CK for prostate cancer: 2nd National Congress of AIRO Giovani, Florence Italy - June 27, 2009

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>>CK for prostate cancer: 2nd National Congress of AIRO Giovani, Florence Italy - June 27, 2009

CYBERKNIFE® TREATMENT FOR LOCALIZED PROSTATE CANCER.
PRELIMINARY EXPERIENCE.

A. Pontoriero, D. Arpa, P. Frosina, C. De Renzis.
Department of Radiological Science, Operative Unit of Radiotherapy University of Messina.


PURPOSE:

Hypofractioned radiosurgical treatment of prostate cancer have been theorized to improve the tumor control over the conventional radiotherapy due to low alpha/beta ratio of prostate. Infact, the low α/ß ratio for prostate cancer require high radiation dose for the tumor control and an hypofractionated schedule with a dose of 38 Gy in four fractions as calculated biologically lethal for the prostate cells cancer. In this report we summarized a preliminary experience with planning target about the volume coverage, rectum, urethra and bladder exposure.

PATIENTS AND METHODS:

The Virtual HDR Cyberknife is indicated for patients with localized cancer prostate (T1-T2b) with favorable prognosis (Gleason score ≤ 6, PSA ≤ 10 ng/ml) and select patients with intermediate prognosis (Gleason score of 7, PSA 10,2-20 ng/ml). The PTV, defined with MRI and CT imaging, included the prostate and seminal vesicle, plus 2 mm of expansion for favorable prognosis or 5 mm for intermediate prognosis in all direction except posteriorly. Prior to treatment planning, one week before, 4 gold fiducials are placed into the prostate with ultrasound guidance.

RESULTS:
For our patients treated with Cyberknife the prescription dose is 38 Gy in four fractions at the median prescription isodose line is 65%. The median PTV was: V100 97%, V125 38%, V150 0,61% and D90 4092 cGy. The median exposure urethra was: DMax 4300 cGy, D10 4150 cGy and D50 3683 cGy. The median bladder dose was DMax 3600 cGy and D10 2600 cGy. The median rectal wall dose was DMax 3300 cGy, D1 3273 cGy, D10 2163 cGy, D25 1578 cGy and V80 1,3 ml. the median rectal mucosa dose was DMax 3000 cGy, D1 2806 cGy, D10 2040 cGy, D25 1600 cGy and V80 0,06 ml. PSA levels have steadily decreased to be normal following post-therapy for all patients.

CONCLUSIONS:

The Cyberknife is a imaging guided device for delivering high radiation doses to a precisely three dimensional target volume. It is a non invasive method with excellent short-term PSA response and very low levels of complications. This preliminary report need of further confirms for late complication and effective tumor control.