Risk Factors for Pelvic Insufficiency Fractures in Locally Advanced Cervical Cancer Following Intensity Modulated Radiation Therapy.
To investigate the incidence of and risk factors for pelvic insufficiency fracture (PIF) after definitive chemoradiation therapy for locally advanced cervical cancer (LACC).



We analyzed 101 patients with LACC treated from 2008-2014. Patients received weekly cisplatin and underwent external beam radiation therapy with 45 Gy in 25 fractions (node-negative patients) or 50 Gy in 25 fractions with a simultaneous integrated boost of 60 Gy in 30 fractions (node-positive patients). Pulsed dose rate magnetic resonance imaging guided adaptive brachytherapy was given in addition. Follow-up magnetic resonance imaging was performed routinely at 3 and 12 months after the end of treatment or based on clinical indication. PIF was defined as a fracture line with or without sclerotic changes in the pelvic bones. D50%and V55Gywere calculated for the os sacrum and jointly for the os ileum and pubis. Patient- and treatment-related factors including dose were analyzed for correlation with PIF.



The median follow-up period was 25 months. The median age was 50 years. In 20 patients (20%), a median of 2 PIFs (range, 1-3 PIFs) were diagnosed; half were asymptomatic. The majority of the fractures were located in the sacrum (77%). Age was a significant risk factor (P<.001), and the incidence of PIF was 4% and 37% in patients aged ≤50 years and patients aged >50 years, respectively. Sacrum D50%was a significant risk factor in patients aged >50 years (P=.04), whereas V55Gyof the sacrum and V55Gyof the pelvic bones were insignificant (P=.33 and P=.18, respectively). A dose-effect curve for sacrum D50%in patients aged >50 years showed that reduction of sacrum D50%from 40 GyEQD2to 35 GyEQD2reduces PIF risk from 45% to 22%.



PIF is common after treatment of LACC and is mainly seen in patients aged >50 years. Our data indicate that PIFs are not related to lymph node boosts but rather to dose and volume associated with irradiation of the elective pelvic target. Reducing the prescribed elective dose from 50 to 45 Gy may reduce the risk of PIF considerably.
Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. Electronic address: anraml@rm.dk.
Anne
A
Ramlov
Department of Radiotherapy, Aarhus University Hospital, Aarhus, Denmark.
Erik Morre
EM
Pedersen
Department of Radiotherapy, Aarhus University Hospital, Aarhus, Denmark.
Lisbeth
L
Røhl
Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark.
Esben
E
Worm
Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.
Lars
L
Fokdal
Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.
Jacob Chr
JC
Lindegaard
Department of Oncology, Aarhus University Hospital, Aarhus, Denmark; Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark.
Kari
K
Tanderup
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D015984:Causality; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D004307:Dose-Response Relationship, Radiation; D005260:Female; D015775:Fractures, Stress / Q000453:epidemiology* / Q000517:prevention & control; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D010384:Pelvic Bones / Q000293:injuries* / Q000528:radiation effects; D011183:Postoperative Complications / Q000453:epidemiology* / Q000517:prevention & control; D000069473:Radiation Dose Hypofractionation; D020266:Radiotherapy, Conformal / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D012307:Risk Factors; D002583:Uterine Cervical Neoplasms / Q000453:epidemiology* / Q000532:radiotherapy*; D055815:Young Adult