CONFORMAL STATIC-FIELD RADIATION-THERAPY TREATMENT OF EARLY PROSTATE-CANCER VERSUS NONCONFORMAL TECHNIQUES - A REDUCTION IN ACUTE MORBIDITY

Patients with early prostate cancer have been definitively treated using our previously described technique of CT-based 3D treatment planning and beam's eye view techniques with patients immobilized in alpha cradle casts. An average of 14% bladder (range 6-31 %) and 14% rectal (range 7-25%) volume receiving a given dose was eliminated using four conformally blocked fields, with a 1.5 cm margin around the prostate contour, when compared to stage matched controls. Treatment-related acute morbidity was compared for 26 patients treated by the conformal techniques (CG) since April 1989 and 20 consecutive patients treated immediately prior to the conformal techniques with prostate only fields from May 1985-March 1989 (NCG). Acute urinary symptoms (frequency, dysuria, hematuria) or acute rectal symptoms (diarrhea, tenesmus, blood) occurred in 77% (20/26) of the CG versus 80% (16/20) of the NCG patients. Only 31% (8/26) of the CG versus 60% (12/20) of the NCG patients (p < .05) experienced symptoms to a degree which prompted physician intervention (medication and/or interruption of treatment). Two of 26 CG patients (8%) required medication for both bladder and rectal symptoms compared to 5/20 (25%) NCG patients (p = .09). Symptoms persisted for an average of 2.5 weeks versus 3.5 weeks in the CG and NCG groups, respectively. Persistent symptoms at or beyond the 1 month follow-up were present in 3/26 (11 %) CG patients (average duration 1.5 months) and were present in 4/20 (20%) of the NCG patients (average duration 2.5 months). Thus, although the percentage of patients who experience acute irritation of the bladder and/or rectum is similar in the two groups, it appears that the percentage requiring medication and/or interruption of treatment is significantly less when 3D treatment planning, rigid immobilization, and conformal blocks are used. The amount of bladder and rectal tissue that is eliminated by our conformal technique is important as shown clinically by the lesser severity and shorter duration of acute symptomatology.