Impact of neoadjuvant hormonal therapy on dose-volume histograms in patients with localized prostate cancer under radical radiation therapy

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ABSTRACT

Introduction. Prostate volume involves a definedtoxicity predictor in the radiation therapy of localizedprostate cancer. Neoadjuvant hormone therapy(nHT) can reduce prostate volume and, therefore,the planned volume. The objective of thisstudy was to establish if the value of nHT reducesthe planned volume and if this reduction correlateswith a reduction of the dose received in thetarget organs.Material and methods. 28 patients diagnosed of localizedprostate cancer and referred to our departmentsfor radiation therapy with radical intention,in the period ranging between April 2002 andOctober 2003, were included prospectively. The patientsreceived nHT (triptorelin + flutamide) for 2months and adjuvant HT until completing 2 yearsin the high-risk cases. A transrectal ultrasoundstudy was performed in all patients, simulation CTand planning before the start of HT and after 2months of treatment. The radiation therapy wascarried out with 6 or 18 MV LINAC photons, with adose fractioning scheme of 5 x 180-200 cGy, a totaldosage of 66-72 Gy to prostate, 56 Gy to seminalvesicles and, in the high-risk cases, 46 Gy to pelviclymph nodes.Results. The distribution according to risk groupwas low risk 3.6%, intermediate risk 28.6% and highrisk 67.9%. By transrectal ultrasound, prostate volumeon diagnosis was 50.65 cc pre HT and 38.97 ccpost HT (p < 0.001), which means a volume reductionof 24%. The comparative analysis of the dosevolumehistograms of the first versus the second CTshows a reduction in the planned volume GTV1(prostate) (81.33 cc vs 63.96 cc, p < 0.05), PTV1(prostate and margin) (197.51 cc vs 168.38 cc, p <0.001) and PTV2 (prostate, vesicles and margin)(340.5 cc vs 307.26 cc, p < 0.05), a reduction of themaximum dose in the seminal vesicles (70.2 versus68.75 Gy, p < 0.05), a reduction of the mean dose inthe seminal vesicles (65.07 Gy versus 63.07 Gy, p <0.05), PTV2 (67.72 Gy versus 66.9 Gy, p < 0.01) andPTV3 (prostate, vesicles, pelvic lymph nodes andmargin) (58.86 Gy versus 57.21 Gy, p < 0.01), a reductionof the D90 in the seminal vesicles (61.83 Gyversus 60.06 Gy, p < 0.05) and PTV2 (61.04 Gy versus59.45 Gy, p < 0.05) and a reduction of V60 of the rectum(32.45% versus 28.22%, p < 0.05) and V60 of thebladder (41.78% versus 31.67%, p < 0.005).Conclusions. Neoadjuvant hormone therapy reducessignificantly prostate volume and as a resultthe planned volume and consequently the rectaland bladder V60 can be significantly reduced