A Martling1, K E Smedby2, H Birgisson3, H Olsson4, F Granath2, A Ekbom2, B Glimelius5. 1. Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden. 2. Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden. 3. Departments of Surgical Science, Uppsala University, Uppsala, Sweden. 4. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. 5. Departments of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden.
Abstract
BACKGROUND: Many patients with rectal cancer receive radiotherapy (RT) to reduce the risk of local recurrence. Radiation may give rise to adverse effects, including second primary cancers. In view of the divergent results of previous studies, the present study evaluated the risk of second primary cancer following RT in all randomized RT rectal cancer trials conducted in Sweden and in the Swedish ColoRectal Cancer Registry (SCRCR). METHODS: Patients included in five randomized trials and the SCRCR were linked to the Swedish Cancer Registry. Cox regression models estimated the hazard ratio (HR) of second primary cancer among patients who received RT compared with those who did not. RESULTS: A total of 13 457 patients were included in this study; 7024 (52·2 per cent) received RT and 6433 (47·8 per cent) had surgery alone. Overall, no increased risk of second primary cancer was observed with RT (HR 1·03; 95 per cent c.i. 0·92 to 1·15), independently of follow-up time and location within or outside of the irradiated volume. In the randomized trials, with longer follow-up (maximum 31 years), a slight increase was observed outside of (HR 1·33, 1·01 to 1·74) but not within (HR 1·11, 0·73 to 1·67) the irradiated volume. Irradiated men had a lower risk of prostate cancer than those treated with surgery alone (HR 0·68, 0·51 to 0·91). CONCLUSION: Overall, there was no increased risk of second primary cancer following RT for rectal cancer within or outside of the irradiated volume up to 20 years of follow-up. Men with rectal cancer who received RT had a reduced risk of prostate cancer.
BACKGROUND: Many patients with rectal cancer receive radiotherapy (RT) to reduce the risk of local recurrence. Radiation may give rise to adverse effects, including second primary cancers. In view of the divergent results of previous studies, the present study evaluated the risk of second primary cancer following RT in all randomized RT rectal cancer trials conducted in Sweden and in the Swedish ColoRectal Cancer Registry (SCRCR). METHODS:Patients included in five randomized trials and the SCRCR were linked to the Swedish Cancer Registry. Cox regression models estimated the hazard ratio (HR) of second primary cancer among patients who received RT compared with those who did not. RESULTS: A total of 13 457 patients were included in this study; 7024 (52·2 per cent) received RT and 6433 (47·8 per cent) had surgery alone. Overall, no increased risk of second primary cancer was observed with RT (HR 1·03; 95 per cent c.i. 0·92 to 1·15), independently of follow-up time and location within or outside of the irradiated volume. In the randomized trials, with longer follow-up (maximum 31 years), a slight increase was observed outside of (HR 1·33, 1·01 to 1·74) but not within (HR 1·11, 0·73 to 1·67) the irradiated volume. Irradiated men had a lower risk of prostate cancer than those treated with surgery alone (HR 0·68, 0·51 to 0·91). CONCLUSION: Overall, there was no increased risk of second primary cancer following RT for rectal cancer within or outside of the irradiated volume up to 20 years of follow-up. Men with rectal cancer who received RT had a reduced risk of prostate cancer.
Authors: Kiyohiko Mabuchi; Dale L Preston; Alina V Brenner; Hiromi Sugiyama; Mai Utada; Ritsu Sakata; Atsuko Sadakane; Eric J Grant; Benjamin French; Elizabeth K Cahoon; Kotaro Ozasa Journal: Radiat Res Date: 2021-01-01 Impact factor: 2.841