2984 - The Need for Breast Board in the Modern Era: A Prospective Study - Lesson Learnt!

Purpose/Objective(s): Adjuvant radiotherapy in breast cancer has an established role in locoregional control and improved disease free interval (DFS). In supine treatment position, unsupported breast falls laterally and superiorly, causing potentially more doses to lung, heart and contralateral breast. This is more often for patients having large pendulous breasts. These patients are more likely to experience severe and often painful radiation dermatitis due to presence of skin folds. The obliquity of the anterior chest wall, tangential fields include a disproportionate volume of lung in craniocaudal direction. This is overcome by elevating the upper torso to make the chest wall horizontal. These issues mandate the need of breast board as an efficient immobilization device which demands additional time and effort in setting up the patient with breast board, which is a point of concern in high volume centers. Our study aims to analyze the difference in target volume coverage and doses to organ at risk (OAR) with and without breast board.

Materials/Methods: In this dosimetric study, forty eight (48) patients of breast cancer requiring adjuvant RT were simulated in wide bore CT simulator with and without breast board. Target volumes and OARs were delineated as per RTOG contouring guidelines. The prescribed dose was 40 Gy/15#. Two sets of 3DCRT (FIF) plans were generated for each patient in a treatment planning system. The target volume coverage and doses to OARs were recorded. The dose volume histogram (DVH) generated for both the plans were compared and analyzed.

Results:

Both the plans were analyzed using a technology company's treatment planning system. Various parameters like target volume coverage and volumetric analysis of OARs were documented. On comparison, mean doses to the ipsilateral (I/L) lung were higher with breast board (range, 6.6 Gy - 14 Gy) than without breast board (range, 2.9 Gy - 10.2 Gy) which was not statistically significant (p=0.065). However, subset analysis of I/L partial lung volumes, doses of V8 and V16 were significantly higher in plans with breast board against the plans without breast board (V8 - 5.7 vs 5.3 with p=0.037) and (V16 - 5 vs 4.7 with p= 0.031) respectively. In contrary, dose maximum (Dmax) doses to the contralateral breast were significantly lesser in plans with breast board when compared to plans without breast board (Dmax 10.36 vs 15.5 with p=0.04)

Conclusion:

Our study demonstrated that the doses to the I/L partial lung volumes were statistically higher with the use of breast board. However, it was observed that doses to the contralateral breast were significantly reduced with the use of breast board. This study mandates the cautious use of breast board in adjuvant radiotherapy after careful risk- benefit analysis of lung toxicity Vs contralateral breast doses.

Abstract 2984 - Table 1

PARAMETERS		Mean	SD	p value
I/L LUNG V8Gy_c	WOBB	5.3	0.9	.037
	WBB	5.7	0.7
I/L LUNG V16Gy_C	WOBB	4.7	0.8	.031
	WBB	5.0	0.7
C/L BREAST Dmax	WOBB	15.5	13.6	.043
	WBB	10.3	11.1