PROGNOSTIC FACTORS FOR TUMOR RESPONSE AND SKIN DAMAGE TO COMBINED RADIOTHERAPY AND HYPERTHERMIA IN SUPERFICIAL RECURRENT BREAST CARCINOMAS

Prognostic factors for complete tumour response and acute skin damage to combined hyperthermia and radiotherapy were analysed in material of patients with breast cancer, recurrent in previously irradiated areas . Radiotherapy was given daily to a total absorbed dose of 30.0 Gy in 2 weeks or 34.5 Gy in 3 weeks. The first radiotherapy schedule was com bined with heat twice weekly, a total of four heat treatments (schedul e A). The second radiotherapy schedule was combined with heat either o nce or twice a week resulting in a total of three (schedule B) or six (schedule C) heat treatments. Heat was induced with microwaves (2450, 915 or 434 MHz) via external applicators and always given after the ra diotherapy fraction. The complete response (CR) rate in evaluable pati ents was 71% (49/69). There was no significant difference in CR rate b etween the three different hyperthermia schedules. The CR rates were 7 4% (14/19), 65% (15/23) and 74% (20/27) for schedules A, B and C respe ctively. The only factor predicting CR, evaluated both uni- and multiv ariately, was the CRE-value for the present radiotherapy dose (p = 0.0 2). If only tumours treated with 915 MHz were taken into account, howe ver, then the highest minimum temperature at a given heat session pred icted complete response (p = 0.03). This was true also in a multivaria te analysis of this subgroup of tumours. A Kaplan-Meier analysis (log rank test) showed no significant difference in duration of CR between the different treatment schedules. Cox's proportional hazards method r evealed three significant factors: tumour size (negatively correlated, p = 0.007), the time interval between the diagnosis of the primary tum our and the present treatment (p = 0.02) and the average temperature ( 0.03). Maximum acute skin reactions in the treatment field were scored according to an ordinal scale of 0-8, modified after WHO 1979. Twenty -six treatment areas (32%) expressed more severe skin damage(score gre ater than or equal to 5) in terms of desquamation with blisters (14%) and necrosis or ulceration (19%). Factors correlated with skin damage were the size of the lesion area (p = 0.011), the highest average maxi mum temperature during a given heat session (p = 0.03) acid the fracti onation schedule of hyperthermia (p = 0.05). The extent of previous ra diotherapy absorbed dose, previous surgery in the treated area or prev ious chemotherapy had no significant influence on the acute skin react ions.