Clinical outcomes of helical tomotherapy for super-elderly patients with localized and locally advanced prostate cancer: comparison with patients under 80 years of age

摘要

A total of 23 patients aged 80 years or older with T1c–T4 non-metastatic prostate cancer (according to the International Union Against Cancer TNM Classification of Malignant Tumors, 7th edition) were treated with IMRT in our hospital between September 2009 and October 2012. All patients were included in the present study. To evaluate the clinical outcomes in super-elderly patients who were 80 years old or above, data were compared with those from 171 patients under the age of 80 years with intermediate-risk, high-risk and castration-resistant prostate cancer (CRPC) who were treated around the same time in our hospital. The institutional review board of our hospital approved this study. IMRT is a powerful tool for improving the quality of the delivered dose distribution in external beam radiation therapy, and this therapy reduces late rectal toxicity in high-dose external beam radiation therapy for prostate cancer [15]. The TomoTherapy Hi-Art system (Accuray Inc., Sunnyvale, CA, USA) is a radiation delivery system that combines dynamic IMRT and an image-guided radiation therapy system [16, 17]. All patients with prostate cancer were treated with IMRT using helical tomotherapy (TOMO) in the present study. Patients were placed in the supine position with a universal fixation device (ESFORM, Engineering System Co., Nagasaki, Japan) to immobilize the lower legs and reduce set-up error. Axial images (3-mm slices) were acquired using a 16-row multi-detector CT (Aquilion LB, Toshiba Medical, Otahara, Japan) for planning CT. Pelvic MRI at 3-mm thickness was performed, and T2-weighted images were fused to the planning CT images to delineate target volumes. Contouring of target volumes and normal structures was performed on the Focal treatment planning system, version 4.3.1 (Focal Eindhoven, Netherlands). The PTVs primarily received 78 Gy in 39 fractions in the present study. Three cases in which the intestines were close to the PTV received 72 Gy in 36 fractions to reduce toxicity. The prescription dose was defined as the minimum dose delivered to 95% of the PTV (D95%). The maximum tolerated dose in the PTV was limited to 105% of the prescription dose. Rectal dose–volume constraints limited V65 Gy (percentage of the rectum volume receiving at least 65 Gy) to ≤17%, V40 Gy to ≤35% and V22 Gy to ≤60%. The bladder dose–volume constraints limited V65 Gy to ≤25% and V40 Gy to ≤50%. Image-guided radiation therapy was performed daily in all patients. Acquired CT images using mega voltage CT (MVCT) were superimposed onto the treatment plans. The patient's position was adjusted according to prostate matching before each treatment. Patients had a tube inserted or were encouraged to defecate when their rectums were dilated for daily MVCT and were re-examined on MVCT. Urologists administered ADT, including medical or surgical castration, to all 23 patients of the aged group and all 171 patients of the younger group. Among the patients aged 80 years and above, the median period of ADT before or concomitant with TOMO was 17 months (range, 5–141 months) for all 23 patients; the median periods of ADT before TOMO were 7 months (range, 5–31 months) for the intermediate-risk group, 11 months (range, 6–46 months) for the high-risk group, and 84 months (range, 45–141 months) for the CRPC group. The median periods of ADT after TOMO were 25 months (range, 10–45 months) for the intermediate-risk group and 31 months (range, 0–46 months) for the high-risk group. Fourteen patients received ADT at the last follow-up. Among the patients under the age of 80 years, the median period of ADT before or concomitant with TOMO was 12 months (range, 5–63 months) for all 171 patients; the median periods of ADT before TOMO were 7 months (range, 5–13 months) for the intermediate-risk group, 10 months (range, 5–29 months) for the high-risk group, and 39 months (range, 24–63 months) for the CRPC group. The median periods of ADT after TOMO were 20 months (range, 0–41 months) for the intermediate-risk group and 32 months (range, 6–55 months) for the high-risk group. A total of 106 patients received ADT at the last follow-up. A urologist and a radiation oncologist conducted patient follow-ups at 3-month intervals for the first 3 years after TOMO and at intervals of 3–6 months thereafter. PSA values were evaluated in each follow-up examination. Biochemical relapse was defined as the nadir PSA level plus 2 ng/ml. CT images were collected once per year after TOMO to assess any metastatic progression. Late toxicity was evaluated according to the Common Terminology Criteria for Adverse Events, version 3.0. Patients with suspected rectal bleeding underwent endoscopic examinations, and late rectal toxicity was confirmed. The overall survival time, biochemical relapse-free time, and cumulative occurrence rates of late toxicity were estimated using the Kaplan–Meier method. Comparisons of the overall survival time, biochemical relapse-free time, and cumulative occurre