPONSE) | Marked reduction | AND | ≥ 30% TTV reduction |
| RG2 (STABLE) | Stable or mildly reduced | AND | <30% increase TTV |
| RG3 (PROGRESSION) | Increasing PSA | OR | > 30% TTV increase |
The motivation for Re-SPECT slides use a combined metric is outlined in several slides in the prognosis lecture. Essentially, while a relatively uncommon observation, it has been reported in four registry studies that discordant changes between PSA and SPECT-CT can occur. Generally, a PSMA SPECT or PSMA PET change that precedes a change in PSA has been observed to be associated with worse OS in several observational studies.
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