Abstract 4385: Unprecedented tumor: immune interaction–clinical and drug-development implications

Abstract Background: Classic therapeutic (RX) oncology principles demand radiographic response or durable stable disease as surrogates of overall survival (OS) prolongation, the ultimate metric of Rx benefit. Progressive disease (PD), however, is an undisputed indication of treatment failure. Immune Oncology (IO) trials reporting individual patient outcomes using swimmers' plot (SP) suggest substantial OS subsequent to PD, unprecedented pre-IO. Hypothesis: Unrecognized phenomenon of OS benefit in the setting of radiographic PD, is tissue-agnostic and prevalent (>15%). Methods: We conducted a retrospective review of IO monotherapy trials in 3 cancers if SP were reported. Percentage of PD patients (Pts) surviving beyond defined time landmarks is reported (Table). Results: Realizing that 3rd or subsequent Rx lines rarely provide > 6 months OS duration in most cancers, our results indicate that 2/3rd of IO-treated pts, regardless of histology, or line of therapy are performing significantly better than expected; 1/3rd surviving > 1 year beyond PD. Discussion: In IO, radiographic bulk may increase despite undeniable OS benefit (in years). We likely underestimated this phenomenon since pts with PD at 1st assessment aren't included in the SP, and with longer follow up, OS of PD pts is likely to improve with longer time to manifest it. This phenomenon–we term 'Disguised Responders' (DRs)–challenges an oncology principal. DRs needs to be considered by clinicians and future drug developers to accurately identify putative novel drugs. A plausible mechanism of DRs posits that 'virulence' of a given subclone, regardless of size or bulk, dictates Rx outcome. Virulence may operate through cachexia-induction, propensity to metastasize or metabolic adaptability, to name a few. Novel experimental approaches are desperately awaited to probe and measure virulence of different tumor subclones in future drug evaluations. Table 1. Clinical Trials of IO Monotherapy Number and (%) of pts surviving beyond clinical PD (months) Tumor Rx Line 1st Author/Yr N PD (n) <6 6-11 12-23 24-35 36-47 > 48 NSCLC* 2nd + Topalian ''19 22 12 1 2 4 1 4 1st + Fredinandus ''21 45 2 1 1 1st + Kim ''22 139 22 13 5 3 N/A Bilger ''22 18 10 3 4 3 2nd Dart ''21 7 3 2 1 2nd + Tozuka (MR) ''20 11 11 4 6 1 2nd + Tozuka (PD) ''20 51 51 29 12 7 2 1 2nd + Waterhouse ''20 39 38 16 14 4 4 Subtotal 332 149 63 (42%) 44 (30%) 28 (18%) 4 (3%) 5 (3%) 4 (3%) Melanoma 1st + Warburton ''20 70 13 1 4 3 4 1 2nd + Topalian ''19 34 21 1 2 10 4 4 2nd + Weber ''15 38 4 2 1 1 2nd + Dimitriou ''21 125 9 3 4 2 Subtotal 267 47 3 (6%) 8 (17%) 10 (21%) 17 (36%) 5 (11%) 4 (8.5%) RCC** 2nd + Topalian 19'' 10 7 1 1 2 3 7 15% 15% 30% 42% Total 609 203 33% 25% 15% 10% 6% 5.4% *Non-small cell lung cancer. ** Renal Cell Carcinoma Citation Format: Farah Mazahreh, Liyan Mazahreh, Brad Fugere, Ahmad Mazin Safar. Unprecedented tumor: immune interaction–clinical and drug-development implications. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4385.