Analysis of risk factors for mandibular bone radionecrosis after exclusive low dose-rate brachytherapy for oral cancer.
BACKGROUND
Brachytherapy is widely adopted as an exclusive treatment of T1/T2 oral cancer with a high probability of definitive cure. Therefore, any major complication, like mandibular bone necrosis, should be avoided. Many risk factors, either clinical or technical, have been considered in the literature.


METHODS
One hundred consecutive interstitial iridium LDR treatments for early cancers of the tongue and floor of the mouth performed from January 1989 to November 1993 were reviewed. An analysis of some simple technical parameters (total dose, dose-rate, reference volume, linear activity, total reference kerma) was performed in order to identify the main physical risk factors. Moreover, total dose was recalculated as extrapolated responsive dose for normal tissue complications.


RESULTS
Bone necrosis was observed in 10 out of 100 patients with a median follow-up of 38 months. No significant incidence of this complication was observed when tumor site (mobile tongue versus floor of the mouth), dental status or total physical dose were considered. A significant correlation between the incidence of bone necrosis and two main parameters was found, i.e. dose-rate (P < 0.02) and reference volume (P < 0.05).


CONCLUSIONS
A threshold value may be suggested both for dose-rate (50 cGy/h) and reference volume (25,000 mm3). Bone necrosis is clearly related to both these parameters since most cases (i.e. 80%) were observed in the subgroup over the volume and dose-rate threshold.
Lozza
L
L
Radiotherapy Department, National Tumors Institute, Milan, Italy.
Cerrotta
A
A
Gardani
G
G
De Marie
M
M
Di Russo
A
A
Kenda
R
R
Tana
S
S
Valvo
F
F
Zucali
R
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008336:Mandibular Diseases / Q000209:etiology*; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000532:radiotherapy*; D010025:Osteoradionecrosis / Q000209:etiology*; D012307:Risk Factors