Clinical investigation: prostate
Short-course intensity-modulated radiotherapy (70 GY at 2.5 GY per fraction) for localized prostate cancer: preliminary results on late toxicity and quality of life

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Abstract

Purpose: To present our preliminary observations on the late toxicity and quality of life (QOL) of patients treated with short-course intensity-modulated radiotherapy (SCIM-RT).

Methods and Materials: Fifty-one patients were treated with SCIM-RT at the Cleveland Clinic Foundation between October 1998 and May 1999. The technique consisted of intensity-modulated radiotherapy using 5 static fields (anterior, 2 laterals, and 2 anterior obliques). Inverse plans were generated by the Corvus treatment-planning system. The treatment delivery was performed with a dynamic multileaf collimator. A total of 70.0 Gy was prescribed in all cases at 2.5 Gy per fraction to be delivered in 28 fractions over 5 and a half weeks. The location of the prostate gland was verified and adjusted daily with the BAT transabdominal ultrasound system. The median follow-up was 18 months (range: 11 to 26 months). The Radiation Therapy Oncology Group (RTOG) scales were used to evaluate late toxicity. The Expanded Prostate Cancer Index Composite (EPIC) was used to evaluate QOL. A total of 24 patients completed the EPIC questionnaire at approximately 2 years after therapy (median time from treatment to questionnaire administration: 24 months; range: 21 to 26 months). The results from the EPIC questionnaires were compared to scores from 46 patients treated during the same time period with conformal radiotherapy (CRT) to 78 Gy at 2 Gy per fraction.

Results: The dose was prescribed to an isodose line ranging from 82.0% to 90.0% (mean: 87.2%). The range of the individual prostate mean doses was 73.5 to 78.5 Gy (average: 75.3 Gy). To date, only 1 patient had Grade 1 late urinary toxicity. To date, only 4 patients had Grade 1 late rectal toxicity. No Grade 2 or 3 late urinary or rectal complications have occurred. The actuarial rectal bleeding rate observed at 18 months was 7%. There were no differences in scores from the urinary, bowel, hormonal, and overall QOL domains between SCIM-RT patients and patients treated with CRT. The overall physical and mental QOL scores were also nearly identical to scores reported for the general U.S. population.

Conclusion: Preliminary late toxicity results up to 2 years after SCIM-RT are encouraging, with a median follow-up of 18 months (range 11 to 26 months). Late toxicity assessed by the physicians using RTOG late toxicity scores has been excellent. QOL reported by the patients using the EPIC questionnaire reveals no difference between patients treated with high-dose CRT at standard fractionation and patients treated with SCIM-RT. SCIM-RT is an alternative method of dose escalation in the treatment of localized prostate cancer. The proposed schedule significantly increases convenience to patients due to the decrease in overall treatment time.

Introduction

Hypofractionation in the treatment of prostate cancer offers several advantages: shorter treatment course, increased convenience for patients, and decreased cost. It also possibly offers an improved therapeutic ratio, due to a presumed low α/β ratio of prostate cancer tissues 1, 2, 3. The technique and acute toxicity associated with short-course intensity-modulated radiotherapy (SCIM-RT) have been previously described (4). With a median follow-up of 18 months, the same initial 51 patients constitute the sample studied in this report. The emphasis in this report is late toxicity. In addition, a thorough quality-of-life (QOL) assessment is done with a newly validated QOL instrument.

Section snippets

Technique

The SCIM-RT technique has been previously described (4). Inverse planning was done on the Corvus planning system. The outlining of the target and critical structures was performed by the treating physician (P.A.K.). Two risk groups were considered with respect to the definition of the target tissues: low-risk (stage T1-T2, pretreatment prostate-specific antigen [PSA] ≤ 10, and biopsy Gleason ≤ 6) and high-risk disease (stage T3 or pretreatment PSA > 10 or biopsy Gleason ≥ 7). The target was the

Acute toxicity

The RTOG acute bladder toxicity scores for the 51 SCIM-RT cases were as follows: 0 in 4 cases (8%), 1 in 37 cases (72%), and 2 in 10 cases (20%). The RTOG acute rectal toxicity scores for SCIM-RT cases were as follows: 0 in 10 cases (19%), 1 in 34 cases (67%), and 2 in 7 cases (14%). No Grade 3 or 4 acute toxicity was observed.

Late toxicity

The late toxicity profile in all 51 cases has been exceptionally unremarkable. Only one patient developed temporary minimal hematuria; this was scored as a Grade 1

Discussion

Dose escalation studies of three-dimensional CRT techniques have been safely used at dose levels as high as 81 Gy, with improved response seen at higher doses 6, 13, 14, 15, 16, 17. However, these schedules involve up to 8 to 9 weeks of daily treatments. In addition to decreasing the inconvenience of lengthy treatments, there could be a biologic benefit in decreasing the overall treatment time by increasing the daily fraction size. Due to our previous experience with doses in the 78 Gy range

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