Predictors of Local Control with Palliative Radiotherapy for Multiple Myeloma

PURPOSE/OBJECTIVE(S)

Palliative radiotherapy (RT) is employed for patients with multiple myeloma to improve or prevent symptoms. However, the optimal dose fractionation is not well defined. The role of cytogenetics in informing RT warrants further study. We performed an institutional analysis of patients with multiple myeloma receiving palliative RT and assessed factors associated with local progression, with a focus on dose fractionation and cytogenetic abnormalities.

MATERIALS/METHODS

We queried a prospectively maintained, departmental database for consecutive patients who received palliative RT for multiple myeloma at our institution from 2015 to 2020. Double- and triple-hit were defined as the presence of two and three high-risk cytogenetic abnormalities. RT dose fractionation data were extracted from the database. Follow-up imaging was used to evaluate for progression.

RESULTS

A total of 239 patients with 362 treated lesions were included. Twenty-five patients (10.4%) with 39 lesions had double-hit cytogenetics, and 4 patients (1.7%) with 7 lesions were triple-hit. Patients had the following number of lesions treated with RT: 1 (156, 65.3%), 2 (53, 22.2%), 3 (17, 7.1%), or >3 (13, 5.4%). The most commonly targeted sites were spine (125, 34.5%), abdomen/pelvis (67, 18.5%), and lower extremity (53, 14.6%). Most lesions received doses of 20 Gy/5 fx (132, 36.5%), 8 Gy/1 fx (93, 25.7%), or 30 Gy/10 fx (48, 13.3%). RT equivalent dose in 2 Gray fractions (EQD2) was <2000 cGy for 126 lesions (34.8%) and ≥2000 cGy for 236 lesions (65.2%). At a median follow-up of 4.3 years, the risk of local progression on a per lesion basis at 1 and 4 years was 7.8% (95% CI: 5.5-11.1) and 13.4% (10.3-17.5), respectively. No cytogenetic abnormalities were correlated with local progression. Factors significant on univariate analysis included female sex [hazard ratio (HR): 1.94 (1.02-3.71), p = .045], LDH at diagnosis [HR per 10 units/liter: 1.04 (1.09-1.08), p = .016], and number of treated lesions [HR per lesion: 1.38 (1.02-1.89), p = .039]. These three covariates were included on multivariable analysis, and the only covariate to approach significance was number of treated lesions [HR for >3 versus 1: 2.43 (0.88-6.74), p = .059]. In the overall cohort, EQD2 did not impact risk of progression. Among those with >3 treated lesions, EQD2 ≥2000 cGy was associated with a significantly lower risk of progression [HR: 0.05 (0.01-0.23), p<.001]. Double- and triple-hit status were not correlated with progression. Median overall survival in all patients was 4.1 years versus 1.5 and 0.6 years in those with double- and triple-hit disease, respectively.

CONCLUSION

In this large, institutional study of patients with multiple myeloma, palliative RT achieves durable long-term local control. Patients with high disease burden may be at increased risk of progression at treated sites. This group may benefit from an EQD ≥2000 cGy. Cytogenetics, including double- and triple-hit status, do not appear to influence RT response.

Change in Blood Counts after Palliative Radiotherapy for Multiple Myeloma

PURPOSE/OBJECTIVE(S)

Radiation therapy (RT) can provide effective palliation and prevent symptomatic local progression of multiple myeloma (MM). However, RT is sometimes avoided due to concerns for secondary impact to bone marrow, potentially decreasing blood cell counts and precluding ability to receive future systemic therapies. We reviewed a series of MM patients who received palliative RT to assess changes in blood counts from pre-RT to post-RT, hypothesizing that blood counts would not significantly decline after treatment with modern RT volumes and techniques.

MATERIALS/METHODS

We utilized a prospectively maintained departmental database and included patients who received palliative RT for MM from 2015 to 2020. Lab values immediately pre-RT (within one month of RT start date) and post-RT (within three months of RT completion) including hemoglobin, lymphocytes, neutrophils, and platelets were collected. Statistical differences from pre-RT to post-RT were assessed using t-tests. ANOVA was used to compare change in blood counts between common dose fractionation regimens (30 Gy in 10 Fractions, 20 Gy in 5, and 8 Gy in 1).

