16 Cervix Carcinoma

338 Cervix Cancer

Fig. 14.14 (continued): was contoured (35 cm 3 ) as well as the rectum (57 cm 3 ) and bladder (261 cm 3 ). The dose distribution is shown on transverse planes at the level of the vaginal sources, 1 and 2 cm above and at the midparasagittal and midparacoronal planes. Isodose lines indicate 89 Gy, 75 Gy, and 60 Gy. These doses are calculated based on the alpha-beta model (10 Gy) and the recommendations of ICRU 38: EBT was 49 Gy at the ICRU point, BT 4 x 7Gy for the isodose encompassing the PTV (no chemotherapy). Maximum reference isodose width was 6 cm (89 Gy) and 9 cm (60 Gy), which was 3.4 cm (89 Gy) and 5 cm, (60 Gy) on the left at the level of the ring and 2.5 cm (89 Gy) and 4.6 cm (60 Gy) on the left at point A, respectively. Maximum reference isodose thickness was 4.5 cm and 6,8 cm, maximum height 7.9 and 10.0 cm. The reference volume (mean) for 85 Gy was 91 cm 3 (104, 108, 90, 63 per fraction (adaptation for tumour shrinkage)), 316 cm 3 for 60 Gy. The isoeffective dose to point A on the right side was 89 Gy, on the left 95 Gy. TRAK was 1.77 cGy at 1 meter.

Fig 14.14: Typical MRI based treatment planning based on ring applicator and stepping source technology (Vienna method) (continued 2)

Fig 14.14.C: DVH evaluation revealed that 85%/96%/100% of the PTV was encompassed by the 89 Gy-, 75 Gy-, 60 Gy-isodose (C1). For the rectum the doses for the 2 cm 3 and 5 cm 3 volumes were 4.1 Gy and 3.5 Gy, respectively, which corresponds to 59% and 50% of the prescribed dose (C2). For the bladder the doses for the 2 cm 3 and 5 cm 3 volumes were 5,9 Gy and 5,2 Gy, respectively, corresponding to 84% and 74% of the prescribed dose (C2). The total dose to the rectum was 49 Gy (EBT) plus a nominal 16.4 Gy (4 x 4.1)/14 Gy (4 x 3.5) to the 2/5 cm 3 volume, which corresponded to the mean dose per fraction for the whole treatment (little variation). The total biologically weighted dose was 71 Gy and 66 Gy. For the bladder this was 4 x 5.9/5.2 Gy in the 2/5 cm 3 volume, the total biologically weighted dose was 90 Gy and 82 Gy, respectively. The doses at the ICRU rectum and bladder reference points averaged 5 Gy (3.6-6.4) and 4.7 Gy (3.5-6.5), for the total dose of brachytherapy 20.1 and 18.7 Gy, respectively. The patient (44 years) was treated 3/99, overall treatment time was 38 days. She was in continuous complete remission at three years. Grade 1 side effects were noticed in the vagina, grade 0 in the rectum and bladder (Lent-Soma Score).