Personalising radiotherapy dose in anal cancer (PLATO) Platform: 6-month patient reported outcomes across ACT3, ACT4 and ACT5 trials.

PURPOSE: The Personalising Radiotherapy Dose in Anal Cancer (PLATO) platform was designed to evaluate risk‑adapted dose optimisation for anal squamous cell carcinoma (ASCC). A key secondary objective was to assess the impact of tailored treatment on patient‑reported outcomes (PROs), using the EORTC QLQ‑ANL27, the first anal cancer-specific validated PRO.

METHODS

PLATO comprises three integrated trials: ACT3 (adjuvant chemoradiotherapy vs observation following local excision of T1N0/x anal margin tumours), ACT4 (reduced‑ vs standard‑dose chemoradiotherapy for T1/2 ≤ 4 cmN0/x ASCC), and ACT5 (three dose‑escalated chemoradiotherapy regimens for T3/4 or TanyN + disease). PROs (EORTC QLQ‑C30, QLQ-ANL27) were collected at baseline, end of treatment, 6-weeks, 6, 12, 24 and 36-months. Descriptive analyses to 6-months defined clinically relevant change as > 10‑point differences in mean scores.

RESULTS

Between 1/2/2017-31/8/2023, 709 patients were recruited across 36 UK sites; 706 formed the mITT population (PRO consent 98.9 %; 86.0 % completion at 6-months). ACT5 patients reported markedly worse function and symptom scores at baseline than ACT3 and ACT4. All treated groups showed large declines at end of treatment, with improvement to baseline by 6-months for most issues; however, ACT5 participants continued to report residual deficits for bowel function compared with ACT3/4 cohorts. Poorer sexual function was reported in the ACT4 standard‑dose and ACT5 arms at 6-months, with interpretation of ACT3 sexual function limited by small numbers.

CONCLUSION

PLATO demonstrates the feasibility of risk‑adapted radiotherapy dosing, with excellent PRO compliance. Most quality-of-life deficits improved by 6-months, although persistent impairments remained in ACT5 patients. Follow‑up to 36-months will further define late effects.