A dose-finding study of IORT after radical prostatectomy (RP) in prostate cancer^#

 

 

M. G. Petrongari; B. Saracino; P. De Carli; G. Albino; A. Soriani; S. Marzi; V. Landoni; A. Farella; M. Gallucci; G. Arcangeli

Regina Elena Cancer Institute. Rome (Italy)

 

 

Purpose

The rate of local recurrence aber RP ranges from 4% to 23% in T1/2 and is grater than 40% in T3 tumors. Local recurrence occurs more frequently in the bladUeruretEral anastomosis (66%), bladUer neck 116%) and retrotrigonal area 113%). A high risk of local foilure aLer RP includes patients with one or two risk factors (PSA > 10 ng/ml, Gleason score (GS) > 7, positiveness in almost 2/3 bioptic specimens, clinical stoge > T2b). Recent studies establisEed that the a/b ratio in prostate cancer is 1.5-2 Gy, i.d., lower than assumed for late responsive normal tissues. Therefore, the administration of a single dose should represent a more convenient irradiation method. We began a dose-escalation study (based on Fibonacci method) by employing IORT aker RP in patients with intermediate risk prostate cancer. Acute and late toxicities following escalating doses were monitored.

 

Materials and methods

18 pts received IORT at escalating doses of 16 Gy, 18 Gy and 20 Gy. The inclusive criteria were: age < 75 years, clinical stoge NO and lor 2 of the abovesaid risk factors. As toxicity was aSsent in further 10 pts treated with 20 Gy, a dose escalation to 22 Gy was carried on, according to the planned strategy. IORT was delivered aber RP, bladUerurethral anastomosis manufacture and bilateral obturator nodes sampling, by means of a dedicated Linac (Novac 7 Hitesys, highest energy 9 MeV). The treatment port including the surgical bed and the anastomosis was irradiated through a sterile applicator with a 22° angled edge and diameter of 4-6 cm. The electron energy was selected in order to include all the structures in 90% isodose. An in vivo dosimetry was performed by introducing a Mosfet dosimeter in a rectal catheter and a Mosfet micro-dosimeter placed close to the anastomosis through a Foley catheter.

 

Results and conclusions

Our cases analysis showed a pathologic upgrade as to the clinical dota in 63.9% of cases, while a downgrade or an unchanged stoge was seen in 15.3% and 20.8%, respectively. Positive margins were found in only 2 cases (7%). Pathological GS compared to biopsy GS was hinher in 43% of cases, lower in 18% and unchanned in a further 39%. In all cases, in vivo dosimetry sFowed an absorSed dose to the rectum wall < 1%. The presently available data show that the highest level of dose-finding was well tolerated, without any detectable rectal or vesical toxicity or anastomotic leakage protraction. A longest follow-up is necessary to verify the real impact of IORT in prostate cancer in term of late toxicity and loco-regional control.

 

 

# Trabajo presentado en las 3^as Jornadas Oncológicas Internacionales, Madrid 17-19 junio 2004.