Assessment of National Patterns of Practice for Postoperative Radiation Therapy in Patients with Long Bone Metastases

Although postoperative radiation therapy (RT) (PORT) for patients with long bone metastases has become common, reliable evidence is lacking. The optimal dose fractionation and irradiation field of PORT are unknown. This study aimed to characterize current patterns of practice regarding PORT and factors that affect dose fractionation. Members of the Japanese Radiation Oncology Study Group (JROSG) completed an internet-based survey. The survey was composed of questions to determine the prescription of various dose fractionations in each institution in 2017, describe dose fractionations in four hypothetical cases in which patients were treated with PORT for impending pathological fractures in a lower limb, and indicate irradiation fields each member would prefer. Case 1 was a patient with limited prognosis of non-small-cell lung cancer. Case 2 was a patient with a single oligometastasis. Case 3 was identical to case 1, except for the presence of a radio-resistant primary tumor, renal cell carcinoma. Case 4 was a patient with breast cancer with expected long-term prognosis. Radiation oncologists who recommended long-course RT in case 1 were asked to explain why they considered long-course RT over short-course RT (i.e., 8 Gy in 1 fraction or 20 Gy in 5 fractions). In total, 89 radiation oncologists from 68 institutions (50% of JROSG institutions) responded. Of the patients treated at these institutions, 151 were eligible for this study, except for 1 patient with an unknown prescribed dose fractionation. Among 22 different dose fractionations prescribed, the most common was 30 Gy in 10 fractions (n=75; 50%), followed by 20 Gy in 5 fractions (n=29; 19%). In all the hypothetical cases, the commonest prescribed regimen was 30 Gy in 10 fractions. For case 1, short-course RT (i.e., 8 Gy in 1 fraction or 20 Gy in 5 fractions) was preferred by 20% of the respondents (n=18). The following factors were most often cited as reasons for preferring long-course RT（i.e., >20 Gy in 5 fractions）: “local control” (54%), “incidence of re-irradiation” (34%), and “time until first increase in pain” (19%). Zero percent of the respondents for case 2, 8% for case 3, and 5% for case 4 prescribed short-course RT. Fractionated dose regimens of >30 Gy in 10 fractions were preferred in patients with oligometastasis (53%) compared to those with radio-resistant tumors (34%) and those with expected long-term prognosis (25%). For the irradiation field, 74% (n=66) of respondents recommended involvement of “the entire orthopedic prosthesis” for PORT. For PORT of long bone metastases, 30 Gy in 10 fractions for the entire orthopedic prosthesis is preferred currently in Japan. Higher dose regimens are preferred for patients with oligometastasis. Our results will guide the designing future clinical trials or research for bone metastases.