The goal of this page is to gather input from providers on a novel system for classification of response assessment on Lu177 PSMA therapy. It combines elements of RECIP 1.0 (Volumetric analysis), PCWG4 (new lesion criteria for progression), and components of the ReSPECT study for assessment of progression, partial response and complete response categories.
Outline of Proposed Classification Scheme
What follows is an outline of a proposed classification scheme under discussion. For more details, click here to review the rationale.
| PSA | Combination | Total Tumour Volume (TTV) Change | New lesions? | |
| SPIDER 0 | Non-increasing OR non-measurable | AND | No measurable disease | No measurable disease on PSMA SPECT – to be confirmed by PET |
| SPIDER 1 (Partial Response) | Marked reduction | AND | ≥ 30% TTV reduction | None |
| SPIDER 2 (Stable) | Stable or mildly reduced | AND | <30% increase TTV | Not meeting PCWG4 Progression |
| SPIDER 3 (Progression) | Increasing PSA | OR | > 20% TTV increase | PCWG4 criteria for new lesions |
Modifiers under Review
A series of criteria modifiers are under development to provide more nuance to reporting, and hopefully allow more personalized future management recommendations once validated against existing datasets. These are still in development.
| Modifier | Meaning |
| L | Low Volume Disease (various proposed definitions under review) |
| S | SPECT finding requiring confirmation with PET |
| N | New lesions but not yet meeting PCWG4 definitions |
| V | Progression by volume alone Not meeting PSA progression Not meeting PCWG4 RECIST or PSMA criteria definitions |
| M | Mixed changes: Cases of meeting one or more progression criteria definitions: 1. Measurable decrease in size of one or more lesions 2. Significantly decreased PSMA expression in one or more sites of previously PSMA avid disease Cases meeting stable or partial response definitions: Measurable increase in size or uptake of 1 or more lesions but not otherwise meeting definitions of progression |
Survey for Criteria Development
This is still being finalized pending some informal discussion with stakeholders. A public poll will be available soon.
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