RESULTS

A total of 334 MM patients receiving 424 courses of RT were included in this analysis. The median age at start of first treatment was 67 (IQR: 60-76) years. One-hundred ninety-five (58%) were male. Median RT dose was 20 (IQR: 8-24.5) Gy delivered over a median 5 (IQR: 1-5) fractions. Between pre-RT and post-RT, there was no significant change in hemoglobin (+0.1 g/dL (IQR: -0.8, +0.5), p = .076), lymphocyte counts (-0.3*10^9 cells/L (IQR: -0.6, 0), p = .435), or neutrophil counts (-0.1*10^9 cells/L (IQR: -1.1, +0.9), p = .310). In contrast, platelet counts significantly decreased from pre-RT (median 165*10^9 cells/L, IQR: 112-210) to post-RT (median 146, IQR: 93-194) by a median of 17.5 *10^9 cells/L (IQR: -52.5, +14.0, p<0.0001). There were no differences in changes in hemoglobin, neutrophils, or platelets between the common dose fractionations. However, there was a significantly greater drop in lymphocytes after 30 Gy in 10 fractions (p = .039, mean lymphocyte count change (in 10^9 cells/L) for 30 Gy in 10: -0.87, 20 Gy in 5: -0.47, and 8 Gy in 1: -0.27).

CONCLUSION

In this large dataset of patients receiving modern palliative RT for MM, hemoglobin, lymphocytes, and neutrophils did not significantly decline from pre-RT to post-RT. In contrast, there was a statistically significant drop in platelet count by a median 17.5*10^9 cells/L from pre-RT to post-RT, which may or may not be clinically significant depending on clinical context. Patients receiving 30 Gy in 10 fractions had greater drops in lymphocytes than those receiving lower doses. Further analyses will be performed to determine clinical, dosimetric, and volumetric predictors of decline in blood counts after radiation.

Assessment of Minimum Dose as a Strong Predictor of Local Failure after Spine SBRT

PURPOSE/OBJECTIVE(S)

Stereotactic body radiation therapy (SBRT) has demonstrated robust clinical benefits in carefully selected patients, improving local control and even overall survival (OS). Even so, a wide range of dose-fractionation schemes are used in clinical practice. We seek to assess a large database to determine clinical and dosimetric predictors of local failure after spine SBRT.

MATERIALS/METHODS

From a large institutional database, spine SBRT treatments with subsequent imaging follow-up to assess local control were identified. Patients were treated with a simultaneous integrated boost technique using 1 or 3 fractions, generally delivering 20-24 Gy in 1 fraction to the high dose volume and 16 Gy to the low dose volume (or 30-36 Gy and 24 Gy for 3 fraction treatments). Exclusions included: lack of imaging follow-up, proton therapy, and benign primary histologies. Statistical analyses included Cox proportional hazards analyses and the robust log-rank statistic for cut-point analysis. The cumulative incidence of local failure with death as a competing risk was considered as the primary endpoint.

RESULTS

A total of 522 eligible spine SBRT treatments (68% single fraction) were identified in 377 unique patients. Patients had a median OS of 43.7 months (95% confidence interval: 34.3-54.4). The cumulative incidence of local failure was 19.3% (15.3-23.2) at 1 year and 25.6% (21.1-29.9) at 2 years. Univariate analysis identified that the minimum dose (normalized for the prescription dose) was a strong predictor of local failure (p = 0.0093). Among patients treated with a single fraction, statistical significance was maintained (p = 0.024). No other dosimetric factors were predictive of local failure. In a cut point analysis, the log-rank statistic was maximized at 15.8 Gy minimum dose for single-fraction treatment (HR = 0.51, 95% CI: 0.34 - 0.75, p = 0.0009). Cumulative incidence of local failure was 15.1% (9.8-20.2) vs. 24.7% (17.2-31.5) at 1 year using this cut-off. Comparable local control was demonstrated with a minimum dose of 14 Gy (HR = 0.57, 95%: 0.37 - 0.87, p = 0.009), with reduced local control with lower minimum doses. Among a range of clinical factors assessed, only epidural and soft tissue involvement were predictive of local failure (HR = 1.80 and 1.98, respectively). Multivariable analyses incorporating soft tissue involvement, epidural extension, and multilevel disease confirmed the 15.8 Gy cutoff for single fraction cases (HR = 0.58, 95% CI: 0.38-0.88, p = 0.011).

