Pelvic irradiation does not increase the risk of hip replacement in patients with gynecological cancer: A cohort study based on 8,507 patients

Background and purpose —

Long-term survivors of cancer can develop adverse effects of the treatment. 60% of cancer patients survive for at least 5 years after diagnosis. Pelvic irradiation can cause bone damage in these long-term survivors, with increased risk of fracture and degeneration of the hip.

Patients and methods —

Analyses were based on linkage between the Cancer Registry of Norway (CRN) and the Norwegian Arthroplasty Register (NAR). All women who had been exposed to radiation for curative radiotherapy of gynecological cancer (40–60 Gy for at least 28 days) were identified in the CRN. Radiotherapy had been given between 1998 and 2006 and only patients who were irradiated within 6 months of diagnosis were included. The control group contained women with breast cancer who had also undergone radiotherapy, but not to the pelvic area. Fine and Gray competing-risk analysis was used to calculate subhazard-rate ratios (subHRRs) and cumulative incidence functions (CIFs) for the risk of having a prosthesis accounting for differences in mortality.

Results —

Of 962 eligible patients with gynecological cancer, 26 (3%) had received a total hip replacement. In the control group without exposure, 253 (3%) of 7,545 patients with breast cancer had undergone total hip replacement. The 8-year CIF for receiving a total hip replacement was 2.7% (95% CI: 2.6–2.8) for gynecological cancer patients and 3.0% (95% CI: 2.95–3.03) for breast cancer patients; subHRR was 0.80 (95% CI: 0.53–1.22; p = 0.3). In both groups, the most common reason for hip replacement was idiopathic osteoarthritis.

Interpretation —

We did not find any statistically significantly higher risk of undergoing total hip replacement in patients with gynecological cancer who had had pelvic radiotherapy than in women with breast cancer who had not had pelvic radiotherapy.After approximately 5 years, two-thirds of cancer patients are still alive (Sant et al. 2009). Research on late adverse effects in cancer survivors has gained increasing interest over the last decade. However, the main interest has been on secondary cancer events (Curtis et al. 2006), cardiovascular complications, and emotional problems (Meyerowitz et al. 2008). The relationship between cancer, skeletal disorders, and treatment has rarely been investigated. Skeletal adverse effects of irradiation include cell death, cellular injury, and abnormal bone repair—although the underlying mechanisms are not fully understood (Yurut-Caloglu et al. 2010).Pelvic insufficiency fractures may be one of the possible late side effects of radiotherapy to the pelvic area. The incidence of such fractures has been reported to be 5–20% in gynecological cancer patients who have undergone radiotherapy (Kwon et al. 2008, Oh et al. 2008, Schmeler et al. 2010, Shih et al. 2013). Less common effects of pelvic irradiation include acetabular protrusion and avascular necrosis of the femoral head (Fiorino et al. 2009). Other studies have not found any increased risk of hip fracture after pelvic irradiation (Feltl et al. 2006, Elliott et al. 2011). We wanted to examine the risk of receiving a total hip replacement in patients with cancer in the pelvic area who had undergone radiotherapy compared to patients with cancer at another location who had not undergone pelvic irradiation. Our hypothesis was that patients who have had high-dose pelvic radiotherapy would have a higher risk of undergoing total hip replacement than women who have had radiotherapy with target fields in other parts of the body.