Total neoadjuvant treatment using short-course radiotherapy and four CAPOX cycles in locally advanced rectal cancer with high-risk criteria for recurrence: a Swedish nationwide cohort study (LARCT-US).

Background: Total neoadjuvant treatment (TNT) for locally advanced rectal cancer (LARC) increases pathologic complete response (pCR) rate and reduces the risk of systemic recurrences over chemoradiotherapy (CRT) in randomised trials, e.g., the RAPIDO trial. A modified RAPIDO schedule was prospectively explored in Sweden to evaluate TNT in routine health care before the RAPIDO results were published.

Methods: Between July 2016 and June 2020, 273 patients with high-risk LARC (clinical tumour stage cT4, clinical nodal stage cN2, extramural vascular invasion, involved mesorectal fascia or enlarged lateral lymph nodes) were treated in a prospective observational cohort study at 16 hospitals (LARCT-US). Another 189 patients at 18 (including the 16) hospitals were similarly treated (ad modum LARCT-US, AdmL) during the same period. Inclusion and exclusion criteria were identical to the RAPIDO trial. Patients received short-course radiotherapy (5 × 5 Gy for 5 days) followed by four cycles of CAPOX or six FOLFOX-6, followed by total mesorectal excision or, if clinical complete response (cCR), inclusion into a watch-and-wait (W&W) study. The primary endpoint was complete response (CR), i.e., the sum of pCR in specimens and cCR exceeding one year in W&W patients. Safety was assessed in all patients.

Findings: Compared to the RAPIDO trial, patients were older, and tumours more advanced. Median follow-up was 4.8 years (IQR 4.2-5.2). In LARCT-US all patients received radiotherapy and 268 (98%) started chemotherapy whereas in AdmL all patients received radiotherapy and chemotherapy. In LARCT-US 34 patients had pCR and 31 sustained cCR resulting in a CR-rate of 24% (95% CI 20-28). In AdmL, results were similar (23%, 95% CI 17-30). Locoregional recurrences were 6% (95% CI 4-10) and 5% (95% CI 2-9), respectively, both at 3 years and at last follow-up. Neurotoxicity, recorded in LARCT-US, was lower than in RAPIDO (EORTC-QLQ-CIPN20 tingling toes or feet mean score 24 (SD 31) vs 43 (SD 37)). One treatment-associated death occurred.

Interpretation: Despite older patients and more advanced tumours, results similar to the RAPIDO trial were obtained. Hence, two chemotherapy cycles less do not compromise the results maintaining a high CR-rate. This TNT schedule resulted in favourable outcomes in a nation-wide real-life situation.

Funding: Swedish Cancer Society.