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Results From National Surgical Adjuvant Breast and Bowel Project Colon Cancer Trials

Roswell Park Cancer Institute Buffalo, NY

To the Editor:Mamounas et al from the National Surgical Adjuvant Breast and Bowel Project (NSABP) have reviewed the results of their four surgical adjuvant trials for Dukes’ B and C colon cancers.¹ In summary, they have demonstrated that fluorouracil plus leucovorin is superior to semustine, vincristine, and fluorouracil (MOF) in preventing death and disease recurrence. Unfortunately, the 95% confidence intervals demonstrated in Figure 1 do not convincingly show that adjuvant MOF is superior to no treatment after surgery.

Proving that an adjuvant treatment is superior to no treatment is difficult because 11% of these patients can be expected to die of causes unrelated to cancer, and only 12% will die of cancer within 5 years.² Treatment must thus be exceedingly effective to have proven benefit in Dukes’ B colon cancer, because the fates of nine of out 10 patients cannot be affected (other than adversely) by further therapy. Note that the 30% reduction in the death rate suggested by the NSABP is three patients in 100.

Demonstration of efficacy in Dukes’ C colon cancer is easier because nearly half of the patients may benefit. Unfortunately, the NSABP never asked the question of whether fluorouracil plus leucovorin is superior to no further therapy. Whether the NSABP trials actually show a benefit of adjuvant therapy must be questioned because there have undoubtedly been subtle improvements in surgical results over the two decades of NSABP colorectal trials.

To analyze the combined results of the inferior arms versus the superior arms of four trials in 3,820 patients (with MOF at varying times being in both the superior and interior arms) seems to be a stretch of statistical manipulation.

REFERENCES

1. Mamounas E, Wieand S, Wolmark N, et al: Comparative efficacy of adjuvant chemotherapy in patients with Dukes’ B versus Dukes’ C colon cancer: Results from four National Surgical Adjuvant Breast and Bowel Project adjuvant studies (C-01, C-02, C-03, and C-04). J Clin Oncol 17:1349-1355, 1999[Abstract/Free Full Text]

2. Nauta R, Stablein DM, Holyoke ED: Survival of patients with stage B2 colon carcinoma: The Gastrointestinal Tumor Study Group experience. Arch Surg 124:180-182, 1989[Abstract]

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