Abstract A051: Spontaneous Remission & Abscopal Responses in Prostate Cancer, a marker of “coldness”?

Abstract Introduction: In 1957 spontaneous regression(SR) was established as most frequently in lymphomas, renal and melanoma and in 1968 used by MacFarlain Burnet, to suggest immune surveillance against cancer was a function of the immune system, and that the frequency was greater in earlier stages of cancer. In 1988 Renal cell cancer reported frequency was 6.6% in 73 cases. Despite SR reports increasing since the success of modern immunotherapeuty, a recent review found only 1 case of metastatic prostate cancer (PC) and there was no PC in a series of 58 cases of Radiation Abscopal response(RAR). Though fitting with PC’s reputation as a “cold” cancer, ie having a low response to modern immunotherapy (<5%), this abstract used alternative words in Urology literature to investigate further. Materials and Method: Three terms, evanescent, “vanished” and T0 were used in PUB med searches against second word Prostate.Active surveillance(AC) PC series with post entry biopsy data were also reviewed for incident of T0. Given the high incidence of obesity in series of PC, as additional evidence, we searched for GLP-1RA and PC. Results: The initial search revealed 16 cohorts of prostatectomy and found to have T0. The largest, Knipper, S. et al 2019, found 358/160,352(0.2%) were T0. Most had low volume disease but pT0 was identified in 13/358 (3.6%) with PSA ≥20 ng/ml, in 69 (19.3%) with biopsy GS ≥7 and in 78 (21.8%) with ≥cT2. In a subset, pT0 was identified in 34 (33.3%) patients with ≥2 positive biopsy cores. Eight series of AC with repeat biopsy revealed 952 T0/2862(33.3%), ranging from 41.45% in series with lowest relapse risk to 11.06% with highest relapse risk . Searching for association of GLP-1RA and Prostate cancer revealed a meta-analysis of 5 series of RR 0.72 (95% CI: 0.610 to 0.832). Conclusion: The Knipper et el series demonstrated SR in advanced Primary PC. The nem series in AS is the same as SR HPV positive pre-cancer of the Cervix and as reports of early Prostate cancer with HPV positive from Australia and Canada, investigation is need to see if T0 patients had HPV present. Autopsy series shows that earliest stages of PC precursors occur between 35 and 45 yrs of age , data on GLP-1RA suggests that could be benefit from exploring their use of in low grade PC patients on AS. Citation Format: Tim Oliver. Spontaneous Remission & Abscopal Responses in Prostate Cancer, a marker of “coldness”? [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86(2_Suppl):Abstract nr A051.