ESTRO 2024 - Abstract Book

S1043

Clinical - Gynaecology

ESTRO 2024

Group ( N )

EBRT + IGABT Dose

D90 HR CTV Mean (± sd)

A (6)

45Gy/25# + 28Gy/4#

92.0 (±5.51)

B (58)

50.4Gy/28# + 21Gy/3#

84.27 (±5.06)

C (6)

Miscellaneous

86.09 (±4.36)

Table 1 – Patient and treatment Characteristics

Although treatment time of <55 days was achieved in 93% of cases, it was not shown to correlate with survival probability. The site of disease recurrence did not correlate with staging or pathology. An Univarate Cox Regression showed increased D90 HRCTV (Gy) improved survival outcomes (hazard ratio: -0.1, P-value = 0.026) (Table 2). Stratifying patients by dose prescription (Groups A/B/C - table 1) did not show a difference in survival outcome (p-value 0.6), however a higher D90 HRCTV was achieved in Group A (p-value 0.012). In patients with recurrence, the mean D90 HRCTV was 81.6Gy, often constrained by doses to pelvic Organs at Risk (OARs).

Variable

Value (±sd, min-max)

Hazard Ratio (P-Value)

D90 High Risk CTV

85.0±5.40(68-99)

-0.10 (0.026)

Time to start treatment

60.74±46.64 (26-382)

-0.01 (0.586)

Duration of treatment

48.66±4.78 (36-61)

-0.66 (0.201)

Age

51.04±12.80 (28-82)

0.021 (0.337)

Table 2 - Univariate Cox regression analysis of overall survival

32 patients (45%) had node positive disease at diagnosis with 97% of these having involved pelvic side wall nodes (diagram 1). Pelvic nodal failures occurred in 8 patients - 3 with pelvic nodes only and 5 with multiple sites of nodal recurrence. At the time of nodal failure, lymph nodes were predominately at the para-aortic region (87%). In cases of regional nodal failure, disease was situated above the upper border of elective nodal irradiation for EBRT or at the field edge. There was 1 patient with local cervical recurrence and review of her treatment showed that the D90 HRCTV was below recommended at 83Gy.

Conclusion:

This study suggests the potential for further enhancements in LACC treatment. An increased D90 HRCTV is associated with increased disease free survival. In our cohort, dose escalation achieved a higher D90 HRCTV however did not show a survival benefit. We believe this is due to the relatively shorter duration of follow-up for these patients, who were treated at a later time frame. The D90 HRCTV is frequently limited by OAR doses and the introduction of interstitial BT in our center may offer improvements in these cases. Increased elective para-aortic irradiation in cases with high risk features would likely also improve outcomes given that nodal recurrences were shown to be at the superior field edge.

Keywords: Cervical, outcome, recurrence

References:

1.National Cancer Registry Ireland. Cancer in Ireland 1994-2020: Annual statistical report of the National Cancer Registry. https://www.ncri.ie/publications/statistical-reports. 2022.