Survival Outcomes by TN Category and AJCC Stage
Relative and observed 5-year survival outcomes by evaluable TN category of disease in the current SEER colon cancer analysis (109,953 patients with invasive cancers) were analyzed. As presented in and , patients with stage I colon cancers (AJCC, sixth edition) have better 5-year relative and observed survival than those with IIA cancers. For patients with T1-2N0 lesions, the 5-year relative survival was 97.1% ± 0.4% versus 87.5% ± 0.4% for T3N0 lesions, and 5-year observed survival for those with T2N0 lesions was 76.3% ± 0.3% versus 66.7% ± 0.3% for those with T3N0 lesions.
SEER Colon Cancer Analysis, Relative Survival by NT Category of Disease
SEER Colon Cancer Analysis, Observed Survival by NT Category of Disease
Survival outcomes for patients with AJCC stage IIA versus IIB cancers (T3N0, T4N0; AJCC, sixth edition) are also presented in and . Both 5-year relative and observed survival were higher for patients with T3N0 versus T4N0 cancers (5-year relative survival for T3N0, 87.5% ± 0.4%; for T4N0, 71.5% ± 0.8%; 5-year observed survival for T3N0, 66.7% ± 0.3%; for T4N0, 55.0% ± 0.6%). Standard errors were small because the number of patients was large (T3N0, n = 40,338; T4N0, n = 8,108).
For patients with stage III cancers, those with T1-2 lesions (confined to bowel wall) have better survival than those with T3-4 lesions by N category of disease. Similar improvements in 5-year relative and observed survival were found for patients with T1-2N1 cancers versus T3N1 and T4N1 cancers and for those with T1-2N2 lesions versus those with T3N2 and T4N2 lesions. For patients with T1-2N1 versus T3N1/T4N1 cancers, the 5-year observed survival was 71.1% ± 1.0% (T1-2N1) versus 54.9% ± 0.4% for T3N1 and 39.6% ± 0.8% for T4N1. In patients with T1-2N2 versus T3N2/T4N2 cancers, 5-year observed survival was 61.5% ± 2.6% (T1-2N2) versus 38.1% ± 0.6% for T3N2 and 21.7% ± 0.9% for T4N2. In the SEER colon cancer analysis, patients with T4N1 lesions have 5-year observed survival (39.6% ± 0.8%) similar to that of patients with T3N2 (38.1% ± 0.6%) or T4N2 (21.7% ± 0.9%) lesions.
Patients with T1-2 versus T3 lesions had improved 5-year survival for each N category; the prognostic value of a T1-2 tumor is approximately the same as a decrease of one N category of disease. Specifically, patients with T1-2N1 cancers have 5-year observed survival (71.1% ± 1.0%) similar to that of patients with T3N0 lesions (66.7% ± 0.3%). For T1-2N2 lesions, 5-year observed survival (61.5% ± 2.6%) is similar to that of patients with T3N0 (66.7% ± 0.3%) and T4N0 (55.0% ± 0.6%) or T3N1 (54.9% ± 0.4%) lesions.
Survival Outcomes by Expanded TN Category of Disease
In view of the large number of patients in the SEER colon cancer database, 5-year relative and observed survival were calculated for each NT category of disease ( and ). Data were generated for the entire group of 130,762 patients (109,953 had invasive cancers [T1-4N0-2]; NX, 18,312; Tis or T1 polyp, 2,497), but the focus was on those with invasive cancers.
The impact of T subcategory within N category of disease was evaluated. Within both the N0 and N1 categories, patients with Tis, T1, and T2 lesions had similar 5-year relative and observed survival (relative 5-year survival for N0Tis, 95.6% ± 1.2%; N0T1, 97.4% ± 0.6%; N0T2, 96.8% ± 0.6%; N1Tis, 87.3% ± 6.0%; N1T1, 87.6% ± 2.0%; and N1T2, 87.7% ± 1.4%). For patients with N2 disease, patients with T1 and T2 lesions had similar survival (5-year relative survival for N2T1, 68.7% ± 7.0%; N2T2, 76.6% ± 3.6%), which was better than that for patients with N2T3 (47.3% ± 0.8%) or N2T4 lesions (27.1% ± 1.1%).
Patients with T4a cancers (tumor penetrates to the surface of visceral peritoneum [revised wording for AJCC seventh edition]) have better survival rates than those with T4b cancers (tumor directly invades or is adherent to other organs or structures) by N category ( and ). For N0T4a versus T4b lesions, relative survival was 79.6% ± 1.0% and 58.4% ± 1.3% and observed 5-year survival was 60.6% ± 0.8% and 45.7% ± 1.0%. For the N1 and N2 categories of disease, the survival differences for T4a versus T4b were also quite marked (for N1, relative survival was 60.6% ± 1.4% versus 34.9% ± 1.5% and observed survival was 47.0% ± 1.1% versus 27.9% ± 1.2%; for N2, relative survival was 33.3% ± 1.6% versus 19.7% ± 1.4% and observed survival was 26.6% ± 1.2% versus 15.8% ± 1.1%).
The number of positive nodes is prognostic for survival for most NT categories of disease ( and ; ). Patients with one involved regional node (N1a) have a 5% to 13% better 5-year survival than those with two to three positive nodes (N1b) by NT category of disease, with differences seen for all NT combinations. Those with four to six involved nodes (N2a) have a 5% to 19% better 5-year survival than those with seven or more positive nodes (N2b) by NT category ( and ), with differences seen in all NT combinations except for T1N1a versus T1N1b.
Fig 1. Interaction among T and N classifications and total nodes examined on 5-year relative survival rate in colon cancer, Surveillance, Epidemiology, and End Results (SEER) analysis. (A-E) Relative survival for pT1-4 by N1a (one positive lymph node), N1b (two (more ...)
SEER Colon Cancer Analysis, 5-Year Relative and Observed Survival by TN Category of Disease in Patients With Invasive Cancer and Evaluable TN Category
The number of nodes examined by the pathologist, in addition to the number of positive nodes, was also prognostic for survival in the current analysis. The relative survival impact of both number of positive nodes and number of nodes evaluated is shown in . Relative survival improves as the number of nodes examined increases for most TN categories, most obvious in the large T3 category of disease (C). Prognosis as a function of percentage of nodes examined was not evaluated.
Of the 109,953 patients with invasive cancer and evaluable TN category, 13 or more nodes were examined in 40,682 patients (37%) and seven or more were examined in 77,419 (70.4%). In the 12,101 patients with N2 category, ≥ 13 nodes were examined in 53.3% of patients and seven or more were examined in 89.7%. In contrast, of the 23,861 patients with T1-2N0 category disease, ≥ 13 nodes were examined in only 26.2% of patients and seven or more were involved in only 56.8%.