Proffered Papers— Radiation Oncology

RADIATION MORBIDITY TWO YEARS POST TREATMENT: RESULTS FROM RANDOMIZED TRIAL OF PRE-VERSUS POSTOPERTATIVE RADIOTHERAPY

Davis AM, O’Sullivan B, Catton CN, Chabot P, Hammond A, Benk V, Turcotte R, Bell RS, Wunder JS, Goddard K, Day A, Sadura A, Pater J, and Zee B. (Canadian Sarcoma Group and the National Cancer Institute of Canada-Clinical Trials Group, Canada)

Purpose: The objectives of this study were: 1) to determine if there was a difference between patients treated with preoperative (preop) vs. postoperative (postop) radiotherapy in the secondary endpoints of the SR.2 trial, specifically RTOG skin and subcutaneous tissue, bone toxicity, joint stiffness and oedema; and, 2) to evaluate the relationship of these endpoints to function as measured by the Musculoskeletal Tumor Rating Scale (MSTS) and the Toronto Extremity Salvage Score (TESS), at 2 years post treatment.

Methods: The sample analyzed included a subgroup of 113 patients from the SR.2 study who were randomized to preoperative (preop) vs. postoperative (postop) radiotherapy and who had primary wound closure. The morbidity endpoints dichotomized at a score of < 2 or => 2 were evaluated by treatment arm using the Chi-square test. Multivariate step-wise logistic regression was used to evaluate the effect of treatment arm, radiation field size, maximal radiation dose, MSTS and TESS scores on skin and subcutaneous tissue, bone toxicity, joint stiffness and oedema.

Results: There was no difference in skin, bone, or joint toxicity in the two treatment arms. 26 of 46 in the postop arm compared to 19 of 67 in the preop arm had grade 2 or greater subcutaneous fibrosis (p=0.003). Oedema grade 2 or greater was more frequent in the postop arm (11 of 46) vs. 5 of 67 in the preop arm (p=0.014). In univariate analysis dmax dose and TESS score were associated with subcutaneous fibrosis, bone and joint toxicity. In multivariate analysis, only field area was associated with skin toxicity (p=0.14); field area (p=0.0002) and maximum radiation dose (p=0.0563) were associated with subcutaneous fibrosis (with treatment arm confounded by field area); bone toxicity was associated with the TESS score (p=0.004); maximal radiation dose (p=0.0052) and MSTS (p=0.0001) were associated with joint toxicity; and, field area was associated with edema (p=0.0054).

Summary and Conclusions: Patients treated with postop radiotherapy have greater subcutaneous tissue toxicity and oedema. However, these effects are confounded by larger radiation field area and maximum dose in the postop treatment arm. Bone and joint toxicity have a significant impact on patient function.