Patterns of local relapse following tumor-targeted dose escalation for localized prostate cancer
Jerusha Padayachee,
New Zealand
PO-1351
Abstract
Patterns of local relapse following tumor-targeted dose escalation for localized prostate cancer
Authors: Jerusha Padayachee1, Noelia Sanmamed1, Jenny Lee1, Zhihui Liu1, Alejandro Berlin1, Tim Craig1, Bernadeth Lao1, Alexandra Rink1, Andrew Bayley2, Charles Catton1, Aravindhan Sundaramurthy3, Warren Foltz4, Andrew McPartlin5, Sangeet Ghai1, Eshetu Atenafu1, Mary Gospodarowicz1, Padraig Warde1, Joelle Helou1, Srinivas Raman1, Cynthia Ménard6, Peter Chung1
1Princess Margaret Cancer Centre, Radiation Medicine Program, Toronto, Canada; 2Sunnybrook Health Sciences Centre, Radiation Oncology, Toronto, Canada; 3Edinburgh Cancer Centre, Clinical Oncology, Edinburgh, United Kingdom; 4University of Toronto, Department of Radiation Oncology, Toronto, Canada; 5The Christie NHS Foundation Trust, Clinical Oncology, Manchester, United Kingdom; 6Centre Hospitalier de l’Université de Montréal (CHUM), Radiation Oncology, Montreal, Canada
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Purpose or Objective
Tumor-targeted
dose escalation may improve local control rates in patients with prostate
cancer, leading to improved biochemical failure-free survival (bFFS). We report
outcomes of dose escalation using a strategy of simultaneous integrated boost
or HDR brachytherapy boost.
Material and Methods
Eighty
patients with localized prostate cancer with GTV identified on multiparametric MRI
(mpMRI) were enrolled in this phase 2 non-randomized trial (2012-2016). Patients
with GTV >5mm and less than 33% of total prostate volume were eligible. All
patients received whole gland prostate VMAT, 76 Gy in 38 fractions. Choice of GTV
dose escalation was by physician and/or patient choice and delivered by
integrated boost VMAT (IB-VMAT) of 95 Gy in 38 fractions (n=40); or MRI-guided
HDR boost of 10 Gy in 1 fraction (n=40). The primary end-point was 3-year local
control rates determined by MRI-guided biopsy and/or MRI alone. Toxicity data
was collected using CTCAE v.4.0. Risk group categorization was comparable between
the arms; 5% low-, 75% intermediate-, and 20% high-risk. Three patients
received 6-months of concurrent/adjuvant ADT.
Results
Median
(IQR) follow-up was 55.2 months (48.1-71.4). The overall 5-year bFFS was 92%
(95% CI, 85-99). Late G2 GU toxicity was 22.5% and 27.5% in IB-VMAT and HDR
boost arms, respectively. Late G2 GI toxicity was 5% in each arm. Two G3 (1 GI,
1 GU) toxicities were seen in IB-VMAT. Local control data was available for 66
patients who agreed to the 3-year
post-treatment biopsy (20) or MRI alone (46); 32 in IB-VMAT and 34 in HDR boost.
Local control within the boost volume was achieved in 61 patients. One patient
in the IB-VMAT arm had persistent disease on biopsy, and subsequently met
criteria for biochemical relapse (BCR). At last follow-up of the 66 patients, 4
developed BCR with evidence of intraprostatic relapse outside the boost volume;
1 treated with IB-VMAT and 3 with HDR boost. The spatial distribution of these relative
to the boost volume were: ipsilateral lobe (IB-VMAT),
marginal/contralateral/bilateral (HDR boost). These relapses appeared to correlate
to sites of known microscopic disease at original diagnosis.
Conclusion
Dose
escalation to mpMRI-defined GTV provided high rates of local and biochemical
control with a favorable late toxicity profile. The majority of local treatment
failures developed beyond the tumor-targeted volume, suggesting that other
treatment intensification strategies may be required to further improve
outcomes.