Complete pathologic response in the primary of rectal or colon cancer treated with FOLFOX without radiation.

Abstract

3649 Background: Stage II/III rectal cancer is treated with chemotherapy (chemo) plus radiation therapy (RT) followed by surgery, and then post-op chemo. Pelvic RT reduces local recurrence, but most studies do not show a survival benefit. We retrospectively reviewed patients who received pre-op FOLFOX without RT as initial management of locally advanced rectal cancer, either because they had suspected metastatic disease, or relative contraindications to RT, or refused RT. We also reviewed preoperative FOLFOX-based chemo in patients with known synchronous metastatic disease who underwent resection of the primary. Methods: Six pts with stage II/III rectal ca (Table) who received pre-op FOLFOX without RT, and 14 pts with synchronous metastatic colon or rectal cancer treated with pre-op FOLFOX ± bevacizumab (bev) followed by resection of the primary were identified. Path reports were reviewed to assess the pathological complete (path CR) and near-complete (>90% treatment effect) response rates. Electronic records were reviewed for local and distant recurrence. Results: Of the 20 colorectal cancer pts treated with FOLFOX or FOLFOX-bev without RT, 7 (35%) achieved a pCR. Of the 6 patients who received pre-op FOLFOX for localized rectal cancer, 2 had pCR and three had 99%, 95%, 90% treatment effect. These 5 remain free of disease at time of last f/u. The sixth pt had minimal treatment effect in the primary:he failed in the liver and lung one year post resection without local failure. Of the 14 pts with metastatic colon or rectal ca, 4 received FOLFOX and 10 received FOLFOX-bev. Of these, 5 had pCR in the primary (4 with FOLFOX-bev, 1 with FOLFOX). Conclusions: Even considering possible recall bias, the path CR rate to FOLFOX seen in these primaries appears much higher than seen in metastases (path CR rate less than 0.5% in metastatic disease). This warrants further study, and supports our prospective trial of pre-op FOLFOX-bev, without RT, in selected patients with locally advanced rectal cancer. Patients with stage II/III rectal cancer treated with FOLFOX Patient ERUS stage at diagnosis Pathologic stage Treatment effect (%) 85 F T3 N1 T0N0 (pCR) 100% 48 M T3 N1 T0N0 (pCR) 100% 45 F T3 N1 T1NO 99% 59 M T2 N1 T2N1 95% 36 F T3 N1 T2N0 90% 53 M T3 N1 T3N1 10% Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Alchemia, Biothera, Delcath, ImClone Systems, Merck, Novartis, Roche Pfizer Amgen, Biothera, Bristol-Myers Squibb, Curetech, Genentech, ImClone Systems, Lilly, Merck, Pfizer, Roche, Tercica