16 Cervix Carcinoma

348 Cervix Cancer

doses are similar, but somewhat higher. Doses at the vagina vary significantly, also dependent on the shielding of the ring, with doses from 8 - 20 Gy per fraction. 9.5.2 Definitive PDR Brachytherapy and EBT in limited disease (Leuven, Vienna) In the Leuven experience the total dose of brachytherapy is the same as for LDR brachytherapy, if a dose per pulse is applied at a dose rate between 50 and 80 cGy per hour. A maximum dose to the PTV is given respecting a maximum dose of 65 - 70 Gy to the rectum and of 70 - 75 Gy to the bladder. In the Vienna experience, a dose per pulse is applied with a dose rate between 50 and 100 cGy per hour. The total dose at point A is 50 - 60 Gy given in two fractions about two weeks apart. The TRAK is 3.4 - 4 cGy at 1 meter. In addition, 25 Gy from external beam therapy is added applying the same technique for shielding as for combination treatment with HDR brachytherapy. 9.5.3 Definitive HDR Brachytherapy and EBT in extended disease (Vienna) (96) For patients with extended disease brachytherapy starts at the latest during the last week of external beam therapy. External beam therapy is given with a four field box technique in 1.8 - 2 Gy fractions up to a total dose of 45 - 50 Gy at the ICRU-point (45 Gy with concomitant cis-platin chemotherapy). Four (3 - 5) single fractions of HDR brachytherapy with 7 Gy are applied over 10 - 20 minutes twice weekly 4 times (3 - 5), partly concomitant with EBT covering the GTV/PTV as much as possible. The overall treatment time is 6 - 7 weeks. TRAK averages 1.4 - 1.9 cGy at 1 meter for 3 - 4 fractions in large tumours. The physical total dose at point A is 73 - 78 Gy in large tumours (4 fractions). The corresponding isoeffective dose (see above) is 80 - 90 Gy, respectively. The doses per fraction at the pelvic side wall, at the internal and common iliac lymph nodes are 1.4, 1.2, and 0.9 Gy, respectively (ICRU points) (at medium dose rate). The treated volume from brachytherapy and EBT (isoeffective dose of 80-90 Gy) has been 87 cm 3 (it is nowadays slightly larger ~ 110 cm 3 ), the 60 Gy reference volume (taking the 3.1/3.4 Gy isodose as isoeffective depending on the total dose of EBT: 50/45 Gy) is 316/290 cm 3 . The mean dose per fraction at the ICRU rectum reference point is 4 - 5 Gy, adding up to 12 - 20 Gy in 4 fractions and together with the dose from EBT (25x2Gy) to a nominal dose of 62-70 Gy. The corresponding isoeffective dose (alpha beta value of 3) is 70 - 80 Gy. Bladder doses are in principle similar, but somewhat higher. Doses at the vagina vary significantly, with doses from 10-30 Gy per fraction. 9.5.4 Definitive PDR Brachytherapy and EBT in extended disease (Leuven, Vienna) In the Leuven experience, treatment starts with 50 Gy external beam therapy (45 Gy with simultaneous cis-Platin chemotherapy) without any shielding of the brachytherapy volume. The total dose of brachytherapy is similar to LDR brachytherapy (50 - 80 cGy per hour). A maximum dose to the PTV is given respecting a maximum dose of 65 - 70 Gy to the rectum and of 70 - 75 Gy to the bladder. In the Vienna experience treatment starts with 50 Gy external beam therapy (45 Gy with simultaneous cis-Platin chemotherapy) without any shielding of the brachytherapy volume. A pulse dose is applied with a dose rate between 50 and 100 cGy per hour. The total dose in point A is 30 Gy given in one fraction. The TRAK is 2 cGy at 1 meter. The maximum biologically weighted dose to the rectum is 70 - 80 Gy and to the bladder 75 - 90 Gy.