Interpectoral and serratus anterior plane blocks in mastectomy: a reply

We thank Gong and Luo for their correspondence [1] regarding our trial [2]. With respect to the lack of difference in acute pain intensity and opioid consumption, we agree that this may challenge conventional models linking early nociceptive input with the development of persistent postsurgical pain. However, in our study, acute postoperative pain was well controlled in both groups, most likely due to the routine use of comprehensive multimodal analgesia. As a result, early pain intensity at 2 h and 24 h was low overall, which may have limited the ability to detect additional analgesic effects attributable to the block strategy. A dissociation between acute and chronic pain outcomes has been reported previously in breast surgery. Fujii et al. showed a significant reduction in chronic pain at 6 months following mastectomy with a pectoral type-2 block compared with serratus plane block alone, despite no significant difference in 24-h postoperative pain scores between groups [3]. These findings, together with ours, suggest that the development of chronic postmastectomy pain is multifactorial and not determined solely by early postoperative pain intensity scores. Potential contributors may include modulation of subclinical neural injury, inflammatory responses and longer-term pain trajectories [4, 5]. We agree that the precise mechanisms linking regional anaesthesia techniques and chronic pain prevention remain incompletely understood and warrant further investigation. Regarding the divergence between intention-to-treat and per-protocol analyses, we acknowledge that the exclusion of three protocol deviations attenuated the statistical significance of the primary outcome. We agree that the proximity of the p value to the conventional threshold suggests that the finding may be fragile and warrants cautious interpretation. For this reason, we identified this as a limitation [2]. Confirmation in larger, adequately powered multicentre studies will be essential. We agree that the clinical impact of reducing the incidence of any pain at 6 months must be interpreted in context. Although fewer patients in the intervention group reported pain, absolute pain intensity was low in both groups, median numeric rating pain scores were 0 and no patient required ongoing analgesics. Persistent pain was defined as any pain at rest, an approach adopted increasingly in postsurgical pain research, including breast surgery trials [6], as even mild persistent pain may reflect ongoing sensory disturbance. That said, we agree that future trials should prioritise patient-centred outcomes such as functional impairment, quality of life, pain interference and moderate-to-severe pain phenotypes to better capture clinically meaningful benefits. In addition, analytical approaches that account for longitudinal pain trajectories, such as mixed-effects models, may provide greater sensitivity to detect clinically relevant differences over time and better characterise the dynamic nature of postsurgical pain. We also acknowledge that differences in pain experience and reporting across racial and ethnic groups may have influenced our observed outcomes.