Influence of body mass index and periprostatic fat on rectal dosimetry in permanent seed prostate brachytherapy

Radiation Oncology

Daniel Taussky¹  Guila Delouya²  Aliza Meissner²  Nelson Gruszczynski²  David Tiberi² 

[1] Centre Hospitalier de l’Université de Montréal (CHUM) – Hôpital Notre-Dame, Department of Radiation Oncology, 1560 rue Sherbrooke E, Montréal, Québec H2L 4 M1, Canada;Département de Radio-Oncologie, Centre Hospitalier de l’Université de Montréal (CHUM) - Hôpital Notre-Dame, Montréal, Québec, Canada

关键词: Rectal dose;    Brachytherapy;    Body mass index;    Adipose tissue;    Prostate cancer;   

Others  :  820708
DOI  :  10.1186/1748-717X-9-93

 received in 2013-12-27, accepted in 2014-04-05,  发布年份 2014

【 摘 要 】

Purpose

We examined the influence of body mass index (BMI) and body fat distribution on rectal dose in patients treated with permanent seed brachytherapy for localized prostate cancer.

Methods and materials

We analyzed 213 patients treated with I¹²⁵ seed brachytherapy for localized prostate cancer. BMI and rectal dosimetry data for all patients were available. Data on visceral and subcutaneous fat distribution at the level of the iliac crest (n = 140) as well as the distribution of periprostatic and subcutaneous fat at the symphysis pubis level were obtained (n = 117). Fat distribution was manually contoured on CT on day 30 after brachytherapy. The correlation between BMI, fat distribution and rectal dose (R100 (in cc), R150 (cc), D2 (Gy)) was analyzed using the Spearman correlation coefficient. Differences in rectal dose between tertiles of body fat distribution were calculated using nonparametric tests.

Results

Periprostatic adipose was only weakly correlated with BMI (r = 0.0.245, p = 0.008) and only weakly correlated with the other fat measurements (r = 0.31-0.37, p < 0.001). On the other hand, BMI was correlated with all other fat measurements (≥0.58, p < 0.001). All the other fat measurements were strongly correlated with each other (r = 0.5-0.87, p < 0.001). Patients with an R100 of >1.3 cc (23% of patients) had less visceral fat (p = 0.004), less subcutaneous fat at the level of the iliac crest (p = 0.046) and a lower BMI (26.8 kg/m² vs. 28.5 kg/m², p = 0.02) than patients with an R100 of <1.3 cc. Results were very similar when comparing an R100 of >1.0 cc (34% of patients) across the tertiles. None of the tested linear regression models were predictive (max 12%) of dose to the rectum.

Conclusion

Dose to the rectum is dependent on BMI and body fat distribution. Periprostatic fat does not influence rectal dose. Dose to the rectum remains difficult to predict and depends on many factors, one of which is body fat distribution.

【 授权许可】

   
2014 Tiberi et al.; licensee BioMed Central Ltd.

【 图 表 】

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