Table 2. Risk of Developing SGMNs in Patients With Rectal Cancer by Statistical Methoda.
| SGMNs | Multivariable competing risk regression(RT vs NRT) | Poisson regression (RT vs NRT) | Poisson regression (RT vs US general population) | Poisson regression (NRT vs US general population) | ||||
|---|---|---|---|---|---|---|---|---|
| Adjusted HR (95% CI) | P value | Adjusted RR (95% CI) | P value | Adjusted SIR (95% CI) | P value | Adjusted SIR (95% CI) | P value | |
| Combined SGMNs | 2.99 (2.23-4.02) | <.001 | 2.83 (2.24-3.60) | <.001 | 2.32 (1.95-2.73) | <.05 | 0.80 (0.69-0.93) | <.05 |
| Cancer of the uterine corpus | 3.06 (2.14-4.37) | <.001 | 3.19 (2.39-4.26) | <.001 | 2.88 (2.33-3.50) | <.05 | 0.93 (0.76-1.12) | NS |
| Ovarian cancer | 2.08 (1.22-3.56) | .007 | 2.26 (1.30-3.91) | .004 | 1.34 (0.85-2.01) | NS | 0.54 (0.38-0.75) | <.05 |
| Cervical cancer | NA | NA | 1.44 (0.48-4.30) | .52 | 1.12 (0.37-2.62) | NS | 0.65 (0.33-1.17) | NS |
| Other SGMNs | 2.02 (0.71-5.57) | .180 | 2.72 (1.43-5.16) | .002 | 2.79 (1.65-4.41) | <.05 | 0.98 (0.63-1.46) | NS |
Abbreviations: HR, hazard ratio; NRT, no radiotherapy; NA, not applicable; NS, no significance; RC, rectal cancer; RR, radiotherapy-associated risk; RT, radiotherapy; SGMN, second gynecological malignant neoplasm; SIR, standardized incidence ratio.
Fine-Gray competing risk regression analyses were used to calculate the HRs and 95% CIs for SGMN in patients with rectal cancer treated with RT vs patients not treated with RT. Covariables that were significant in univariable competing risk regression analysis (P < .05) are included in the multivariable analysis. The HR (RT vs NRT) for cervical cancer in univariable competing risk regression was not significant (P > .05), so the cervical cancer data were left blank in multivariable competing risk regression. Poisson regression analyses were used to calculate the RR and 95% CIs of SGMNs for patients with RT vs patients with NRT. Similarly, Poisson regression analyses were used to calculate the SIR and 95% CIs of SGMNs for patients with RT and NRT vs the US general population. Both RR and SIR were adjusted for age at RC diagnosis and calendar year of RC diagnosis in our analysis.