ESTRO 2022 - Abstract Book

S449

Abstract book

ESTRO 2022

1 Albert Einstein College of Medicine and Montefiore Medical Center, Radiation Oncology, Bronx, USA; 2 Albert Einstein College of Medicine, Radiation Oncology, Bronx, USA; 3 Montefiore Medical Center, Radiation Oncology, Bronx, USA Purpose or Objective Compare the outcomes, occurrence of hemato-immunological toxicity, and their association with dose to active bone marrow (ABM) after definitive chemoradiation for patients with anal cancer living with HIV (PLWH) or without HIV infection (HIV-). Materials and Methods Patients treated for anal cancer at a single institution between 2007-2020 were identified and hemato-immunological and clinical data were tabulated. Dose to ABM was evaluated by overlaying bone contours within the irradiated volume on pre- treatment PET/CT scans. Areas of bone with SUV exceeding the mean bone SUV were designated as ABM. Evaluated hematologic quantities were pre-treatment values, value at and time to nadir (TTN) and recovery (TTR), and occurrence of grade ≥ 3 hematologic toxicity. Results 97 patients with anal cancer were identified, of which 44 were PLWH. Complete CBC counts were available for 90 patients. Radiation therapy was commonly prescribed to 50.4-54 Gy using IMRT; 3 patients underwent RT alone (all PLWH); Chemotherapy was 5-FU+Mitomycin-c (34 HIV-/27 PLWH), Capecitabine+Mitomycin-c (16 HIV-/11 PLWH), or other (3 HIV- /3 PLWH). Median follow-up was 55 months in HIV- patients (rg: 10-150) vs. 59 months in PLWH (rg: 5-164). Among HIV- patients there were 45% stage I/II and 55% stage III, in PLWH there were 40% stage I/II and 60% stage III. There were 10/53 vs. 7/44 loco- regional recurrences in the HIV- vs. PLWH group, 9 vs. 2 distant metastases, and 9 deaths in both. Outcomes (HIV- vs. PLWH) were comparable with 2-year PFS at 76.9% vs. 83.8% (p=.40) and OS at 92.3% vs. 92.8% (p=0.93). Substitution of 5- FU with capecitabine had no effect on outcomes in either group (p>0.73). G3+ Lymphopenia occurred in 83% (n=44) vs. 89% (n=32) (p=.35), G3+ neutropenia occurred in 21% (n=11) vs. 56% (n=20) (p<.01), and G3+ thrombocytopenia occurred in 8% (n=4) vs. 33% (n=12) (p<.01) of patients in the HIV- and PLWH groups, respectively. Absolute ABM V 5Gy to V 40Gy was associated with delayed recovery in platelet counts for HIV- (0.40-0.56; p ≤ .04) and PLWH (0.41; p=.04) patients (Fig.1), with a sharp increase at volumes above 275cm 3 (HIV-) and 350cm 3 (PLWH), while rel. V 5Gy (-0.29; p<.04) for HIV- and abs. V 5Gy to V 40Gy (-0.43; p ≤ .02) for PLWH were associated with a more rapid drop in lymphocytes showing no threshold (Fig.2).

Figure 1. Time to recovery association with ABM V 5Gy and V 15Gy .

Figure 2. Time to nadir association with volumetric ABM dose metrics.

Conclusion