Table 4.
Associations between percentage of heart volume receiving ≥5-40 Gy and rate of myocardial infarction
| Percentage of heart volume receiving ≥5-40 Gy (V5-V40) |
Median value (IQR) | Cases |
Controls |
Rate ratio∗ | 95% CI† | P‡ | ||
|---|---|---|---|---|---|---|---|---|
| Total§ | 170 (N) | 100 (%)‖ | 169 (N) | 100 (%)‖ | ||||
| V5 | 40.2 (11.1-87.6) | |||||||
| <10% | 44 | 25.9 | 62 | 36.7 | 1.00¶ | 0.68-1.47 | - | |
| 10%-29% | 29 | 17.1 | 35 | 20.7 | 1.20 | 0.73-1.99 | .57 | |
| ≥30% | 97 | 57.1 | 72 | 42.6 | 2.02 | 1.43-2.85 | .008 | |
| V10 | 37.1 (8.8-60.7) | |||||||
| <10% | 63 | 37.1 | 88 | 52.1 | 1.00¶ | 0.70-1.43 | - | |
| 10%-29% | 21 | 12.4 | 15 | 8.9 | 1.96 | 0.99-3.87 | .09 | |
| ≥30% | 86 | 50.6 | 66 | 39.1 | 1.97 | 1.40-2.78 | .007 | |
| V15 | 29.3 (8.0-40.5) | |||||||
| <10% | 64 | 37.7 | 91 | 53.8 | 1.00¶ | 0.72-1.39 | - | |
| 10%-29% | 22 | 12.9 | 15 | 8.9 | 2.01 | 1.03-3.93 | .07 | |
| ≥30% | 84 | 49.4 | 63 | 37.3 | 2.05 | 1.41-2.98 | .005 | |
| V20 | 17.1 (7.4-36.5) | |||||||
| <10% | 73 | 42.9 | 97 | 57.4 | 1.00¶ | 0.71-1.41 | - | |
| 10%-29% | 34 | 20.0 | 33 | 19.5 | 1.42 | 0.87-2.30 | .25 | |
| ≥30% | 63 | 37.1 | 39 | 23.1 | 2.28 | 1.53-3.41 | .002 | |
| V25 | 10.7 (6.8-19.1) | |||||||
| <10% | 77 | 45.3 | 104 | 61.5 | 1.00¶ | 0.73-1.37 | - | |
| 10%-29% | 53 | 31.2 | 46 | 27.2 | 1.60 | 1.04-2.45 | .08 | |
| ≥30% | 40 | 23.5 | 19 | 11.2 | 2.86 | 1.67-4.90 | .001 | |
| V30 | 6.6 (4.4-11.4) | |||||||
| <10% | 119 | 70.0 | 140 | 82.8 | 1.00¶ | 0.78-1.29 | - | |
| 10%-29% | 25 | 14.7 | 14 | 8.3 | 2.15 | 1.11-4.13 | .033 | |
| ≥30% | 26 | 15.3 | 15 | 8.9 | 2.12 | 1.12-4.01 | .033 | |
| V35 | 3.0 (1.2-6.2) | |||||||
| <10% | 132 | 77.7 | 149 | 88.2 | 1.00¶ | 0.76-1.31 | - | |
| 10%-29% | 24 | 14.1 | 12 | 7.1 | 2.32 | 1.17-4.58 | .025 | |
| ≥30% | 14 | 8.2 | 8 | 4.7 | 2.11 | 0.89-5.03 | .11 | |
| V40 | 0.3 (0-5.4) | |||||||
| <10% | 143 | 84.1 | 154 | 91.1 | 1.00¶ | 0.88-1.13 | - | |
| 10%-29% | 23 | 13.5 | 14 | 8.3 | 1.77 | 0.88-3.57 | .12 | |
| ≥30% | 4 | 2.4 | 1 | 0.6 | 5.29 | 0.57-49.4 | .15 | |
Abbreviations: CI = confidence interval; IQR = interquartile range; MI = myocardial infarction.
Univariable rate ratios for MI for different levels of each factor were calculated using logistic regression conditioning on strata defined by the matching variables.
Wald method CIs were used to derive CIs for each category, including the reference category.
P value for difference of dose-volume categories of cases and controls, calculated within strata (defined by matching variables), with <10% as a fixed reference group.
This model includes 339 patients. Twenty-six patients were dropped: for one irradiated case and one irradiated control, dosimetry was not performed. For 22 patients (11 cases and 11 controls) it was not possible to estimate dose-volume parameters study because they had a combination of orthovoltage and electron/megavoltage treatment (manual planning). One case and one control were additionally dropped because they were the only patient left in the stratum.
Percentages may not total 100 because of rounding.
Reference category.