Patterns of local relapse following tumor-targeted dose escalation for localized prostate cancer
Padayachee, J. Sanmamed, N. Lee, J. Liu, Z. Berlin, A. Craig, T. Lao, B. Rink, A. Bayley, A. Catton, C.
Padayachee, J.
Sanmamed, N.
Lee, J.
Liu, Z.
Berlin, A.
Craig, T.
Lao, B.
Rink, A.
Bayley, A.
Catton, C.
Citations
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Abstract
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.
Materials 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 endpoint 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.
Description
Date
2021
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Padayachee J, Sanmamed N, Lee J, Liu Z, Berlin A, Craig T, et al. Patterns of local relapse following tumor-targeted dose escalation for localized prostate cancer. Radiotherapy and Oncology. 2021;161:S1109-S.