CONCLUSION

Spine SBRT offers favorable local control using a range of dose-fractionation schemes; however, minimum dose has a strong association with local control, unlike any other dosimetric factors tested. Furthermore, statistical significance was maintained even when considering epidural extension and potential limitations from dose to the spinal cord. Our data suggests that the minimum dose should be prioritized during treatment planning, ideally to at least 14 - 15.8 Gy for single fraction.

Proton vs. Photons for Breast Cancer Patients with Immediate, Implant-Based Reconstruction Receiving Postmastectomy Radiotherapy: A Multicenter Pooled Analysis

PURPOSE/OBJECTIVE(S)

Proton therapy improves postmastectomy radiotherapy (PMRT) normal tissue sparing compared with photon techniques. However, little is understood about its effect on reconstruction outcomes. The primary objective was to evaluate complication rates in breast cancer patients treated with proton (PRO) versus photon (PHO) PMRT following immediate, implant-based breast reconstruction.

MATERIALS/METHODS

Consecutive patients with breast cancer who underwent mastectomy and immediate reconstruction with a tissue expander (TE) or permanent implant (PI) and PRO or PHO PMRT between 2011 and 2022 were included from two institutions. Complication rate was defined as the sum of reconstruction failure (explantation without replacement), unplanned prosthesis exchange, and other unplanned revisional surgery. Each complication type was analyzed as an independent endpoint.

RESULTS

Among 733 patients, median follow-up was 4.4 years; 36.5% (267) were treated with PRO and 63.5% (466) with PHO. There was no difference in age, BMI, or comorbidities between the two groups. PRO was more likely to have had, two-stage reconstruction and pre-pectoral implant placement (p<.01). Median dose was 50-50.4 Gy in 25-28 fractions, with only 50 receiving hypofractionation. Bolus was used in all PHO patients. Regional nodes were more likely to be included in PRO (99.6% v. 83.7% PHO, p<.01). Although there was no difference in the use of chest wall boost between groups, the axillary nodes were more frequently boosted in PRO (25.1% vs 2.8% PHO, p<.01). The overall rate of complications at 4 years was 26.7% (95% CI = 23.3-30.5). The 4-year rate of reconstruction failure, unplanned exchange, and other surgery was 8.2% (95% CI = 6.3-10.7), 17.4% (95% CI = 14.6-20.8), and 12.5% (95% CI = 10.1-15.5), respectively. On MVA, PRO did not confer an increased risk of reconstruction complications compared to PHO. Significant risk factors for reconstruction failure included TE-to-autologous approach [HR versus direct-to-implant reference: 4.05 (95% CI = 1.60-10.22)], TE-to-permanent implant approach [HR = 2.06 (95% CI = 1.12-3.79)], chest wall boost [HR = 2.20 (95% CI = 1.21-4.02)], and any lymph node boost [HR = 2.33 (95% CI = 1.10-4.97)]. Compared to direct-to-implant, two-stage reconstruction was also associated with a higher rate of unplanned exchange [HR for TE/PI = 1.49 (95% CI = 1.01-2.20)] and revisional surgery [HR for TE-to-autologous = 3.95 (95% CI = 1.64-9.52)]. Prepectoral implant placement was correlated with reduced risk of revisional surgery, relative to subpectoral placement [HR = 0.42 (95% CI = 0.22-0.81)].

CONCLUSION

This represents the largest combined series to date comparing PRO and PHO PMRT. Despite a higher rate of two-stage reconstruction, nodal irradiation, and nodal boost in PRO, there was no significant difference in the risk of complications between protons and photons. Differences in PRO delivery techniques between institutions and dosimetric details such as skin dose will be presented in person.

