Toxicity analysis of dose escalation from 75.6 gy to 81.0 gy in prostate cancer.

OBJECTIVE

Several randomized trials have demonstrated a biochemical control advantage to an increase from the "conventional" 66 to 70 Gy range to the "high-dose" 75 to 81 Gy range; these trials have also, however, demonstrated a toxicity disadvantage. Our objective was to perform a toxicity analysis of a minor dose escalation (from 75.6 to 81.0 Gy) within this "high-dose" range.

METHODS

A total of 189 patients comprised the study population-119 received 75.6 Gy and 70 received 81.0 Gy. Acute, late, and final (at most recent follow-up) gastrointestinal (GI) and genitourinary (GU) toxicity were charted for each group and compared using the χ test. Ordered logit regression analyses were performed on each toxicity end point, using all major demographic, disease, and treatment factors as covariates.

RESULTS

The 81.0 Gy group had higher rates of grade 2 acute GU (P < 0.001), late GU (P = 0.001), and late GI (P = 0.082) toxicity, a lower rate of acute GI toxicity (P = 0.002) and no notable differences in final GU (P = 0.551) or final GI (P = 0.194) toxicity compared with the 75.6 Gy group. The ordered logit regression analyses showed that only age (P = 0.019) and radiotherapy dose (P = 0.016) correlated with acute GU toxicity and only radiotherapy dose (P = 0.018) correlated with late GU toxicity. Only intensity modulated radiotherapy use (P = 0.001) correlated with acute GI toxicity; no factors correlated with late GI toxicity or final GU or GI toxicity.

CONCLUSIONS

Although some increases in acute and late toxicity rates were observed with even a minor dose escalation from 75.6 to 81.0 Gy, notably no increases in final late GI or GU toxicity rates were observed.