Treatment of prostate c ancer o ligometastases : A systematic r eview

1. No. 160 Treatment of prostate cancer oligometastases: A systematic review Matthew KH Hong1, Niall M Corcoran2, Shankar Siva3, Farshad Foroudi3 1. Division of Urology, Department of Surgery, University of Melbourne, Royal Melbourne Hospital, Parkville, Victoria 2. Australian Prostate Cancer Research Centre, Epworth Richmond, Victoria 3. Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria Posters Proudly Supported by: Introduction Oligometastases describes an intermediate state of metastatic cancer whereby the number and site of metastatic deposits is limited1. It has been hypothesized that localized treatment of oligometastases may present an opportunity for cure2. Both surgery and stereotactic ablative body radiotherapy (SABR) are being used with curative intent for solitary or oligometastases after initial primary therapy for a range of cancers. Up to 95% of men with metastases after radical prostatectomy present with a solitary metastatic site3. Prostate cancer patients with such limited metastases may have a different clinical behaviour to those with widespread metastases4, and there is evidence that correlates lower extent of metastases on bone scan to survival5. There are now a number of studies examining the specific effect of treating prostate cancer oligometastases, particularly after previous radical prostatectomy or ablative therapy. Results A total of 89 articles on oligometastases were identified, from which there were 2 case reports and 7 series including prostate cancer patients. Five of these studies involved standard radiotherapy and 3 involved SABR. Two studies reported a dedicated prostate cancer series. Of the 56 results for solitary metastases in prostate cancer over the last decade, 16 articles were relevant but limited to case reports. Bone and abdominal lymph node metastases were predominantly treated with radiotherapy (Table 1), whereas solitary pulmonary or testicular metastases were surgically excised (Table 2). For radiotherapy series, 1-year progression-free survival ranged from 44% to 56% and 2-year overall survival ranged from 31% to 85%. Within the cases of treated solitary metastases by surgical excision, median biochemical-free survival was 24 months (10 to 144). These figures compare with a mean overall survival of 48 months (2 to 154) in patients with five or fewer metastases treated with palliative intent4. There are few series dedicated to prostate cancer oligometastases with focus on metastases to specific regions rather than the site of primary cancer. The specific management of primary prostate cancer was also omitted in case series. This made it difficult to interpret the data in the context of prostate cancer treatment. The short follow up of patients and the variable definitions of oligometastases used were also limitations of the literature. Aim We performed a systematic literature review to assess the number of studies on treatment of solitary or oligometastases in prostate cancer and, when available, to determine survival and progression rates. Table 1: Reported studies using radiotherapy techniques to treat solitary or oligometastases. * 18 patients had previous radical therapy, 10 with radical prostatectomy; + Number of prostate cancer patients only, part of larger series of patients. Overall survival (OS) and progression free survival (PFS) pertain to overall series rather than isolated to prostate cancer patients unless indicated. Methods A structured systematic PubMed search was performed using keywords and MeSH headings for “oligometastatic prostate cancer”, “oligometastases”, and “solitary metastasis prostate cancer”. References in review articles were manually searched. Selected articles included any reports on treatment of limited prostate cancer metastases through surgery or radiotherapy where patient outcomes were reported. Studies of mixed primary malignancies were included if a subgroup of prostate cancer cases were described. Studies focusing on other malignancies were excluded and in the case of solitary prostate cancer metastases, only studies from the last ten years were sought. Conclusions Long term survivors have been reported after local aggressive treatment of prostate cancer oligometastases. However, the literature on this treatment strategy is limited and there is a need for more robust prospective studies to establish its efficacy. References 1. Hellman S, Weichselbaum RR. Oligometastases. Journal of clinical oncology : official journal of the American Society of Clinical Oncology 1995;13:8-10. 2. Weichselbaum RR, Hellman S. Oligometastases revisited. Nature Reviews Clinical Oncology 2011;8:378-82. 3. Yossepowitch O, Bianco FJ, Jr., Eggener SE, Eastham JA, Scher HI, Scardino PT. The natural history of noncastrate metastatic prostate cancer after radical prostatectomy. European urology 2007;51:940-7; discussion 7-8. 4. Singh D, Yi WS, Brasacchio RA, et al. Is there a favorable subset of patients with prostate cancer who develop oligometastases? International journal of radiation oncology, biology, physics 2004;58:3-10. 5. Soloway MS, Hardeman SW, Hickey D, et al. Stratification of patients with metastatic prostate cancer based on extent of disease on initial bone scan. Cancer 1988;61:195-202. Table 2: Case reports on surgical excision to treat solitary metastases. Isolated solitary lesions were reported except for some bilateral testicular metastases. Overall survival (OS); Progression free survival (PFS). * Patient also underwent radiotherapy.