Randomised clinical trial of adjuvant postoperative RT vs. sequential postoperative RT plus 5-FU and levamisole in patients with stage II-III resectable rectal cancer: a final report

BACKGROUND AND OBJECTIVES: A randomised clinical trial was performed in patients undergoing radical surgery for rectal cancer to compare the efficacy and toxicity of adjuvant postoperative radiation therapy (RT) to sequential RT and chemotherapy (CT) with 5-fluorouracil (5-FU) plus levamisole (LEV). The primary end point was overall survival (OS); secondary end points were disease-free survival (DFS), the rate of loco-regional recurrence, and treatment-related toxicity; the final results of this trial are reported. METHODS: Patients in arm I underwent RT (50 Gy) in daily fractions of 2 Gy, 5 days/week for 5 weeks. Patients in arm II began with 5-FU (450 mg/sqm/day intravenous (i.v.) bolus, days 1-5) plus LEV (150 mg/day orally, days 1-3); postoperative RT was delivered during week 2 at the same dosage and schedule as in arm I. The other five cycles of CT (5-FU every 28 days and LEV every 15 days for the length of 5-FU administration) continued after the end of RT if clinical and hemato-biochemical parameters were in the normal range. RESULTS: From May 1992 to December 1998, 218 patients were enrolled into the randomised clinical trial (144 men, 74 women; age range: 28-75, median 64 years). The median follow-up time was 58.1 months (range: 1-3,271 days). No significant difference was observed between the two arms of treatment as regards OS and DFS (P = 0.18 and P = 0.66, respectively). Cox regression analysis for OS confirmed what was observed by univariate analysis for all variables except age. Older age (>60 years) and pathologic lymph-node involvement defined the subgroups with the worst prognosis. Cox regression analysis for DFS confirmed what was observed by univariate analysis for all variables: the only independent variable in predicting DFS was pathologic lymph-node involvement. CONCLUSIONS: Our findings suggest no difference in OS, loco-regional and distant site progressions of postoperative RT alone compared to sequential postoperative RT and CT; notably, this latter regimen was associated with higher toxicity which seriously impaired the patient's compliance to CT. The low loco-regional recurrence rate (9.2%) observed in our patients undergoing postoperative RT alone compared to similarly treated patients in previously performed clinical trials (20-25%) underline the role of radical surgery (mesorectal excision) coupled with a complete postoperative RT regimen. On the other hand, the similar efficacy of these two adjuvant modalities of treatment might be conditioned by both the low compliance (59%) to the CT regimen as well as the sequential, instead of concurrent, schedule of administration of RT and CT, which may have decreased further the expected efficacy of the combined regimen.