Modified FOLFIRINOX (mFOLFIRINOX) as neoadjuvant therapy and 'salvage' in patients with high risk locally advanced rectal cancers - tolerance and early outcomes.

BACKGROUND: There is limited data with regard to the use of modified 5-fluoroural-leucovorin-irinotecan-oxaliplatin (mFOLFIRINOX) in terms of tolerance and enabling total mesorectal excision (TME) of locally advanced rectal adenocarcinomas (LARC) with high-risk characteristics (T4b status, signet ring histology etc) post standard neoadjuvant long course chemoradiation (NACTRT) or short course radiation (SCRT) and chemotherapy.

MATERIALS AND METHODS: Patients with LARC from January 2018 to December 2020 receiving mFOLFIRINOX post NACTRT/SCRT to facilitate TME were evaluated. The primary endpoint was assessment of grade 3 and grade 4 treatment related toxicity and TME rates. Event free survival (EFS), where event was defined as disease progression or recurrence post resection after mFOLFIRINOX, was calculated by Kaplan Meier method.

RESULTS: Forty-seven patients were evaluated with a median age of 33 years (Range:18-59), 45% T4b status, 96% radiological circumferential margin (CRM) involved (79% CRM positive post NACTRT/SCRT), 43% extramural venous invasion (n=33) and 36% signet ring histology. 62% had received prior NACTRT and 38% had received SCRT with chemotherapy before receiving mFOLFIRINOX. The most common grade 3 and grade 4 treatment related side effects included diarrhoea (7%), anaemia (4%) and infections (4%). Intended duration of mFOLFIRINOX or beyond was completed in 94% of patients. 60% of patients underwent curative local resection with R0 resection rates of 100% (n=28) and pathological complete response rates of 21%. The most common surgeries done were exenterations and abdominoperineal in 22% and 17% patients respectively. With a median follow up of 19 months, 24 patients had recurred or progressed for a median EFS of 20 months [95% confidence interval (CI): 15-24].

CONCLUSIONS: Locally advanced rectal cancers with high-risk characteristics are a niche group of cancers with less-than-optimal outcomes post standard neoadjuvant strategies. mFOLFIRINOX appears to be well tolerated and enables TME in a significant proportion of these patients.