[Clinical characteristics of 16 neonates infected with SARS-CoV-2 during Omicron variant outbreak]

Objective: To analyze the clinical characteristics of the neonates infected with SARS-CoV-2 during the Omicron outbreak in Shanghai 2022. Methods: In this retrospective case series study, all the 16 neonates with SARS-CoV-2 Omicron infection who were admitted to the neonatal unit in Shanghai Public Health Clinical Center from March 1^st to May 31^st, 2022 were enrolled. Their epidemiological history, clinical manifestations, nucleic acid cycle threshold (Ct) value and outcomes were analyzed. Based on maternal vaccination, they were divided into vaccinated group and unvaccinated group. Rank sum test and Chi-square test were used for the comparison between the groups. Results: Among the 16 neonates, 10 were male, and 6 were female. All the infants were full-term. The infection was confirmed at the age of 12.5 (8.0, 20.5) days. All the neonates had a history of exposure to infected family members, and thus horizontal transmission was the primary mode. Four infants were asymptomatic, 12 were symptomatic, and there were no severe or critical cases. The most common clinical manifestation was fever (11 cases), with the highest temperature of 38.1 (37.9, 38.3) ℃ and a course of 1-5 days. Other clinical manifestations included nasal obstruction (3 cases), runny nose (2 cases), cough (2 cases), poor feeding (2 cases), vomiting (1 case), and mild tachypnea (1 case). The complete blood counts of all neonates were within the normal range, and the C-reactive protein increased slightly in 1 infant. Chest imaging was performed in 2 infants, showing mild focal exudative changes. Nucleic acid turned negative (Ct value ≥35) within 7-15 days after diagnosis. All neonates fully recovered after supportive treatment, and the length of hospitalization was 13 (10, 14) days. In the telephone follow-up 2 weeks after discharge for all 16 cases, no infant showed reoccurrence of clinical manifestations or nucleic acid reactivation. Maternal vaccination was not significantly correlated with symptomatic infection or the persistence of positive nucleic acid result in neonates (all P>0.05). Conclusions: Horizontal transmission is the primary mode for neonatal SARS-CoV-2 Omicron infection. Neonatal infections are usually mild or asymptomatic, with good short-term outcomes. And their clinical manifestations and laboratory examinations are nonspecific.

[Management and short-term outcomes of neonates born to mothers infected with SARS-CoV-2 Omicron variant]

Objective: To summarize the management and short-term outcomes of neonates delivered by mothers infected with SARS-CoV-2 Omicron variant. Methods: A retrospective study was performed on 158 neonates born to mothers infected with SARS-CoV-2 Omicron variant admitted to the isolation ward of Children's Hospital of Fudan University from March 15^th, 2022 to May 30^th, 2022. The postnatal infection control measures for these neonates, and their clinical characteristics and short-term outcomes were analyzed. They were divided into maternal symptomatic group and maternal asymptomatic group according to whether their mothers had SARS-CoV-2 symptoms. The clinical outcomes were compared between the 2 groups using Rank sum test and Chi-square test. Results: All neonates were under strict infection control measures at birth and after birth. Of the 158 neonates, 75 (47.5%) were male. The gestational age was (38⁺³±1⁺³) weeks and the birth weight was (3 201±463)g. Of the neonates included, ten were preterm (6.3%) and the minimum gestational age was 30⁺¹ weeks. Six neonates (3.8%) had respiratory difficulty and 4 of them were premature and required mechanical ventilation. All 158 neonates were tested negative for SARS-COV-2 nucleic acid by daily nasal swabs for the first 7 days. A total of 156 mothers (2 cases of twin pregnancy) infected with SARS-CoV-2 Omicron variant, the time from confirmed SARS-CoV-2 infection to delivery was 7 (3, 12) days. Among them, 88 cases (56.4%) showed clinical symptoms, but none needed intensive care treatment. The peripheral white blood cell count of the neonates in maternal symptomatic group was significantly higher than that in maternal symptomatic group (23.0 (18.7, 28.0) × 10⁹ vs. 19.6 (15.4, 36.6) × 10⁹/L, Z=2.44, P<0.05). Conclusions: Neonates of mothers infected with SARS-CoV-2 Omicron variant during third trimester have benign short-term outcomes, without intrauterine infection through vertical transmission. Strict infection control measures at birth and after birth can effectively protect these neonates from SARS-CoV-2 infection.