Late effect of multiple daily fraction palliation schedule for advanced pelvic malignancies (RTOG 8502)

Determine late complication incidence for pelvic palliation using accelerated multiple daily fraction radiation [Radiation Therapy Oncology Group (RTOG) 8502].

Prospective evaluation of a palliative radiation schedule for advanced pelvic malignancies was conducted from 1985 to 1989 by RTOG 8502. The dose was 44.40 Gy in 12 fractions (3.7 Gy BID) with a rest after 14.80 Gy and 29.60 Gy. The pilot part of the study allowed for a variable rest interval of 3-6 weeks. The rest interval was then randomized between 2 and 4 weeks to determine effect on tumor control. No difference in tumor control was identified (p = 0.59). The pilot segment accrued 151 patients and the randomized segment accrued 144 patients. A total of 290 cases were analyzable (four ineligible or canceled) for late effects. To minimize actuarial bias, only patients surviving 90 days (193) were analyzed for late effect risk. The primary site consisted of gynecologic (40%), colorectal (28%), genitourinary (25%), and miscellaneous (7%). The extent of tumor consisted of pelvis only (62%) and additional tumor outside the pelvis (38%). Most of the patients were elderly (76% > 60 years, 47% > 70 years). Karnofsky performance status (KPS) was > or = 80 in 60% of patients and < 80 in 40%.

None of the patients with < 30 Gy (less than three courses) developed late toxicity. A total of 11/193 (6%) developed Grade 3+ late toxicity (nine Grade 3, one Grade 4, one Grade 5). Actuarial analysis of complication rate by survival time for Grades 3, 4, and 5 shows a cumulative incidence for complications after 6 months that plateaus at 6.9% by 18 months. The cumulative incidence for Grades 4 and 5 is 2.0% by 12 months. The difference in late effect for the 2-week rest vs. 4-week rest was not statistically different (p = .47). Patient factors evaluated for increased risk of late complications included prior surgeries, age, sex, KPS and primary. None were found to have significant statistical correlations with late effects.

The crude late complications rate is 6%. Actuarial analysis using cumulative incidence shows 6.9% by 18 months. This represents a significant decrease in late complications from 49% seen with higher dose per fraction (10 Gy x 3) piloted by Radiation Therapy Oncology Group (7905) for a similar group of patients. Long-term analysis of late complication indicates this schedule can be used in the pelvis with relatively low incidence of complication. This schedule has significant logistic benefits and has been shown to produce good tumor regression and excellent palliation of symptoms.