The Radiation Oncology Feed For radiation oncologists · physicists · RTTs · dosimetrists
high relevance gynecologic toxicity

Pelvic insufficiency fractures affected nearly one-third after gynecologic IMRT

Pelvic insufficiency fractures occurred in 29.2% of patients, with postmenopause and elevated baseline t-PINP independently predicting risk.

RadOncToday · ·1 min read

KEY POINTS

  • This single-centre prospective phase II study analyzed 113 patients treated with pelvic IMRT: 85 with cervical cancer and 28 with endometrial cancer. Thirty-two received definitive treatment and 81 postoperative radiotherapy; median follow-up was 26 months.
  • External-beam treatment generally delivered 45–50.4 Gy in 25–28 fractions. Definitive treatment could include a nodal simultaneous integrated boost to 60 Gy in 28 fractions, followed by image-guided brachytherapy of 6–7 Gy per fraction for five to six fractions.
  • Serial multiparametric pelvic MRI identified insufficiency fractures in 33 of 113 patients (29.2%). Median onset was 8.6 months after IMRT, with a range of 3.5–13.5 months.
  • At diagnosis, 57.6% of affected patients were symptomatic and 66.7% had at least two lesions. The most common sites were the sacrum (33.3%), ilium (28.2%), and para-acetabular region (25.6%).
  • The median individual lesion area was 1.97 cm². Fracture burden continued to evolve after initial detection, reaching a median peak at 15.8 months, when patients had a median of four lesions and a maximum total area of 9.27 cm².
  • Neither fracture number nor total lesion area remained independently associated with pain severity. Most patients were managed conservatively with analgesia, rest, and avoidance of weight-bearing; one patient underwent surgery in the setting of additional trauma.
  • Postmenopausal status was independently associated with fracture risk (OR 18.85, 95% CI 1.40–254.58; p = 0.027), although the confidence interval was extremely wide. Baseline total procollagen type I N-terminal propeptide of at least 55 ng/mL was also predictive (OR 4.74, 95% CI 1.26–17.92; p = 0.022).
  • Fracture risk was not significantly associated with pelvic bone dose-volume metrics, chemotherapy, age above 53 years, osteoporosis, vitamin D, or other measured bone biomarkers. Definitive radiotherapy showed a higher unadjusted fracture incidence than adjuvant treatment, 43.8% versus 23.5%.

CLINICAL TAKEAWAY

Pelvic insufficiency fractures are common after contemporary gynecologic IMRT and may be multifocal, evolving, and difficult to distinguish from bone metastases. Clinicians should maintain a low threshold for MRI in patients developing pelvic pain, especially after menopause, but baseline t-PINP is not ready for routine risk stratification without multicentre validation.

SOURCE

International Journal of Radiation Oncology, Biology, Physics