Radiotherapy in metastatic castration resistant prostate cancer patients with oligo-progression during abiraterone-enzalutamide treatment: a mono-institutional experience.
BACKGROUND
Some patients experience oligo-progression during androgen receptor targeted therapy (ARTT) treatments. This progression might not indicate a real systemic drug resistance, but a selective monoclonal resistance. With the aim to delay the start of new line treatments we treated oligo-progressive sites with radiotherapy.


METHODS
From June 2011 to Febrary 2019, 29 consecutive metastatic castration resistant prostate cancer (mCRPC) patients were submitted to radiotherapy for oligo-progression (1-3 sites) during ARTT for a total of 37 lesions treated. Thirty-one (83.8%) lesions were treated with conformal radiotherapy and 6 (16.2%) with stereotactic radiotherapy. After radiotherapy all patients continued ARTT.


RESULTS
Median OS (calculated from ARTT start) was 46,6 months (range 4.4-97.5 months), 2 and 3-year OS were 82.8 and 70.7%, respectively. Median PFS was 18,4 months (range 4.4-45.3 months), 2 and 3-year PFS were 38.3 and 8.5%, respectively. Median overall duration of ARTT treatment was 14.8 months (range 4.4-45.3 months) and median duration of ARTT after radiotherapy was 4.6 months (range 1-33.8 months). Patients submitted to radiotherapy > 6 months from the start of ARTT presented a better PFS (p < 0.001) and a trend toward a better OS (p = 0.101). None patient presented RT and drug related toxicities.


CONCLUSIONS
Radiotherapy of oligoprogressive sites may prolong the duration of disease control under ARTT in mCRPC patients with a possible delay in the start of new line treatment. Patients progressing within 6 months from the start of ARTT did not benefit from this approach. More studies are necessary to confirm our results and to evaluate other prognostic factor in order to select patients with high benefit from this approach.
['Valeriani|Maurizio|M|http://orcid.org/0000-0002-1670-3005', 'Marinelli|Luca|L|', 'Macrini|Serena|S|', 'Reverberi|Chiara|C|', 'Aschelter|Anna Maria|AM|', 'De Sanctis|Vitaliana|V|', 'Marchetti|Paolo|P|', 'Tronnolone|Lidia|L|', 'Osti|Mattia Falchetto|MF|']
D000368:Aged D000369:Aged, 80 and over D059002:Androgen Receptor Antagonists D000736:Androstenes D000970:Antineoplastic Agents D001549:Benzamides D003131:Combined Modality Therapy D018450:Disease Progression D018572:Disease-Free Survival D019008:Drug Resistance, Neoplasm D006801:Humans D008297:Male D008875:Middle Aged D009362:Neoplasm Metastasis D009570:Nitriles D010669:Phenylthiohydantoin D011379:Prognosis D017430:Prostate-Specific Antigen D064129:Prostatic Neoplasms, Castration-Resistant D016634:Radiosurgery D020266:Radiotherapy, Conformal D011944:Receptors, Androgen D012189:Retrospective Studies D016896:Treatment Outcome
Androgen receptor targeted therapy Conformal radiotherapy and stereotactic body radiotherapy Oligoprogressive castration resistant prostate cancer