1. Dosimetric Parameters Associated
With The Development Of Acute
Toxicity In Breast Irradiation Volume
Using 3DCRT.
Ignacio Sisamón1, Ricardo Cendales1, José Manuel Díaz Cobos2, Pedro Pablo Escolar Pérez2,
Adriana Fondevilla2, Fernando Mata2, Luis Schiappacasse3.
1 Fundación Grupo IMO. Instituto Madrileño de Oncología, Madrid, Spain
Introduction 2 Unidad de RT Grupo IMO. IOSE, Murcia, Spain
3 Unidad de RT Grupo IMO. Clinica La Milagrosa, Madrid, Spain
Several data suggests less toxicity in
breast irradiation using IMRT1-4. But there are not
recommendation about wich patients has more risks with
3DCRT.
Purpose Dosimetric parameters of radiation treatment.
To identify dosimetric parameters associated with acute (cm3) Mean Median Q 25% Q 75% Min. Max.
PTV 800,6 777,0 549,0 1011,0 201,0 1667,0
toxicity when breast is irradiated using 3DCRT technique in
V47.5 1237,5 1225,0 908,0 1513,0 394,0 2256,0
standard fractionation.
V50 650,7 632,0 436,0 795,0 204,0 1546,0
V53.5 72,8 42,0 12,0 100,0 0,0 763,0
Materials V47.5 - PTV 436,9 424,0 317,0 546,0 62,0 999,0
Retrospective analysis of acute toxicity related to total PTV/V47,5 0,6 0,6 0,6 0,7 0,4 0,9
irradiated breast volume (PTV), V50, V53.5 (107%), conformal PTV/V50 1,3 1,3 1,1 1,4 0,6 2,2
index (PTV/V47.5), and homogeneity index (V53.5/V47.5). V53,5/V47,5 0,1 0,0 0,0 0,1 0,0 0,5
V53,5/V50 0,1 0,1 0,0 0,1 0,0 0,6
Patients with invasive breast carcinoma were treated with
V60 284,6 237,0 164,0 341,0 68,0 1005,0
3DCRT after conservative surgery. We used tangential opposite V66 107,0 80,0 56,0 124,0 10,0 509,0
wedged beams and standard fractionation (50/2Gy to the whole V70 5,7 0,0 0,0 5,0 0,0 72,0
breast volume and 16Gy boost). No patient received lymph Boost/V60 0,5 0,4 0,4 0,5 0,2 0,9
node irradiation. Acute toxicity according to RTOG scale was Lung V10 18,6 19,0 14,0 23,0 5,0 35,0
collected from medical records during treatment and Lung V20 13,2 13,0 9,0 18,0 2,0 26,0
photographic records after 50Gy and 66Gy. Lung V30 10,7 10,0 6,0 14,0 1,0 23,0
Results
107 Tis-T3, N0-1 breast cancer patients were treated between
Univariate analysis for acute toxicity G2-3 December 2008 and February 2010, without lymph node chain
PTV (ml) OR IC 95 irradiation. Mean age was 58 years.
57% received chemotherapy before RT (n= 62); 11% received
< 474 1 Trastuzumab (n = 12), and hormone therapy in 87% (n = 93).
474-602 1,5 0,21 10,3 103 patients received radiotherapy until 66Gy, having a boost with
electrons (72%) or photons with wedges (28%). The reported acute
602-777 3,75 0,63 22,04
skin toxicity was G0 5%, G1 63%, G2 25%, and G3 7%; no patient
777-897 4,41 0,03 28,68 had G4 toxicity. Mean breast PTV volume was 777ml (IQR 550-1010).
897-1168 6,00 1,04 34,31
Mean V50Gy was 630ml (IQR 435-795). Mean V53.5Gy (107%) was
42ml (IQR 12-100).
>1168 26,25 4,13 166,45 15 of the 28 pts who received boost with photons developed grade
2 or 3 toxicity (53%). However this only occurred in 17 of the 75 pts
who received electrons boost (22%). Several factors were associated
Multivariate analysis for acute tox. G2-3 with acute grade 2 or 3 toxicity in the bivariate analysis (PTV volume,
PTV (ml) OR IC 95 V47.5Gy, V47.5Gy not included in the PTV, V50Gy, V53.5Gy,
< 1149 1 PTV/V47.5Gy, V53, 5/47,5) but in multivariate analysis, only the
>=1150 * 11,37 2,57 50,34 volume of the PTV showed significant differences.
>=1150 ** 7,69 1,55 38,03 Patients who have a breast PTV volume higher than 1150 ml
(*) OR adjusted for PTV/V47.5 and V53.5/V47.5 are at 7.7 times more risk of grade 2 or 3 toxicity (95%CI 1,56-38),
(**) OR adjusted for PTV/V47.5 and V53.5/V47.5, and for regardless of the shape index, homogeneity and the type of
boost energy (electrons vs photons) energy used for the administration of boost.
Conclusions
The volume of the breast PTV is directly correlated with the
development of acute grade 2 or greater toxicity, being this risk
significantly higher when exceeding 1150 ml.
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