Abstract
ObjectivesTo investigate whether radiotherapy as metastasis-directed therapy (MDT) on oligo-progressive sites in metastatic castration-resistant prostate cancer (mCRPC) patients during treatment with androgen receptor-targeted therapy (ARTT) may lead to control resistant lesions, prolonging ARTT. We analysed progression free survival, overall survival and prognostic parameters that can identify patients that best suit to this approach.Patients and MethodsRetrospective analysis of a total of 67 lesions in 42 mCRPC patients treated with ablative or palliative RT to oligoprogressive lesions during ARTT. Twenty-eight patients (67%) underwent ARTT with Abiraterone acetate and 14 patients (33%) underwent ARTT with Enzalutamide. Median time between the start of ADT and ARTT beginning was 50.14 months (range 3.37-219 months). We treated 58 lesions (87%) with 3D conformal radiotherapy (3DCRT) and nine lesions (13%) with stereotactic body radiotherapy (SBRT). The Kaplan Meier method was used to assess the median overall survival (OS) and the progression-free survival (PFS).ResultsMedian follow-up was 28 months (range 3-82 months). Median OS was 32.5 months (95% CI 25.77-39.16), 1 and 2-year OS were 71.6% and 64.1%, respectively. Median PFS was 19,8 months (95% CI 11.34–28.31), 1 and 2-year PFS were 67.2% and 47.4%, respectively. Median OS for patients that underwent radiotherapy before 6 months from the start of ARTT was 23.4 months (95% CI 2.04-44.89) and 45.5 months (95% CI 31.19-59.8) for patients that underwent radiotherapy after 6 months (p = 0.009).ConclusionLocal ablative radiation therapy directed to progressive metastasis is a non-invasive, well tolerated treatment with efficacy on prolonging clinical benefit of systemic therapies with ARTT. Patients who underwent RT >6 months from the start of ARTT presented a statistically better OS and PFS compared with patients who underwent radiotherapy <6 months from the start of ARTT.
Highlights
Due to the increased sensitivity and specificity of modern imaging modalities, the oligometastatic prostate cancer (PC) is diagnosed more often, many patients considered nonmetastatic on conventional imaging (computed-tomography (CT) and bone scintigraphy) turn out to be oligometastatic even at a low prostate-specific antigen (PSA) serum level.There is currently no definite biologic definition of oligometastatic disease, that is defined relying on clinical and radiographic evidence, including the number of lesions and number of sites of metastasis
Median progression-free survival (PFS) and PF2 for patients treated with Androgen Receptor Targeted Therapy (ARTT) as first line therapy was 19.8 months and 5 months compared to patients treated as second-third-fourth approach 18.4 months (p = 0.79) and 9.5 months (p = 0.62)
Median PFS for patients treated with stereotactic body radiotherapy (SBRT) was 27.7 months and 19.8 months for those treated with 3D conformal radiotherapy (3DCRT) (p = 0.49)
Summary
Due to the increased sensitivity and specificity of modern imaging modalities, the oligometastatic prostate cancer (PC) is diagnosed more often, many patients considered nonmetastatic on conventional imaging (computed-tomography (CT) and bone scintigraphy) turn out to be oligometastatic even at a low prostate-specific antigen (PSA) serum level.There is currently no definite biologic definition of oligometastatic disease, that is defined relying on clinical and radiographic evidence, including the number of lesions and number of sites of metastasis. According to the European Association of Urology guideline, castration resistance is defined by biochemical progression (three consecutive rises in PSA 1 week apart resulting in two 50% increases over the nadir, with PSA >2 ng/ml) or radiological progression (appearance of two or more new bone lesions on bone scan or enlargement of a soft tissue lesion using RECIST 1.1) with a serum testosterone
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