A. Calculated permissible dose per fraction to 2 cc rectum and urinary bladder in different dose-fractionations of HDR brachytherapy, considering total EQD2 75 Gy for 2 cc rectum and sigmoid colon and 90 Gy for 2 cc urinary bladder (α/β = 3 Gy), and assuming full dose of external beam therapy in the volume of interest
| Number of BT fractions (a) | CTV | Rectum | Sigmoid colon | Urinary bladder | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Common PD per fraction during BT (b) | EBRT EQD2 given (c) | Total EQD2 (EBRT + BT) prescribed (α/β = 10 Gy) | Total permissible EQD2 for 2 cc rectum after EBRT (75-c) | Calculated permissible dose per fraction to 2 cc rectum (d) | Permissible dose as percentage of PD (d in Gy/b%) (e) | Total permissible EQD2 for 2 cc sigmoid colon after EBRT (75-c) | Calculated permissible dose per fraction to 2 cc sigmoid colon (p) | Permissible dose as percentage of PD (p in Gy/b%) (q) | Permissible EQD2 for 2 cc urinary bladder after EBRT (90-c) | Calculated permissible dose to 2 cc urinary bladder per fraction (bb) | Permissible dose as percentage of PD (bb in Gy/b%) (cc) | |
| 2 | 8.5 Gy | 50 Gy | 76.2 Gy | 25 Gy | 654 cGy | 76.9% (f) | 25 Gy | 654 cGy | 76.9% (r) | 40 Gy | 861 cGy | 101.3% (dd) |
| 45 Gy | 71.2 Gy | 30 Gy | 729 cGy | 85.8% (g) | 30 Gy | 729 cGy | 85.8% (s) | 45 Gy | 921 cGy | 108.4% (ee) | ||
| 3 | 7 Gy | 50 Gy | 79.8 Gy | 25 Gy | 512 cGy | 73.1% (h) | 25 Gy | 512 cGy | 73.1% (t) | 40 Gy | 680 cGy | 97.1% (ff) |
| 45 Gy | 74.8 Gy | 30 Gy | 572 cGy | 81.7% (i) | 30 Gy | 572 cGy | 81.7% (u) | 45 Gy | 729 cGy | 104.1% (gg) | ||
| 3 | 8 Gy | 50 Gy | 86 Gy | 25 Gy | 512 cGy | 64% (j) | 25 Gy | 512 cGy | 64% (v) | 40 Gy | 680 cGy | 85% (hh) |
| 45 Gy | 81 Gy | 30 Gy | 572 cGy | 71.5% (k) | 30 Gy | 572 cGy | 71.5% (w) | 45 Gy | 729 cGy | 91.1% (ii) | ||
| 4 | 7 Gy | 50 Gy | 89.7 Gy | 25 Gy | 428 cGy | 61.1% (l) | 25 Gy | 428 cGy | 61.1% (x) | 40 Gy | 572 cGy | 81.7% (jj) |
| 45 Gy | 84.7 Gy | 30 Gy | 480 cGy | 68.5% (m) | 30 Gy | 480 cGy | 68.5% (y) | 45 Gy | 614 cGy | 87.7% (kk) | ||
| 5 | 5.5 Gy | 50 Gy | 80.5 Gy | 25 Gy | 372 cGy | 67.6% (n) | 25 Gy | 372 cGy | 67.6% (z) | 40 Gy | 500 cGy | 90.9% (ll) |
| 45 Gy | 85.5 Gy | 30 Gy | 417 cGy | 75.8% (o) | 30 Gy | 417 cGy | 75.8% (aa) | 45 Gy | 537 cGy | 97.6% (mm) | ||
HDR – high-dose-rate, BT – brachytherapy, EBRT – external beam radiotherapy, PD – prescribed dose to point A or 90% volume (D90), EQD2 – 2 Gy equivalent dose