br Of the patients were male Table Median
Of the 36 patients, 18 were male (Table 1). Median age at diagnosis was 61.5 years (range, 39-78 years). Mean IMRT dose was 54.8 Gy ±2.9 Gy. The clinical stage and KPS of pre-CRT and post-CRT are shown in Table 1. T-test results indicate that there was no significant difference between patient cohorts of both institutions.
3.2 Pelvic total bone marrow
After segmentation of both the pre-CRT and post-CRT pelvic TBM, the mean volumes of pre- and post-
CRT (Fig. 1(b)) and post-CRT (Fig. 1(c)). The results of pairwise T-test show that no significant difference
3.3 Differences of Dynasore metabolic activity between pre- and post-CRT
The change in metabolic activity due to CRT treatment was compared with respect to SUVmean for TBM, LSBM, and LPBM, as shown figure 2. Patients’ post-CRT SUVmean was significantly lower than those in pre-CRT, with the SUVmean of the LSBM (p<<0.0001) decreased more significantly than the LPBM (p=0.011).
3.4 Difference of pelvic active bone marrow (ABM) between pre- and post-CRT
The ABM was segmented using SUV of bone marrow that was higher than the mean SUV of extra-pelvic bone marrow. We compared the difference between normalized ABM prior to and after CRT treatment (Fig 1B-C). The ABM in the whole pelvic region, was significantly reduced from 50% of pre-CRT to 40% of post-CRT (p=0.0012) (supplemental figure B). Regional analysis also indicated the lumbosacral ABM was more significantly (p<<0.0001) reduced than LP-pelvis region (p=0.006).
3.5 Acute and post-treatment hematologic toxicity
Different cell types reached their nadirs at different time points: the fifth or sixth week for WBC, ANC, Hg, and LC, versus the third week for PLT nadir (see supplemental figure C). Consistently across all cell types, the greatest reduction toward nadir occurred between week 1 and 3 followed by a persistent negative slope through the course of treatment, and recovery in all cases two weeks post-CRT. The exception was PLT counts, which recovered shortly after week 3 nadir during treatment. Average WBC count significantly decreased from pre-CRT (7.8±2.4 k/μL) to week 4 (4.5±1.9 k/μL) then remained low through weeks 5, 6 and 7. WBC counts post treatment increased (5.1±1.5 k/μL). A similar trend was observed in ANC, and LC, Hg.
3.6 Predictors of hematologic toxicity
We further examined the correlation between HT and image-defined variables (SUVmean, ABM) and dosimetric parameters. Acute and post-CRT HT in relation to PET defined variables and dosimetric parameters are represented in Table 2. WBC, ANC, LC, and Hg significantly correlated with multiple variables, listed in bold on table 2. No significant correlations were found for PLTs. The parameters most significantly correlated with ∆WBC and ∆ANC were the ∆SUVmean and ∆ABM for the LSBM. In terms of sub-regional HT, LS-pelvic region had more significant associations (e.g ∆SUVmean, ∆ABM) than LP-pelvic region. To better interpret the relationship between HT and clinical imaging and dosimetric variables, we further performed linear regression modeling for ABM and HT as well as radiation dose distribution and HT.
3.6.1 Correlation between ABM and HT
3.6.2 The correlation between radiation dose and HT
TBM and ABM within increasing dosimetric subregions (V10Gy, V20Gy, V30Gy, V40Gy, and V50Gy) were correlated with HT (Table 2). The pre-CRT ABM and TBM were used for dose-volume histograms. The V50Gy of ABM was significantly associated with acute HT for ∆WBC (p=0.021) and ∆ANC(p=0.028). The V50 of TBM was significantly associated with acute HT for ∆ANC (p=0.027) and ∆LC (p=0.033). These results in conjunction with the RTOG 0529 bone marrow constraints, resulted in a linear regression analysis of ABM V40 Gy, seen in Figure 6. A negative linear regression can be seen for ∆WBC and ∆ANC related to ABM V40Gy. With linear regression, the ∆WBC can be modeled as a function of ABM V40,