IMRT LESS TOXIC THAN SBRT FOR PROSTATE CANCER

Stereotactic body radiotherapy (SBRT) might be less expensive and faster for patients with prostate cancer, but it also might be more toxic than intensity-modulated radiation therapy (IMRT), according to a new comparative study.

"SBRT is an exciting potential technology, but our study does raise some caution that there may be more urinary side effects with the treatment," said first author James B. Yu, MD, from the Department of Therapeutic Radiology at the Yale School of Medicine in New Haven, Connecticut.

The study results were published online March 10 in the Journal of Clinical Oncology.

This research has "generated the concerning but testable hypothesis" that when the cost of treatment for increased GU toxicity is considered, SBRT is still less expensive than IMRT, writes Anthony V. D'Amico, MD, from Brigham and Women's Hospital and the Dana-Farber Cancer Institute in Boston, in anaccompanying editorial.

There has been a dramatic increase in the use of IMRT in recent years, allegedly driven by financial incentives, as previously reported by Medscape Medical News. IMRT is reimbursed by Medicare at a higher rate than other treatment approaches, such as brachytherapy and prostatectomy. In addition, once a practice has invested in an IMRT device, patients are more likely to be referred for this treatment.

"In this day and age, when the national conversation is about overtreatment and the cost of treatment, SBRT has been put forth as more cost-effective," Dr. Yu explained. " SBRT still may be more cost-effective, but there could be slightly more side effects. It needs further study."

Retrospective Comparative Review

Dr. Yu and his colleagues conducted their retrospective review of a national sample of Medicare beneficiaries 66 to 94 years of age who received primary treatment with SBRT or IMRT for prostate cancer from 2008 to 2011. The cohort consisted of 1335 patients treated with SBRT and 2670 matched patients treated with IMRT.

All patients were followed for 6, 12, or 24 months. Toxicity was measured using data from Medicare claims.

Mean cost was lower with SBRT than with IMRT ($13,645 vs $21,023).

However, there were considerably more toxic effects with SBRT than with IMRT. In addition, the mean cost per patient to diagnose and investigate the associated toxicities was $145 (range, $69 - $221) for SBRT and $69 (range, $44 - $95) for IMRT (P < .001).

At 6 months, more SBRT patients than IMRT patients had a Medicare claim for treatment-related GU toxicity (15.6% vs 12.6%; odds ratio [OR], 1.29; P = .009).

That trend continued at 12 months (27.1% vs 23.2%; OR, 1.23; P = .01) and at 24 months (43.9% vs 36.3%; OR, 1.38; P = .001).

Most of the GU toxicity with SBRT was related to urethra and bladder toxicities. SBRT patients had significantly more claims than IMRT patients for diagnostic procedures for incontinence and obstruction at 6-, 12-, and 24-month follow-up. SBRT patients also had more claims indicative of a diagnosis or procedures for urethritis, urethral strictures, and obstruction at 12- and 24-month follow-up (P < .003).

GI toxicities were also higher with SBRT than with IMRT at 6 months (5.8% vs 4.1%; OR, 1.42; P = .02). However, at 12- and 24-month follow-up, there were no differences between the groups.

No toxic effects other than GU and GI effects were reported in either group.

During the year after treatment, the mean cost of care was higher with SBRT than with IMRT ($2963 vs $1978; P < .001).