Stereotactic body radiation therapy for prostate cancer

Volumetric-based image guidance is superior to marker-based alignments for stereotactic body radiotherapy of prostate cancer

Purposes

The aim of this study was to evaluate a dual marker‐based and soft‐tissue based image guidance for inter‐fractional corrections in stereotactic body radiotherapy (SBRT) of prostate cancer.

Methods/Materials

We reviewed 18 patients treated with SBRT for prostate cancer. An endorectal balloon was inserted at simulation and each treatment. Planning margins were 3 mm/0 mm posteriorly. Prior to each treatment, a dual image guidance protocol was applied to align three makers using stereoscopic x ray images and then to the soft tissue using kilo‐voltage cone beam CT (kV‐CBCT). After treatment, prostate (CTV), rectal wall, and bladder were delineated on each kV‐CBCT, and delivered dose was recalculated. Dosimetric endpoints were analyzed, including V_{36.25 Gy} for prostate, and D_{0.03 cc} for bladder and rectal wall.

Results

Following initial marker alignment, additional translational shifts were applied to 22 of 84 fractions after kV‐CBCT. Among the 22 fractions, ten fractions exceeded 3 mm shifts in any direction, including one in the left‐right direction, four in the superior‐inferior direction, and five in the anterior‐posterior direction. With and without the additional kV‐CBCT shifts, the average V_{36.25 Gy} of the prostate for the 22 fractions was 97.6 ± 2.6% with the kV x ray image alone, and was 98.1 ± 2.4% after applying the additional kV‐CBCT shifts. The improvement was borderline statistical significance using Wilcoxon signed‐rank test (P = 0.007). D_{0.03 cc} was 45.8 ± 6.3 Gy vs. 45.1 ± 4.9 Gy for the rectal wall; and 49.5 ± 8.6 Gy vs. 49.3 ± 7.9 Gy for the bladder before and after applying kV‐CBCT shifts.

Conclusions

Marker‐based alignment alone is not sufficient. Additional adjustments are needed for some patients based kV‐CBCT.

Emerging applications of stereotactic body radiotherapy

Stereotactic body radiotherapy (SBRT) has been used extensively in patients with lung, liver and spinal tumors, and the treatment outcomes are very favorable. For certain conditions such as medically inoperable stage I non-small-cell lung cancer, liver and lung oligometastases, primary liver cancer and spinal metastases, SBRT is regarded as one of the standard therapies. In the recent years, the use of SBRT has been extended to other disease conditions and sites such as recurrent head and neck cancer, renal cell carcinoma, prostate cancer, adrenal metastasis, pancreatic cancer, gynecological malignancies, spinal cord compression, breast cancer, and stage II-III non-small-cell lung cancer. Preliminary data in the literature show promising results but the follow-up intervals are short for most studies. This paper will provide an overview of these emerging applications.

Best of International Stereotactic Radiosurgery Society Congress 2013: stereotactic body radiation therapy. Part II: nonspinal tumors

The 11th biennial International Stereotactic Radiosurgery Society Congress represented another historical gathering of professionals in the field of stereotactic radiosurgery. This congress was held on 16-20 June 2013 in Toronto (ON, Canada), and the chairman was Arjun Sahgal, co-chair was Michael Schwartz and president of the society was Jean Regis. The congress attracted 550 attendants from all over the world and over 300 abstracts were presented. Among the abstracts presented, 62 (36 oral) were pertaining to stereotactic body radiation therapy (SBRT). Exciting new findings were presented by colleagues from North America, Europe and Asia. This short conference scene (part II) provides a summary of the best abstracts on SBRT for nonspinal tumors presented in the congress. A separate conference scene on SBRT for spinal tumors (part I) also appears in this issue of Future Oncology.

Hypofractionated external-beam radiation therapy (HEBRT) versus conventional external-beam radiation (CEBRT) in patients with localized prostate cancer: a systematic review and meta-analysis

BACKGROUND

The purpose of this work was to conduct a systematic review and meta-analysis of all randomized controlled trials comparing the efficacy and side effect profile of hypofractionated versus conventional external-beam radiation therapy for prostate cancer.

METHODS

Several databases were searched, including Medline, EmBase, LiLACS, and Central. The endpoints were freedom from biochemical failure and side effects. We performed a meta-analysis of the published data. The results are expressed as the hazard ratio (HR) or risk ratio (RR), with the corresponding 95% confidence interval (CI).

RESULTS

The final analysis included nine trials comprising 2702 patients. Freedom from biochemical failure was reported in only three studies and was similar in patients who received hypofractionated or conventional radiotherapy (fixed effect, HR 1.03, 95% CI 0.88-1.20; P = 0.75), with heterogeneity [χ(2) = 15.32, df = 2 (P = 0.0005); I2 = 87%]. The incidence of acute adverse gastrointestinal events was higher in the hypofractionated group (fixed effect, RR 2.02, 95% CI 1.45-2.81; P < 0.0001). We also found moderate heterogeneity on this analysis [χ(2) = 7.47, df = 5 (P = 0.19); I2 = 33%]. Acute genitourinary toxicity was similar among the groups (fixed effect, RR 1.19, 95% CI 0.95-1.49; P = 0.13), with moderate heterogeneity [χ(2) = 5.83, df = 4 (P = 0.21); I2 = 31%]. The incidence of all late adverse events was the same in both groups (fixed effect, gastrointestinal toxicity, RR 1.17, 95% CI 0.79-1.72, P = 0.44; and acute genitourinary toxicity, RR 1.16, 95% CI 0.80-1.68, P = 0.44).

CONCLUSION

Hypofractionated radiotherapy in localized prostate cancer was not superior to conventional radiotherapy and showed higher acute gastrointestinal toxicity in this meta-analysis. Because the number of published studies is still small, future assessments should be conducted to clarify better the true role of hypofractionated radiotherapy in patients with prostate cancer.

Serious complications associated with stereotactic ablative radiotherapy and strategies to mitigate the risk

The clinical applications of stereotactic body radiotherapy or stereotactic ablative radiotherapy (SABR) for the treatment of primary and metastatic tumours of different organ sites have been expanding rapidly in the recent decade. SABR requires advanced technology in radiotherapy planning and image guidance to deliver a highly conformal ablative dose precisely to targets (or tumours) in the body. Although this treatment modality has shown promising results with regard to tumour control, some serious complications have been observed and reported. In order to achieve a favourable therapeutic ratio, strategies to mitigate the risk of complications must be in place. This overview will summarise the reported serious complications caused by SABR and strategies to mitigate the risk will be discussed.